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Biology & Life Science
Q:
rDNA in eukaryotes is typically redundant.
Q:
Gene duplications provide an explanation for the origin of gene families.
Q:
The chromosomal aberration that causes cri du chat syndrome can be referred to as a segmental deletion.
Q:
Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 36 chromosomes would be triploid.
Q:
Assume that an organism has a haploid chromosome number of 7. There would be 14 chromosomes in a monoploid individual of that species.
Q:
An autotriploid may arise when three sperm cells are involved in fertilization of a single egg.
Q:
Assume that an organism has a diploid chromosome number of 14. There would be 28 chromosomes in a tetraploid.
Q:
Doubling the chromosomes of a sterile species hybrid with colchicine or cold shock is a method used to produce a fertile species hybrid (amphidiploid).
Q:
In Drosophila melanogaster (2n = 8), a fly with seven chromosomes could be called a haplo-IV.
Q:
Chorionic villus sampling (CVS) is sometimes preferred to amniocentesis because results can be provided earlier in the pregnancy.
Q:
An individual with Patau syndrome would be called a triploid.
Q:
An expected meiotic pairing configuration in a triploid would be a trivalent.
Q:
Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 25 chromosomes would be triploid.
Q:
Nondisjunction is viewed as a major cause of aneuploidy.
Q:
The term aneuploidy is synonymous with the term segmental deletion.
Q:
Fragile X syndrome (or Martin-Bell syndrome) is the most common form of inherited mental retardation in humans. Is it more common in males or females? What is FMR1?
Q:
Under what circumstance can an individual with Down syndrome have 46 chromosomes?
Q:
What is meant by the terms acentric and dicentric?
Q:
Clearly illustrate the pairing configuration of an inversion (paracentric) heterokaryotype.
Q:
Inversion heterokaryotypes are often characterized as having reduced crossing over and reduced fertility. Assume that you were examining a strain of organisms you knew to be inversion heterokaryotypes and saw a relatively high number of double chromatid bridges extending between anaphase I nuclei. What would be a likely explanation for this observation? Explain with a labeled diagram.
Q:
Describe Bar mutations in Drosophila melanogaster.
Q:
Provide an example of gene redundancy that occurs in both eukaryotes and prokaryotes.
Q:
Deletions are chromosomal aberrations in which some portion of a chromosome is missing. Describe a method using Drosophila deletions to determine the actual, physical location of a gene.
Q:
Colchicine is an alkaloid derived from plants. What is its effect on chromosome behavior?
Q:
Given that a human normally contains 46 chromosomes, give the chromosome number for each of the following conditions:
Turner syndrome (female, no Barr bodies)
Klinefelter syndrome (male, one Barr body)
Triploid
Down syndrome (trisomic)
Trisomy 13
Q:
Name the polyploid condition that is formed from the addition of an extra set of chromosomes identical to the normal diploid complement of the same species.
Q:
Trisomics are observed in humans; monosomics are not. Why?
Q:
Name two methods used in genetic prenatal diagnostic testing in humans.
Q:
In what way might gene duplication play a role in evolution?
Q:
Describe the maternal age effect associated with Down syndrome.
Q:
What explanation is generally given for lethality of monosomic individuals?
Q:
Recently, a gene located on chromosome 3 in humans, FHIT, has been shown to be associated with the significant human malady known as ________.
A) cancer
B) Huntington disease
C) "mad-cow" disease
D) Klinefelter syndrome
E) XYY/XY mosaicism
Q:
A genomic condition that may be responsible for some forms of fragile X syndrome, as well as Huntington disease, involves ________.
A) plasmids inserted into the FMR-1 gene
B) various lengths of trinucleotide repeats
C) multiple breakpoints fairly evenly dispersed along the X chromosome
D) multiple inversions in the X chromosome
E) single translocations in the X chromosome
Q:
Although the most frequent forms of Down syndrome are caused by a random error, nondisjunction of chromosome 21, Down syndrome occasionally runs in families. The cause of this form of familial Down syndrome is ________.
A) an inversion involving chromosome 21
B) a chromosomal aberration involving chromosome 1
C) too many X chromosomes
D) a translocation between chromosome 21 and a member of the D chromosome group
E) a maternal age effect
Q:
The condition known as cri-du-chat syndrome in humans has a genetic constitution designated as ________.
A) 45, X
B) heteroplasmy
C) 46, 5p-
D) triploidy
E) trisomy
Q:
Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. While there is reduced fertility in both sexes, females have higher fertility than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3(2):6569) summarize data involving children born of Down syndrome individuals. Given the fact that conceptuses with 48 chromosomes (four #21 chromosomes) are not likely to survive early development, what percentage of surviving offspring would be expected to have Down syndrome if both parents have Down syndrome?
A) One-third of the surviving offspring would be expected to have Down syndrome.
B) All the children would be expected to have Down syndrome.
C) None of the surviving offspring would be expected to have Down syndrome.
D) Two-thirds of the surviving offspring would be expected to have Down syndrome.
E) One-half of the surviving offspring would be expected to have Down syndrome.
Q:
Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. Although fertility is reduced in both sexes, females have higher fertility rates than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3(2): 65-69) summarize data involving children born of Down syndrome individuals. Assume that children are born to a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome?
A) One-third of the offspring would be expected to have Down syndrome.
B) Two-thirds of the offspring would be expected to have Down syndrome.
C) All the children would be expected to have Down syndrome.
D) None of the offspring would be expected to have Down syndrome.
E) One-half of the offspring would be expected to have Down syndrome.
Q:
The condition that exists when an organism gains or loses one or more chromosomes but not a complete haploid set is known as ________.
A) polyploidy
B) euploidy
C) aneuploidy
D) triploidy
E) trisomy
Q:
In Drosophila, sex is determined by the ratio of the number of X chromosomes to the number of haploid sets of autosomes.
Q:
In Drosophila, the female is the heterogametic sex.
Q:
Dosage compensation is accomplished in humans by inactivation of the Y chromosome.
Q:
A typical XX human female has one Barr body.
Q:
An individual with Turner Syndrome has no Barr bodies.
Q:
An individual with Klinefelter syndrome generally has one Barr body.
Q:
Normally in humans, all the sons of a female homozygous for a sex-linked recessive gene will inherit that trait.
Q:
Normally in humans, all the sons of a male showing a sex-linked phenotype will inherit the trait.
Q:
In humans, the male is the homogametic sex.
Q:
In Drosophila, the sex of a fly with the karyotype XO:2A is ________.
Q:
Data produced by C. Bridges in the early part of this century indicate that sex in Drosophila is determined by ________.
Q:
Assuming a normal number of autosomes, what would be the sex of the following: XXY mouse, XXY Drosophila?
Q:
Give the sex of the following organisms assuming that the autosomes are present in the normal number.
Q:
In Drosophila, an individual female fly was observed to be of the XXY chromosome complement (normal autosomal complement) and to have white eyes as contrasted with the normal red eye color of wild type. The female's mother and father had red eyes. The mother, however, was heterozygous for the gene for white eyes. Knowing that white eyes are X-linked and recessive, present an explanation for the genetic and chromosomal constitution of the XXY, white-eyed individual. It is important that you state in which parent and at what stage the chromosomal event occurred that caused the genetic and cytogenetic abnormality.
Q:
In Drosophila, an individual female fly was observed to be of the XXY chromosome complement (normal autosomal complement) and to have white eyes as contrasted with the normal red eye color of wild type. The female's father had red eyes, and the mother had white eyes. Knowing that white eyes are X-linked and recessive, present an explanation for the genetic and chromosomal constitution of the XXY, white-eyed individual. It is important that you state in which parent and at what stage the chromosomal event occurred that caused the genetic and cytogenetic abnormality.
Q:
Give the sex-chromosome constitution (X and Y chromosomes) and possible genotypes of offspring resulting from a cross between a white-eyed female (Xw XwY) and a wild-type male (normal chromosome complement) in Drosophila melanogaster. Include all zygotic combinations whether viable or inviable.
Q:
What is the composition of a Barr body?
Q:
Dosage compensation in mammals typically involves the random inactivation of one of the two X chromosomes relatively early in development. Such X chromosome inactivation often leads to phenotypic mosaicism. Assume that black fur in cats is due to the X-linked recessive gene b, whereas its dominant allele B produces yellow fur. A Bb heterozygote is a mosaic called "tortoise shell" or "calico." Using appropriate gene symbols, diagram a mating between a black male and a calico female. Give the phenotypes and genotypes of all the offspring.
Q:
What can cause phenotypic mosaicism for X-linked genes in female mammals?
Q:
How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?
Q:
Dosage compensation leads to a variety of interesting coat color patterns in certain mammals. For instance, a female cat that is heterozygous for two coat color alleles, say black and orange, will usually have the "calico" or mosaic phenotype. Describe the chromosomal basis for the mosaicism (calico) in the female. Explain why chromosomally normal male cats do not show the mosaic phenotype, but XXY male cats can be calico.
Q:
A cross is made between a female calico cat and a male cat having the gene for black fur on his X chromosome. What fraction of the offspring would one expect to be calico?
Q:
A color-blind, chromatin-positive male child (one Barr body) has a maternal grandfather who was color blind. The boy's mother and father are phenotypically normal. Construct and support (using appropriately labeled diagrams) a rationale whereby the chromosomal and genetic attributes of the chromatin-positive male are fully explained.
Q:
Describe three distinct genetic regions of the human Y chromosome.
Q:
Describe an experiment in which transgenic mice were used to identify the male-determining region of the Y chromosome.
Q:
Studies done in the 1960s suggested that individuals with the XYY condition were prone to criminal behavior. What conclusions presently seem appropriate concerning this chromosomal condition?
Q:
Klinefelter and Turner syndromes have how many chromosomes, respectively?
Q:
Although triple-X human females typically have normal offspring, what kinds of gametes, with respect to the X chromosomes, would you expect from such XXX females? Draw meiotic stages that show the gametes that are expected to be produced.
Q:
A color-blind woman with Turner syndrome (XO) has a father who is color blind.
Given that the gene for the color-blind condition is recessive and X-linked, provide a likely explanation for the origin of the color-blind and cytogenetic conditions in the woman.
Q:
Under what condition might a human female have the XY sex chromosome complement?
Q:
A small part of the human Y chromosome contains the gene that is responsible for determining maleness. What is the name of this gene?
Q:
What particular karyotype was at one time considered to be related to criminal predisposition?
Q:
Individuals have been identified who have two different karyotypes, such as 45, X/46, XY or 45, X/46, XX. Such individuals are called ________.
Q:
List three abnormalities involving numbers of X chromosomes.
Q:
The accompanying figure is a pedigree of a fairly common human hereditary trait; the boxes represent males and the circles represent females. Filled in symbols indicate the abnormal phenotype. Given that one gene pair is involved, a) Is the inheritance pattern X-linked or autosomal?
b) Give the genotype of each individual in the pedigree. If more than one genotypic possibility exists, present all possible alternatives.
Q:
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is inherited as an X-linked recessive gene in humans. A woman whose father suffered from G6PD marries a normal man.
a) What proportion of their sons is expected to be G6PD?
b) If the husband were not normal, but were G6PD deficient, would you change your answer in part (a)?
Q:
Assume that you are told that a particular organism, Drosophila, has the XO chromosome complement. You are also told that the autosomal complement is a normal 2n. You know that in humans the XO complement is female determining. Would you be correct in assuming that the Drosophila sex for XO is also female? Choose the answer that includes the correct explanation.
A) Yes, because sex determination in humans and insects is essentially the same.
B) No, sex determination in Drosophila is dependent on the presence or absence of the Y chromosome.
C) No, the chromosomal basis for sex determination in Drosophila is based on the balance between the number of X chromosomes and haploid sets of autosomes.
D) Yes, the presence of an X chromosome determines a female in both organisms.
E) No, it takes two X chromosomes to produce a female in humans and a Y chromosome to produce a male in Drosophila.
Q:
For an individual with the XXY chromosomal composition, the expected number of Barr bodies in interphase cells is ________.
A) variable
B) one
C) two
D) three
E) zero
Q:
In Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of ________.
A) telomeres
B) centromeres
C) X chromosomes
D) Y chromosomes
E) nucleolar organizers
Q:
Assume that a man who carries an X-linked gene has children. Assuming normal meiosis and random combination of gametes, the man would pass this gene to ________.
A) half of his daughters
B) all of his daughters
C) all of his sons
D) half of his sons
E) all of his children
Q:
Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition?
A) 47, XXY
B) 47, 21+
C) 45, X
D) 47, XYY
E) triploidy
Q:
In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.
A) a portion of the Y chromosome
B) one X chromosome
C) a balance between the number of X chromosomes and the number of haploid
D) sets of autosomes
E) high levels of estrogen
F) multiple alleles scattered throughout the autosomes