• Author / Uploaded
• Faye Faye

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1. In cabbage butterflies, White wings are dominant to yellow wings. If a Ww butterfly is crossed with a ww butterfly, what are the possible genotypes and phenotypes of the offspring and the percent chance for each?

W

w

W

Ww

ww

w

Ww

ww

Fill in the table: Genotype

Phenotype

Chance

Ww

White wings

50%

ww

Yellow wings

50%

2. In dogs, there is a hereditary type of deafness caused by a recessive gene. Two dogs who carry the gene for deafness but have normal hearing are mated. What are the possible genotypes and phenotypes of their offspring and the percent chance for each?

D

d

D

DD

Dd

d

Dd

dd

Fill in the table: Genotype

Phenotype

Chance

DD

Normal hearing

25%

Dd

Normal hearing

50%

dd

Deafness

25%

3. In guinea pigs, short hair is dominant over long hair. If a short haired SS guinea pig is crossed with along haired ss guinea pig, what are the possible genotypes and phenotypes of their offspring and the percent chance for each?

S

S

s

Ss

Ss

s

Ss

Ss

Fill in the table: Genotype

Phenotype

Chance

Ss

Short hair

100%

4. Can you curl your tongue up on the sides? Tongue-curling in humans is a dominant genetic trait. Suppose a man who is Tt for a tongue –curling marries a woman who is also Tt for this trait. What are the possible genotypes and phenotypes of their children and the percent of chance for each?

T

t

T

TT

Tt

t

Tt

tt

Fill in the table: Genotype

Phenotype

Chance

TT

Tongue - curling

25%

Tt

Tongue – curling

50%

tt

Cannot tongue – curl

25%

5. In guinea pigs, rough coats (with lots of swirly cowlicks) are dominant over smooth coats. If an RR guinea pig is crossed with a Rr guinea pig, what are the genotypes and phenotypes of the offspring? What are the chances of each?

R

R

R

RR

RR

r

Rr

Rr

Fill in the table: Genotype

Phenotype

Chance

RR

Rough coats

50%

Rr

Rough coats

50%

1. Tom and Tina decided they wanted to start a family. Tom knew his grandfather had a sicklecell disease. Sickle-cell disease is a recessive disorder that causes blood cells to stiffen and take on a crescent shape. These blood cells have a difficult time moving through the blood vessels and can cause health problems. Tina didn’t know of any family members that had it. Still. Before they got pregnant they both went to the doctor for genetic tests. The doctor found that even though Tom and Tina were healthy, they both carried the gene for sickle-cell diseases. Make a Punnett square to determine the probability of Tom and Tina’s child having sickle-cell disease.

s

S S

Ww

ww

s

Ww

ww

Genotype

Phenotype

Chance

SS

Normal

25%

Ss

Normal

50%

ss

Sickle – cell disease

25%

2. Some cattle are naturally hornless, a condition called “polling”. Polling is dominant over the more common horned trait. A polled bull is mated with three cows with the ff. offspring: Cow A (horned) = polled calf Cow B (horned) = horned calf Cow C (horned) = horned calf What are the genotypes of the four parents?  Cow A

P

p \ p p

p

Pp

pp

Pp

pp

Offspring: Polled Calf 

Cow B

P p \ p p

p

Pp

pp

Pp

pp

Offspring: Horned Calf



Cow C

p

P P

PP

Pp

p

Pp

pp

Offspring: Horned Calf 3. Short hair is dominant over long hair in guinea pigs. A long-haired male guinea pig and a heterozygous short-haired female are kept in the same cage and mate numerous times, ultimately producing 32 total offspring. What is the most likely distribution of short hair and long hair among their offspring?

H

h

h

Hh

hh

h

Hh

hh

Genotype

Phenotype

Chance

Hh

Heterozygous short hair

50%

16 Heterozygous short hair

hh

Long hair

50%

16 Long hair

4. Tay-Sachs disease is due to a homozygous recessive genotype (nn). A bout 4% of the alleles in a given population are “n”. the means that about 96% of the alleles are “N”. use the Punnett square below to determine the approximate percentage of each genotype within the population. N = 0.96

n = 0.04

N = 0.96

0.9216

0.0384

n = 0.04

0.0384

0.0016

Genotype

Chance

NN

92.16%

Nn

7.68%

nn

0.16%