Question 1

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

Accepted Answer

Incomplete dominance produces an intermediate phenotype in heterozygotes, while codominance results in both alleles being fully and separately expressed.

Question 2

A woman with genotype $$X^B X^b ($$carrier for color blindness) marries a man with genotype $$X^b Y ($$color-blind). What fraction of their daughters will be color-blind?

Accepted Answer

50%

Question 3

In a biosynthetic pathway $$A \rightarrow B \rightarrow C$$, gene1 controls $$A \rightarrow B$$ and gene2 controls $$B \rightarrow C. If $$gene2 is mutated but gene1 is normal, what compound will accumulate?

Accepted Answer

Intermediate B

Question 4

Which mode of inheritance is ruled out if an affected father passes a trait to his son?

Accepted Answer

X-linked recessive

Question 5

A diploid cell with $$2n = 4$$ undergoes meiosis. How many possible haploid chromosome combinations can result from independent assortment?

Accepted Answer

$$4$$

Question 6

Which statement about Barr bodies is correct?

Accepted Answer

Barr bodies are formed from inactivated X chromosomes; their number is the total X chromosomes minus one.

Question 7

A pedigree shows a trait affecting both sexes equally, skipping generations, and unaffected parents producing affected children. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 8

Which event during meiosis increases genetic diversity beyond independent assortment?

Accepted Answer

Crossing over during prophase I

Question 9

A man with Huntington’s disease (genotype $$Hh) $$marries a woman with no family history (genotype $$hh). $$What is the probability their first child will have Huntington’s disease?

Accepted Answer

$$\frac{1}{2}$$

Question 10

Which of the following best describes the difference between aneuploidy and polyploidy?

Accepted Answer

Aneuploidy is the gain or loss of individual chromosomes; polyploidy is the gain of one or more complete sets of chromosomes.

Question 11

Which of the following is true about the SRY gene?

Accepted Answer

It is located on the Y chromosome and triggers male development.

Question 12

A bacteriophage integrates its DNA into the host genome and remains dormant. This process is called:

Accepted Answer

Lysogenic cycle

Question 13

A woman with genotype $$X^B X^b ($$carrier for an X-linked recessive disease) has two sons. What is the probability that both sons are affected?

Accepted Answer

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

Question 14

Which of the following statements about plasmids in prokaryotes is correct?

Accepted Answer

Plasmids are circular, double-stranded DNA molecules found in the cytosol.

Question 15

In birds, which sex is heterogametic and what is their sex chromosome composition?

Accepted Answer

Female; ZW

Question 16

A double mutant in a biosynthetic pathway accumulates precursor A. What does this indicate about the pathway?

Accepted Answer

The first gene is upstream and its mutation blocks the pathway before the second gene acts.

Question 17

Which of the following best describes the outcome of nondisjunction in meiosis I?

Accepted Answer

All four gametes are aneuploid.

Question 18

Which process allows bacteria to acquire DNA from the environment without direct cell-to-cell contact?

Accepted Answer

Transformation

Question 19

A pedigree shows an affected father passing a trait to all his daughters but none of his sons. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Question 20

A plant cross produces offspring in a 1:2:1 phenotypic ratio. Which inheritance pattern is most likely responsible?

Accepted Answer

Codominance

Genetics Midterm Study Guide: Mendelian Genetics, Cell Division, Pedigrees, Prokaryotic Genetics, Sex Determination, Chromosomal Variation

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