Mendel cultivated pea plants and tested some plants He found that true-breeding plants make offspring retained traits of the Parents every time. Experimental data, Mendel deduced that an organism has two genes ) for each inherited characteristic

Site of

Gregor

Mendel’s

experimental

garden in the

Czech

Republic

Mendel’s peas • Mendel looked at seven traits

or characteristics of pea plants:

1. Flower color purple or white

2. Flower position axial or terminal

3. Stem length Tall or Dwarf

4 . Seed shape round or wrinkled

5. Seed color yellow or green

6. Pod shape inflated or constricted

7. Pod color green or yellow

are used to show the mating of two parents and the possible offspring they can produce.

STEPS:

TT and t t Cross

T T t t

T t

T t

T t

T t

T T

t t

Genotypes: 100% T t

Phenotypes: 100% Tall plants

T T t t

T T

T t

T t

t t

T t

T t

• A heterozygous with a homozygous

T t t t

T

t

t

T t

t t

You can still use the shortcut!

LAW PARENT CROSS OFFSPRING

DOMINANCE TT x tt tall x short

100% Tt Tall

SEGREGATION Tt x Tt tall x tall

75% tall 25% short

RrGg x RrGg round & green

x round & green

9/16 round seeds & green pods

INDEPENDENT ASSORTMENT

3/16 round seeds & yellow pods

3/16 wrinkled seeds & green pods

1/16 wrinkled seeds & yellow pods

and

F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties.

Example: snapdragons (flower)

Rr

Rr

Rr Rr

produces the F1 generation

All Rr = pink

• Two alleles are expressed (multiple alleles) in heterozygous individuals.

: blood group

1. type A

2. type B

3. type AB =

4. type O =

= IAIA or IAi

= IBIB or IBi

IAIB

ii

homozygous male Type B (IBIB)

x

heterozygous female Type A (IAi)

IAIB IBi

IAIB IBi

1/2 = IAIB

1/2 = IBi

IB

IA i

IB

IAi IBi

IAi IBi

1/2 = IAi

1/2 = IBi

i

male Type O (ii) x

female type AB (IAIB) IA IB

i

18

If a boy has a blood type O and his sister has blood type AB

boy - type O (ii) X girl - type

IAIB

ii

Parents: genotypes =IAi and IBi phenotypes = A and B

IB

Answer:

IA i

i