Question 1

One parent has one copy of a dominant allele for gene 87 and one recessive allele for Gene 87.The other parent has two copies of the recessive allele for Gene 87.What is the chance that their children will inherit the dominant condition (two copies of Gene 87)? You may need to draw a Punnett square to figure this out.

Accepted Answer

The answer of One parent has one copy of a...

Question 2

Two people with Huntington disease,an autosomal dominant disorder,have a son.What are the chances he will get the disease? (Draw a Punnett square to help you determine the answer.)

Accepted Answer

Huntington's disease is caused by a dominant allele, which means that if one parent has the disease, there is a 50% chance that each child will inherit the disease-causing allele. In this case, both parents have the disease, so they would both be heterozygous (Hh). Using a Punnett square with Hh x Hh, there is a 75% chance (or 3 out of 4) that the child will inherit at least one H allele and therefore develop the disease.

Question 3

Two healthy individuals have a child who has Huntington disease,an autosomal dominant disease.How did this happen?

Accepted Answer

Huntington disease is an autosomal dominant condition, meaning that having just one copy of the mutated gene (allele) is enough to cause the disease. If both parents are healthy and do not show symptoms of Huntington disease, it implies they do not carry the mutated gene. Therefore, the condition could not have been inherited from these two parents. The scenario might involve a new mutation in the child or an error in the assumption about the parents' health status regarding Huntington disease.

Question 4

In a cross between an individual with Huntington disease and an unaffected individual,what are the chances their progeny will have the disease,considering that it is a dominant trait?

Accepted Answer

Huntington disease is a dominant trait, which means that an affected individual must have at least one copy of the Huntington disease allele. When an affected individual (heterozygous for the disease) mates with an unaffected individual (homozygous for the normal allele), each offspring has a 50% chance of inheriting the disease allele and developing the disease. Therefore, the answer is 50%.

Question 5

One parent has one copy of a dominant allele for gene 87 and one recessive allele for Gene 87.The other parent has two copies of the recessive allele for Gene 87.What is the chance that their children will inherit the recessive condition (two copies of Gene 87)? You may need to draw a Punnett square to figure this out.

Accepted Answer

The answer of One parent has one copy of a...

Question 6

Sickle-cell anemia is a recessively inherited disease that causes red blood cells to become rigid and deformed.What is the probability that a child will have sickle-cell anemia if the father has the disease and the mother is heterozygous for the disease? What is the probability that a child will be a carrier? Use a Punnett square to show your work and use the letters "A" and "a" to designate dominant and recessive alleles,respectively.

Accepted Answer

The answer of Sickle-cell anemia is a recessively inherited disease...

Question 7

Achondroplasic dwarfism is a dominant characteristic."D" represents the allele for achondroplasic dwarfism,and "d" represents the allele for normal height.A couple who both exhibit achondroplasic dwarfism marry and have three children.All of the children are dwarves.What is the genotype of their children? Show possible Punnett squares.

Accepted Answer

The answer of Achondroplasic dwarfism is a dominant characteristic."D" represents...

Question 8

A phenotypically normal woman marries a man with Wilson disease,a autosomal recessive disorder.They have a son who has Wilson disease.If you need two copies of the recessive allele to be affected and the mother doesn't have the disease,how did the son get it?

Accepted Answer

The son inherited one recessive allele from the father with Wilson disease and one recessive allele from the mother who is a carrier of the disease-causing allele but not affected by the disease. This results in the son having two copies of the recessive allele and hence showing the symptoms of Wilson disease.

Question 9

Which describes a genotype heterozygous for a single trait?

Accepted Answer

A genotype heterozygous for a single trait will have two different alleles for that trait, written as Aa (dominant-recessive relationship). Options A and B are both homozygous genotypes, while option C is also homozygous but is missing the second allele. Option E is also homozygous, but the two alleles are the same. Only option D fits the criteria of a heterozygous genotype for a single trait.

Question 10

Achondroplasic dwarfism is a dominant characteristic."D" represents the allele for achondroplasic dwarfism,and "d" represents the allele for normal height.A couple who both exhibit achondroplasic dwarfism marry and have four children.Three of the children are dwarves and one is of normal height.What is the genotype of the child with normal height? What is the genotype of the parents?

Accepted Answer

The answer of Achondroplasic dwarfism is a dominant characteristic."D" represents...

Question 11

One parent has one copy of a dominant allele for gene 87 and one recessive allele for Gene 87.The other parent has two copies of the dominant allele for Gene 87.What is the chance that their children will inherit the recessive condition (two copies of Gene 87)? You may need to draw a Punnett square to figure this out.

Accepted Answer

The recessive condition requires two recessive alleles. Since one parent has two dominant alleles, all children will inherit at least one dominant allele, making it impossible for them to have two recessive alleles.

Question 12

Having free earlobes is dominant to having attached earlobes.If the father and mother are both heterozygous for the trait,what is the probability that a child will be born with attached earlobes? Use a Punnett square to show your work and use the letters "E" and "e" to designate dominant and recessive alleles,respectively.

Accepted Answer

The answer of Having free earlobes is dominant to having...

Question 13

A woman who is blood type A gave birth to a child who is blood type O.The child's father is blood type O.Which of these three-mother,father,or child-is heterozygous for blood type? Use a Punnett square to explain.

Accepted Answer

The answer of A woman who is blood type A...

Question 14

A phenotypically normal woman marries a man with CMT disease,an autosomal dominant disorder.They have a son who has CMT disease.How did the son get it?

Accepted Answer

CMT disease is an autosomal dominant disorder, which means that only one copy of the mutated gene is needed to express the disease. The father must have had at least one dominant allele, which he passed on to his son, resulting in the expression of the disease in the son. The mother may have been phenotypically normal but could have carried a recessive allele for the disease, which would not have been expressed in her but could have been passed on to her son.

Question 15

Two normal individuals have a child who has cystic fibrosis,an autosomal recessive disease.What were the chances of this happening? (Draw a Punnett square to help you determine the answer.)

Accepted Answer

Cystic fibrosis is an autosomal recessive disease, which means that an individual needs to inherit two copies of the faulty gene (one copy from each parent) to develop the disease. The Punnett square for two normal individuals (who are both carriers of the faulty gene) is as follows:

|  | A   | a  |
|---|---|---|
| **A** | AA  | Aa  |
| **a** | Aa  | aa  |

As you can see, there is a 1 in 4 chance (or 25%) of the child inheriting two copies of the faulty gene (aa) and developing cystic fibrosis. Therefore, the chances of this happening are 1:4.

Question 16

Which describes a genotype homozygous dominant for a single trait?

Accepted Answer

An individual with a homozygous dominant genotype has two copies of the dominant allele, represented by uppercase letters. In this case, the genotype is simply "AA."

Question 17

Both parents have one copy of a dominant allele for gene 87 and one recessive allele for Gene 87.What is the chance that their children will inherit the recessive condition (two copies of Gene 87)? You may need to draw a Punnett square to figure this out.

Accepted Answer

The answer of Both parents have one copy of a...

Question 18

A phenotypically normal woman marries a man with CMT disease,a autosomal dominant disorder.They have a son who has CMT disease.What were the chances he would get the disease? (Draw a Punnett square to help you determine the answer.)

Accepted Answer

The answer of A phenotypically normal woman marries a man...

Question 19

Two normal individuals have a child who has cystic fibrosis,an autosomal recessive disease.How did this happen?

Accepted Answer

For a child to have cystic fibrosis, they must inherit two recessive alleles (one from each parent). This means that both parents must be carriers of the recessive allele (because they each have one normal allele and one recessive allele). Choice D is the only option that meets this requirement.

Question 20

Which represents a cross between 2 individuals heterozygous for a single trait?

Accepted Answer

When two individuals are heterozygous for a single trait, they each carry one dominant allele and one recessive allele. The offspring of this cross will inherit one allele from each parent, resulting in a 1:2:1 genotypic ratio of homozygous dominant, heterozygous, and homozygous recessive offspring. The only option among the choices provided that represents this type of cross is E, Aa × Aa.

Quiz 11: Single-Gene Inheritance and Meiosis Rock for a Cause