Question

Answer all questions and include explanations

1) Which one of the following statements is false regarding dosage compensation?

a) all eukaryotes have the same mechanism for controlling gene expression from x-linked genes when different numbers of x chromosomes are presents.

b) Dosage compensation is also referred to as x-inactivation

c) X-linked genes in male Drosophila are expressed at twice the rate of those in female Drosophila.

d) Drosophila with a chromosomal formulation of 3X:3A is considered a female.

------------------------------------

3) Which one of the following statements is true regarding non-disjunction?

a) Normal haploid gametes cannot be produced when non-disjunction occurs during Meiosis II.

b) Normal haploid gametes cannot be produced when non-disjunction occurs during Meiosis I.

c)The chromosomal karyotype for an individual with Klinefelter Syndrome can be written (45,X)

d) Turner Syndrome is not caused by non-disjunction

--------------------------------------------------

4) Which of the following is true regarding sex determination?

a) Phenotypic dimorphism only occurs in humans

b) Secondary sexual differentiation involves formation of gonads.

c) Hermaphroditism in organisms can be either sequential or simultaneous

d) The term heteromorphic has the same meaning as hermaphroditic.

Answer 1

1.a) all eukaryotes have the same mechanism for controlling gene expression from x-linked genes when different numbers of x chromosomes are presents.

Because there are different mechanisms for controlling gene expression from x-linked genes

for e.g.

-Random inactivation of one female X chromosome.

-Two-fold increased transcription of a single male X chromosomes.

-Decreased transcription of both hermaphroditic X chromosomes by half i.e. both active and each form half product.

3. b) Normal haploid gametes cannot be produced when non-disjunction occurs during Meiosis I.

explanation- If non-disjunction occurs during meiosis I, this means that at least one pair of homologous chromosomes did not separate. This results in formatin of two cells that have an extra copy of one chromosome and two cells that are missing that chromosome.

4. c) Hermaphroditism in organisms can be either sequential or simultaneous.

Explanation-

Sequential hermaphroditism occur in those species in which the individual is born as one of the sex, but can later change into the opposite sex.

Simultaneous hermaphroditism is that in which an adult organism have both male and female sexual organs at the same time.