genetics. 11.1 – gregor mendel heredity inheritance of traits - study of heredity
TRANSCRIPT
Genetics
11.1 – Gregor Mendel
Heredity
Inheritance of traits
- study of heredity
Genetics
Gregor Mendel
Suggested
carry inherited traits.
how traits were inherited by studying pea plants
The Role of Fertilization
- male and female reproductive cells to produce a cell.
The Role of Fertilization
The Role of Fertilization
• -breeding plants
• Produce offspring to parent
• - a specific characteristic
• Ex) Seed color and shape.
• Varies
The Role of Fertilization
• - Offspring of parents with different traits.
Genes and Alleles gen –
• - Offspring of generation.
• In each cross, one parent’s traits seemed to have
.
Genes and Alleles
•
are
by genes that are
from parents to offspring.
Dominant and Recessive Traits
• –
Some alleles are dominant, others are recessive.
• Express dominant trait if at least
allele is present.
• Express recessive trait if
alleles present
• Only recessive alleles present.
Alleles
forms of a gene
Organisms have alleles for each trait.
One from . One from .
Segregation
• What happened to the recessive alleles?
• hybrids self-pollinate.
• Offspring of F1 called generation.
The F1 Cross
• In plants, recessive
traits .
• of F2 plants had recessive trait.
Explaining the F1 Cross
• Alleles segregated, or ,
during formation of the sex cells, or
.
Tongue Roll Dominant trait
Recessive attached ear lobesDominant Free Ear Lobes
Hitch hiker’s thumb
Dominant
Regular thumb
Recessive
Recessive trait
Dominant trait
Seed shape
Seed color
Flower color
Flower position
Pod color
Pod shape
Plant height
round yellow purpleaxial (side) green inflated tall
wrinkled green whiteterminal
(tips) yellow constricted short
11.2 – Applying Mendel’s Principles
Dominant gene (allele)
gene
Represented by letter
Written first Example: for tall plant
height
Recessive gene (allele)
gene
if dominant genes present.
Represented with letters
Example: for short plant height
Pure (Homozygous)
Two of the genes (alleles) for a trait
Example: (homozygous
) or (
recessive)
Hybrid (Heterozygous)
Two alleles for a trait
Example: Tall or short?
Probability
– The likelihood
that an event will occur. Example: Flipping a coin
Probability of flipping heads?
1
2Number of total outcomes
Number of outcomes
Probability
Example: Flipping a coinProbability of flipping heads
three times?
½ x ½ x ½ =
Genotype
Combination of for a
certain traitExample:
Phenotype
How it physically looksExample:
Genotype or Phenotype?
TtRoundBlackBBSmoot
hrrTall
In pea plants, green (G) pods are completely dominant over yellow (g).
What are the genotypes?
Homozygous yellowHeterozygous greenHomozygous dominantHybrid
In pea plants, green pods are completely dominant over yellow.
Pure yellow Homozygous recessivePure greenHeterozygous Yellow
In guinea pigs, short hair is dominant over long hair
What hair length will be represented by a capital S?
What hair length will be represented by a lower case s?
What phenotypes would result from the following genotypes?
SS ssSs
All tall plants
Phenotypes of parents?
If both parents are pure, what are their genotypes?
Which allele will each parent pass on to offspring?Phenotype of offspring?
Genotype of offspring?
In pea plants, round is dominant over wrinkled texture. What is the genotype of the following?
homozygous roundheterozygouswrinkledpure dominanthybrid round
In pea plants, round is dominant over wrinkled texture. What is the genotype of the following?
pure recessiveheterozygous roundpure wrinkledhybridpure round
Punnett Squares
Punnett squares –
the
from a cross.
Monohybrid crossesMonohybrid crosses
Heterozygous tall parent
T t
T t
T t
T
t
Heterozygous tall parent
How To Make a Punnett Square for a One-Factor Cross
Write the of the
parents.
Ex) Cross a male and female bird that are heterozygous for large beaks. Genotypes of Bb.
Bb x Bb
How To Make a Punnett Square Draw a Punnett square. Put one parent on the
, one parent on the
. Put one
from each parent on each side of each section.
How To Make a Punnett Square
Fill in the table by combining the gametes’ genotypes.
Mom
Dad
-Determine the genotypes and phenotypes of each offspring.
How To Make a Punnett Square
Probability of having…
A large beak? A small beak? Homozygous dominant? Heterozygous? Homozygous recessive?
Independent Assortment
Principle of–
genes
independently.
One gene effect another.
I.e. - Hair color does not effect eye color.
Dihybrid Cross
Two factor cross
involved.
The Two-Factor Cross: F1
Cross two true-breeding plants:
One produced only
peas One produced only
peas.
The Two-Factor Cross: F1
-peas had
genotype -Homozygous
.
The Two-Factor Cross: F1
-
peas had genotype
- Homozygous
The Two-Factor Cross: F1
All F1 offspring were .
Shows yellow and round alleles are
over green and wrinkled.
Punnett square shows genotype of F1 offspring as ,
for both seed shape and seed color.
The Two-Factor Cross: F2
Crossed plants to produce offspring.
Crossed with
Dihybrid cross instructions
Cross the parent alleles.
Outside has
of each allele
Inside has
alleles, two from each parent
Mom
Dad
The Two-Factor Cross: F2
Different genes
each other’s inheritance.
The Two-Factor Cross: F2
Dihybrid cross has
ratio.Principle of
– genes for different traits segregate independently.
11.3 - Other Patterns of Inheritance
Incomplete dominance
Alleles (mix)
Neither gene is dominant
phenotype is a blend.
Like colors of paintRed + White = Pink
Codominance
alleles are dominant
expresses both.There is NO “blending”
Red + White = Red and White
Red cow + white cow = roan cattle. Roan cattle have
hairs.
Codominance
Codominance
Example: White chicken
(WW) x black chicken (BB) = black and white checkered chicken (BW)
Codominance
Incomplete or Codominance?
A white cow and a red cow produce a roan cow, one that has both white and red hairs.
A red flower and a white flower produce pink flowers.
A black cat and a tan cat produce tabby cats, cats where black and tan fur is seen together.
Incomplete or Codominance?
A blue blahblah bird and a white blahblah bird produce offspring that are silver.
A certain species of mouse with black fur is crossed with a mouse with white fur and all of the offspring have grey fur.
A woman with blood type A and a man with blood type B have a child with blood type AB.
Multiple AllelesSingle gene with
alleles.
example: human blood type
Blood Types (codominant)
Blood type is codominant
and are dominant.
is recessive4 different blood
types
Phenotype(Blood type)
Genotype(Alleles or genes for blood type)
A IAIA, IAi
B IBIB, IBi
AB IAIB
O ii
Polygenic Traits Traits controlled by
genes
of phenotypes.
example: human skin color has four different genes
Skin color genes: AaBbCcDd
Genes and the Environment Genes provide a plan for development,
but also depends on the environment.
Both
14.1 – Human
Chromosomes
Karyotype
of chromosome .
Shows – full set of genetic information.
Karyotype
Normal Female
KaryotypeFemale with Down Syndrome
Sex Chromosomes
chromosomes
Determine the sex of the offspring
Females are Males are
Sex Chromosomes
All other chromosomes are
.Everyone has 46 chromsomes:
sex chromosomes and
autosomes.
Sex-linked Traits
Traits inherited on X and Y chromosomes.
Most on chromosomeEx) Color blindness recessive
sex-linked trait on X-chromosome show
traits more than females
Sex-linked Traits
Heterozygous females are
X-Chromosome Inactivation
In female cells, one X chromosome is randomly switched off, forming a
.
Not found in because only have one X chromosome.
Pedigree Study
Method of determining the genotype of individuals by looking at
Pedigrees illustrate
inheritance
Pedigrees illustrate
inheritance
Male
Female
Affected male
Affected female
Mating
Parents
Siblings
Known heterozygotes for recessive allele
Death
Human Pedigrees This diagram shows what the symbols
in a pedigree represent.
Human Pedigrees This pedigree shows how one human trait
—a white lock of hair just above the forehead— through three
generations of a family.
The allele for the white forelock trait is
.
Human Pedigrees Top of the chart is grandfather with the white
forelock trait. of his
children inherited the trait.
grandchildren have the trait, but do not.
Human Pedigrees Because the white forelock trait is dominant,
all family members lacking this trait must have
alleles.
One of the grandfather’s children lacks the white forelock trait, so the grandfather must be
for this trait.