Human Genetics Flashcards
Red-green color blindness is X-linked in humans. If a male is red-green color blind, and both parents have normal color vision, which of the male’s grandparents is most likely to be red-green color blind?
A. maternal grandmother
B. maternal grandfather
C. paternal grandmother
D. paternal grandfather
E. either grandfather is equally likely
B. maternal grandfather
In this problem, an X-linked recessive allele is passed from an affected male, to a daughter who is a heterozygous carrier, and subsequently to an affected grandson.
When RFLP analysis is used to search for a human gene, the strategy is to first locate?
A. a known gene on the same chromosome
B. an homozygous individual with a simple RFLP pattern
C. a DNA sequence anywhere on the same chromosome
D. any DNA marker co-inherited with the genetic trait of interest
E. an exon of the disease gene
D. any DNA marker co-inherited with the genetic trait of interest
Genes and anonymous DNA markers that are located near each other on the same chromosome are “linked,” and do not segregate independently during meiosis.
Which of the following is not one of the objectives of the Human Genome Project?
A. Create a detailed genetic map of every human chromosome, with an average of 2-5% recombination frequency between markers.
B. Obtain a detailed physical map of every human chromosome, based on overlapping recombinant DNA molecules cloned as yeast artificial chromosomes.
C. Clone human beings.
D. Determine the sequence of all expressed human genes by cDNA cloning and sequencing.
E. Determine the complete DNA sequence of each human chromosome.
C. Clone human beings
Cloning humans, a horrifying thought just a few months ago, is now being debated very seriously.
A couple has a female child with Tay Sachs disease, and three unaffected children. Neither parent nor any of the four biological grandparents of the affected child has had this disease. The most likely genetic explanation is that Tay Sachs disease is inherited as a(n) ______________ disease.
A. autosomal dominant
B. autosomal recessive
C. sex-linked recessive
D. sex-linked dominant
E. cannot make a reasonable guess from this information
B. autosomal recessive
The disease is recessive because both parents are unaffected, and autosomal because a female child is affected but her father is not.
A human geneticist determined the pedigree shown in the diagram with filled symbols showing the affected individuals. How is this pattern of inheritance described?
A. autosomal dominant
B. autosomal recessive
C. sex-linked recessive
D. sex-linked dominant
E. none of these
A. autosomal dominant
A genetic trait that is passed from generation to generation to generation, from both fathers to daughters and mothers to daughters, is typically autosomal dominant.
Diagnosis of chromosome aneuploidy of unborn children is normally done by a combination of amniocentesis, cell culture, and _______________.
A. enzyme assay.
B. RFLP analysis.
C. pedigree analysis.
D. karyotyping.
E. somatic cell fusion.
D. karyotyping
A karyotype is used to display the number, types and appearance of chromosomes. Analysis of chromosomes of an unborn child can be carried out with cells obtained from the amniotic fluid within the mother’s uterus.
Which statement about Down’s syndrome is false?
A. The frequency increases dramatically in mothers over the age of 40.
B. The cause is a non-disjunction when chromosomes do not separate during the first meiotic division.
C. Affected individuals have an extra autosome.
D. The long time lag between onset of meiosis in ovarian tissue (during fetal development) and its completion (at ovulation) is most likely the reason for increased incidence in older mothers.
E. None, all statements are true.
E. None, all statements are true.
Down syndrome is also known as trisomy 21.
A human male carrying an allele for a trait on the X chromosome is:
A. heterozygous
B. homozygous
C. hemizygous
D. monozygous
E. holozygous
C. hemizygous
Males have a single copy of the X-chromosome.
Why would you predict that half of the human babies born will be males and half will be females?
A. Because of the segregation of the X and Y chromosomes during male meiosis.
B. Because of the segregation of the X chromosomes during female meiosis.
C. Because all eggs contain an X chromosome.
D. Because, on average, one-half of all eggs produce females.
E. Because of the formation of the Barr body early during embryonic development.
A. Because of the segregation of the X and Y chromosomes during male meiosis.
Sex is determined by the sex chromosome in the sperm that fertilizes the female egg. Half of the sperm have an X-chromosome and half have a Y-chromosome.
A man who had purple ears came to the attention of a human geneticist. The human geneticist did a pedigree analysis and made the following observations:
In this family, purple ears proved to be an inherited trait due to a single genetic locus. The man’s mother and one sister also had purple ears, but his father, his brother, and two other sisters had normal ears. The man and his normal-eared wife had seven children, including four boys and three girls. Two girls and two boys had purple ears. The purple-ear trait is most probably:
A. autosomal, dominant
B. autosomal, recessive
C. sex-linked, dominant
D. sex-linked, recessive
E. cannot be determined from this information
A. autosomal, dominant
A genetic trait that is passed from generation to generation to generation, from both fathers to daughters and mothers to daughters, is typically autosomal dominant.
Klinefelter’s syndrome (XXY) is an example of chromosomal aneuploidy that can be readily diagnosed by:
A. Behavioral analysis
B. Somatic cell genetics
C. Karyotyping
D. Biochemical analysis
E. Pedigree analysis
C. Karyotyping
A karyotype is used to display the number, types and appearance of chromosomes. An extra X chromosome in a Klinefelter’s individual could be readily diagnosed by karyotyping.
By examining a number of somatic-cell hybrid lines for enzyme activities and their human chromosome constitution, scientists can determine
A. on which human chromosome the gene for a particular enzyme is located
B. the number of genes for enzymes in the human genome
C. the number of chromosomes in the human genome
D. the number of human chromosomes in each cell
E. Scientists cannot determine any of these things
A. on which human chromosome the gene for a particular enzyme is located
It is possible to correlate enzyme activity with a specific chromosome in a somatic-cell hybrid
Which is NOT a common method used in human genetic analysis?
A. pedigree analysis
B. karyotyping
C. RFLP analysis
D. test cross
E. somatic cell genetics
D. test cross
Deliberate crosses are not used in studying human inheritance.
A Barr body is:
A. the cause of Down’s syndrome
B. an amplified gene
C. a polytene chromosome
D. a ribonucleoprotein particle
E. an inactivated X chromosome
E. an inactivated X chromosome
One of the two X chromosomes in female somatic cells is visualized as a densely staining body within the nucleus known as a “Barr body.”
Which of the following is a useful marker for genetic or physical mapping of human chromosomes? (More than one answer could be correct)
A. RFLPs, “restriction fragment length polymorphisms”
B. ESTs, “expressed sequence tags”
C. STRPs, “short tandem repeat polymorphisms”
D. STSs, “sequence tagged sites”
E. all of the above
E. all of the above
RFLPs are genetic markers detected by Southern hybridization. ESTs, STRPs, and STSs are markers detected by PCR.
