Genetics

What do Bart,

Lisa & Maggie

all have in

common?

Why?

Traits can be…DOMINANT

More likely to be seen

Dominant overpowers the recessive traits.

recessive

Less likely to be seen

Can sometimes be

“hidden” within your genes.

or

Most of

these

characters

are the

same

species.

But how

are they

different?

Genes – the instructions for traits

We inherit our traits from our parents

We get 23 chromosomes from Mom and 23 from Dad.

This equals 46 chromosomes.

Alleles

every trait is decided by two alleles (one from Mom, and one from Dad)

They can be dominant or recessive

We represent these alleles with letters.

Brown hair- dominant allele - B

Blond hair- recessive allele - b

Alleles

• Examples – Curly hair – Dominant – C – Straight hair – recessive – c

• Examples – Dimples – Dominant – D – No dimples – recessive – d

PhenotypeThe appearance of the organism.

PHENO is like PHOTO

What you would be able to see in a photo?

brown hair, curly hair, brown eyes, freckles, dimples, face shape

spotted coat, short hair, long hair, floppy ears short ears

Genotype

The genetic makeup of an organism.This is not visible, but inside their genes

(DNA).Tongue rolling – dominant allele – TNot able to roll tongue- recessive - t

Can roll tongue – TT, Tt Cannot roll tongue - tt

PUNNETT SQUARES

• First, make a box with 4 squares inside it

• Second, put both parents Alleles in the right spot. – Mom, Rr, can roll

tongue– Dad, rr, can’t roll

tongue

R r

r

r

• Bring down each letter

• Bring over each letter

• This will make 4 possible combinations

R r

r

r

Rr

Rr

rr

rr

PUNNETT SQUARES

• What are the possible Genotypes?

• What are the possible phenotypes?

• Give a ratio for each

PUNNETT SQUARES

R r

r

r

Rr

Rr

rr

rr

Mutations