Q: Which of the following equations best represents the compaction of human chromosome 22 during mitosis, given that its extended length is 1.5 cm and its mitotic length is 2 microns?

$$\text{Compaction} = \frac{1.5 \ \text{cm}}{2 \times 10$$^{-4}$$ \ \text{cm}} = 10,000$$

Question 1

Which of the following best describes the structure of a nucleosome in eukaryotic chromosomes?

Accepted Answer

A segment of DNA wrapped around an octamer of histone proteins

Question 2

Which enzyme is responsible for adding acetyl groups to histone tails, and what is the effect of this modification?

Accepted Answer

Histone acetyltransferase (HAT); increases regions of active genes

Question 3

A scientist treats eukaryotic chromatin with a low concentration of DNase I. According to the beads-on-a-string model, what size DNA fragments should be most abundant after gel electrophoresis?

Accepted Answer

Approximately 200 base pairs

Question 4

Which of the following statements about bacterial chromosomes is correct?

Accepted Answer

They are typically found in a region called the nucleoid, which is not membrane-bound

Question 5

Which of the following best explains why there is no correlation between chromosome number and organismal complexity?

Accepted Answer

Genome size and chromosome number can vary independently due to differences in non-coding DNA and repetitive sequences

Question 6

Which of the following is a function of telomeres in eukaryotic chromosomes?

Accepted Answer

They protect chromosome ends and are important for replication and stability

Question 7

What is the primary role of SMC proteins in chromosome structure?

Accepted Answer

They help form and stabilize loop domains by wrapping around DNA segments

Question 8

Which of the following best describes the difference between constitutive and facultative heterochromatin?

Accepted Answer

Constitutive heterochromatin is always inactive and highly repetitive, while facultative heterochromatin can switch between active and inactive states

Question 9

Which of the following is true regarding the movement of transposable elements (TEs)?

Accepted Answer

Some TEs move via an RNA intermediate, while others move directly as DNA

Question 10

A maize kernel shows a spotted phenotype due to the activity of a transposable element. Which of the following best explains this observation?

Accepted Answer

A TE excises from a gene, restoring its function in some cells but not others

Question 11

Which of the following equations best represents the compaction of human chromosome 22 during mitosis, given that its extended length is 1.5 cm and its mitotic length is 2 microns?

Accepted Answer

$$	ext{Compaction} = \frac{1.5 \ 	ext{cm}}{2 	imes 10$$^{-4}$$ \ 	ext{cm}} = 10,000$$

Question 12

Which of the following best describes the 'selfish DNA theory' regarding transposable elements?

Accepted Answer

TEs proliferate within the genome as long as they do not significantly harm the host organism

Question 13

Which of the following is a direct result of DNA supercoiling in bacterial chromosomes?

Accepted Answer

Increased compaction of the chromosome

Question 14

Which of the following statements about the human genome is correct?

Accepted Answer

A large portion of the genome is derived from transposable elements

Question 15

Which of the following best explains why histones are able to bind DNA non-specifically?

Accepted Answer

Histones are rich in positively charged amino acids, which interact with the negatively charged DNA backbone

Question 16

Which of the following is a characteristic of euchromatin?

Accepted Answer

It is less condensed and transcriptionally active

Question 17

Which of the following best describes the role of condensin during mitosis?

Accepted Answer

It promotes chromosome condensation by compacting loop domains

Question 18

Which of the following is true about the abundance of transposable elements in eukaryotic genomes?

Accepted Answer

They can make up more than 50% of the genome in some species

Question 19

Which of the following best describes the process of retrotransposition?

Accepted Answer

A transposable element moves via an RNA intermediate, which is reverse transcribed into DNA

Molecular Structure and Organization of Chromosomes

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