Q: Which of the following crosses would be used as a test cross to determine if a trait is lethal in females in Morgan’s experiments?

$$X^wY \times X$$^{w+}$$X^{w+}$

Question 1

Which of the following is NOT an experimental advantage of using Drosophila melanogaster (fruit flies) as a model organism in genetic studies?

Accepted Answer

They are expensive to maintain in the laboratory.

Question 2

According to the chromosomal theory of inheritance, which statement best explains the biological mechanism underlying Mendel’s laws?

Accepted Answer

Genes are located on chromosomes, which segregate and independently assort during meiosis.

Question 3

In Morgan’s experiments with fruit flies, what was the significance of discovering a white-eyed mutant male?

Accepted Answer

It provided evidence that some traits are linked to sex chromosomes.

Question 4

A male fruit fly has the genotype $$X^wY$$ for eye color, where $$X^w is $$the white-eye allele. What is the phenotype of this fly?

Accepted Answer

White eyes

Question 5

Why are X-linked recessive disorders more common in males than in females?

Accepted Answer

Males only need one copy of the recessive allele to express the trait, while females need two.

Question 6

A woman who is a carrier for red-green color blindness ($$X^{w+}X^c$) marries a man with normal vision (X$$^{w+}$$Y). $$What proportion of their sons will be color blind?

Accepted Answer

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

Question 7

Which of the following best describes the inheritance pattern of hemophilia in European royal families?

Accepted Answer

Sex-linked recessive

Question 8

In a pedigree, which pattern suggests a sex-linked recessive trait?

Accepted Answer

Trait skips generations and predominantly affects males.

Question 9

A pedigree shows a trait that does not skip generations and is transmitted from affected fathers to both sons and daughters equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 10

If a female calico cat (genotype $$X^B X^R) $$mates with a black male cat ($$X^B Y$$), what proportion of their male offspring will be orange?

Accepted Answer

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

Question 11

Which of the following is a key feature of a pedigree for an autosomal recessive trait?

Accepted Answer

Trait skips generations and affects males and females equally.

Question 12

A man with red-green color blindness ($$X^cY) $$marries a woman with normal vision who is not a carrier ($$X^{w+}X$$^{w+}$). What proportion of their daughters will be color blind?

Accepted Answer

None

Question 13

Which of the following statements about sex chromosomes is correct?

Accepted Answer

The X chromosome carries genes for many traits unrelated to sex.

Question 14

A pedigree shows that affected fathers never transmit a trait to their sons, but the trait appears in every generation and affects both sexes. What is the most likely mode of inheritance?

Accepted Answer

Sex-linked dominant

Question 15

If a woman with genotype $$X^cX^c ($$color blind) has children with a man with normal vision ($$X^{w+}Y$), what is the expected proportion of color-blind children?

Accepted Answer

All sons will be color blind, all daughters will be carriers (but not color blind).

Question 16

Which of the following best explains why affected fathers do not transmit X-linked traits to their sons?

Accepted Answer

Sons inherit their X chromosome from their mother and Y chromosome from their father.

Question 17

A pedigree shows a trait that affects both males and females equally, skips generations, and affected fathers can transmit the trait to their sons. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 18

Which of the following crosses would be used as a test cross to determine if a trait is lethal in females in Morgan’s experiments?

Accepted Answer

$$X^wY 	imes X$$^{w+}$$X^{w+}$

Question 19

Which of the following is a real-world example of a sex-linked dominant trait?

Accepted Answer

Vitamin D-resistant rickets

Question 20

A pedigree shows that a trait is present in every generation, affects both sexes equally, and affected fathers transmit the trait to their sons. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

The Chromosomal Basis of Inheritance: Morgan, Fruit Flies, and Patterns of Genetic Transmission

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