Question 1

Which of the following statements best explains why bacterial chromosomes can be compacted into the nucleoid despite lacking the histone proteins found in eukaryotes?

Accepted Answer

Bacterial chromosomes are associated with HU and H-NS proteins, which fold and bend DNA to create coils for compaction.

Question 2

A researcher isolates DNA from mitochondria and chloroplasts of a plant cell. Which of the following features would most likely be observed in both organellar DNAs?

Accepted Answer

Both are circular, double-stranded DNA molecules largely free of associated proteins.

Question 3

Which of the following best describes the role of histone acetylation in chromatin remodeling?

Accepted Answer

Histone acetylation adds acetyl groups to lysine residues, neutralizing their positive charge and increasing gene expression.

Question 4

A geneticist is studying a chromosome with highly repetitive DNA found only in the centromeric region. Which type of DNA is most likely being analyzed?

Accepted Answer

Satellite DNA

Question 5

Which of the following statements about polytene chromosomes is correct?

Accepted Answer

They are formed by many rounds of DNA replication without strand separation or cytoplasmic division, resulting in visible banding patterns.

Question 6

Which of the following best explains why CpG islands are important in gene regulation?

Accepted Answer

CpG islands are regions where cytosine is methylated, forming 5-methyl cytosine, which is negatively correlated with gene activity.

Question 7

A forensic scientist is analyzing DNA samples using short tandem repeats (STRs). Which property of STRs makes them useful for DNA fingerprinting?

Accepted Answer

STRs are moderately repetitive sequences that vary in number among individuals, allowing for unique genetic profiles.

Question 8

Which of the following is a key difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin appears unstained during interphase and is transcriptionally active, while heterochromatin is condensed, stained, and mostly inactive.

Question 9

A mutation in the gene encoding histone H4 results in the loss of its unstructured tail. Which chromatin function is most likely to be affected?

Accepted Answer

The ability of nucleosomes to connect with adjacent nucleosomes, affecting higher-order chromatin structure.

Question 10

Which of the following best describes the organization of nucleosomes in eukaryotic chromatin?

Accepted Answer

Nucleosomes are composed of DNA wrapped around a core of eight histone proteins, forming a 'beads on a string' structure.

Question 11

A patient is diagnosed with a genetic disorder caused by a mutation in a region of DNA that is not transcribed and has undergone significant insertions and deletions. This region is best described as:

Accepted Answer

A pseudogene

Question 12

Which of the following statements about mitochondrial DNA (mtDNA) is correct?

Accepted Answer

mtDNA is a double-stranded closed circle, largely free of chromosomal proteins, and its replication depends on nuclear-encoded enzymes.

Question 13

Which of the following best explains the function of the centromere during cell division?

Accepted Answer

It is the primary constriction that binds kinetochore proteins, facilitating chromosome movement by attaching to spindle fibers.

Question 14

Which of the following is a characteristic of lampbrush chromosomes?

Accepted Answer

They are large meiotic chromosomes with extensive DNA looping, found in oocytes during diplotene of prophase I.

Question 15

Which of the following chemical modifications of histones is most directly associated with the regulation of gene expression by altering chromatin structure?

Accepted Answer

Acetylation, methylation, and phosphorylation of histone tails

Question 16

A scientist is studying a repetitive DNA sequence that can relocate within the genome via an RNA intermediate. Which type of sequence is being investigated?

Accepted Answer

Retrotransposon (such as a LINE)

Question 17

Which of the following equations correctly represents the relationship between the number of nucleosomes ($$n$$), the total length of DNA in base pairs ($$L$$), and the average number of base pairs per nucleosome ($$b$$)?

Accepted Answer

$$n = \frac{L}{b}$$

Question 18

Which of the following best describes the difference between satellite DNA and SINEs (Short Interspersed Elements)?

Accepted Answer

Satellite DNA is highly repetitive and found in centromeric regions, while SINEs are mobile elements dispersed throughout the genome.

Question 19

A chromosome banding technique stains only the centromeric regions of chromosomes. Which technique is being used?

Accepted Answer

C-banding

Question 20

Which of the following statements about the proportion of protein-coding genes in the eukaryotic genome is correct?

Accepted Answer

Only a small portion (2–10%) of the eukaryotic genome constitutes protein-encoding genes.

Chromosome Structure and DNA Sequence Organization

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