quiz session 3 - units.it...in rabbits, white fur (b) is dominant to black fur (b) and long ears (e)...

QUIZ SESSION 3Punnett squares

Prof. Sabrina Pricl A.Y. 2020-2021

In rabbits, white fur (B) is dominant to black fur (b).

Q1. If you cross a BB male (P1) with a Bb female (P2), what are the possible genotypes (G) and phenotypes (P) of the 1st gen offspring? What is the percentage of each? Explain.

A1. 1. Fill the relevant G/P Punnett square

2. Fill in the Table

Quiz #1 – Punnett squares (Lesson 15)

2

B B

B

b

BBwhite

BBwhite

Bbwhite

Bbwhite

P1

P2

BB

Bb

white

white

50%

50%

Genotype ratio 1:1 Phenotype ratio: - (100% white)

Elements of Chemical and Molecular Biology – QUIZ SESSION 3

In cabbage butterflies, white wings (W) are dominant to yellow wings (w).Q2. If a Ww butterfly (P1) is crossed with a ww butterfly (P2), what are the possible genotypes (G) and phenotypes (P) of the 1st gen offspring? What is the percentage of each?A2. 1. Fill the relevant G/P Punnett square



3

W w

w

w

Wwwhite

wwyellow

P1

P2

Wwww

whiteyellow

50%50%

wwyellow

Wwwhite

Genotype ratio 1:1 Phenotype ratio: 1:1


In dogs there is a hereditary type of deafness caused by a recessivegene (d). Two dogs who carry the gene for deafness but have normal hearing are mated.Q3a. What is the genotype of the two mating dogs?A3a. Both dogs must have genotype Dd


4Elements of Chemical and Molecular Biology – QUIZ SESSION 4

In dogs there is a hereditary type of deafness caused by a recessive gene (d). Two dogs who carry the gene for deafness but have normal hearing are mated.Q3b. what are the possible genotypes (G) and phenotypes (P) of the 1st gen offspring? What is the percentage of each?A3b. 1. Fill the relevant G/P Punnett square



5

D d

D

d

DDnormal

Ddnormal

P1

P2

DD

dd

normal

deaf

25%

25%dddeaf

Ddnormal

Dd normal 50%

Genotype ratio 1:2:1 Phenotype ratio: 1:2:1Elements of Chemical and Molecular Biology – QUIZ SESSION 3

Quiz #4 – Punnett squares gets more complicatedIn rabbits, white fur (B) is dominant to black fur (b) and long ears (E) is dominant to short ears (e). Q4. If a breeder mates two rabbits heterozygous for both traits, which is the probability for the 1st generation offspring to be black with long ears?A4. 1. Write the genotypes of the mating rabbits à BbEe

2. Write the crossing à BbEe x BbEe3. Fill in the Punnett square for the corresponding

genotype4. Look for black fur and long ear rabbits and

remember:- to be black (recessive) genotype MUST be…(bb)- to have long ears (dominant) genotype must be…either (EE) or (Ee)

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BE bEBe beP1

P2

BE

Be

bE

be

BBEE BBEe BbEE BbEe

BBEe BBee BbEe Bbee

BbEE BbEe bbEE bbEe

BbEe Bbee bbEe bbee


Quiz #4 – Punnett squares gets more complicated4. Look for black fur and long ear rabbits and remember:

- to be black (recessive) genotype MUST be…(bb)

- to have long ears (dominant) genotype must be…either (EE) or (Ee)

5. There are 16 possibilities in total- you must discard all the genotypes that contain the

dominant allele B (otherwise white fur)- you must discard the genotype bbee (otherwise

short ears)- you are left with:

one genotype bbEE with probability 1/16one genotype bbEe with probability 2/16

Therefore, the probability to have a black rabbit with long ears by mating two rabbits with heterozygous genotypes for both traits is 3/16

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BE bEBe beP1

P2

BE

Be

bE

be

bbEE

BBEE BBEe BbEE BbEe

BBEe BBee BbEe Bbee

BbEE BbEe

BbEe Bbee

bbEe

bbEe bbee


Co-dominant traits



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Colors in some cows shows codominance. The genotypes for black and white cows are (BB) and (WW), respectively, while black and white cows are heterozygous (BW).

Q5. What are the possible genotypes (G) and phenotypes (P) of the 1st gen offspring obtained by crossing two black and white cows? What is the percentage of each?


2. Fill in the TableB W

B

W

BBblack

BWblack and

white

P1

P2

WWwhite

BWblack and

white

BB

WW

black

white

25%

25%

BW black and white 50%

Genotype ratio 1:2:1 Phenotype ratio: 1:2:1


Incomplete dominant traits



11

Colors in flowers shows incomplete dominance. The genotypes for red and white flowers are (RR) and (ww), respectively, while pink flowers are heterozygous (Rw).

Q6. What are the possible genotypes (G) and phenotypes (P) of the 1st gen offspring obtained by crossing two pink flowers? What is the percentage of each?


2. Fill in the TableR w

R

w

RRred

Rwpink

P1

P2

wwwhite

Rwpink

RR

ww

red

white

25%

25%

Rw pink 50%

Genotype ratio 1:2:1 Phenotype ratio: 1:2:1


A fundamental example of co-dominance:The blood group genes


The human blood group genes


Quiz #7 – Punnett squares & blood groups

15

A male with blood type AB mates with a woman who is heterozygous for type A blood.

Q7. What are the possible genotypes (G) and phenotypes (P) of the 1st gen blood groups? What is

the percentage of each? Explain

A4. 1. The male G is (AB), the woman G is (AO)

2. Fill the relevant G/P Punnett square

3. Fill in the TableA B

A

O

AAA

ABAB

P1

P2

BOB

AOA

AA, AO

BO

A

B

50%

25%

AB AB 25%

Genotype ratio 1:1:1:1 Phenotype ratio: 2:1:1


Sex-linked recessive traits


Sex-linked recessive traits• Sex-linked diseases are passed down through families through one of the X

or Y chromosomes (sex chromosomes)

• Dominant inheritance occurs when an abnormal gene from one parent causes disease, even though the matching gene from the other parent is normal• The abnormal gene dominates

• In recessive inheritance, both matching genes must be abnormal to cause disease• If only one gene in the pair is abnormal, the disease does not occur or it is mild

• Someone who has one abnormal gene (but no symptoms) is called a carrier• Carriers can pass abnormal genes to their children


Sex-linked recessive traits• The term sex-linked recessive most often refers to X-linked recessive• X-linked recessive diseases most often occur in males• Males have only one X chromosome. A single recessive gene on that X

chromosome will cause the disease• The Y chromosome is the other half of the XY gene pair in the male• The Y chromosome does NOT contain most of the genes of the X

chromosome• Because of that, it does not protect the male from the disease

• Diseases such as hemophilia and Duchenne muscular dystrophy occur from a recessive gene on the X chromosome• X-linked diseases are rare in women


X-linked recessive traits – Quiz #8

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Human colorblindness is a typical human X-linked recessive trait.

Q7. If a man (P1) with colorblindness marries a woman (P2) who is not colorblind but carries the recessive allele, what can we say about the 1st gen offspring?

Xr Y

Xr

XR

P1

P2

XrXr

f,CBXrY

m,CBXRY

m,NCBXRXr

f,NCB

25% female with disease25% healthy female25% male with disease25% healthy male


quiz session 3 - units.it...in rabbits, white fur (b) is dominant to black fur (b) and long ears (e)...

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