Introduction: Sex-related disorders are inherited in families via one of the X or Y chromosomes. The chromosomes X and Y are sex chromosomes. When a defective gene from one parent causes disease, even when the matching gene from the other parent is normal, this is called dominant inheritance. The aberrant gene takes precedence.

  1. All genes on the sex chromosomes are gender-specific.

a.) True

b) False 

The answer is b

Explanation: The sex chromosomes X and Y contain a homologous area. Thus, the genes present exhibit a typical inheritance pattern.

  1. It would appear that an X-linked recessive gene would

a) Equally expressed in males and females

b) Generation-skipping 

c) Lethal

d) Gradually degrade

The answer is b

Explanation: Sex-linked genes, particularly recessive sex-linked genes, skip generations before expressing. It is more prevalent in males than females and is not always fatal.

  1. A gene with a Y chromosome

a) Is expressed exclusively in homozygotes

b) Is located near the telomere of the human long arm 

c) Is carried by the mother 

d) Is expressed exclusively in men

The answer is d

Explanation: A Y-linked gene is expressed exclusively in males and never in females due to the lack of a Y chromosome in females. It is not expressed in homozygous individuals, but rather in hemizygous individuals, as it is present in just one copy. Because the region surrounding that telomere is shared by both sexes, it is not sex-linked.

  1. Genes found in the homologous area of the X and Y chromosomes are referred to as______________.

a) Autosomal 

b) Sex-related 

c) Partially sex-related

d) Unrelated

The answer is c

c Explanation: Genes located in the homologous region of the X and Y chromosomes are referred to as partially sex-linked genes. While they are located on the sex chromosome, their inheritance pattern is similar to that of regular genes.

  1. Pick the outlier.

a) Color blindness 

b) Haemophilia 

c) Duchenne muscular dystrophy 

d) Porcelain defects

The answer is d

Explanation: While the first three disorders are recessive through the X chromosome, the final two, namely defective tooth enamel and decolonization, are dominant.

  1. In heterozygous females, the X linked dominant characteristic is typically milder. Indicate if the statement is true or false.

a.) True 

b.) False 

The answer is a

Females have two copies of the X gene, and if only one of them is mutant, there is a 50% probability that the mutant X gene will be silenced in a cell owing to dosage compensation. As a result, the mutant gene product’s effect is diluted.

  1. In a family of four, apart from the impaired son, who has a normal mother, a normal father, a colorblind son, and a normal son, who do you believe possesses the defective X gene?

a) The mother

b) The father 

c) The normally developing son 

d) The affected son alone

The answer is a

Explanation: Males have only one X chromosome, thus if the father or a normal son possessed the faulty X gene, the phenotypic result would occur. Due to the fact that females have two copies of the X chromosome, recessive genes such as color blindness are expressed only in homozygous form. Thus, mother is a carrier.

  1. A Klinefelter child with normal eyesight is born to a colorblind mother and a normal father. Where do you believe the nondisjunction occurred?

a) Mother’s first meiotic division 

b) Father’s second meiotic division

c) Mother’s second meiotic division 

d) Father’s first meiotic division

The answer is  d

Explanation: Because the child was not colorblind, the non-disjunction must be in the male parent. This is only feasible if one X chromosome was normal, which was inherited from the father in this case. Additionally, because the disjunction generated XY and not two identical copies of the same chromosome, it must have occurred during first division.

  1. Which of the following is not true if colorblindness is a dominant trait?

a) It would be expressed in heterozygous females 

b) It would be expressed in males

c) It would never be silenced 

d) It would never skip generations

The answer is c

Explanation: Because dosage compensation randomly turns off X chromosomes, the mutant X might just as easily be turned off in heterozygotes. Additionally, it will harm future generations due to its dominance. Both options a and b are true.

  1. What is the probability that a colorblind father’s son will also be colorblind?

a) 0

b) 1/4 

c) 1/2 

d) 1 

The answer is a

Explanation: Sons get the Y chromosome from their father, whereas daughters inherit the X chromosome from their mother. Thus, unless the mother is also a carrier, the son is unlikely to be colorblind.

  1. Y-linked inheritance is also referred to as _____________ inheritance.

a) Crisscross

b) Straight

c) Loop

d) Jumping

The answer is  b

Answer: b Explanation: The Y linked gene inherits in a straight line from father to son. These characteristics are inherited exclusively by males.

12.Which of the following is incorrect?

a) The Y chromosome is deficient in dosage compensation.

b) X-linked genes are inherited in a crisscross pattern 

c) Y-linked genes, such as haemophilia, are passed down from father to son

d) Females carry X-linked recessive genes

The answer is c

Explanation: While it is true that Y-linked genes are passed down from father to son, Haemophilia is not a Y-linked gene. It is an X-linked recessive gene.

  1. Which of the following is a gene with a Y chromosome?

a) Dental enamel deficiency 

b) Haemophilia 

c) Hypertrichosis 

d) Phenyl ketone urea

The answer is c

c  Only hypertrichosis has a Y chromosome linkage. It is a condition caused by the presence of hair in the ear. It inherits according to the Y connected rule.

  1. Which of the following is a condition that is partially sex-related?

a) Colorblindness in its entirety

b) Hypertrichosis 

c) Porcelain deficiency 

d) Haemophilia

The answer is a

Explanation: While colorblindness is an X-linked recessive trait, red-green colorblindness is an autosomal recessive trait. However, complete colorblindness is a partially sex-related gene in man.

  1. A child born to normal parents who is a turner is haemophilic. Where did the disjunction take place?

a) Mother

b) Father

c) Zygote

The answer is b

Explanation: The mother could have been a carrier in this case. The egg inherited the faulty X chromosome from its mother and lacked a sex chromosome from its father. Thus, the father lacked disjunction. The resulting offspring was designated AA+ X’O. (X’=mutant).