GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Chromosome Abnormalities

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

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Example Questions

Example Question #1 : Help With Chromosome Abnormalities

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

Possible Answers:

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

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 : Help With Chromosome Abnormalities

Which chromosome abnormality affects chromosome 21?

Possible Answers:

Cri-du-chat syndrome

Klinefelter syndrome

Turner syndrome

Down syndrome

Williams 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 #3 : Help With Chromosome Abnormalities

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 #4 : Help With Chromosome Abnormalities

 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).

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

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