Question 1

A diploid cell with 2n = 8 undergoes S phase. Immediately after S phase but before mitosis, how many chromosomes and chromatids are present in the cell?

Accepted Answer

8 chromosomes and 16 chromatids

Question 2

In a dihybrid cross AaBb × AaBb, what is the probability of producing an offspring with genotype aaBb?

Accepted Answer

$$P(aa) = \frac{1}{4}$$, $$P(Bb) = \frac{1}{2}$$, so $$P(aaBb) = \frac{1}{4} 	imes \frac{1}{2} = \frac{1}{8}$$

Question 3

A plant with genotype AaBBCcDd can produce how many genetically distinct gamete types, assuming independent assortment?

Accepted Answer

8

Question 4

A chromosome fails to attach to spindle fibers during metaphase. Which cell cycle checkpoint is responsible for preventing progression to anaphase?

Accepted Answer

Spindle (metaphase) checkpoint

Question 5

A testcross is performed between a plant with unknown genotype for a dominant trait and a homozygous recessive plant. The offspring are 50% dominant and 50% recessive. What was the unknown genotype?

Accepted Answer

Heterozygous

Question 6

Which Mendelian law explains why an individual with genotype RrYy can produce gametes RY, Ry, rY, and ry in equal proportions?

Accepted Answer

Law of Independent Assortment

Question 7

A cross between red and white snapdragons produces pink F1 flowers. When two pink F1s are crossed, what is the expected phenotype ratio in the F2 generation?

Accepted Answer

1 red : 2 pink : 1 white

Question 8

A carrier mother (X^N X^n) and an unaffected father (X^N Y) have children. What fraction of their sons are expected to be affected by an X-linked recessive trait?

Accepted Answer

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

Question 9

Ten individuals have the same disease-associated genotype, but only eight show the phenotype. Which genetic concept does this illustrate?

Accepted Answer

Incomplete penetrance

Question 10

In an Hfr interrupted-mating experiment, gene A enters at 5 minutes, gene B at 11 minutes, and gene C at 18 minutes. What is the order and approximate map distances between the genes?

Accepted Answer

Order: A - B - C; A-B: 6 min, B-C: 7 min, A-C: 13 min

Question 11

A normally diploid species has 2n = 20. What chromosome number would a trisomic individual have?

Accepted Answer

21

Question 12

After meiosis II, a gamete is found to have n+1 chromosomes. Which meiotic division did nondisjunction occur in?

Accepted Answer

Meiosis II

Question 13

A plant has four complete chromosome sets, all derived from the same species. What is the best description of its ploidy?

Accepted Answer

Autotetraploid

Question 14

A chromosome changes from ABCDEFG to ABEDCFG. What type of chromosomal rearrangement has occurred?

Accepted Answer

Inversion

Question 15

During bacterial transformation, two genetic markers are frequently cotransformed. What does this suggest about their physical relationship?

Accepted Answer

They are closely linked on the chromosome

Question 16

Two phage mutants each show the same defective phenotype alone. When both genomes are present in the same cell, wild-type function returns. What does this indicate?

Accepted Answer

The mutations are in different genes (cistrons)

Question 17

A healthy parent carries a balanced reciprocal translocation. Why can reproductive problems still occur?

Accepted Answer

Meiosis can produce unbalanced gametes with duplications and deletions

Question 18

Why might an inversion help preserve an adaptive combination of alleles in a population?

Accepted Answer

Recombination within the inverted region is suppressed in heterozygotes

Question 19

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

Accepted Answer

Transformation

Question 20

A mutation changes a codon, but the protein functions normally and the organism's phenotype is unchanged. What type of mutation is this?

Accepted Answer

Neutral mutation

Genetics Exam 1 Study Guide: Mitosis, Meiosis, Mendelian Genetics, Extensions, Bacterial Genetics, and Chromosomal Mutations

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