is the science of heredity. heredity is the transmission of ......heterozygous- contains 2 different...

Genetics

• Is the science of heredity.

• Heredity is the transmission of genetic and physical traits from parent to offspring.

Gregor Mendel

• Austrian Monk – born 1822

• Considered the “Father of Heredity”

• He conducted plant breeding experiments in their monastery garden using peas.

• Developed the Laws of Inheritance.

– Dominance

– Recessive

Common Name Diploid Number

Monkey 42

Dog 78

Human 46

Mouse 40

Frog 26

Flatworm 16

Corn 20

Yeast 32

Potato 48

Green Algae 20

Fruit Fly 8

Do chromosome numbers increase as

species become more advanced?

Sex Determination

• Female can contribute only an X chromosome towards the sex of their offspring.

• Male can contribute an X or a Y chromosome toward the sex of their offspring.

• So, what is the genotype of a FEMALE? MALE?

Medieval Days

• King Henry the 8th

• He killed some of his wives for not giving birth to a son.

• They didn’t know back then that it was the man’s gamete that determined the gender of the child.

Genes

• Some traits are inherited directly from one set of genes.

• Some traits are inherited through several sets of genes.

• A chromosome is a combination of many genes

Terms to know

• Homozygous- contains 2 identical alleles for the same trait, AA, BB, cc Heterozygous- contains 2 different alleles for the same trait, Aa, bB, Cc

• Phenotype- Physical appearance of a trait, coat color, blood type. description

• Genotype- Genetic makeup AA, Aa, aa. letters

• Allele- Specific gene for specific trait.

• F-one = First cross offspring mating.

• F-two = Second cross offspring

Let’s practice . . .• Are these homozygous or heterozygous?• EE

• AA

• Cc

• dd

• t t

• Bb

• LL

• Pp

• jj

What are dominant genes?

• The gene that expresses itself

• These hide the recessive gene if there is complete dominance.

• Some examples of dominant traits in humans are:

– Broad lips (BB or Bb)

– Second toe longer (TT or Tt)

– Brown eyes (BB or Bb)

– Freckles (FF or Ff)

– Rolling tongue (RR or Rr)

– Detached earlobe (EE or Ee)

What are Recessive Genes?• The gene that is overshadowed by a

dominant gene – hidden by dominant

• Recessive genes can only express themselves when there are two (aa)

• Some examples of recessive traits in humans are:

– Thin lips (bb)

– Color blindness (cc)

– Near sightedness (nn)

– No dimples (dd)

– Attached earlobes (ee)

Let’s practice . . .• Are these dominant or recessive?• EE

• AA

• Cc

• dd

• t t

• Bb

• LL

• Pp

• jj

Other Phenotypic Results• Codominance Both alleles show,

there is no dominance. Results in BOTH phenotypes being visible.

Black bunny and White bunny make Black and White spotted bunnies

Red flower and White flower make a red and white striped flower

Other Phenotype Results

• Incomplete Dominance Neither allele is dominant, heterozygotes show a BLEND, there is no dominance.

– Black bunny and White bunny make a grey bunny

– Red flower and White flower make a pink flower

Mendel’s Laws

•Law of Segregation

– During meiosis all alleles separate from each other

– Alleles for a trait are then "recombined" at fertilization

Mendel’s Laws• Law of Independent Assortment

– Alleles for different traits are distributed to offspring independently of one another.

– Red hair and freckles does not travel together!

– NO TWO TRAITS TRAVEL TOGETHER! These laws are why siblings look different even though they have the same parents!

Punnett Square (MonoHybrid)Fill in this square on your paper.

What does a Punnett square show?

B b

b

b

Bb bb

Bb bb

The dominant trait is black fur, the recessive is white. What are the genotypic and phenotypic results?

B b

b

b

Bb bb

Bb bb

Genotypes: Bb, bbPhenotypes: Black, White

B b

b

b

Bb bb

Bb bb

RATIOS:Genotypes: Bb, bb (50:50 = 1:1)Phenotypes: Black, White (50:50)

B b

b

b

Bb bb

Bb bb

Fill in this square on your paper and give the genotypes, phenotypes and their ratios.

B b

b

b

Bb bb

Bb bb

Geno: BB, Bb, bb (1:2:1) or 25%, 50%, 25%Pheno: Black, White (3:1) or 75% to 25%

B b

b

b

Bb bb

Bb bb

No-Fail steps to working a Punnett square!

•1. Make a key of genotypes

•2. Add phenotypes

•3. Draw Punnett square

•4. Get parent cross

•5. Work square.

• In cats, long tails are dominant over short tails. Cross one heterozygous long tailed cat with a short tailed cat. What is the chance there will be a short tailed cat born?

• Step One: Make a key:

LL –

Ll –

ll -


• Step Two: Add the phenotypes!

LL – Long tail

Ll – Long tail

ll - Short tail


• Step Three: Get parent cross

LL – Long tail

Ll – Long tail

ll - Short tail

Get the parent cross = Ll X ll

(heterozygous long and short)


• Step Four: Work square

L l

l

l

Ll

Ll

l l

l l

What is the chance

there will be a short

tailed cat?


• Step Four: Work square

L l

l

l

Ll

Ll

l l

l l

What is the chance

there will be a short

tailed cat? 50%

Incomplete Dominance

• Blue parakeets and yellow parakeets make green parakeets. Cross a blue parakeet with a green parakeet. What is the phenotypic ratio of the offspring?

• Step one and two: Make a key– BB - Blue

– BY - Green

– YY - Yellow

Incomplete Dominance• Blue parakeets and yellow parakeets

make green parakeets. Cross a blue parakeet with a green parakeet. What is the phenotypic ratio of the offspring?

• Step three and four: Parent cross and work the square.

B B

B

Y

BB

BY

BB

BY

What is the

phenotypic ratio of

the offspring?

Incomplete Dominance• Blue parakeets and yellow parakeets

make green parakeets. Cross a blue parakeet with a green parakeet. What is the phenotypic ratio of the offspring?


B B

B

Y

BB

BY

BB

BY

What is the

phenotypic ratio of

the offspring? 1:1

(2 blue: 2 green = 1:1)

Co-Dominance• Black chupacabras and white

chupacabras make black and white striped chupacabras. Cross a black chup and a white chup. What is the genotypic ratio and what will the offspring look like?

• Step one and two: Make a key

•BB - Black

•BW – Striped Black and White

•WW - White

Co-Dominance• Black chupacabras and white chupacabras

make black and white striped chupacabras. Cross a black chup and a white chup. What is the genotypic ratio and what will the offspring look like?


B W

B

W

BB

BW

BW

WW

What is the genotypic ratio

and what will the offspring

look like?

Co-Dominance• Black chupacabras and white chupacabras

make black and white striped chupacabras. Cross a black chup and a white chup. What is the genotypic ratio and what will the offspring look like?


B W

B

W

BB

BW

BW

WW

What is the genotypic ratio

and what will the offspring

look like? Geno: 1:2:1

Pheno: Black, Striped, White

Regular Biology Classes STOP HERE!

PreAP Biology continue with the notes.

Sex Linked Genes:

• There are genes that are only linked on the X chromosome, which means if you are a male you inherited it from your mom (your dad gave you a Y)! Females can get it from both since dad gives them an X

• Trait examples would be

– Male Pattern Balding - Yep! From your mom!

– Colorblindness

Sex-Linked• Color blindness is a sex linked recessive

trait carried on the X chromosome. Cross a colorblind male with a female carrier. What is the chance of a colorblind child?

• Make a key – let’s do this together.

– XCXC - Normal vision female

– XCXc – Normal vision/carrier female

– XcXc – Colorblind female

– XCY – Normal vision male

– XcY– Colorblind male

Sex-Linked• Color blindness is a sex linked recessive

trait carried on the X chromosome. Cross a colorblind male with a female carrier. What is the chance of a colorblind child?

• KEY: Now work the square:

• PC: _ XcY ___ X __ XCXc ____

– XCXC - Normal vision female Xc Y

– XCXc – Normal vision/carrier female XC

– XcXc – Colorblind female

– XCY – Normal vision male Xc

– XcY– Colorblind male

• Chance of colorblind child?_50%_(one boy & one girl)__

• Chance of colorblind daughter?_ 50%_(one of the girls)__

XCXc

XcXc

XCY

XcY

Colorblind Statistics:

• 1 out of 4 people have colorblindness to some degree.

• 1 out of 12 men are colorblind.

• 1 out of 100 women are colorblind.

Sex-Linked• Male patterned baldness is a recessive sex

linked trait. Cross a female carrier with a Normal man. What is the chance their child will have male patterned baldness?

• Make a key – Your turn, do this on your own.

– XBXB – Normal female

– XBXb – Normal/carrier female

– XbXb – Balding female

– XBY – Normal male

– XbY– Balding male

Sex-Linked• Male patterned baldness is a recessive sex

linked trait. Cross a female carrier with a Normal man. What is the chance their child will have male patterned baldness?

• KEY: Now work the square:• PC: __ XBXb ___ X __ XBY ___

XBXB – Normal female XB Y

XBXb – Normal/carrier female

XbXb – Balding female XB

XBY – Normal male

XbY– Balding male Xb

Chance of child with baldness?__25% (a boy)_

Chance of daughter with baldness?___0%___

Chance of son with baldness? ___50%___

XBXB XBY

XBXb XbY

5. Multiple Allele

Blood Types have 3 alleles!

A, B and O (O is recessive to A and B)

AA, AO = Type A blood

BB, BO = Type B blood

AB = Type AB blood

OO = Type O blood

SIX possible combinations for parents

Cross a Type O mom with a Type AB dad.

What are the possible phenotypes of the offspring?

5. Multiple Allele• Cross a Type O mom with a Type AB

dad. What are the phenotypes of the offspring?

• Parent Cross: OO x AB

Offspring phenotypes?

Can a man with AB blood

ever have a Type O baby?

B b

b

b

Bb bb

Bb bb

A B

O

O

?

?

?

?

5. Multiple Allele• Cross a Type O mom with a Type AB

dad. What are the phenotypes of the offspring?

• Parent Cross: OO x AB

Offspring phenotypes:

Type A and Type B

50% chance of either

Can a man with AB blood

ever have a Type O baby?

No, always passes an A or B

B b

b

b

Bb bb

Bb bb

A B

O

O

AO

AO

BO

BO

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