All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #1 : Chromosomes
Which term refers to a picture of the chromosomes of a single cell, arranged in descending order of size?
Radionuclide reflux imaging
Physiological imaging
Chromatography
Karyotype
Phage type
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 #2 : Chromosomes
Which of the following choices might occur due to a chromosomal translocation?
Gene fusions
Abnormal expression of genes located in the translocated region
Formation of non-functional genes that were functional before the translocation event
All of these could result from a chromosome translocation
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 #3 : Chromosomes
Which chromosome abnormality affects chromosome 21?
Cri-du-chat syndrome
Klinefelter syndrome
Williams syndrome
Turner syndrome
Down 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 #4 : 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 #5 : Chromosomes
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 #6 : Chromosomes
Which of the following histone proteins is NOT in the nucleosome core of chromatin?
H3
H2A
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 #1 : Help With Chromosome Structure And Function
What is a telomere?
A special type of chromosome used to help determine gender
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 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.
Example Question #7 : Chromosomes
The __________ is the end of a chromosome that is elongated by an enzyme known as __________.
centromere . . . telomerase
centromere . . . extendase
telomere . . . telomerase
telomere . . . extendase
telomere . . . telomerase
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 #1 : Chromosomes
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
Lengthening of telomeres
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 #1 : Chromosomes
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?
Cannot be determined from the information given
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.
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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
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