Question 1

Which of the following best describes 'penetrance' in the context of pedigree analysis?

Accepted Answer

The proportion of individuals with a particular genotype that actually displays the associated phenotype.

Question 2

A woman with blood type O has a child with blood type O. Which of the following men could NOT be the father?

Accepted Answer

A man with genotype I\^A I\^B

Question 3

In a dihybrid cross AaBb x AaBb, assuming independent assortment and complete dominance, what is the expected phenotypic ratio among the offspring?

Accepted Answer

$$9:3:3:1$$

Question 4

A pedigree shows a trait that appears in every generation and is equally distributed among males and females. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 5

A man with Klinefelter syndrome has the following sex chromosome complement:

Accepted Answer

XXY

Question 6

How many Barr bodies would you expect to find in a human cell with an XXYY karyotype?

Accepted Answer

One

Question 7

During which stage of meiosis do homologous chromosomes separate, leading to Mendel's law of segregation?

Accepted Answer

Anaphase I

Question 8

A plant with genotype FfYy is testcrossed (crossed with ffyy). What is the expected phenotypic ratio among the offspring?

Accepted Answer

$$1:1:1:1$$

Question 9

A woman whose husband worked at the Chernobyl nuclear reactor gives birth to a hemophilic son. Which is the most likely explanation?

Accepted Answer

She should not blame the accident because she carried the hemophilia allele.

Question 10

If a human cell is in metaphase II of meiosis, how many chromosomes are present?

Accepted Answer

$$23$$

Question 11

A trihybrid plant (AaBbCc) is self-fertilized. What is the probability that an offspring will have the dominant phenotype at all three loci?

Accepted Answer

$$27/64$$

Question 12

Which of the following is a reason Mendel's work was not appreciated until 1900?

Accepted Answer

There was no known physical basis for Mendel's 'gene' concept at the time.

Question 13

A pedigree shows a trait that skips generations and is equally distributed among males and females. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 14

In a family with four children, what is the probability that there will be exactly one girl and three boys?

Accepted Answer

$$1/4$$

Question 15

A woman with normal vision whose father was colorblind has children with a man with normal color vision. What is the probability that their first child will be colorblind? (Red-green color blindness is X-linked recessive.)

Accepted Answer

$$1/4$$

Question 16

How many different phenotypes can be expressed in a character controlled solely by a one-gene, two-allele system, in which the alleles are codominant?

Accepted Answer

Three

Question 17

A dihybrid plant was crossed, and the F2 generation consisted of 860 tall plants with purple flowers, 285 dwarf, purple plants, 340 tall, pink plants, and 115 dwarf, pink plants. The data remind you of a $$9:3:3:1$$ ratio. What is the chi-square value for this test?

Accepted Answer

$$10.11$$

Question 18

A pedigree shows a father with a genetic disease, all his daughters are affected, but none of his sons are. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Question 19

How many tetrads are there in metaphase I of meiosis in human beings?

Accepted Answer

$$23$$

Question 20

A male fruit fly and a female fruit fly are heterozygous for detached wings (det). What is the probability that of their first ten offspring, any five will be females with detached wings?

Accepted Answer

$$(10!/5!5!)(1/8)^5$(3/8)^5$

Genetics Exam 1 Study Guide: Transmission Genetics, Pedigree Analysis, and Cell Division

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