genetics. 11.1 – gregor mendel heredity inheritance of traits - study of heredity

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

Incomplete Dominance R R

W

W

www.nerdscience.com 11-3

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.