All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
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?
Reversed replication fork
Gap in the newly replicated DNA strand
Catenane formations
Collapsed replication fork
Collapsed replication fork
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?
Cyclic initiation
DNA scrunching
Abortive initiation
Repressive transcription
Promoter clearance
Abortive initiation
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?
Replication fork
None of these
Pyrimidine dimers
Spliceosome
Holliday junction
Holliday junction
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?
Phage type
Radionuclide reflux imaging
Chromatography
Physiological imaging
Karyotype
Karyotype
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?
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
All of these could result from a chromosome translocation
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?
Turner syndrome
Down syndrome
Klinefelter syndrome
Williams syndrome
Cri-du-chat syndrome
Down syndrome
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)?
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?
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?
H2A
H3
H4
H1
H1
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?
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
A region of nucleotide sequence that repeats at the ends of chromosomes
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.