Question 1

Which of the following statements best explains why autosomal dominant disorders, such as Huntington's disease, can persist in a population despite their severe effects?

Accepted Answer

The symptoms often appear after reproductive age, allowing affected individuals to pass on the allele before knowing they have the disorder.

Question 2

A couple, both unaffected by a certain autosomal recessive disorder, have a child who is affected. What is the most likely genotype of the parents?

Accepted Answer

Both parents are heterozygous carriers.

Question 3

Which of the following best describes the inheritance pattern of Marfan syndrome, which affects multiple seemingly unrelated traits such as limb length, heart function, and vision?

Accepted Answer

Pleiotropy

Question 4

A woman with type AB blood (genotype $$I^A I^B) $$and a man with type O blood (genotype $$ii) $$have children. What are the possible blood types of their children?

Accepted Answer

Type A or Type B

Question 5

In a population, the trait for skin color is controlled by three separate genes, each with two alleles. Which inheritance pattern does this represent, and what is the expected distribution of phenotypes?

Accepted Answer

Polygenic inheritance; a continuous range of phenotypes

Question 6

A pedigree shows a trait that appears in every generation and affects males and females equally. Which type of inheritance is most likely?

Accepted Answer

Autosomal dominant

Question 7

A man with hemophilia (an X-linked recessive disorder) and a woman who is a carrier have a child. What is the probability that their son will have hemophilia?

Accepted Answer

$$50\%$$

Question 8

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered plants produces pink-flowered offspring.

Question 9

Which of the following best explains why males are more likely than females to express X-linked recessive disorders?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will be expressed.

Question 10

A woman with polydactyly (extra fingers or toes), a dominant trait with incomplete penetrance, has a child who does not have polydactyly. What does this suggest about the penetrance of the allele?

Accepted Answer

The dominant allele does not always result in the phenotype due to incomplete penetrance.

Question 11

If two parents are both heterozygous for cystic fibrosis (an autosomal recessive disorder), what is the probability that their child will be a carrier but not affected?

Accepted Answer

$$50\%$$

Question 12

Which of the following is a real-world example of a treatment that takes advantage of the underlying genetic mechanism of a disorder?

Accepted Answer

Regular blood donation for hereditary hemochromatosis to reduce iron overload.

Question 13

Which of the following best describes codominance, as seen in human ABO blood types?

Accepted Answer

Both alleles are fully expressed in the heterozygote.

Question 14

A pedigree shows that only males are affected by a certain disorder, and the trait skips generations. Which inheritance pattern is most likely?

Accepted Answer

X-linked recessive

Question 15

Which of the following scenarios best illustrates the concept of multiple alleles?

Accepted Answer

Rabbit coat color is determined by four different alleles, but each rabbit only has two alleles at the locus.

Question 16

A woman who is a carrier for colorblindness (an X-linked recessive trait) has children with a man who has normal vision. What is the probability that their daughter will be colorblind?

Accepted Answer

$$0\%$$

Question 17

Which of the following best explains why type O blood is considered the universal donor?

Accepted Answer

Type O blood lacks A and B antigens, so it is not recognized as foreign by any recipient's immune system.

Question 18

Which of the following is a likely outcome if two second cousins, both carriers for an autosomal recessive disorder, have children together?

Accepted Answer

Their children have an increased risk of being affected due to the higher chance of inheriting two recessive alleles.

Question 19

Which of the following best describes the effect of environmental factors on polygenic traits such as height?

Accepted Answer

Environmental factors like nutrition and disease can influence the expression of polygenic traits, leading to variation even among individuals with similar genotypes.

Beyond Mendelian Inheritance: Human Genetic Disorders and Complex Patterns

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