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Exam 2 Quiz Questions
Terms in this set (70)
In a cross between two individuals, AaBbCc and aabbcc, how many different genotypes are possible in the offspring (assuming independent assortment)?
The presence of which chromosome determines sex in human beings?
Red-green colorblindness is an X-linked recessive trait in humans. If a male is red-green colorblind, and both parents have normal color vision, which of the male's grandparents is most likely to be red-green colorblind?
A reciprocal cross is used to determine which of the following?
if a trait is autosomal or sex-linked
What are gene loci?
the physical location of a gene on a chromosome, the loci will not vary between individuals of the same species
If a male is produced from an unfertilized haploid egg, this is an example of what type of sex determination system?
A diploid individual with only one copy of a gene is called __________:
A chromosome is stained with Giemsa stain and the banding pattern analyzed by a cytogeneticist. What would the nomenclature 3q23 mean in this analysis?
associated with chromosome 3, long arm, band 23
What is the name of the DNA protein network seen in eukaryotic nuclei?
What is a Barr body?
an inactivated X chromosome; it is a condensed, darkly staining structure in the nucleus
How does Drosophila compensate for the fact that males have one X chromosome and females have two?
the genes on the X chromosome are hyperactivated to increase their expression to that of the XX female
A chromosome that contains the same set of genes as the chromosome to which it is compared is called:
Recessive X linked traits appear more frequent in humans than recessive autosomal traits. Why?
males only have one X chromosome and so only need to inherit one recessive allele to have the trait
Mendel's law of independent assortment, as applied to the behavior of chromosomes in meiosis, means that _______.
two genes will show independent assortment if located on different chromosomes
Mendel's law of segregation, as applied to the behavior of chromosomes in meiosis, means that _______.
alleles of a gene separate from each other when homologues separate in meiosis I
In genetics, "n" describes:
1. one set of chromosomes
2. the haploid genome
3. all of the genes in a diploid organism
both 1 and 2
A gene that is only seen in one copy, such as on the X chromosome in human males is termed:
Studies of X-linked inheritance and sex chromosomes provided direct evidence for which of the following?
chromosomal theory of inheritance
Which of the following is a true statement about eukaryotic chromosomes?
genes are situated at different loci on the chromosome, each locus is in the same location between individuals of the same species
In birds, the color of the feathers is often determined by sex-linked genes. The lutino mutation in cockatiels is similar to the albino mutation in mammals as it leads to a white bird with red eyes. The lutino allele is inherited in a sex-linked recessive pattern. If a male lutino cockatiel is mated with a female gray wildtype cockatiel, which proportion of their female offspring will likely have lutino feathering? (Keep in mind that birds use a different sex determination system than mammals!)
Which of the following does a cytogeneticist study?
analysis of stained chromosomes
Which of the following describes the failure of chromosomes to separate during anaphase of meiosis?
The process of stopping dividing cells in mitosis to prepare them for cytological analysis disables what?
the mitotic spindle
This image shows a human karyotype from an baby boy born with a heart defect and multiple other health issues leading to a very poor prognosis of survival. What is the diagnosis for this case?
In a diploid organism, deletion of part of a chromosome makes part of the genome:
Which of the following algebraic expressions would denote a trisomic organism?
2n + 1
This image shows a human karyotype. This individual is a ______.
Amniocentesis of a pregnant mother is a method that allows for _______.
genetic testing of the embryo
This image shows a human karyotype. This individual is a ______.
female with XXX syndrome
Given the following sequence of genes on a chromosome, determine what change in chromosome structure has occurred. (The * indicates the centromere.)
Before: A B C D
E F G H After: A C D
E F G H
Which of the following chromosomal combinations could be classified as polyploidy?
AAA BBB CCC
Down syndrome is a condition based on an extra chromosome 21. How would you write the karyotype of a male with this disorder?
47, XY, +21
When two pieces of two non-homologous chromosomes are interchanged without a net loss of genetic material, this is termed:
The ploidy of an organism is:
the number of sets of chromosomes it possesses
This image shows a human karyotype from an baby girl born severely underweight and with multiple birth defects indicative of a genetic disorder. What is the diagnosis for this case?
The type of chromosome rearrangement where a segment is detached, flipped 180o, and reattached to the rest of the chromosome is called:
Klinefelter and Turner syndrome are examples of which of the following?
sex chromosome aneuploidy
Which of the following chromosome mutations rarely has an effect on the phenotype of the individual who carries it?
The following karyotype was found in a prenatal diagnostic of an unborn child's chromosomes. Is there a genome abnormality present, and if so, which type?
yes, this child has a trisomy
A karyotype is a(n) _________.
Photographic representation of the chromosomes of a cell
When testing whether two traits are linked in a testcross, your null hypothesis for the chi square analysis should be _______.
that the traits are assorting independently
In a mapping experiment involving three genes on the same chromosome, the phenotypic class with the least number of offspring represents what?
double crossover events
While mapping two genes in Drosophila you observe 30 recombinants among 200 total offspring. What is the distance between these genes?
15 map units
We wish to know whether two genes in Drosophila are linked. The first trait is vestigial wings (vg), which is recessive to normal wings (vg+). A second trait, brown eyes (bw) is recessive to normal eyes (bw+). A female fly who is heterozygous for these traits is crossed to a male fly who is homozygous recessive. The following offspring are produced: 92 vg+ bw+ 154 vg+ bw 158 vg bw+ 96 vg bw When doing a chi square analysis to test for linkage, what is the expected number of offspring in each phenotypic class of this cross?
When one crossover inhibits the occurrence of another, this is called:
What is cytogenetic mapping?
localizing previously mapped genes to cytological markers, such as bands on chromosomes
What is the physical mechanism for recombination?
What is significant about recombination in terms of the evolutionary process?
recombination can allow favorable alleles to come together in an organism
What is the maximum recombination rate that you can observe between genes on the same chromosome due to crossing over in meiosis?
In Drosophila, a cross was made between females expressing three X-linked recessive traits, scute bristles (sc), sable body (s), and vermillion eyes (v), and wild type males (+ indicates wild type alleles). In the F1 generation, all females were wild type, while all the males expressed all three mutant traits. The cross was carried to the F2 generation and 1000 offspring were counted, with the following results. No determination of sex was made in the F2 generation. sc s v 314 sc s + 10 sc + + 156 sc + v 46 + s + 30 + s v 150 + + v 14 + + + 280 What were the parental genotypes?
+ + + and sc s v
You are performing a three-point test cross in order to map the order and distance between three genes, designated X, Y, and Z, and you obtain the following results:
Which genes exhibit coupling (cis) configuration?
X and Y
In Drosophila, a cross was made between females expressing three X-linked recessive traits, scute bristles (sc), sable body (s), and vermillion eyes (v), and wild type males (+ indicates wild type alleles). In the F1 generation, all females were wild type, while all the males expressed all three mutant traits. The cross was carried to the F2 generation and 1000 offspring were counted, with the following results. No determination of sex was made in the F2 generation. What is the proper order of the genes on the X chromosome?
sc - v - s
Suppose you have constructed the following genetic map:
A 13.2 mu B 25.4 mu C
If you conducted a mapping cross and obtained 1000 offspring, how many individuals would you expect to have phenotypes that show recombination between A and B?
Which of the following defines the principle of linkage in general?
two or more genes that are physically connected on a chromosome and transmitted to the next generation as a group
For a given heterozygote, five genes are arranged in cis configuration in this order:
Which of the following gametic combinations would you expect to observe as a result of a single crossover?
During a dihybrid cross involving two linked genes, 14% of the resulting gametes showed a recombinant genotype. These two linked genes are _____ map units apart.
The middle gene of a three gene mapping experiment can be determined by examining the genotypes of which of the following?
offspring that exhibit double crossover events
To test for gene linkage, a testcross is always performed between the individual that is heterozygous for the genes to be tested and an individual who is ____________.
Homozygous recessive for the genes
You have calculated the interference value to a given mapping experiment to be 0.3 (30%). What does this mean?
30% fewer double crossovers occurred than expected.
In a two-point test cross, which of the following is true?
the average of the number of recombinant offspring indicates the relative distance between the two genes
In birds, the color of the feathers is often determined by sex-linked genes. The lutino mutation in cockatiels is similar to the albino mutations in mammals as it leads to a white bird with red eyes. The lutino allele is inherited in a sex-linked recessive pattern.
If a male lutino cockatiel is mated with a female gray wildtype cockatiel, which percentage of their female and male offspring will likely have lutino feathering, respectively?
100% lutino females and 0% lutino males
You are helping out with feeding the cats in a feral cat colony. You notice that the cats in this colony are all either black, orange, or torties (with black and orange patches). You find an abandoned litter of kittens that consists of an orange female, two tortie females, two orange males and a black male. What are the colors of the parents for this litter of kittens?
calico mother and orange father
Cancer cells mutate very rapidly. The karyotype below was found in a tumor excised from a human patient. What type of mutations happened here? Select all that apply.
all of these mutations occurred
You have identified three linked recessive traits in German cockroaches, which you decide to call a, b and d. You cross a female who is heterozygous for the three loci with a homozygous recessive male. You obtain the following phenotypes in the F2 offspring (+ indicates wild type): What is the order of these genes on the chromosome and the distances between them?
d is in the middle 14.6 mu from a and 12.2 mu from b
If you conducted a typical mapping cross and obtained 1000 offspring, how many individuals would you expect to have phenotypes that show recombination between the loci for short/long legs and purple/red eyes based on this map?
About 70% of white North Americans can taste the chemical PTC (phenylthiocarbamide). The ability to taste this chemical is determined by the dominant allele T while the inability to taste it is determined by the recessive allele t.
Assuming that the population of white North Americans is in Hardy-Weinberg equilibrium, what are the allele frequencies for T and t?
T: 0.45; t: 0.55
You are studying the local population genetics of phenylthiocarbamide-tasting ability and have collected data on the population of a small town in an isolated Appalachian valley. Thanks to a new PCR-based molecular gene test, you are able to distinguish between homozygote and heterozygote individuals in the group of people who can taste the chemical. You have identified: What are the frequencies of the alleles T and t in this local population?
T: 0.416; t: 0.584
The frequency of cystic fibrosis, caused by a homozygous recessive condition, is approximately 0.04% (1 in every 2,500 births) in those of European descent. What would be the estimated frequency of carriers (heterozygous genotype) in this population?
Cystic fibrosis often leads to infertility, and therefore should have a selection coefficient close to 1. Nevertheless, it occurs with much higher frequency among people of European descent than other recessive disorders. What could be a possible reason for its frequency being unexpectedly high in European populations?
Heterozygote advantage under conditions found in Europe
Given the following data set, calculate the proportional contributions of each genotype to the next generation. What type of selection is demonstrated by this genetic trait?
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