Monohybrid crosses 10.2-11.1

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Work to be done

The LessonUp about Monohybrid crosses/ pedigrees

AND

Assessment questions:

Glencoe page 289: question 12, 13 and 16-20

Glencoe page 319: question 1-6 and 8

Study the image

What is true?

This organism is...

1. homozygous for the left gene heterozygous for the middle gene heterozygous for the right gen
2. heterozygous for the left gene heterozygous for the middle gene homozygous for the right gene
3. homozygous for the left gene homozygous for the middle gene heterozygous for the right gene
4. homozygous for the left gene heterozygous for the middle gene homozygous for the right gene

If your ear lobe is attached to your head or not is a hereditary trait that is monogenetic. It is caused by one single gene. The allele for loose lobes is dominant.

What gametes will a heterozygous father produce?

1. 100% of his spermcells are Aa
2. 50% of his sperm cells are A 50% of his sperm cells are a
3. 75% of his sperm celles are A 25% of his sperm cells are a
4. 100% of his sperm cells are a

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.

Why do you think that Huntington’s disease is still around (1 in 20.000 people) whereas other dominantly inherited diseases are not that common?

A man who gets Huntington’s disease at the age of 40 had two children with a woman who doesn’t have it. He had himself tested and he turns out to be a heterozygote. What is the chance both his children will get it? Explain by using Punnett squares.

A man who is a carrier of cystic fibrosis wants to have a child with a woman whose parents are carriers of cystic fibrosis. She doesn’t know if she is a carrier. What is the chance that the child will get cystic fibrosis? Is it advisable to get herself tested?

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

You can't tell what the genotype of person 5 is.

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.