GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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GRE Subject Test: Biochemistry, Cell, and Molecular Biology › GRE Subject Test: Biochemistry, Cell, and Molecular Biology

Questions 1 - 10
1

Researchers first identified parts of genes that are spliced out of mRNA and not included in the final protein product by observing that not all of the original gene hybridizes to the cognate mRNA. What are these regions called?

Introns

Exons

Internal transcribed spacers

Inter genic regions

Micro RNAs

Explanation

Introns are regions included in genes that are not actually part of the final protein generated. Scientists first observed that some areas of genes are removed before mRNA translation by visualizing that not all of a gene hybridizes with its cognate mRNA, and hence there are pieces that are spliced out and not used. Note that splicing of introns, like all other post-transational modifications, only occurs in eukaryotes. The function of intron regions is thought to be mostly regulatory.

2

What is the concentration of hydroxide ions in a 1M hydrochloric acid solution?

Explanation

To solve this question we need to first look at the relationship between hydroxide and hydrogen ion concentrations:

where is concentration of hydrogen ions and is the concentration of hydroxide ions. Solve for :

We can solve for the concentration of hydrogen ions in this solution by writing the dissociation of hydrochloric acid in solution:

The question states that it is a 1M solution. Since and are in 1:1 ratio, the concentration of hydrogen ions will equal the concentration ; therefore, . Note that this won’t be the case if the acid was weak. For a weak acid, the concentration of will be less than the concentration of acid, even if it was 1:1 ratio. This occurs because a weak acid does not dissociate completely.

We can now use the to solve for .

Therefore, concentration of hydroxide ions in this solution is

3

What is the concentration of hydroxide ions in a 1M hydrochloric acid solution?

Explanation

To solve this question we need to first look at the relationship between hydroxide and hydrogen ion concentrations:

where is concentration of hydrogen ions and is the concentration of hydroxide ions. Solve for :

We can solve for the concentration of hydrogen ions in this solution by writing the dissociation of hydrochloric acid in solution:

The question states that it is a 1M solution. Since and are in 1:1 ratio, the concentration of hydrogen ions will equal the concentration ; therefore, . Note that this won’t be the case if the acid was weak. For a weak acid, the concentration of will be less than the concentration of acid, even if it was 1:1 ratio. This occurs because a weak acid does not dissociate completely.

We can now use the to solve for .

Therefore, concentration of hydroxide ions in this solution is

4

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.

5

Researchers first identified parts of genes that are spliced out of mRNA and not included in the final protein product by observing that not all of the original gene hybridizes to the cognate mRNA. What are these regions called?

Introns

Exons

Internal transcribed spacers

Inter genic regions

Micro RNAs

Explanation

Introns are regions included in genes that are not actually part of the final protein generated. Scientists first observed that some areas of genes are removed before mRNA translation by visualizing that not all of a gene hybridizes with its cognate mRNA, and hence there are pieces that are spliced out and not used. Note that splicing of introns, like all other post-transational modifications, only occurs in eukaryotes. The function of intron regions is thought to be mostly regulatory.

6

In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?

3 white : 1 pink blossom

1 white : 3 pink blossom

All white blossoms

All pink blossoms

1 white : 1 pink blossom

Explanation

The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.

7

Researchers first identified parts of genes that are spliced out of mRNA and not included in the final protein product by observing that not all of the original gene hybridizes to the cognate mRNA. What are these regions called?

Introns

Exons

Internal transcribed spacers

Inter genic regions

Micro RNAs

Explanation

Introns are regions included in genes that are not actually part of the final protein generated. Scientists first observed that some areas of genes are removed before mRNA translation by visualizing that not all of a gene hybridizes with its cognate mRNA, and hence there are pieces that are spliced out and not used. Note that splicing of introns, like all other post-transational modifications, only occurs in eukaryotes. The function of intron regions is thought to be mostly regulatory.

8

Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

9

Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

10

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.

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