Chromosomes

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1

Which term refers to a picture of the chromosomes of a single cell, arranged in descending order of size?

Karyotype

Physiological imaging

Radionuclide reflux imaging

Phage type

Chromatography

Explanation

A karyotype is produced by staining and photographing the chromosomes of a dividing cell. Pictures of the individual chromosomes are cut out and arranged in descending order of size. The chromosomes occur in homologous pairs that are similar in both staining patterns and size and have similar genetic material.

Physiological imaging is the visual representation of the functions of an organ, for example its blood flow, electrical activity, metabolism, and oxygen uptake. Radionuclide reflux imaging is a nuclear medicine scan used to determine whether an infant has gastroesophageal reflux. Phage type involves distinguishing subgroups of bacteria by the type of bacteriophage associated with that specific bacterium. Chromatography is the separation of two or more chemical compounds by their removal at different rates based on differential absorption and solubility.

2

Which term refers to a picture of the chromosomes of a single cell, arranged in descending order of size?

Karyotype

Physiological imaging

Radionuclide reflux imaging

Phage type

Chromatography

Explanation

A karyotype is produced by staining and photographing the chromosomes of a dividing cell. Pictures of the individual chromosomes are cut out and arranged in descending order of size. The chromosomes occur in homologous pairs that are similar in both staining patterns and size and have similar genetic material.

Physiological imaging is the visual representation of the functions of an organ, for example its blood flow, electrical activity, metabolism, and oxygen uptake. Radionuclide reflux imaging is a nuclear medicine scan used to determine whether an infant has gastroesophageal reflux. Phage type involves distinguishing subgroups of bacteria by the type of bacteriophage associated with that specific bacterium. Chromatography is the separation of two or more chemical compounds by their removal at different rates based on differential absorption and solubility.

3

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

Lengthening of telomeres

mRNA splicing

Post-translational modifications

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

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.

4

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

Lengthening of telomeres

mRNA splicing

Post-translational modifications

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

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.

5

Which of the following choices might occur due to a chromosomal translocation?

All of these could result from a chromosome translocation

Abnormal expression of genes located in the translocated region

Formation of non-functional genes that were functional before the translocation event

Gene fusions

Explanation

All of the given choices describe potential outcomes of chromosomal translocations. A translocation event occurs when recombination occurs between non-homologous chromosomes. The result is two chromosomes, each with genetic material from two different sets of genes that are generally kept separate.

Being present in a new environment may affect the expression of a gene (either an increase or decrease). Also, it is possible for translocations to occur in the middle of genes. The result of this could be newly formed non-functional (broken) genes or gene fusions between two coding regions that were originally separate. These alterations of gene expression have been implicated in many human diseases, including various cancers.

6

Which of the following choices might occur due to a chromosomal translocation?

All of these could result from a chromosome translocation

Abnormal expression of genes located in the translocated region

Formation of non-functional genes that were functional before the translocation event

Gene fusions

Explanation

All of the given choices describe potential outcomes of chromosomal translocations. A translocation event occurs when recombination occurs between non-homologous chromosomes. The result is two chromosomes, each with genetic material from two different sets of genes that are generally kept separate.

Being present in a new environment may affect the expression of a gene (either an increase or decrease). Also, it is possible for translocations to occur in the middle of genes. The result of this could be newly formed non-functional (broken) genes or gene fusions between two coding regions that were originally separate. These alterations of gene expression have been implicated in many human diseases, including various cancers.

7

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

H1

H2A

H3

H4

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.

8

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

H1

H2A

H3

H4

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.

9

What is a telomere?

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

The site of attachment of sister chromatids

A special type of chromosome used to help determine gender

A protein that coats chromosomes and helps protect them from degradation

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.

10

What is a telomere?

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

The site of attachment of sister chromatids

A special type of chromosome used to help determine gender

A protein that coats chromosomes and helps protect them from degradation

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.

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