Q: Which of the following equations correctly represents the X/A ratio that determines sex in Drosophila melanogaster (fruit flies)?

$$X/A = \frac{\text{number of X chromosomes}}{\text{number of sets of autosomes}}$$

Question 1

Which of the following best describes the difference between isogamous and heterogamous species in terms of gamete production?

Accepted Answer

Isogamous species produce gametes that are morphologically similar, while heterogamous species produce gametes that are morphologically different.

Question 2

During meiosis, which principle of the chromosome theory of inheritance explains Mendel's law of independent assortment?

Accepted Answer

Different types of nonhomologous chromosomes segregate independently during gamete formation.

Question 3

A geneticist is studying a species of bird with a Z-W sex determination system. Which of the following statements is correct regarding the sex chromosomes of males and females in this species?

Accepted Answer

Males are homogametic (ZZ) and females are heterogametic (ZW).

Question 4

In the X-0 sex determination system found in some insects, what is the chromosomal composition of a male and how does it differ from the human system?

Accepted Answer

Males are X0 (one X chromosome, no Y), whereas in humans, males are XY.

Question 5

A researcher observes that in a certain reptile species, the sex of the offspring is determined by the temperature at which eggs are incubated. Which term best describes this phenomenon?

Accepted Answer

Temperature-dependent sex determination (TSD)

Question 6

Which of the following equations correctly represents the X/A ratio that determines sex in Drosophila melanogaster (fruit flies)?

Accepted Answer

$$X/A = \frac{	ext{number of X chromosomes}}{	ext{number of sets of autosomes}}$$

Question 7

In honey bees, males develop from unfertilized eggs and are haploid, while females develop from fertilized eggs and are diploid. If a drone (male bee) has 16 chromosomes, how many chromosomes would a worker bee (female) have?

Accepted Answer

$$32$$

Question 8

Which of the following statements about human sex determination is correct?

Accepted Answer

Males are heterogametic (XY) and females are homogametic (XX).

Question 9

A plant species is dioecious. Which of the following is true about its reproductive structures?

Accepted Answer

Individual plants produce either male or female gametophytes, but not both.

Question 10

Which principle of the chromosome theory of inheritance explains why offspring inherit a full complement of genes from each parent?

Accepted Answer

Each parent contributes one set of chromosomes to its offspring, and the sets are functionally equivalent.

Question 11

A genetic counselor is explaining to a couple that their child will inherit 44 autosomes and two sex chromosomes. If the child is female, what is the chromosomal composition?

Accepted Answer

$$44 + XX$$

Question 12

Which of the following best explains how Mendel's law of segregation is related to chromosome behavior during meiosis?

Accepted Answer

Homologous chromosomes pair and segregate into different gametes during meiosis.

Question 13

In a species with the Z-W sex determination system, what is the expected chromosomal composition of a female chicken?

Accepted Answer

$$76 + ZW$$

Question 14

Which of the following scenarios is an example of environmental sex determination?

Accepted Answer

Alligator eggs incubated at higher temperatures develop as females, while those at lower temperatures develop as males.

Question 15

If a fruit fly has two X chromosomes and two sets of autosomes, what is its X/A ratio and what sex will it develop as?

Accepted Answer

$$X/A = \frac{2}{2} = 1.0$$, so it will develop as a female.

Question 16

Which process describes the formation of gametes in animals, and what are its two main types?

Accepted Answer

Gametogenesis; spermatogenesis (formation of sperm) and oogenesis (formation of eggs).

Question 17

A researcher finds a species where males are haploid and females are diploid. Which sex determination system is most likely present?

Accepted Answer

Haplodiploid system

Question 18

Which of the following is NOT a fundamental principle of the chromosome theory of inheritance?

Accepted Answer

Each chromosome is inherited only from the mother.

Question 19

In which of the following organisms does the Y chromosome NOT determine maleness?

Accepted Answer

Drosophila melanogaster (fruit fly)

Question 20

Which of the following best describes the functional equivalence of chromosome sets contributed by each parent, according to the chromosome theory of inheritance?

Accepted Answer

Each set carries a full complement of genes, so both maternal and paternal sets are functionally equivalent.

Chromosome Transmission During Cell Division and Sexual Reproduction

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