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18 Cards in this Set
- Front
- Back
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A child born to a man and a woman who are both carriers of the mutant allele responsible for cystic fibrosis has a ___ chance of having the disease.
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25% - CF is the most common lethal autosomal recessive disease among Caucasians. Because the disease allele is recessive, there is a 1 in 4 chance that the children of two heterozygous carriers will have the disease.
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A methionine auxotroph...
A. can grow on minimal medium with no supplements. B. can not grow in the presence of methionine. C. can grow on minimal medium supplemented with methionine. D. can not grow on a complete medium. |
C - Nutritional mutants that require supplements in the medium for growth are auxotrophic. A methionine auxotroph requires the amino acid methionine as a supplement.
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A person who was homozygous for the recessive mutant allele h, and was IAi at the ABO locus, would have which blood type?
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O - Individuals homozygous for the recessive mutant allele, h, do not make the H antigen, and therefore, regardless of the presence of IA or IB alleles at the ABO locus, no A or B antigens can be produced.
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In PKU, the absence of enzyme activity affects which step in the phenylalanine metabolism pathway?
A. conversion of tyrosine to melanin B. conversion of phenylalanine to tyrosine C. conversion of phenylalanine to phenylpyruvic acid. D. conversion of phenylpyruvic acid to melanin |
B - The absence of phenylalanine hydroxylase prevents the conversion of the amino acid phenylalanine to the amino acid tyrosine.
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The frequency of cystic fibrosis (CF) in Caucasian populations is ___ the frequency of the disease in people of African descent.
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greater than
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The frequency of PKU in Caucasian populations is approximately
A. 1/10 B. 1/10,000 C. 1/1,000,000 D. 1/1 mil |
1/10,000
PKU occurs in about 1 in 12,000 Caucasian births; it is most commonly caused by a recessive mutation of a gene on chromosome 12 (an autosome) at position 12q24.1, and individuals must therefore be homozygous for the mutation in order to exhibit the condition. |
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The Guthrie test for PKU requires the use of which microorganism?
A. Escherichia coli B. Bacillus subtilis C. Neurospora crassa D. Saccharomyces cerevisiae |
B -All U.S. states require that newborns be screened for PKU. The screen - the Guthrie test - is conducted by placing a drop of blood on a filter-paper disc and placing the disc on solid culture medium containing the bacterium Bacillus subtilis and the chemical b-2-thienylalanine.
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A woman heterozygous for the Lesch-Nyhan allele could have an affected:
son daughter grandson thru her daughter grandson thru her son |
son & grandson thru her daughter -
Lesch-Nyhan syndrome is caused by an X-linked recessive allele. The woman has a 50% chance of passing the allele to her sons and daughters. Only the sons would be affected in this case, but a carrier daughter could give the allele to one of her sons, so there could be an affected grandson. |
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"Inborn errors of metabolism" is a phrase coined by British physician Archibald Garrod in 1908. This phrase refers to
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defects in metabolic enzymes.
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The mutant gene responsible for Tay-Sachs disease is located on:
A. chromo 3 B. chromo 10 C. chromo 15 D. the X chromo |
C - Tay-Sachs disease is caused by homozygosity for a rare recessive mutation of a gene on chromosome 15 at 15q23-q24.
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The mutation responsible for sickle cell disease affects ___ in the hemoglobin gene.
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a single base pair
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The normal version of the mutant gene responsible for albinism in humans encodes an enzyme that converts:
A. phenylalanine to tyrosine. B. DOPA to melanin. C. sine to DOPA. D. phenylalanine to DOPA. |
B - The mutation affects a gene for tyrosinase, an enzyme used in the conversion of tyrosine to DOPA from which the brown pigment melanin derives.
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The one gene-one enzyme hypothesis was proposed by ___ in 1942.
Garrod Beadle/Tatum Meselson/Stahl Morgan |
Beadle & Tatum
From the results of their experiments, Beadle and Tatum proposed that a specific gene encodes a single enzyme. This proposed relationship between an organism's genes and the enzymes that catalyze the steps in a biochemical pathway is called the one gene-one enzyme hypothesis. |
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The study of which genetic disease led Garrod to propose that there is a special relationship between genes and enzymes?
A. phenylketonuria B. sickle cell disease C. Tay-Sachs disease D. Alkaptonuria |
D - Garrod's study of the disease alkaptonuria provided the first evidence of a specific relationship between genes and enzymes.
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The test organism that helped researchers elucidate the one gene-one enzyme hypothesis was:
A. Neurospora crassa B. Saccharomyces cerevisiae. C. Escherichia coli. D. Streptococcus pneumoniae. |
Neurospora crassa
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Which disease is caused by a mutation in a gene located on the X chromosome?
A. PKU B. Albinism C. Lesch-Nyhan D. Tay-Sachs |
Lesch-Nyhan:Lesch-Nyhan syndrome is an ultimately fatal human trait caused by a recessive mutation in an X chromosome gene located at Xq26-q27.2.
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The H antigen is a glycolipid precursor to the blood group antigens A and B. The mutant recessive allele h affects expression of the ABO gene, providing a good example of:
A. dominance interactions B. co-dominance C. epistatis D. polygenic inheritance |
C - Epistasis is the term for one gene masking the expression of another gene.
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Which of the following is characterized as a lysosomal storage disease?
A. PKU B. Tay-Sachs C. sickle cell anemia D. cystic fibrosis |
B - The best-known lysosomal storage disease is Tay-Sachs disease, also called infantile amaurotic idiocy.
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