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

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

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

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #12 : Dna

If a double strand break (DSB) is not repaired during G1 phase of the cell cycle, what type of replication error would result during S phase at the site of the DSB?

Possible Answers:

Reversed replication fork

Gap in the newly replicated DNA strand

Catenane formations

Collapsed replication fork

Correct answer:

Collapsed replication fork

Explanation:

Unrepaired doublestrand breaks will result in collapse of the DNA fork because the replication fork cannot continue beyond the area that has the doublestrand break. The other answers require the presence of at least one continuous strand of DNA.

Example Question #151 : Molecular Biology And Genetics

What term best describes when RNA polymerase binds promoters and synthesizes and releases short mRNA transcripts in cycles before the RNA holoenzyme leaves the  promoter? 

Possible Answers:

Cyclic initiation

DNA scrunching 

Abortive initiation

Repressive transcription 

Promoter clearance

Correct answer:

Abortive initiation

Explanation:

The correct answer is abortive initiation. This is a normal transcription event is found in both prokaryotes and eukaryotes and occurs prior to promoter clearance, or the event when RNA polymerase escapes the promoter and begins elongation of synthesized transcripts. Abortive initiation is thought to occur when the RNA polymerase complex is not stable enough on the DNA. DNA scrunching describes the mechanism by which RNA polymerase transcribes, rather than RNA polymerase moving along DNA, it actually pulls DNA into the complex and unwinds it. 

Example Question #22 : Dna Replication And Repair

Branched nucleic acid structures containing 4 double-stranded arms that are intermediates in genetic recombination and DNA repair are best known as? 

Possible Answers:

Replication fork

None of these

Pyrimidine dimers

Spliceosome 

Holliday junction

Correct answer:

Holliday junction

Explanation:

The correct answer is Holliday junction. These intermediates in genetic recombination have symmetrical sequence and are mobile to preserve specific base pairing at recombination and damage loci. Repair enzymes recognize and subsequently localize to this DNA structure to facilitate locus specific enzymatic activity. 

Example Question #1 : Chromosomes

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

Possible Answers:

Phage type

Radionuclide reflux imaging

Chromatography

Physiological imaging

Karyotype

Correct answer:

Karyotype

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. 

Example Question #1 : Chromosomes

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

Possible Answers:

Abnormal expression of genes located in the translocated region

All of these could result from a chromosome translocation

Gene fusions

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

Correct answer:

All of these could result from a chromosome translocation

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. 

Example Question #2 : Chromosomes

Which chromosome abnormality affects chromosome 21?

Possible Answers:

Turner syndrome

Down syndrome

Klinefelter syndrome

Williams syndrome

Cri-du-chat syndrome

Correct answer:

Down syndrome

Explanation:

Down syndrome is also referred to as trisomy 21. In about one in every 900 births, the child has an extra copy of the 21st chromosome.

Klinefelter syndrome is the result of a male being born with two X chromosomes and one Y chromosome. A deletion on the short arm of chromosome 5 causes Cri-Du-Chat syndrome; these children have respiratory problems and distinctive facial features. Williams syndrome is the result of genetic material missing from chromosome 7—in particular the gene for elastin, which causes disorders of the circulatory system and heart. A missing or incomplete X chromosome causes Turner syndrome. People who have Turner syndrome develop as females. 

Example Question #2 : Chromosomes

In the human population, what is the chance that a baby is born with a chromosomal abnormality (due to aneuploidy, deletions, or translocations)?

Possible Answers:

Correct answer:

Explanation:

About  newborns have a chromosomal abnormality, whether due to inheritance or as a result of meiotic events such as nondisjunction. 

Example Question #157 : Molecular Biology And Genetics

 of human pregnancies are spontaneously aborted in the first three months of development. Of these, what percent of the unsuccessful pregnancies are due to chromosomal abnormalities? 

Possible Answers:

Correct answer:

Explanation:

Nearly half of all spontaneously aborted pregnancies are due to chromosomal abnormalities. This includes aneuploidy (an excess or loss of 1+ chromosomes), deletions (a loss of a piece of a chromosome), and translocations (the transfer of one chromosome piece to another).

Example Question #1 : Chromosomes

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

Possible Answers:

H2A

H3

H4

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 #504 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What is a telomere?

Possible Answers:

A protein that coats chromosomes and helps protect them from degradation 

The site of attachment of sister chromatids 

A special type of chromosome used to help determine gender

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

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.

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

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