TV4 - Monohybrid crosses

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Monohybrid inheritance

TV4

Ch 19

Inheritance

Learning objectives

You can apply inheritance principles to the following types of crosses: 

• regular monohybrid crosses 
• monohybrid crosses involving incomplete dominance 
• monohybrid crosses involving co-dominance 
• monohybrid crosses involving lethal alleles 

Kitty is a long-haired female cat and has mated with Kobus. In her litter we find both long-haired kittens and short-haired kittens. The allele for long hair is recessive. Three statements about Kitty's genotype:
1) Kitty is for sure heterozygous for long hair
2) Kitty is for sure homozygous for long hair
3) Kitty could be heterozygous or homozygous for long hair
Which statement is correct?

1. none
2. statement 1
3. statement 2
4. statement 3

Kitty is a long-haired female cat and has mated with Kobus. In her litter we find both long-haired kittens and short-haired kittens. The allele for long hair is recessive

Give the genotypes of both parents, show a punnett square of the cross and explain the expected phenotype ratio in the offspring. Complete this on paper, take a picture and upload here.

In cattle, the allele for a rough tongue is dominant over the allele for a smooth tongue. A cow is heterozygous for the gene. This cow has a calf with a bull that is also heterozygous for this gene.

What is the chance this calf is also heterozygous for this gene? Explain your answer by drawing a punnett square on paper, taking a picture and uploading that here.

In guinea pigs the allele for rough hair is dominant over smooth hair. A rough-haired heterozygous female has a litter. The offspring are all rough-haired. It is unknown who is the father. There are three options:
Male 1: smooth-haired
Male 2: rough-haired (homozygote)
Male 3: rough-haired (heterozygote)
Organise the males from most likely to be the father to least likely.

With newborn babies they extract a bit of blood to get tested. A child is tested and they find it has a metabolic abnormality called PKU. The child will have to follow a special diet. Neither of the parents shows symptoms of this disease. The parents would like to have another child. What is the chance their second child will also have PKU?

1. 12,5%
2. 25%
3. 50%
4. 100%

A rose breeder performs a cross. In this species of rose there are two phenotypes with regard to leave edges. A plant with serrated edges is crossed with a plant with smooth edges. All offspring have leaves with serrated edges. Explain the phenotype of the offspring.

The same rose breeder has a plant with serrated edges, but he doesn't know if it is heterozygote or homozygote. He uses a cross to figure it out. Based on the phenotype of the other parent plant and the phenotypes of the offspring he can determine the genotype of his original parent plant. What should be the genotype of the other parent plant to determine the genotype of the original plant? Write down a punnett square, take a picture and upload here.

In cattle there are three coat phenotypes: white, roan and red. A cow with A white cow is crossed with a bull with a red coat. All offspring has a roan coat. Show the punnett square that explains these phenotypes.

See previous cross. Two of the roan offspring from the F1 cross are crossed with each other. Give the phenotype ratios you expect from this F2 cross. Show it with a punnett square.

In petunias there are three flower colours. The colour is determined by two alleles: one for white flowers and one for purple flowers. In the phenotypes we can find white and purple, but also pink. A petunia with pink flowers is crossed with a petunia with white flowers. Show the punnett square and the colours you expect in the offspring.

The breeder performs countless crosses with the same two petunias. From this cross he gets 74 pink petunias, 38 white petunias and 37 purple petunias. What is true about the parent plants?

1. one is white, the other purple
2. one is white, the other pink
3. one is purple, the other pink
4. both are pink

In the crested canary the presence of the crest is determined by one gene. The allele for a crest is dominant. In the case of a homozygous dominant canary-embryo this leads to malformations during embryonic development and the death of the embryo. Two heterozygous canaries are crossed. What is the chance of the first offspring to have no crest?

1. 0%
2. 25%
3. 33%
4. 50%

In the crested canary the presence of the crest is determined by one gene. The allele for a crest is dominant. In the case of a homozygous dominant canary-embryo this leads to malformations during embryonic development and the death of the embryo. Two heterozygous canaries are crossed. What is the chance of the first and second offspring to have no crest?

1. 0%
2. 11%
3. 33%
4. 66%

pedigrees

Healthy male

Healthy female

Male/female with genetic abnormality

Is this condition dominant or recessive?

1. dominant
2. recessive

True or false:

Person 2 is heterozygous

1. true
2. false

True or false:

The genotype of person 5 can not be determined with absolute certainty.

1. true
2. false

True or false:

The chance of person 8 being heterozygous is 25%

1. true
2. false

True or false:

Person 7 must be heterozygous

1. true
2. false

For persons 12 and 13 it is yet unknown if they have the disease or not.

Calculate the chance of person 12 having the disease.