Q: Given that both II-3 and II-4 are unaffected but each has a sibling with an autosomal recessive disorder, what is the probability that their first child (III-1) will have the disorder?

$$\frac{1}{9}$$ \text{ (using conditional probability)}$

Question 1

In the pedigree shown, individuals II-2 and II-5 are affected by an autosomal recessive disorder. What is the probability that their unaffected siblings (II-3 and II-4) are carriers of the recessive allele?

Accepted Answer

$$\frac{2}{3}$$

Question 2

Given that both II-3 and II-4 are unaffected but each has a sibling with an autosomal recessive disorder, what is the probability that their first child (III-1) will have the disorder?

Accepted Answer

$$\frac{1}{9}$$ 	ext{ (using conditional probability)}$

Question 3

If a woman is heterozygous for an X-linked recessive disorder and mates with a normal male, what proportion of their sons will be affected?

Accepted Answer

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

Question 4

Which of the following best describes the inheritance pattern of hemophilia A?

Accepted Answer

X-linked recessive

Question 5

A male with an X-linked dominant disorder mates with a homozygous recessive female. What proportion of their daughters will be affected?

Accepted Answer

$$1$$

Question 6

In Drosophila, what is the expected F2 ratio of red-eyed to white-eyed males when a true-breeding red-eyed female is crossed with a white-eyed male?

Accepted Answer

2 red : 1 white (actual ratio from Morgan's experiment)

Question 7

Which gene is responsible for initiating male sex determination in mammals?

Accepted Answer

SRY

Question 8

What is the expected number of Barr bodies in a cell from a female with a karyotype of $$XXY$$?

Accepted Answer

1

Question 9

Which of the following best explains why calico cats are almost always female?

Accepted Answer

Calico coloration results from random X-chromosome inactivation in heterozygous females

Question 10

A human embryo ends up with a karyotype of $$XXY. At $$what stage of gamete development did nondisjunction most likely occur?

Accepted Answer

Meiosis I

Question 11

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the mitotic spindle before proceeding?

Accepted Answer

Metaphase checkpoint

Question 12

In birds, which sex chromosome combination determines a female?

Accepted Answer

ZW

Question 13

If a female carrier of an X-linked recessive disorder mates with a male affected by the disorder, what proportion of their daughters will be carriers?

Accepted Answer

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

Question 14

Which term describes a genotype where only one allele is present for a gene, as seen in males for X-linked traits?

Accepted Answer

Hemizygous

Question 15

What is the probability that a child will inherit an autosomal recessive disorder if both parents are carriers?

Accepted Answer

$$\frac{1}{4}$$

Question 16

Which of the following is a feature of X-linked recessive inheritance?

Accepted Answer

Trait is more common in males due to hemizygosity

Question 17

What is the probability that a child will inherit an autosomal recessive disorder if one parent is a carrier and the other is homozygous dominant?

Accepted Answer

$$0$$

Question 18

Which protein is responsible for holding sister chromatids together during meiosis?

Accepted Answer

Cohesin

Question 19

What is the effect of aging on cell cycle checkpoints?

Accepted Answer

Checkpoints are more likely to have errors, increasing risk of cancer and chromosomal abnormalities

Question 20

Which region allows the X and Y chromosomes to pair during male meiosis?

Accepted Answer

Pseudoautosomal regions (PARs)

Pedigree Analysis and Sex-Linked Inheritance: Mendelian and Chromosomal Genetics CH3 NEW SEM

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