Q: A couple, both carriers for cystic fibrosis (an autosomal recessive disorder), are planning to have a child. What is the probability that their first two children will both have cystic fibrosis?

$$\frac{1}{4} \times \frac{1}{4} = \frac{1}{16}$$

Question 1

Which of the following best explains why sexual reproduction leads to greater genetic variation in a population compared to asexual reproduction?

Accepted Answer

Sexual reproduction allows for the independent assortment of chromosomes, crossing over during meiosis, and random fertilization.

Question 2

A human cell in G2 phase contains 46 chromosomes. How many sister chromatids are present in this cell?

Accepted Answer

$$92$$

Question 3

Which of the following events occurs during prophase I of meiosis but NOT during prophase of mitosis?

Accepted Answer

Synapsis and crossing over between homologous chromosomes

Question 4

A woman with blood type AB (genotype $$I^A I^B) $$and a man with blood type O (genotype $$ii) $$have a child. What is the probability that the child will have blood type A?

Accepted Answer

$$0.5$$

Question 5

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Sister chromatids are identical copies formed by DNA replication; homologous chromosomes are similar but not identical, each inherited from a different parent.

Question 6

A couple, both carriers for cystic fibrosis (an autosomal recessive disorder), are planning to have a child. What is the probability that their first two children will both have cystic fibrosis?

Accepted Answer

$$\frac{1}{4} 	imes \frac{1}{4} = \frac{1}{16}$$

Question 7

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects multiple traits, such as the sickle-cell allele causing anemia, pain, and resistance to malaria

Question 8

In a dihybrid cross between two individuals heterozygous for both seed color (Yy) and seed shape (Rr), what is the probability of obtaining an offspring with yellow, round seeds (YYRR)?

Accepted Answer

$$\frac{1}{16}$$

Question 9

Which of the following statements about cancer cells is TRUE?

Accepted Answer

Cancer cells divide excessively because they have escaped normal cell cycle controls.

Question 10

A plant with genotype $$AaBb is $$testcrossed with $$aabb. $$What proportion of the offspring are expected to have the genotype $$Aabb if $$the genes assort independently?

Accepted Answer

$$\frac{1}{4}$$

Question 11

Which of the following best explains why a person with genotype $$IAIB$$ has blood type AB?

Accepted Answer

The $$IA$$ and $$IB$$ alleles are codominant, so both types of carbohydrates are expressed on the red blood cells.

Question 12

Which of the following is a direct result of the law of independent assortment?

Accepted Answer

Each pair of alleles segregates independently during gamete formation.

Question 13

In a population, the dominant allele for polydactyly (extra fingers) is rare, yet some individuals express the trait. Which statement best explains this observation?

Accepted Answer

Dominant alleles are not necessarily more common than recessive alleles in a population.

Question 14

A woman who is a carrier for sickle-cell disease (heterozygous) marries a man who is also a carrier. What is the probability that their child will have sickle-cell disease?

Accepted Answer

$$\frac{1}{4}$$

Question 15

Which of the following best describes the process of cytokinesis in plant cells?

Accepted Answer

Vesicles from the Golgi apparatus coalesce at the center of the cell to form a cell plate, which develops into a new cell wall.

Question 16

In Labrador retrievers, black coat color (B) is dominant to brown (b), and the presence of pigment (E) is dominant to absence (e). If two dogs with genotype $$BbEe$$ are crossed, what is the expected phenotypic ratio of their offspring?

Accepted Answer

9 black : 3 chocolate : 4 yellow

Question 17

Which of the following mechanisms does NOT contribute to genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 18

A genetic counselor is working with a couple, both of whom had a brother with a recessive genetic disorder but neither parent nor themselves show symptoms. What is the probability that their first child will have the disorder?

Accepted Answer

$$\frac{1}{9}$$

Question 19

Which of the following best describes the difference between incomplete dominance and codominance?

Accepted Answer

Incomplete dominance results in a phenotype intermediate between the two homozygotes, while codominance results in both phenotypes being fully expressed.

Cell Division, Meiosis, and Mendelian Genetics: Study Guide

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