Mendel’s GeneticsChapter 11

Who was Gregor Mendel?– He was known as the

“FATHER OF GENETICS” – He discovered how traits

were inherited• GENETICS – study of

heredity

• HEREDITY – the passing of traits from parents to offspring

Mendel’s Peas–Mendel did his

study on pea plants

– Pea plants have many traits (tall/short, purple flowers/white flowers)

– Pea plants can beself-fertilized or cross-fertilized

True Breeding• Meaning that if

they are allowed to self-pollinate, they will produce offspring identical to themselves– Self-pollinate: some

plants have both male and female flowers

– One plant is producing both male and female gametes that are fertilized

Dominance• Some traits are dominant over

others.

• Tall x Short = all tall offspring (hybrids)

• *Tall is the dominant trait• * Short is recessive

Genes and Alleles• Mendel

discovered that each trait is controlled by two factors (alleles)

• Genes – factors that determine your traits

Mendel’s Experiments

The Cross• Monohybrid Cross, that is

Explaining the Cross• When a parent makes sperm or eggs,

their genes separate        (PRINCIPLE/LAW OF SEGREGATION)

• The GAMETES (egg or sperm) contain either a T allele (tall) or a t allele (short)– This works for various traits like hair

color

More on the Cross

Genes→Traits• GENOTYPE  -  what genes ( letters)

the organism has (TT, Tt, tt)• PHENOTYPE   - what it looks like

(tall or short)

Understanding Check1.  A one-eyed purple people eater is crossed with a

two eyed purple people eater.  All of their offspring have two eyes.   Which trait is dominant?

• 2.  If you use the letter E for this gene.   What is the genotype of the offspring? 

•      Are these offspring the F1 or F2 generation?

• 4.  If you crossed the offspring with each other?  How many ofthe new offspring would you expect to have two eyes?

Incomplete Dominance• When both alleles are expressed,

making colors somewhere in the middle–More like a mixing of the two alleles

Codominance• When both alleles

are expressed equally– Not mixing, but

blotched usually

Another Cross• Dihybrid Cross–When you do a

cross for two traits at the same time

– For example: a cross for eye AND hair color

Example Cross• What do you get when you

cross a tall purple flower plant with a short white flower plant???