All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #502 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
Which of the following choices might occur due to a chromosomal translocation?
Formation of non-functional genes that were functional before the translocation event
Gene fusions
Abnormal expression of genes located in the translocated region
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 #2 : Help With Chromosome Abnormalities
Which chromosome abnormality affects chromosome 21?
Williams syndrome
Turner syndrome
Down syndrome
Cri-du-chat syndrome
Klinefelter 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 #24 : Dna
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 #25 : Dna
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).
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