Question 1

Which of the following best describes the mechanism by which steroid hormones regulate gene expression in eukaryotic cells?

Accepted Answer

Steroid hormones diffuse through the plasma membrane, bind to cytoplasmic steroid hormone receptors, which then dimerize, translocate to the nucleus, and bind to hormone response elements (HREs) to regulate gene expression.

Question 2

What is the primary function of the zinc finger motif in steroid hormone receptors?

Accepted Answer

It enables the receptor to bind specifically to DNA at hormone response elements (HREs).

Question 3

RU486 (mifepristone) is used as an emergency contraceptive. What is its molecular mechanism of action?

Accepted Answer

It binds to the progesterone receptor, preventing progesterone from activating the receptor and thus blocking gene expression necessary for implantation.

Question 4

Which of the following sequences best represents a consensus hormone response element (HRE) for steroid hormone receptors?

Accepted Answer

$$\mathrm{RGGTCAN_3TGACCY}$$

Question 5

Tamoxifen is used in the treatment of certain breast cancers. How does it exert its therapeutic effect at the molecular level?

Accepted Answer

It binds to the estrogen receptor, but the tamoxifen-receptor complex cannot bind to the estrogen response element, thus preventing gene expression required for cancer cell proliferation.

Question 6

In Drosophila embryonic development, what is the role of maternal effect genes such as bicoid?

Accepted Answer

They are expressed from the mother's genome, and their mRNAs are deposited in the egg to establish anterior-posterior polarity.

Question 7

A Drosophila embryo lacking both maternal bicoid alleles will most likely develop into:

Accepted Answer

A larva lacking anterior structures, with duplicated posterior segments (double-posterior phenotype).

Question 8

Which of the following best describes the function of Hox (homeobox) genes in animal development?

Accepted Answer

They determine the anatomical identity of body segments by encoding transcription factors with a conserved homeodomain.

Question 9

Which of the following statements about stem cells is correct?

Accepted Answer

Totipotent stem cells can differentiate into any tissue type, including extraembryonic tissues, and can form a complete organism.

Question 10

Which of the following is a direct consequence of a mutation in a Hox gene in Drosophila?

Accepted Answer

Transformation of one body segment into another, such as legs developing in place of antennae.

Question 11

Which of the following best explains why the study of Drosophila developmental genes is relevant to human biology?

Accepted Answer

Developmental genes, including Hox genes, are highly conserved across species, and insights from Drosophila help understand human development and stem cell biology.

Question 12

Which of the following is NOT a function of the Bicoid protein in Drosophila embryogenesis?

Accepted Answer

Acts as a translational repressor of hunchback mRNA at the posterior.

Question 13

Which of the following best describes the role of chaperone protein HSP70 in steroid hormone receptor function?

Accepted Answer

HSP70 binds to the steroid hormone receptor in the cytoplasm, keeping it inactive until the hormone binds.

Question 14

Which of the following is a correct sequence of events in the activation of gene expression by a steroid hormone?

Accepted Answer

Steroid hormone binds to receptor in cytoplasm → HSP70 dissociates → receptor dimerizes → dimer enters nucleus → binds HRE → gene expression is modulated.

Question 15

Which of the following best describes the effect of the Antennapedia mutation in Drosophila?

Accepted Answer

Antennae are replaced by legs due to misexpression of thoracic Hox genes in the head segment.

Question 16

Which of the following statements about hormone response elements (HREs) is correct?

Accepted Answer

HREs are palindromic DNA sequences recognized by dimerized steroid hormone receptors.

Question 17

Which of the following best explains the clinical use of synthetic steroids such as prednisone?

Accepted Answer

They are used as anti-inflammatory agents by modulating gene expression through steroid hormone receptors.

Question 18

Which of the following is a correct description of the function of Nanos protein in Drosophila embryogenesis?

Accepted Answer

Nanos acts as a translational repressor of hunchback mRNA at the posterior end.

Question 19

Which of the following best describes the difference between pluripotent and multipotent stem cells?

Accepted Answer

Pluripotent stem cells can differentiate into many, but not all, cell types, while multipotent stem cells can differentiate into a limited range of related cell types.

Regulation of Gene Expression in Eukaryotes: Steroid Hormones and Embryonic Development

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드