What is Genetics?What is Genetics?GeneticsGenetics is the study of heredity. is the study of heredity.

HeredityHeredity is how traits are passed down from is how traits are passed down from generation to generation.generation to generation.

“Father of Genetics”.

He studied the way characteristics are passed on in pea plants in the 1800’s.

Gregor Mendel

Mendel’s DiscoveryMendel’s Discovery Mendel discovered that a pea plant’s characteristics Mendel discovered that a pea plant’s characteristics

such as height, seed color and pod color are determined such as height, seed color and pod color are determined by an inheritance factor. He observed 14 different by an inheritance factor. He observed 14 different characteristicscharacteristics

These inheritance factors where later called These inheritance factors where later called genesgenes. . GenesGenes are a unit of heredity. They contain the are a unit of heredity. They contain the instructions for a instructions for a traittrait..

A A traittrait is a characteristic (color, height) coded for by two is a characteristic (color, height) coded for by two or more genes.or more genes.

Fourteen Traits of Pea Plants:

Flower Color

Pink Flower

White Flower

Seed ColorYellow Seed

Green Seed

Seed ShapeRound Seed

Wrinkled Seed

Pod Color Green Pod Yellow Pod

Pod ShapeSmooth

PodWrinkled

Pod

Flower Position

Along Stem

At the Tip

Plant Size Tall Plant Short Plant

AlleleAllele: 2 forms of a gene: 2 forms of a geneDominant:Dominant:

The gene that covers up the effect of the other one.The gene that covers up the effect of the other one.

Use a capital letter. Example “T” or “G”Use a capital letter. Example “T” or “G”

Recessive:Recessive:

The effect of the gene is hidden (unless two are present).The effect of the gene is hidden (unless two are present).

Use a lower case letter. Example “t” or “g”Use a lower case letter. Example “t” or “g”

Mendel developed true breeding plants for each trait because true bred plants always gave the same results every time.

He found when breeding different pure forms of the same trait that one trait would always show up while the other one did not. It was for this reason that he labeled the trait that always showed up in these crosses DOMINANT and the trait that did not show up RECESSIVE

PURE PURE

PURE

RECESSIVE

PURE

DOMINANT

PURE

All Dominant

But NOT PURE

This proved that the parents and offspring have 2 genes for each trait. How else could the parents have offspring

that showed different traits than the parents.

He tested many characteristics and found that this was true for all of the traits. They had a dominant trait and a recessive trait.

He did his experiment again using the offspring from the first cross. His results were very strange. From two parents showing the dominant trait, he got offspring that showed the recessive trait.

Not Pure Not Pure

????

Offspring from the Pink and White Cross

WEIRDWEIRD

http://www.accessexcellence.org/RC/VL/GG/human.html

Females are listed by XX.Females are listed by XX.

Males are listed by XY.Males are listed by XY.

Genetic disorders:Genetic disorders:

Tay-Sachs:Tay-Sachs: Caused by a gene mutation Caused by a gene mutation on chromosome 15on chromosome 15

Down Syndrome:Down Syndrome: An extra copy of An extra copy of chromosome 21 is present.chromosome 21 is present.

Look up other Look up other genetic disorders..

DNADNA makes up makes up genesgenes. . GenesGenes make up make up chromosomeschromosomes..

There are 23 pairs (46 total) chromosomes in each non-sex cell There are 23 pairs (46 total) chromosomes in each non-sex cell for humans. 23 chromosomes in sex cells.for humans. 23 chromosomes in sex cells.

DNADNA GENESGENES ChromosomesChromosomes

Traits are ways to describe living things. Traits are ways to describe living things.

We are going to focus on human traits during genetics. We are going to focus on human traits during genetics.

Traits that we may discuss include: hair color, eye Traits that we may discuss include: hair color, eye color, blood type.color, blood type.

PhenotypePhenotype: What the organism looks like. Its : What the organism looks like. Its Physical makeup. Physical makeup. Examples : Tall, Short, round or wrinkledExamples : Tall, Short, round or wrinkled

GenotypeGenotype: The genetic make-up of a trait. What : The genetic make-up of a trait. What 2-letter gene combination it is made from.2-letter gene combination it is made from.Examples TT, Tt, ttExamples TT, Tt, tt

Punnett Square: Determine the probability that offspring will or Determine the probability that offspring will or will not have a given trait.will not have a given trait.

Pure Tall plant ( T T ) crossed with a Pure Short Plant ( t t )Each parent can give one trait gene to the offspring so each offspring will get half their trait genes from each parents. The chances of any parent giving a particular trait gene are random. We always start off with what we know in a KEY:

Key:T- Tall Plantt – Short Plant

We put these on a grid and see what possible outcomes we can get…

Then we show the cross:

Cross Pure Tall with Pure ShortT T X t t

The Pure Tall parent can give a T or a T.The Pure Tall parent can give a T or a T.

The Pure Short parent can give a t or a t

The Pure Short parent can give a t or a t

One parent goes on the top of the box and the other goes on the side

The possible offspring will appear in the boxes

By looking at these results, you can see that the offspring will all be Tall but not Pure Tall.

They are all mixed. This is called Hybrid.

T T X t tT T

TT

TTt

t tt

tt You fill in the squares with the appropriate letter

T t

The Phenotype of the offspring is:The Phenotype of the offspring is:100 % TALL100 % TALL

The Genotype of the offspring is:The Genotype of the offspring is:100% mixed… We call this Hybrid100% mixed… We call this Hybrid

When we write genes we use one letter (G or g, T or t, etc.)When we write genes we use one letter (G or g, T or t, etc.)

Traits or characteristics are determined by one or more pair Traits or characteristics are determined by one or more pair of genes.of genes.

Half of your genes come from your Half of your genes come from your mothermother and half of your and half of your genes come from your genes come from your fatherfather..

Purebred or Homozygous Purebred or Homozygous : Both genes are the same. : Both genes are the same.

Example: TT or tt are Example: TT or tt are BOTHBOTH Homozygous. It doesn’t matter if they are Homozygous. It doesn’t matter if they are dominant or recessive…just that they are the same.dominant or recessive…just that they are the same.

Hybrid or Heterozygous Hybrid or Heterozygous : Both genes are different.: Both genes are different.Example Tt is Heterozygous. Heterozygous offspring always show the Example Tt is Heterozygous. Heterozygous offspring always show the dominant trait.dominant trait.

Punnett Squares practicePunnett Squares practice

We looked at green seeds and yellow seeds. If both plants are We looked at green seeds and yellow seeds. If both plants are homozygous, what are their genotypes?homozygous, what are their genotypes?

Key: G – Green seedsKey: G – Green seeds

g – Yellow seedg – Yellow seed

Plant 1 (green) = GGPlant 1 (green) = GG Plant 2 (yellow) = ggPlant 2 (yellow) = gg

Identify the genes that are present in each plants’ sex cells.Identify the genes that are present in each plants’ sex cells.

GGGG gggg

GG GG gg gg

We are now going to determine the possible genotypes and We are now going to determine the possible genotypes and phenotypes of the offspring using a Punnett Square.phenotypes of the offspring using a Punnett Square.

GG GG x x gggg

gg

GG

gg

GG GGggGGgg

GGggGGgg

Genotype

Phenotype

gg =

Gg =

GG =

0/4 = 0%

4/4 = 100%

0/4 = 0%

Green =

0/4 = 0%

4/4 = 100%

Yellow =

Determine the genotype and phenotype probabilities for a Determine the genotype and phenotype probabilities for a cross between two heterozygous plants from the previous cross between two heterozygous plants from the previous problem.problem.

Parents = Parents = GGgg X X GGgg

GG gg

GG GGGG GGgg

gg GGgg gggg

GenotypeGenotype

PhenotypePhenotype

gggg = =

GGgg = =

GGGG = =

1/4 = 25%1/4 = 25%

2/4 = 50%2/4 = 50%

1/4 = 25%1/4 = 25%

Green Green ==

YellowYellow = =

3/4 = 75%3/4 = 75%

1/4 = 25%1/4 = 25%

When you look closely at it, there are only six crosses that When you look closely at it, there are only six crosses that deal with two alleles. They are: (using G and g as example deal with two alleles. They are: (using G and g as example traits)traits)

GG x GG Pure Dominant x Pure DominantGG x GG Pure Dominant x Pure DominantGG x Gg Pure Dominant x HybridGG x Gg Pure Dominant x HybridGG x gg Pure Dominant x Pure RecessiveGG x gg Pure Dominant x Pure RecessiveGg x Gg Hybrid x HybridGg x Gg Hybrid x HybridGg x gg Hybrid x Pure RecessiveGg x gg Hybrid x Pure Recessivegg x gg Pure Recessive x Pure Recessivegg x gg Pure Recessive x Pure Recessive

If you can memorize these six crosses and their phenotype If you can memorize these six crosses and their phenotype and genotype ratios, you will never see a genetics problem and genotype ratios, you will never see a genetics problem you can’t solve.you can’t solve.

Also remember that anything crossed with a Pure Also remember that anything crossed with a Pure Recessive is a Test Cross. It is a control to show what Recessive is a Test Cross. It is a control to show what recessive traits you may have.recessive traits you may have.

Practice ProblemPractice ProblemMendel also studied the heights of pea plants during his Mendel also studied the heights of pea plants during his

experiments.experiments.

He determined that tall pea plants were dominant over He determined that tall pea plants were dominant over short pea plants.short pea plants.

Step 1: Create a key. Pick a letter to represent genes.Step 1: Create a key. Pick a letter to represent genes.

Dominant = Tall (T) Dominant = Tall (T)

Recessive = short (t)Recessive = short (t)

Use the key to help you answer the following questions:Use the key to help you answer the following questions:

1. Determine the 1. Determine the phenotypephenotype of a plant that is of a plant that is TtTt..

2. Determine the 2. Determine the genotypegenotype of a of a homozygoushomozygous smallsmall plant. plant.

3. Would a 3. Would a heterozygousheterozygous plant show the plant show the dominantdominant or or recessiverecessive trait?trait?

Dominant = Tall (T) Dominant = Tall (T)

Recessive = short (t)Recessive = short (t)

1.1. Determine the Determine the phenotypephenotype of a plant that is of a plant that is TtTt..

Phenotype means what it looks like. It will be tall because it Phenotype means what it looks like. It will be tall because it has one dominant gene (T).has one dominant gene (T).

2. Determine the 2. Determine the genotypegenotype of a of a homozygoushomozygous smallsmall plant. plant.

Genotype means genetic make-up. Homozygous means the Genotype means genetic make-up. Homozygous means the same and small is recessive (small letter).The answer is tt.same and small is recessive (small letter).The answer is tt.

3. Would a 3. Would a heterozygousheterozygous plant show the plant show the dominantdominant or or recessiverecessive trait?trait?

Heterozygous means different. (Tt) The answer is dominant Heterozygous means different. (Tt) The answer is dominant because there is at least one big T. To show recessive you because there is at least one big T. To show recessive you have to have two small t’s.have to have two small t’s.

1. Brown hair is dominant over blonde.1. Brown hair is dominant over blonde.

A. Create a key for the traits.A. Create a key for the traits.

B. What would the genotype for a blonde be?B. What would the genotype for a blonde be?

C. What would the phenotype be for a person that is C. What would the phenotype be for a person that is

heterozygous?heterozygous?

2. Freckles is dominant over non-freckles. Mom is purebred for 2. Freckles is dominant over non-freckles. Mom is purebred for freckles. Dad is heterozygous for freckles. Dad is heterozygous for freckles.freckles.

A. Create a key for the traits.A. Create a key for the traits.

B. Determine the genotypes for Mom and Dad.B. Determine the genotypes for Mom and Dad.

C. Could any of their children C. Could any of their children NOTNOT have freckles? Explain have freckles? Explain your answer.your answer.

Vocabulary Practice Problems

Maybe Baby DirectionsMaybe Baby Directions4. 4. You now have to record the genotypes and phenotypes for You now have to record the genotypes and phenotypes for

the alleles you determined yesterday.the alleles you determined yesterday.Make sure you read carefully. Not all traits are going to Make sure you read carefully. Not all traits are going to

be seen. Put NA in the genotype and phenotype box if that be seen. Put NA in the genotype and phenotype box if that trait is not visible for your child.trait is not visible for your child.

5. 5. Get your data sheet signed by the teacher after you Get your data sheet signed by the teacher after you sketch the characteristics.sketch the characteristics.

6. Begin drawing your child as a teenager. 6. Begin drawing your child as a teenager. USE USE PENCIL!!!!PENCIL!!!! You need to draw front view and side You need to draw front view and side view of your child. Your drawing must include:view of your child. Your drawing must include:

Your child’s name on the front.Your child’s name on the front. All 30 characteristics between the two drawings.All 30 characteristics between the two drawings. Your name and your partner’s name on the back.Your name and your partner’s name on the back.

Star your name on the back!!!!Star your name on the back!!!!

1A. Key: 1A. Key: B = brown = dominantB = brown = dominant

b = blonde = recessiveb = blonde = recessive

1B. Blonde is recessive. 1B. Blonde is recessive. “bb”“bb”

1C. Heterozygous means different. 1C. Heterozygous means different.

Phenotype means what it looks like.Phenotype means what it looks like.

““Brown hair”Brown hair”

2A. Key: 2A. Key: F = freckles = dominantF = freckles = dominant

f = non-freckles = recessivef = non-freckles = recessive

2B. Mom = 2B. Mom = FFFF Dad = Dad = FfFf

2C. 2C. There is no possibility that any of their children could not have There is no possibility that any of their children could not have freckles. Mom has two big F genes, which means she will freckles. Mom has two big F genes, which means she will always give her children a F. Therefore all of the children will always give her children a F. Therefore all of the children will have freckles. You need two little f’s for non-freckles.have freckles. You need two little f’s for non-freckles.

Pedigree ChartPedigree Chart

Follows the passing of a trait from generation to Follows the passing of a trait from generation to generation.generation. Looks like a family tree. Looks like a family tree.

= male= male

= female= female

Shaded shapeShaded shape means that the means that the recessive traitrecessive trait is expressed. is expressed.

Half shaded shapeHalf shaded shape means that they are a means that they are a carriercarrier of the trait. of the trait.

CarriersCarriers have one gene but do not express or show the trait. have one gene but do not express or show the trait.

marriagemarriage

parentsparents

childrenchildren

Generation 1Generation 1

Generation 2Generation 2

Oldest child to the leftOldest child to the left

Youngest child to the rightYoungest child to the right

Number of rows = number of generationsNumber of rows = number of generations

Count from the top to the bottomCount from the top to the bottom

11 22

6633 44 55

88 10109977

1111

1.1. How many males?How many males?

2.2. How many females?How many females?

3.3. How many generations?How many generations?

4.4. How many marriages?How many marriages?

Normal skin is dominant Normal skin is dominant over albino skin.over albino skin.

Key:Key:

Normal = N = dominantNormal = N = dominant

Albino = n = recessiveAlbino = n = recessive

Recessive trait is colored in!Recessive trait is colored in!

55

66

44

33

nnnn

nnnn nnnn

nnnnNnNnNnNn

NnNn NnNn

NnNn N_N_

N_N_

1

3

698

10 12

5

11

7

2

4

nn

nnnn nn

nn

nn

N

N

N

N

N Nnn

nn

n

_

N = normal vision = dominant

n = nearsighted = recessive

Shaded = recessive trait

Page 6 in PacketPage 6 in Packet

Green seeds are dominant over yellow seeds. A Green seeds are dominant over yellow seeds. A homozygous recessive plant (1) is mated with a homozygous recessive plant (1) is mated with a homozygous dominant plant (2).homozygous dominant plant (2).

1.1. Make a key.Make a key.

2.2. Determine the genotypes of the two plants.Determine the genotypes of the two plants.

3.3. Determine the phenotype of the two plants.Determine the phenotype of the two plants.

4.4. Could their offspring have yellow seeds? Explain.Could their offspring have yellow seeds? Explain.

5.5. What is a trait?What is a trait?

6.6. How many chromosomes do human sex cells have?How many chromosomes do human sex cells have?

Dimples are dominant over non-dimples

Shaded areas represent the recessive trait.

1.1. Make a key!Make a key!

2.2. How many males?How many males?

3.3. How many females?How many females?

4.4. How many generations?How many generations?

5.5. How many marriages?How many marriages?

6.6. How many children did the parents in the first How many children did the parents in the first generation have?generation have?

7.7. How many males have dimples?How many males have dimples?

8.8. How many females do not have dimples?How many females do not have dimples?

More Pedigree PracticeMore Pedigree Practice

21

1514139

753 4 6

8 10 11 12

21

1514139

753 4 6

8 10 11 12

DdDd DdddddddDddd

DdddDdddDd

ddDd

1.1. D = dimples = dominantD = dimples = dominant

d = non-dimples = recessived = non-dimples = recessive

2.2. 8 males8 males

3.3. 7 females7 females

4.4. 3 generations3 generations

5.5. 3 marriages3 marriages6.6. 3 children3 children7.7. 5 males have 5 males have

dimplesdimples8.8. 4 females don’t have 4 females don’t have

dimples.dimples.

Pedigree Chart Pedigree Chart PracticePractice

Widow’s peak is dominant Widow’s peak is dominant over non-widow’s peakover non-widow’s peak

1.1. Make a key.Make a key. 4. What is the dominant trait?4. What is the dominant trait?

2.2. Determine genotypes for all.Determine genotypes for all. 5. How many males have a widow’s 5. How many males have a widow’s peak? peak?

3.3. How many generations are there?How many generations are there? 6. How many marriages are 6. How many marriages are shown?shown?

Key:Key:

W= widow’s peak = dominantW= widow’s peak = dominant

w = non- peak = recessivew = non- peak = recessive

c) 4 generationsc) 4 generations

d) Having the widow’s peak is dominant.d) Having the widow’s peak is dominant.

e) 5 males have a widow’s peak.e) 5 males have a widow’s peak.

f) 4 marriagesf) 4 marriages

II

IVIV

IIIIII

IIII

WwWw

wwwwWwWw

WwWwWwWw

wwww WwWw

W_W_ wwww W_W_ W_W_

WwWw WwWw W_W_ W_W_

Vocabulary QuizVocabulary QuizFree (unattached) earlobes are dominant over Free (unattached) earlobes are dominant over attached earlobes. Mom is heterozygous and attached earlobes. Mom is heterozygous and Dad is homozygous recessive. Use this Dad is homozygous recessive. Use this information to answer the questions below.information to answer the questions below.

1.1. Make a key.Make a key.

2.2. Determine the genotypes:Determine the genotypes:

• Mom = Mom = Dad =Dad =

3.3. Determine the phenotypes:Determine the phenotypes:

• Mom = Mom = Dad =Dad =

4.4. Is it possible for their children to have attached earlobes? Is it possible for their children to have attached earlobes? Why or why not?Why or why not?

5.5. What is the difference between a gene and a trait?What is the difference between a gene and a trait?

Mitosis:Mitosis:

• Occurs in body cells. Occurs in body cells.

• One cell divides into two.One cell divides into two.

• Both cells have the same genetic material as the Both cells have the same genetic material as the parent cell.parent cell.

Four Four chromosomeschromosomes

Four Four chromosomes chromosomes

copiedcopied

Four chromosomes Four chromosomes go into each cell go into each cell during divisionduring division

Four chromosomes Four chromosomes in each identical cellin each identical cell

Meiosis:Meiosis:

• Occurs in sex cells (egg and sperm).Occurs in sex cells (egg and sperm).

• One cell divides into four.One cell divides into four.

• The four daughter cells have ½ the genetic material as The four daughter cells have ½ the genetic material as the parent cell.the parent cell.

Stage 1:Stage 1:

Stage 2:Stage 2:

1.1. Make a key. Make a key.

2.2. Determine the genotypes for each person using your key.Determine the genotypes for each person using your key.

3.3. How many males are there?How many males are there?

4.4. How many females are there? How many females are there?

5.5. How many marriages are present?How many marriages are present?

6.6. How many generations are shown?How many generations are shown?

7.7. How many males are PTC non-tasters?How many males are PTC non-tasters?

8.8. How many females are PTC tasters?How many females are PTC tasters?

9.9. How many children did 1 and 2 from the first generation How many children did 1 and 2 from the first generation have?have?

Determine the genotype and phenotype probabilities for a Determine the genotype and phenotype probabilities for a cross between a heterozygous plant and a short plant. The cross between a heterozygous plant and a short plant. The trait we are studying is plant height. Tall is dominant over trait we are studying is plant height. Tall is dominant over short.short.

TT tt

tt TtTt tttt

tt TtTt tttt

Parents = Tt X ttParents = Tt X ttT = tall = dominantT = tall = dominant

t = short = recessivet = short = recessiveGenotypeGenotype

PhenotypePhenotype

Tall =Tall =

Short =Short =

2/4 = 50%2/4 = 50%

2/4 = 50%2/4 = 50%

TT =TT =

Tt =Tt =

tt =tt = 2/4 = 50%2/4 = 50%

2/4 = 50%2/4 = 50%

0/4 = 0%0/4 = 0%

Punnett Square Practice Problems

1. Normal skin pigment is dominant over albino. Show a cross of an albino man with a heterozygous normal woman.

2. Brown eyes are dominant over blue eyes. Using a Punnett Square, determine the probability that the offspring will be homozygous recessive if both parents are heterozygous dominant.

3. Determine the genotypes for the individuals in the pedigree chart below. Widow’s peak is dominant over non-peak.

a. Make a key

b. Determine genotypes

c. Determine number of generations

d. What is the dominant trait?

e. How many males have peak?

f. How many marriages?

1. Key:1. Key: N = normal = dominantN = normal = dominant

n = albino = recessiven = albino = recessive

Parents: Parents: Male = nnMale = nn Female = NnFemale = Nn

nn

nn

NN NnNnNnNn

nnnnnnnn

nn GenotypeGenotype

PhenotypePhenotype

normal =normal =

albino =albino =

2/4 = 50%2/4 = 50%

2/4 = 50%2/4 = 50%

NN=NN=

Nn =Nn =

nn =nn = 2/4 = 50%2/4 = 50%

2/4 = 50%2/4 = 50%

0/4 = 0%0/4 = 0%

2. Key:2. Key: B = brown = dominantB = brown = dominant

b = blue = recessiveb = blue = recessive

Parents: Parents: Male = BbMale = Bb Female = BbFemale = Bb

BB

bb

BB BbBbBBBB

bbbbBbBb

bb GenotypeGenotype

PhenotypePhenotype

brown =brown =

blue =blue =

3/4 = 75%3/4 = 75%

1/4 = 25%1/4 = 25%

BB=BB=

Bb =Bb =

bb =bb = 1/4 = 25%1/4 = 25%

2/4 = 50%2/4 = 50%

1/4 = 25%1/4 = 25%

GenotypeGenotype

PhenotypePhenotype

Parent cross = ________ x ________Parent cross = ________ x ________

____________

____________

____________ ____________

____________ ____________

________________________

_____ = _______ = _____ %_____ = _______ = _____ %

_____ = _______ = _____ %_____ = _______ = _____ %

_____ = _______ = _____ %_____ = _______ = _____ %

_______ = _______ = _____ %_______ = _______ = _____ %

_______ = _______ = _____ %_______ = _______ = _____ %

Red flowers is dominant over white flowers. Red flowers is dominant over white flowers.

1.1. A plant (1) is homozygous dominant is crossed A plant (1) is homozygous dominant is crossed with a heterozygous plant (2). Use a Punnett with a heterozygous plant (2). Use a Punnett Square to determine the probability that the Square to determine the probability that the offspring will be white.offspring will be white.

2.2. Use a Punnett Square to determine the Use a Punnett Square to determine the probability the offspring will be white if two probability the offspring will be white if two heterozygous plants were crossed.heterozygous plants were crossed.

3.3. A homozygous dominant plant (3) is crossed with A homozygous dominant plant (3) is crossed with a homozygous recessive plant (4). Determine the a homozygous recessive plant (4). Determine the probability the offspring will be red using a probability the offspring will be red using a Punnett Square.Punnett Square.

1

9 13 14 15 16

2

43 5 6 7 8

10 11 12

Tall is dominant over short.Tall is dominant over short.

Recessive trait is shaded.Recessive trait is shaded.

1.1. Make a key.Make a key. 4. How many males are tall?4. How many males are tall?

2.2. Determine the genotypes.Determine the genotypes. 5. How many females are short?5. How many females are short?

3.3. How many marriages.How many marriages. 6. How many generations?6. How many generations?

Vocabulary QuizVocabulary QuizFree earlobes are dominant over attached Free earlobes are dominant over attached earlobes. Mom is heterozygous and Dad is earlobes. Mom is heterozygous and Dad is homozygous recessive. Use this information to homozygous recessive. Use this information to answer the questions below.answer the questions below.

1.1. Make a key.Make a key.

2.2. Determine the genotypes:Determine the genotypes:

• Mom = Mom = Dad =Dad =

3.3. Determine the phenotypes:Determine the phenotypes:

• Mom = Mom = Dad =Dad =

4.4. Is it possible for their children to have attached earlobes? Is it possible for their children to have attached earlobes? Why or why not?Why or why not?

5.5. What is the difference between a gene and a trait?What is the difference between a gene and a trait?

Sex-linked traitsSex-linked traits

• Sex-linked traits are caused by genes found on the X Sex-linked traits are caused by genes found on the X chromosome.chromosome.

• Sex-linked traits are recessive.Sex-linked traits are recessive.

• Fewer females are afflicted with these traits because they Fewer females are afflicted with these traits because they have two X chromosomes and the other is usually normal. have two X chromosomes and the other is usually normal.

• Males only have one X chromosome, so when they Males only have one X chromosome, so when they inherit the sex-linked gene, they display the trait.inherit the sex-linked gene, they display the trait.

• Examples: color-blindness, hemophiliaExamples: color-blindness, hemophilia

XXXX XX-XX- X-X-X-X- XYXY X-YX-YNormalNormal

femalefemale

CarrierCarrier

femalefemale

AfflictedAfflicted

femalefemale

NormalNormal

malemale

AfflictedAfflicted

malemale

Sex-linked traits practice problemsSex-linked traits practice problems

1.1. A man normal for blood clotting marries a woman who A man normal for blood clotting marries a woman who is a carrier for hemophilia. What are the chances they is a carrier for hemophilia. What are the chances they will have a child with hemophilia? Use a Punnett will have a child with hemophilia? Use a Punnett Square to prove your answer.Square to prove your answer.

2.2. What is the probability that a woman with normal vision What is the probability that a woman with normal vision who marries a color-blind man will have a color-blind who marries a color-blind man will have a color-blind child?child?

3.3. A man with normal vision and a woman with normal A man with normal vision and a woman with normal vision have three sons. Two of the sons have normal vision have three sons. Two of the sons have normal vision and one of them is color-blind. What are the vision and one of them is color-blind. What are the probable genotypes of the parents?probable genotypes of the parents?

Intermediate InheritanceIntermediate Inheritance

• Not all traits are either dominant or recessive.Not all traits are either dominant or recessive.

• For some traits, heterozygous individuals are different For some traits, heterozygous individuals are different than both homozygous parents.than both homozygous parents.

CodominanceCodominance Incomplete DominanceIncomplete Dominance

• Both alleles are expressed in Both alleles are expressed in heterozygous offspringheterozygous offspring

• Both alleles are dominantBoth alleles are dominant

• Both are different capital lettersBoth are different capital letters

• Both alleles are blended in Both alleles are blended in heterozygous offspringheterozygous offspring

•Both are different capital lettersBoth are different capital letters

Red coat = CRed coat = CRR C CRR

White coat = CWhite coat = CW W CCWW

Roan coat = CRoan coat = CRR C CWW

(both red and white are seen)(both red and white are seen)

Red flowers = RRRed flowers = RR

White flowers = WWWhite flowers = WW

Pink flowers = RWPink flowers = RW

Multiple Alleles:Multiple Alleles:• When there are more than 2 (multiple) alleles for a trait.When there are more than 2 (multiple) alleles for a trait.

• Examples: Human blood groups have 3 alleles. (A, B, O)Examples: Human blood groups have 3 alleles. (A, B, O)

A and B are both dominant, O is recessiveA and B are both dominant, O is recessive

• The possible combinations of these blood alleles are:The possible combinations of these blood alleles are:

PhenotypePhenotype Genotype(s)Genotype(s)

AA IIAA I IAA , I , IAA i i

BB IIBB I IBB, I, IBB i i

ABAB IIAA I IBB

OO iiii

Dihybrid Crosses• Study two traits at the same time.

• Determine the outcome for both traits together.

A pure tall plant with blue flowers is mated with a short plant with white flowers. Determine the genotypes and phenotypes of the offspring. Tall and blue flowers are both dominant traits.

T =

t =

B =

b =

tall

short

blue

white

Parents: TTBB X ttbb

TTBB ttbb

TB TBtb tb

TBTB

tb

tbTtBb

TtBb TtBb

TtBb

Genotype Phenotype

TtBb = 100% Tall and blue = 100%

Now mate two of the offspring to determine the possible genotypes and phenotypes.

TtBb X TtBb

TB Tb

tB tb

TB

Tb

tB

tb

TB Tb

tb

tB

Tb

TB

tbtB

TTBB TTBb TtBB TtBb

TTBb TTbb TtBb Ttbb

TtBB TtBb ttBB ttBb

TtBb Ttbb ttBb ttbb

GenotypeGenotype

PhenotypePhenotype

ttbbttbbttBbttBb

TtBbTtBb

TtbbTtbbttBBttBB

TtBBTtBB

TTBBTTBB

TTbbTTbbTTBbTTBb

Tall, blue = 9/16 (56.25%)Tall, blue = 9/16 (56.25%)

Short, blue = 3/16 (18.75%)Short, blue = 3/16 (18.75%)

Tall, white = 3/16 (18.75%)Tall, white = 3/16 (18.75%)

Short, white = 1/16 (6.25%)Short, white = 1/16 (6.25%)

= 1/16 = 6.25%= 1/16 = 6.25%

= 1/16 = 6.25%= 1/16 = 6.25%= 2/16 = 12.5%= 2/16 = 12.5%

= 4/16 = 25%= 4/16 = 25%= 2/16 =12.5%= 2/16 =12.5%= 1/16 = 6.25%= 1/16 = 6.25%= 2/16 = 12.5%= 2/16 = 12.5%

= 1/16 = 6.25%= 1/16 = 6.25%

= 2/16 = 12.5%= 2/16 = 12.5%

You must show ALL possible You must show ALL possible

genotypes and phenotypes!genotypes and phenotypes!

1.1. When a mouse with black fur is crossed with a mouse with When a mouse with black fur is crossed with a mouse with white fur, all Fwhite fur, all F11 generation offspring have gray fur. What are generation offspring have gray fur. What are

the probable genotypes and phenotypes for the Fthe probable genotypes and phenotypes for the F22

generation? Is this an example of codominance or incomplete generation? Is this an example of codominance or incomplete dominance?dominance?

2.2. What would the possible genotypes and phenotypes be for a What would the possible genotypes and phenotypes be for a cross between a roan-coated cow (Ccross between a roan-coated cow (CRR C CWW) and a red-coated ) and a red-coated cow (Ccow (CRR C CRR)? Is this an example of codominance or )? Is this an example of codominance or incomplete dominance?incomplete dominance?

Incomplete dominance & Codominance

1.1. A couple preparing for marriage have their blood typed. A couple preparing for marriage have their blood typed. They are both AB. They are curious about the possible blood They are both AB. They are curious about the possible blood types their children might have. What are the possible types their children might have. What are the possible phenotypes of their children?phenotypes of their children?

2.2. A type A person marries a type A person. Their firstborn has A type A person marries a type A person. Their firstborn has type O blood. What are the genotypes of the parents and the type O blood. What are the genotypes of the parents and the child?child?

3.3. A wealthy elderly couple die together in an accident. Soon a A wealthy elderly couple die together in an accident. Soon a man shows up to claim their fortune, claiming he is their long man shows up to claim their fortune, claiming he is their long lost son. Other relatives dispute the claim. Hospital records lost son. Other relatives dispute the claim. Hospital records show that the deceased couple were blood types AB and O. show that the deceased couple were blood types AB and O. The person claiming to be their son is type O. Do you think The person claiming to be their son is type O. Do you think this man is an impostor? Explain why.this man is an impostor? Explain why.

Blood Type ProblemsBlood Type Problems