DO NOW: How could all of these puppies come from the same parents? (Write down your answer)

Patterns of Inheritance: Genetics

Modern genetics began in 1860’s

• Czech Monk- Gregor Mendel

• Playing with peas in his garden

“THE MAN”

Gregor Mendel

• Used peas to study how physical traits passed from parent to offspring - heredity

• Mendel measured 7 traits in peas, each trait with 2 forms.

Examples of two Pea traits (Shape & Color) that Mendel studied

How did Mendel do all this?• Step 1: Identify true

breeding plants

• When pure plants are self-fertilized, they ALWAYS produce offspring identical to the parent generation after generation.

• How could you ensure self pollination?

• Mendel crossed true breeding plants with two distinct traits using cross-fertilization.

Hybrids

• Offspring of two different true-breeding varieties.

• P – parental generation• F1 – offspring of P

generation• F2 – offspring of self

fertilized or cross fertilized members of F1 generation

Mendel’s 1st RuleThe Law of Segregation:

• For each trait (i.e. pod color or plant height) an individual has 2 factors

• The 2 factors may be the same or different

• When making kids, each parent will contribute only 1 factor

• The 2 factors a parent has will separate when making a kid (Meiosis)

The Law of Segregation

• Each parent will pass on 1 factor during sex (gamete production)

• Kids get 1 factor (for each trait) from each parent...

Factors

The Factors

• Each individual has 2 factors for each trait…pod color, height, eyes, hair...

• If both factors for a trait are the same, you are homozygous for that trait…

• If you have 2 different factors for a trait, you are heterozygous for that trait

How to Label these factors?

• G for Green pods

• Y for yellow pods

• B for brown hair

• x for blond hair

But…we don’t do this!!

The Factors

• You have 2 factors, but only 1 factor for each trait is typically used (expressed)..

• This is the dominant factor

• The other one is the recessive factor

So; How we do Label the factors?

• Dominant factor is written in

upper case… i.e. “B”

• Recessive factor in lower case, using the dominant abbreviation.. i.e. “b”

• B is for brown hair (which is dominant)

• b is for blond

Mendel’s Factors = Genes

• Every normal human has thousands of genes

• Each gene describes the information for one human trait.

• You have two genes for each trait

• Where are these genes located?

How to Predict which factor you’ll give your

kids? • Each parent has 2 factors for each trait

• But, each gamete you produce has only 1 factor for each trait

• Which factor goes to which kid?

• Best described by a Punnett Square

Punnett Square..• Used to predict how offspring will get

their share of factors…

• Parents mate (x): BB X bb

• What possible offspring will each make?

B B

b

b

FemaleGametes

Male Gametes

Possible Offspring…. Or, F1 Generation

B B

b

b

Bb Bb

Bb Bb

Each F1 Offspring has the same traits for hair color… Bb

Try this one!

In summer squash, white fruit color is dominant to yellow fruit color.

What would the genotype and phenotype be for the F1 generation if the parental cross was homozygous white and yellow?

Another Example..Trait for Seed Shape (S)

Text pg 181

Mendel’s 2nd Law

Law of Independent Assortment:• Factors for each trait segregate into gametes

independently of each other• The factor for hair color (B or b) will segregate

independently of the factor for height (T or t)• Consider a dihybrid cross… Two traits at once

• Example: Say Parents are Bbtt x bbTT

Dihybrid Cross

• If a Bbtt male mates with a bbTT female?

• What are the possible gametes for each?

Male Bbtt x

Female bbTT

Bt bt

bT

bT

BbTt bbTt

BbTt bbTt

gametes

gametesNew individuals (with two factors for each trait)

So What?

• What does Mendel and his Peas have to do with you?

• Chromosomes and Heredity…

On Chromosomes• We each have 46

chromosomes in each cell

• 23 chromosomes came from Mom, 23 from Dad

• Each chromosome contains hundreds of genes…

An example using the FISH techniqueof identifying the location of one geneon a chromosome.

Gene location on Chromosomes