$$\text{Number of Barr bodies} = \text{Number of X chromosomes} - 1$$

Question 1

A female patient is found to have a karyotype of 47,XXX. Which of the following is the most likely clinical presentation?

Accepted Answer

Tall stature, may have learning difficulties, but is phenotypically female

Question 2

Which of the following best explains why individuals with Klinefelter syndrome (47,XXY) are male?

Accepted Answer

The presence of the Y chromosome determines maleness

Question 3

A geneticist observes a Barr body in a cell nucleus. Which of the following is the correct formula to determine the number of Barr bodies present?

Accepted Answer

$$	ext{Number of Barr bodies} = 	ext{Number of X chromosomes} - 1$$

Question 4

Which experiment provided the strongest evidence that DNA, not protein, is the genetic material in bacteriophages?

Accepted Answer

Hershey-Chase experiment using radioactive isotopes

Question 5

A plant breeder wants to create a new variety with larger fruit by increasing the number of chromosome sets. Which process is most likely to be used?

Accepted Answer

Inducing autopolyploidy using colchicine

Question 6

A patient with Down syndrome is found to have 46 chromosomes, but with a fusion between chromosomes 21 and 14. What is the most likely cause?

Accepted Answer

Robertsonian translocation

Question 7

Which of the following statements about DNA replication is correct?

Accepted Answer

The leading strand is synthesized continuously in the 5' to 3' direction

Question 8

A woman with the genotype XO is diagnosed with Turner syndrome. Which of the following is a typical symptom?

Accepted Answer

Short stature and underdeveloped ovaries

Question 9

Which of the following best describes the Lyon hypothesis?

Accepted Answer

One X chromosome in females is randomly inactivated early in development, leading to mosaicism

Question 10

A DNA sample is found to have 30% adenine. According to Chargaff's rule, what percentage of guanine is present?

Accepted Answer

$$20\%$$

Question 11

Which of the following chromosomal rearrangements is most likely to result in gene redundancy and potentially new traits?

Accepted Answer

Duplication

Question 12

A scientist is studying mitochondrial inheritance in a plant. Which of the following statements is correct?

Accepted Answer

Traits are inherited only from the mother

Question 13

Which protein is responsible for relieving supercoiling during DNA replication?

Accepted Answer

Gyrase (Topoisomerase)

Question 14

A child inherits a shell coiling pattern determined by the mother's genotype, regardless of its own genotype. This is an example of:

Accepted Answer

Maternal effect

Question 15

Which of the following best describes the outcome of the Meselson-Stahl experiment?

Accepted Answer

Confirmed the semiconservative model of DNA replication

Question 16

A chromosome segment is reversed end to end, but the centromere is not included in the inversion. This is called:

Accepted Answer

Paracentric inversion

Question 17

Which of the following is a function of telomerase?

Accepted Answer

Extends chromosome ends to prevent loss of DNA after replication

Question 18

A cell with a karyotype of 2n+1 is best described as:

Accepted Answer

Trisomic

Question 19

Which of the following best explains why polyploidy is more common and beneficial in plants than in animals?

Accepted Answer

Polyploidy is usually lethal in animals but can increase size and hardiness in plants

Question 20

During gel electrophoresis, DNA fragments are separated based on which property?

Accepted Answer

Size and charge

Genetics Study Guide: Chromosome Variation, Sex Determination, Extranuclear Inheritance, and DNA Replication

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