Deck 3: The Nucleus

Question 1

Which of the following facilitates breakdown of the nuclear envelope during the onset of mitosis?

A) Disassembly of nucleosomes in the associated constitutive heterochromatin
B) Increased export of material by the nuclear pore complexes into the perinuclear space
C) Phosphorylation of lamin subunits by a CDK
D) Activities triggered at a restriction point late in $\mathrm{G}_{1}$
E) The activity of proteasomes

Answer 1

Phosphorylation of lamin subunits by a CDK

Question 2

Binding of histone $\mathrm{H} 1$ proteins to importins is important for which of the following?

A) Transport through the nuclear pores complexes
B) Properly directed vesicular transport through the Golgi apparatus
C) Transport from the granular part of the nucleolus
D) Further binding to the "linker DNA" and proper assembly of nucleosomes
E) Phosphorylation of cyclins

Answer 2

Transport through the nuclear pores complexes

Question 3

Which of the following is a region of chromatin that is well developed in large neurons active in protein synthesis?

A) Heterochromatin
B) The nucleolus
C) The Nissl substance (neuronal RER)
D) The Barr body
E) The nucleosome

Answer 3

The nucleolus

Question 4

A newborn boy is diagnosed with Apert syndrome. He has craniosynostosis, hypoplasia of the middle part of the face with retrusion of the eyes, and syndactyly that includes fusion of the skin, connective tissue, and muscle of the first, middle, and ring fingers with moderate fusion of those digits. There is very limited joint mobility past the first joint. Which one of the following is most likely decreased in cells of the interdigital regions of the developing hand of this newborn child?

A) Random DNA degradation
B) Inflammation
C) Cell swelling
D) Bcl-2
E) DNA degradation by endonucleases

Question 5

Transitions in the cell cycle from one phase to the next are regulated by protein kinases whose activity depends on what other proteins?

A) Tumor suppressors
B) Cyclins
C) Actins
D) Lamins
E) Importins

Question 6

Mitotic figures visible in a tissue section from the lining of the small intestine are most likely to belong to which of the following categories?

A) Terminally differentiated cells
B) Partially differentiated cells
C) Blood cells
D) Stem cells
E) Progenitor cells

Question 7

Key differences between apoptotic and necrotic cell death include which of the following?

A) Apoptotic cells do not release factors that induce inflammation.
B) Necrosis does not trigger inflammation.
C) Apoptosis does not utilize intracellular proteases.
D) Apoptosis usually follows lethal physical damage to a cell. e. Necrosis is involved in formation of some organs during embryonic development.

Question 8

A 29 -year-old woman presents with a $101^{\circ} \mathrm{F}$ fever, pericardial effusions and Libman-Sachs endocarditis, arthralgia, and facial rash across the malar region ("butterfly rash") that is accentuated by sun exposure. Laboratory tests show creatine $1.7 \mathrm{mg} / \mathrm{dL}$ (normal 0.5-1.1 $\mathrm{mg} / \mathrm{dL}$ ), high titers of antinuclear autoantibodies (ANA), Smith antigen, and antinucleosome antibodies in the blood. Which one of the following is most likely to be directly affected by the disruption of nucleosomes in this patient?

A) Packaging of genetic material in a condensed form
B) Transcribing DNA
C) Forming pores for bidirectional nuclear-cytoplasmic transport
D) Forming the nuclear lamina
E) Holding together adjacent chromatids

Question 9

A 32-year-old man and his 30-year-old wife are referred for a reproductive endocrinologist infertility (REI) consult after 2 years of "trying to get pregnant." He is diagnosed with oligozoospermia. Ejaculated mature sperm are collected and undergo genetic analysis. Using gene linkage analysis, his REI specialist determines that he has aberrations in spermatogenic meiotic recombination, including both diminished frequency and suboptimal location, resulting in high frequency of aneuploid sperm. In explaining the diagnosis, she explains meiosis and recombination attributing the problem to a specific phase of the meiosis. Which part of meiosis is most closely associated with recombination?

A) Metaphase I
B) Anaphase I/Telophase I
C) Prophase I
D) Prophase II
E) Anaphase II/Telophase II