GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Chromosome Structure and Function

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Chromosome Structure And Function

Which of the following histone proteins is NOT in the nucleosome core of chromatin?

Possible Answers:

H3

H4

H2A

H1

Correct answer:

H1

Explanation:

DNA exists in the condensed chromatin form in order to fit into the nucleus. Negatively charged DNA loops twice around positively charged histone proteins to form a nucleosome bead. This nucleosome core is made up of two proteins each of histones H2A, H2B, H3 and H4.

H1 is the only histone protein that is not in the nucleosome core, and ties the nucleosome beads together in a string. H1 is located on the nucleosome exterior and help link DNA to the other proteins of the histone structure.

Example Question #2 : Help With Chromosome Structure And Function

What is a telomere?

Possible Answers:

A region of nucleotide sequence that repeats at the ends of chromosomes

The site of attachment of sister chromatids 

A protein that coats chromosomes and helps protect them from degradation 

A special type of chromosome used to help determine gender

Correct answer:

A region of nucleotide sequence that repeats at the ends of chromosomes

Explanation:

Telomeres are located at the ends of chromosomes and primarily serve the function of protecting the chromosome from degradation and fusion with neighboring chromosomes. The centromere is the site of attachment of two sister chromatids. Telomeres are not proteins; they are simply specialized portions of DNA. The sex chromosomes contain telomeres, but are only known as the sex chromosomes, allosomes, or chromosome 23.

Example Question #3 : Help With Chromosome Structure And Function

The __________ is the end of a chromosome that is elongated by an enzyme known as __________.

Possible Answers:

centromere . . . telomerase

telomere . . . telomerase

telomere . . . extendase

centromere . . . extendase

Correct answer:

telomere . . . telomerase

Explanation:

Telomeres are the non-coding terminal ends of chromosomes, which help maintain the integrity of the chromosome and prevent it from being degraded. During normal DNA replication, the ends of the telomeres are not replicated and, therefore, must be lengthened by a different process. Telomerase is an enzyme that uses reverse transcription to extend the telomere.

Centromeres are the regions of chromosomes that link sister chromatids. Extendase function is observed in some polymerases, and involves extending the DNA strand beyond the template (typically by the addition of an adenine nucleotide). 

Example Question #4 : Help With Chromosome Structure And Function

Which of the following would be affected by inhibiting a cell's ability to perform reverse transcription?

Possible Answers:

mRNA splicing

Post-translational modifications

Lengthening of telomeres

None of these answers; cells do not regularly use reverse transcription

Correct answer:

Lengthening of telomeres

Explanation:

The only choice that involves a process that uses reverse transcription is the lengthening of telomeres. Telomerase is an enzyme that uses reverse transcription to extend telomeres after replication. mRNA splicing and post-translational modifications do not directly use the process of reverse transcription. 

Example Question #5 : Help With Chromosome Structure And Function

You have discovered a new species of fish with a diploid number of 116. The gametes of this organism, just like human gametes, are haploid. You also discover that each gamete has 2 sex chromosomes, and sex of the zygote is determined by various combinations of the 4 possible sex chromosomes. What is the number of autosomes in a gamete of this new species?

Possible Answers:

Cannot be determined from the information given

Correct answer:

Explanation:

If the diploid number is 116,  haploid number in the gamete. Subtract 2 sex chromosomes, gives 56 autosomes in the gamete. This required knowing the distinction between autosomes and sex chromosomes and remembering to work from the haploid number since we are asked how many autosomes are in a gamete, not in an adult.

Example Question #6 : Help With Chromosome Structure And Function

Which of the following are not true about homologous pairs of chromosomes? 

Possible Answers:

The failure of homologous chromosomes to separate during meiosis is called non-disjunction

Recombination occurs between homologous chromosomes to generate new gene combinations

Genetic loci on homologous chromosomes are in roughly the same order

The pair is made up of one maternal chromosome and one paternal chromosome

The alleles on each chromosome in the pair are the same

Correct answer:

The alleles on each chromosome in the pair are the same

Explanation:

The alleles on the chromosome are not the same. The gene loci is the same, but which allele a chromosome carries depends on the donor. For example, if the maternal parent had blue eyes and the paternal parent had green eyes, then at the gene for eye color there could be 2 different alleles in their progeny.

Example Question #7 : Help With Chromosome Structure And Function

During interphase, the genome is packed into chromatin, a complex of DNA and protein that orders the DNA. Most of the chromatin is loosely packed but certain regions a highly condensed. What is this condensed chromatin called?

Possible Answers:

Betachromatin

Heterochromatin

Homochromatin

Euchromatin

Alphachromatin

Correct answer:

Heterochromatin

Explanation:

During interphase, DNA is complexed with protein into a structure called chromatin. Euchromatin refers to chromatin that is loosely packed. Heterochromatin refers to chromatin that is highly condensed, and largely unavailable for transcription.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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