PCB 3603 Questions
If thymine makes up 15% of the bases, what percentage of the bases must be cytosine?
35%
Cellular organelles with inheritance independent of the nucleus are_____________ and ____________
Chloroplasts and mitochondria
When cells withdraw from the continuous cycle and enter a "quiescent" phase, they are said to be in what stage?
G0
Which modes of inheritance are influenced by the sex of the individual?
X linked, y linked, sex linked
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?
0%
Ability to roll the tongue is caused by a dominant allele. A woman is a "roller" but one of her parents is not. The woman is expecting a child with a man who is a "nonroller". What is the probability that their child will be a roller?
1/2
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AABBCCdd?
1/256
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?
1/4
In the following cross, what proportion of individuals will have the bombay phenotype? AB Hh x AB Hh
1/4
One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia?
1/4
What is the probability of the embryo in line III inheriting the trait shown in this pedigree? [image of pedigree]
1/4
10% recombination is equal to how many map units?
10 mu
If they live long enough, the penetrance of individuals carrying the Huntington's Disease allele will be what?
100%
In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with white flowers, what proportion of the offspring will have pink flowers?
100%
In a healthy female, how many secondary oocytes would be expected to form from 100 primary oocytes? How many first polar bodies would be expected from 100 primary oocytes?
100; 100
A typical somatic cell has 32 chromosomes, how many chromosomes are expected in each gamete
16
A diploid somatic cell from a rat has a total of 42 chromosomes (2n=42). As in humans, sex chromosomes determine sex:XX in females and XY in males. What is the total number of telomeres in a rat cell in G2?
168
With incomplete dominance, a likely ratio resulting from a monohybrid cross would be
1:2:1
What types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair where all the genotypic combinations are of equal viability
1:2:1, 3:1
Mitosis ends with _______, while meiosis ends with _______
2 diploid cells, 4 haploid cells
Myrmecia pilosula actually consists of several virtually identical, closely related species, with females having chromosome numbers of 18, 20, 32, 48, 60, 62, and 64. Assume one crossed a female of species (A) with 32 chromosomes and a male of species (B) with 9 chromosomes (males are haploid, and each gamete contains the n complement). How many chromosomes would one expect in the body (somatic) cells of the female offspring?
25
A trihybrid cross is a cross b/w two individuals who are heterozygous for three genes. Assuming these three genes are unlinked and assorting independently, what segregation ration would be observed?
27:9:9:9:3:3:3:1
The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring of a cross were made between a male heterozygous for the lethal allele and a normal female?
2:1 male to female
The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes the death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for lethal allele and a normal female?
2:1 male to female
In one strand of DNA, the nucleotides sequence is : 5 - ATGC - 3. The complementary sequence in the other strand must be
3 - TACG - 5
In one strand of DNA, the nucleotide sequence is a 5'-ATGC-3'. The complementary sequence in the other strand must be:
3'-TACG-5'
Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition?
47, XXY
Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism. If you examined 200 primary oocytes, in how many would you expect to see a chiasma between the two loci mentioned above?
48
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, What is the chance of producing an offspring with the homozygous recessive phenotype
50%
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
50%
The horse (Equus caballus) has 32 pairs of chromosomes, whereas the donkey (Equus asinus) has 31 pairs of chromosomes. How many chromosomes would be expected in the somatic tissue of a mule?
63
How many different F2 phenotypes would you expect in a cross with four heterozygous gene pairs?
81
In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically ABCD?
81/256
Assume that a dihybrid cross is made in which the genes' loci are autosomal, independently assorting, and incompletely dominant. How many different phenotypes are expected in the offspring?
9
Assuming Mendel's Second Law is correct, what is the expected segregation ratio for traits in a dihybrid cross?
9:3:3:1
Genetic differences within a given linkage group
?
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?
A color-blind female
Red-green color blindness is X-linked recessive. A woman with normal vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?
A color-blind female
In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ___
A portion of the Y chromosome
Which of the following parental genotypes will produce only heterozygous F1 offspring?
AA x aa
Which of the following human genotypes is associated with Klinefelter syndrome?
All of the above
Genes come in different versions is called
Alleles
An allele is
An alternate form of a gene
Which types of ratios are likely to occur in crosses (F2) when one is dealing with two interacting, epistatic gene pairs?
Answer: 9:7, 9:3:4, 12:3:1, 15:1
Genetic distances within a given linkage group
B and C [would definitely prefer to see the options here]
Genetic distances within a given linkage group:
Both B and C
What conditions are likely to apply if the progeny from the cross AaBb X AaBb appears in the 9:3:3:1 ratio?
Complete dominance Independent assortment No gene interaction
During interphase of the cell cycle:
DNA content essentially doubles
Genetic information can be carried in which of the following biomolecules?
Either DNA or RNA
Mice homozygous for mutations in one gene exhibit polydactyly (i.e. extra toes) while in another gene (limb deformity), homozygous mutants lack all parts of the limb below the wrist. A mutant that is doubly homozygous for extra toes and limb deformity mutations will NOT exhibit polydactyly because it is missing the distal limbs, where the toes are located. This type of genetic relationship is called
Epistasis
Assume that an organism has a diploid chromosome number of six. Two chromosomal pairs are telocentric, and the other pair is metacentric. Assume that the sex chromosomes are morphologically identical. The drawing above could represent which stage(s)?
First polar body (metaphase) Secondary oocyte (metaphase) Secondary spermatocyte
When cells withdraw from the continuous cell cycle and enter a "quiescent" phase, they are said to be in what stage?
G0
When cells withdraw from the continuous cell cycle and enter a "quiescent" phase, they are said to be in what stage?
G0
During the cell cycle, chromosome replication occurs in Interphase Prophase Telophase Metaphase
Interphase
The following are features and characteristics of the DNA molecule except ____
Is used as genetic material by all organisms
Where on the chromatid are the microtubules attached?
Kinetochore
When two genes fail to assort independently, the term normally applied is
Linkage
Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with the following circumstance:
Linkage with approximately 33 map units between the two gene loci
Often a mutation in a gene results in a reduction of the product of that gene. The term given for this type of mutation is:
Loss-of-function or null(in the case of complete loss)
Crossing over occur during
Meiosis 1 prophase
sister chromatids separate during what phase
Meiosis 2 anaphase and mitosis anaphase.
A situation where there are more than two alternative forms of a given gene would be called
Multiple alleles
The phenomenon in which one crossover increases the likelihood of crossovers in nearby regions is called:
Negative interference
Assume you are told that a particular organism, Drosophilia, 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 Drosophilia sex for XO is also female?
No, the chromosomal basis of an X chromosome determines a female in both organisms
In a three-point mapping experiment, what three general classes of offspring are expected (assuming crossover occur)?
Noncrossovers Single crossovers Double crossovers
A rare dominant trait, when exhibited in men, is transmitted to half their sons and to half their daughters. The gene for this trait is carried:
On an autosome
For an individual with the XXY chromosomal composition, the expected number of Barr bodies in interphase cells is
One
The F1 offspring of Mendel's classic pea cross always looked like one of the two parental varieties because
One allele was completely dominant over another
The Chi-square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as
One less than the number of classes being compared
The DNA of a eukaryotic chromosome is:
One long double helix
Crossing over occurs during
Prophase
Mendel's law of independent assortment has its physical basis in the:
Random assortment of chromosomes on the metaphase plate in meiosis I
What is the mechanism that ensures mendel's first law of segregation
Segregation of homologous chromosomes
What is the outcome of synapsis, a significant event in meiosis?
Side-by-side alignment of homologous chromosomes
What is the outcome of synapsis, a significant event in meiosis
Side-by-side alignment of homologous chromosomes
Methods for determining the linkage group and genetic map in humans involve which of the following?
Syntenic testing and lod score determination
A chromosome with a centromere at the very end is called
Telocentric
Human blood types are an example of codominance because:
The A and B alleles both expressed equally in individually with both alleles
Human blood types are an example of codominance because:
The A and B alleles both expressed equally in individuals with both alleles
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably all the white-eyed flies were male. What was the explanation for this result?
The gene involved is on the X chromosome
The expected ratio of phenotypes among the progeny of a test cross is 1:1:1:1. Out of 200 total resulting progeny, 48 occur in one of the four phenotypic classes. Given this info, which of the following must also be true?
The value of observed - expected for this cells = -2
Prokaryotic chromosomes do not have telomeres because:
They are circular
Which of the following statements about homologous chromosomes are true?
They occur together in diploid cells
Which are abnormalities involving numbers of X chromosomes?
Turner Syndrome Klinefelter Syndrome OTHERS UNKNOWN
n Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of
X chromosomes
In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.
a portion of the Y chromosome
Drosophilia melangaster, the fruit fly, has a 2n chromosome number of 8. Assuming that a somatic G2 nucleus contains about 8.0 picograms of DNA, how many picograms of nuclear DNA would you expect in:
a-d : 8,8, 4,4 [I don't even know what this answer means...]
Assume that a black guinea pig crossed with an albino pig produced 5 black offspring. When the albino was crossed with a second black one, 4 black and 3 albino offspring were produced. What genetic explanation would apply to these data?
albino= recessive; black=dominant
Which of the following human genotypes is associated with Klinefelter syndrome? XXY XXYY XXXY all of the above
all of the above
Genes come in different versions called
alleles
What phenomenon describes a genetic trait that is expressed more strongly or earlier in development with each generation?
anticipation
in the G0 stage of the cell cycle, which of the following is true:
b. the cell exits the cell cycle
Linked genes _____
co-segregate
Because of the mechanism of sex determination, males of many species can neither be homozygous nor heterozygous. Such males can are said to be:
hemizygous
Males with an X-linked gene are said to be ___________ for these X-linked genes
hemizygous
Codominant alleles are expressed in individuals that are ______
heterozygous
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible partial genotype for the son? A) IBIB B) IAIA C) IBIA D) ii E) IBi
iBi
Assume that a cross is made between AaBb and aabb plants and that all of the offspring are: AaBb, Aabb, aaBb, aabb these results are consistent with the following circumstance
independent assortment
Assume that a cross is made between AaBb and aabb plants and the offspring fall into approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results are consistent with
independent assortment
When two genes fail to assort independently, the term normally applied is:
linkage
assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb 48 Aabb, 52 aaBb, 95 aabb, these results are consistent with
linkage with approximately 33 map units between two gene loci
A mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ________.
loss of function or null (in the case of complete loss)
The phenomenon in which one cross over increases the likelihood of crossovers in nearby regions is called:
negative interference
The phenomenon in which one crossover increases the likelihood of crossovers in nearby regions is called
negative interference
Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in the female two chromosomal pairs are metacentric and that two pairs are acrocentric. What stage is represented in the drawing above? (Genes "P" and "C" are not relevant to this question).
primary oocyte (metaphase)
The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called
segregation
Hemizygosity would most likely be associated with which of the following?
sex-linked inheritance
