Genetics Final (multiple choice)
a
19. You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a pure-breeding brown spider with a pure-breeding green spider. Predict the genotype of the progeny. A) B/bg B) Br/bg C) br/by D) by/bg E) B/by
c
A Barr body is a(n): A) gene on the X chromosome that is responsible for female development. B) patch of cells that has a phenotype different from surrounding cells because of variable X inactivation. C) inactivated X chromosome, visible in the nucleus of a cell that is normally from a female mammal. D) extra X chromosome in a cell that is the result of nondisjunction. E) extra Y chromosome in a cell that is the result of nondisjunction.
a
A cell possessing two nuclei derived from different cells through cell fusion is called A) a heterokaryon. B) a haplotype. C) recombinant. D) nonrecombinant. E) None of the above is correct.
e
A change in allele frequency within a population over time leads to a. a genome. b. a phenotype. c. a genotype. d. mutations. e. evolution.
b
A deletion of a small region on the long arm of chromosome 15 causes a developmental disorder in children called Prader-Willi syndrome when the deletion is inherited from the father. However, the deletion of this same region of chromosome 15 can also be inherited from the mother, but this inheritance results in a completely different set of symptoms, called Angelman syndrome. What type of genetic phenomenon does this represent? A) Sex-influenced B) Genomic imprinting C) Cytoplasmic inheritance D) Maternal effect E) Paternal effect
a
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 chromosomes in a polar body cell from a rat? a. 21 b. 40 c. 41 d. 42 e. 84
e
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). What is the total number of telomeres in a rat cell in G2? a. 21 b. 42 c. 84 d. 126 e. 168
d
A female with androgen-insensitivity syndrome, a sex-linked recessive condition, has A) two X chromosomes, both carrying mutant alleles in the gene that makes the androgen receptor. B) a pair of ovaries that overproduce estrogen. C) a XXX chromosome constitution that causes her not to produce testosterone. D) a pair of testes that produce testosterone. E) an inactive SRY gene.
b
A form of a gene that has a slightly different sequence than other forms of the same gene but encodes the same type of an RNA or protein, is called a(n) a. locus. b. allele. c. homologous chromosome. d. heterozygote. e. homozygote.
a
A measurable or observable trait or characteristic is called a a. phenotype. b. genotype. c. single-nucleotide polymorphism. d. Small interfering RNA. e. gene bank.
d
A mother of blood type A gives birth to a child with blood type O. Which of the following could NOT be the blood type of the father? A) A B) B C) O D) AB E) Any of the above is a possible blood type of the father.
a
A space capsule crashes to earth with an alien life form aboard. Two creatures emerge from the capsule, one with green skin and one with yellow skin. The yellow creature soon gives birth to offspring fathered by the green creature, producing 12 green and 8 yellow offspring. Green skin in these diploid creatures is dominant to yellow skin. You are curious to find out if the number of offspring significantly different from expected Mendelian ratios, so you perform a chi-square test. Your calculations reveal a chi-square test value of (0.8). What are your degrees of freedom (d.f.)? a. 1 b. 2 c. 3 d. 4
c
A woman is phenotypically normal, but her father had the sex-linked recessive condition of red-green colorblindness. If she has children with a man with normal vision, what is the probability that their first child will have normal vision and their second child will be colorblind? A) 1/16 B) 3/8 C) 3/16 D) 3/6 E) 8/27
d
Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia:1 normal. What is the most likely explanation for these observations? A) Achondroplasia is incompletely dominant to the normal condition. B) Achondroplasia is codominant to the normal condition. C) The allele that causes achondroplasia is a dominant lethal allele. D) The allele that causes achondroplasia is a recessive lethal allele. E) The allele that causes achondroplasia is a late-onset lethal allele.
c
An individual has the following genotype. Gene loci (A) and (B) are 15 cM apart. What are the correct frequencies of some of the gametes that can be made by this individual? A) Ab = 7.5%; AB = 42.5% B) ab = 25%; aB = 50% C) AB = 7.5%; aB = 42.5% D) aB = 15%; Ab = 70% E) aB = 70%; Ab = 15%
e
Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What is the genotype of the pink progeny? A) A_ B_ B) A_ bb C) aa B_ D) aa bb E) A_ B_ and A_ bb
b
Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What kind of gene interaction is this? A) Recessive epistasis B) Dominant epistasis C) Duplicate recessive epistasis D) Duplicate dominant epistasis E) Dominant and recessive epistasis
d
DNA primase requires ______nucleotides and a _______ template to initiate primer synthesis. A. DNA; DNA B. RNA; RNA C. DNA; RNA D. RNA; DNA E. leading strand; DNA
a
DNA/ RNA polymerases read the template strand in the ____ to ____ direction. A. 3′ , 5' B. 5′ , 3' C. James, Watson D. 5′ phosphate, 3'base E. leading, lagging
a
DNA/RNA polymerases synthesize new DNA by adding nucleotides to the _____ of the growing DNA chain. A. 3′ OH B. 5′ OH C. 3′ phosphate D. 5′ phosphate E. nitrogenous base
c
Defined, diploid cells are cells with a. a single set of chromosomes. b. circular chromosomes. c. two sets of chromosomes. d. many sets of chromosomes. e. Two pairs of chromosomes
d
During transcription, which parts of a DNA molecule are transcribed into RNA? A. All of the nucleotides in DNA on both strands B. All of the nucleotides on one strand of DNA C. Only parts of the DNA that encode messenger RNA D. Only regions of the DNA that contain RNA coding sequences E. Only regions of the DNA that encode ribosomal RNA
b
For which of the following is the "end-replication problem" relevant? A. Circular DNA B. Linear chromosomes C. The centromere region of a chromosome D. prokaryotic genomes E. none of the above
c
Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. The man has fathered a child with a woman that does not have freckles. What is the probability that their child has freckles? a. 1/4 b. 1/3 c. 1/2 d. 2/3 e. 3/4
a
Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow. What type of gene interaction does this represent? A) Recessive epistasis B) Dominant epistasis C) Duplicate recessive epistasis D) Duplicate dominant epistasis E) Dominant and recessive epistasis
E
Heat can disrupt hydrogen bonding between DNA strands. The intensity of the heat required to break the bond is directly proportional to the number of bonds present. Which of the following DNA strands would denature (break down) at the lowest temperature? A. 10% AT and 90% GC B. 30% AT and 70% GC C. 50% AT and 50% GC D. 70% AT and 30% GC E. 90% AT and 10% GC
c
How many hydrogen bonds will be involved in base pairing in a DNA molecule of 50 base pairs that contains 15 cytosine bases? A. 45 B. 100 C. 115 D. 135 E. 150
d
If a DNA molecule is 30% cytosine (C), what is the percentage of adenine (A)? A. 30% B. 40% C. 35% D. 20% E. 15%
b
If a healthy cell passes the G1/S checkpoint, a. it will enter the G0 stage of the cell cycle. b. DNA will be replicated. c. it will not divide. d. it will proceed immediately to cytokinesis. e. it will die.
c
If an organism of genotype Aa is used for a test cross, what is the genotype of the other individual used in the cross? a. AA b. Aa c. aa d. The genotype cannot be known e. Either a or b
e
If ribonucleotides (RNA nucleotides) were depleted from a cell during S phase, how would DNA synthesis be affected? A. There would be no effect because ribonucleotides are used in RNA synthesis, not DNA synthesis. B. DNA synthesis would continue, but at a slower rate. C. There would only be an effect during M phase, not in S phase. D. DNA synthesis would not be affected because ribonucleotides are only used during the process of transcription. E. Replication would cease because ribonucleotides are required to initiate DNA synthesis.
e
If the recombination frequency between genes (A) and (B) is 5.3%, what is the distance between the genes in map units on the linkage map? A) 53 cM B) 5.3 cM C) 0.53 cM D) 10.6 cM E) 25 cM
c
In Labrador retrievers, black coat color is dominant to brown. Suppose that a black Lab is mated with a brown one and the offspring are 4 black puppies and one brown. What can you conclude about the genotype of the black parent? a. The genotype must be BB b. The genotype must be bb c. The genotype must be Bb d. The genotype could be either BB or Bb e. The genotype cannot be determined from this data
a
In Mendel's peas, purple flower color is dominant to white. From which of the following descriptions can you not infer the genotype completely? (if given info in (a) - (e) below, which one could you not tell me the exact genotype?) a. Purple b. White c. Pure-breeding purple d. Heterozygous e. More than one of the above
c
In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure- breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation? a. 0% b. 25% c. 50% d. 75% e. 100%
c
In animals, the inability to make the pigment melanin results in albinism, a recessive condition. Two unaffected parents, who have decided to have three children, have a first child that has albinism (genotype aa). What is the probability that the second and third children will also have albinism? a. 1/4 b. 1/2 c. 1/16 d. 9/16 e. 1 (100%)
c
In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only. Two heterozygous birds are mated. What fraction of the male offspring is expected to exhibit cock feathering? A) 0 B) 1/8 C) 1/4 D) 1/2 E) 3/4
b
In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only. What type of inheritance is exhibited by this trait? A) Sex-linked B) Sex-limited C) Sex-influenced D) Autosomal recessive E) Autosomal dominant
c
In order to be functional, a eukaryotic chromosome requires all of the following except a. a centromere. b. origins of replication. c. a plasmid. d. telomeres.
a
In species of birds, males are the homogametic sex and females the heterogametic sex. Which of the following is TRUE in this system of sex determination? A) The gender of the offspring is determined by the female parent. B) Male offspring have a ZW chromosome constitution. C) The gender of the offspring is determined by the male parent. D) Female offspring have a ZZ chromosome constitution. E) Female and male offspring have the same chromosome constitution.
c
In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black:2 gray:1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance? A) One gene pair with black dominant to white B) One gene pair with codominance C) One gene pair with incomplete dominance
a
Interactions among the human ABO blood group alleles involve _______ and ________. A) co-dominance; complete dominance B) codominance; incomplete dominance C) complete dominance; incomplete dominance D) epistasis; complementation E) continuous variation; environmental variation
d
Is it possible for two different genes located on the same chromosome to assort independently? A) No, if two genes are on the same chromosome, they will be linked and the recombination frequency will be less than 50%. B) Yes, if the two genes are close enough to each other, there are a limited number of crossover events between them. C) No, there will be a very high crossover interference such that the recombination frequency will be reduced significantly. D) Yes, if the genes are far enough apart on the same chromosome, a crossover occurs between them in just about every meiotic event. E) Yes, but only if the two genes are both homozygous.
d
Linked genes A) assort randomly. B) can't crossover and recombine. C) are allelic. D) co-segregate (segregate together) E) will segregate independently.
c
Mendel's first law, the Principle of Segregation states the following... a. diploid organisms possess 2 alleles for each trait, but only the dominant allele will make it to gametes b. diploid organisms possess 2 alleles for each trait and these 2 alleles will occupy the same gamete after meiosis. c. diploid organisms possess 2 alleles for each trait, but only one allele will end up in each gamete produced by meiosis. d. diploid orgamisms posess 2 alleles for each trait and these two alleles do not behave as discrete units during meiosis.
b
Most somatic cells do not express (produce) the telomerase enzyme. As a result, they cannot regenerate their telomeres and experience progressive telomere shortening with age. What might be the outcome if somatic cells did acquire the ability to produce a functional telomerase enzyme. A. Premature Aging B. Cancer Development C. Lower rates of replication D. James Watson E. Early termination of replication
a
Now that you have the chi-square value (0.8) and degrees of freedom you refer to the chi-square table and come to the following conclusion regarding the #s of green and yellow aliens... (assume our significance threshold is probability (p)=0.05). a. There is no significant difference between observed and expected values. The documented difference 5 is likely due to normal variation or "chance". b. There is no significant difference between observed and expected values. Epigenetics eliminated all of the variation. c. There is a significant (true) difference between observed and expected values. These differences are likely due to more complicated genetic phenomena. d. There is a significant (true) difference between observed and expected values. The differences are due to normal variation or "chance".
a
Polydactyly is the condition of having extra fingers or toes. Some polydactylous persons possess extra fingers or toes that are fully functional, whereas others possess only a small tag of extra skin. This is an example of A) variable expressivity. B) complete dominance. C) independent assortment. D) complementation. E) cytoplasmic inheritance.
e
Recombination occurs through A) crossing over and chromosome interference. B) chromosome interference and independent assortment. C) somatic-cell hybridization and chromosome interference. D) complete linkage and chromosome interference. E) crossing over and independent assortment.
a
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) A color-blind female B) A color-blind male C) A noncolor-blind female D) A noncolor-blind male
c
Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is dominant to green seeds (y). A true- breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a round, yellow seed in the F2? a. 3/4 b. 1/16 c. 9/16 d. 3/16 e. 1/2
d
Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is dominant to green seeds (y). A true- breeding plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. What is the genotype of the F1 progeny? a. RRYY b. RrYY c. RRYy d. RrYy e. rryy
c
Species in which individuals have only male or only female reproductive structures are called A) hermaphrodites. B) diploids. C) dioecious. D) homogametic. E) monoecious.
d
Suppose that a diploid cell contains 8 chromosomes (2n = 8). How many different combinations in the gametes are possible? a. 2 b. 4 c. 8 d. 16 e. 64
c
Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 60% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes? A) 0.05 B) 0.10 C) 0.15 D) 0.25 E) 0.33
e
Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule include radioactive nucleotides.C The cells are then harvested and placed in new medium with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive. What proportion of DNA molecules will contain radioactivity after two rounds of semi-conservative replication? (a DNA molecule = a double strand of DNA) A. 0 B. 1/8 C. 1/4 D. 1/3 E. 1/2
c
Suppose that the "fabulous" phenotype is controlled by two genes, A and B, as shown in the diagram below. Allele A produces enough enzyme 1 to convert "plain" to "smashing." Allele a produces no enzyme 1. Allele B produces enough enzyme 2 to convert "smashing" to "fabulous." Allele b produces no enzyme 2. The A and B genes are both autosomal and assort independently. What will be the phenotype(s) of the F1 offspring of a true-breeding "fabulous" father and a true-breeding "plain" mother (aa bb)? A) All "plain" B) All "smashing" C) All "fabulous" D) Plain" females and "fabulous" males E) "Fabulous" females and "smashing" males
d
Telomerase activity is most likely to be found in which cells in humans? A. Red blood cells B. Muscle cells C. Neurons D. Germ line E. James Watson Cells
c
The ability to curl one's tongue into a U-shape is a genetic trait. Curlers always have at least one curler parent but noncurlers can have one or both parents who are curlers. Using C and c to symbolize the alleles that control this trait, what is the genotype of a noncurler? a. CC b. Cc c. cc d. Any of the above could be correct.
c
The phenomenon in which a gene's expression is determined by its parental origin is called A) sex-influenced. B) sex-limited. C) genomic imprinting. D) maternal effect. E) paternal effect.
c
The presence of a beard on some goats is determined by an autosomal gene that is dominant in males and recessive in females. Heterozygous males are bearded, while heterozygous females are beardless. What type of inheritance is exhibited by this trait? A) Sex-linked B) Sex-limited C) Sex-influenced D) Autosomal recessive E) Autosomal dominant
a
The process of splitting the cytoplasm, which separates one cell into two, is termed a. cytokinesis. b. mitosis. c. anaphase. d. diakinesis. e. fusion.
c
The quantity of DNA per cell of a particular species is measured in cells found at various stages of meiosis. If the amount of DNA present in a cell at G1 = 7.3 picograms (pg), how much should be present in Gap 2 (G2)? a. 7.3 b. 3.1 c. 14.6 d. 21.9
c
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AABB zygote (offspring) from a cross AaBb × AaBb? a. 1/4 b. 1/2 c. 1/16 d. 9/16 e. 1 (100%)
a
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AaBb individual? a. 1/4 b. 1/2 c. 1/16 d. 9/16 e. 1 (100%)
d
Two genes, A and B, are located 30 map units apart. The dihybrid shown below is mated to a tester aa bb. What proportion of the offspring is expected to be dominant for both traits? A) 0% B) 15% C) 30% D) 35% E) 70%
a
Two individuals with the following genotypes are crossed (Aa Bb Cc dd Ee x Aa bb Cc Dd Ee). What proportion of the progeny (offspring) will have the following genotype : AA BB CC DD EE ? a. 0 b. 1/32 c. 1/64 d. 1/256
b
Two individuals with the following genotypes are crossed (Aa Bb Cc dd Ee x Aa bb Cc Dd Ee). What proportion of the progeny (offspring) will have the following genotype : Aa Bb Cc Dd Ee? a. 0 b. 1/32 c. 1/64 d. 1/256
c
Two linked genes, (A) and (B), are separated by 18 cM. A man with genotype Aa Bb marries a woman who is aa bb. The man's father was AA BB. What is the probability that their first child will be Aa bb? A) 0.18 B) 0.41 C) 0.09 D) 0.25 E) 0.50
b
Unlike eukaryotes, prokaryotic cells do not have an organized nucleus. Another major difference relating to their DNA is that eukaryotic DNA complexes with proteins called ___________, while prokaryotic DNA does not. a. RNA b. histones c. chromatin d. linear DNA
a
What is the apparent purpose for X inactivation in humans and other mammals? A) It allows for the levels of expression of genes on the X chromosome to be similar in males and females. B) It allows for the levels of expression of genes on the autosomes to be similar to the levels of genes on the X chromosome. C) It suppresses the expression of genes on the Y chromosome in males. D) It reduces the amount of nondisjunction during meiosis in females. E) It enhances the level of pairing between the two X chromosomes during meiosis in females.
c
What is the function of DNA gyrase? A. Connects Okazaki fragments by sealing nicks in the sugar- phosphate backbone B. Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork C. Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding D. Binds to oriC and causes a short section of DNA to unwind E. Prevents the formation of secondary structures within single-stranded DNA
c
What is the function of single-strand-binding proteins? A. Connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone B. Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork C. Prevents re-annealing of the DNA strands and formation of secondary structure D. Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding E. Binds to oriC and causes a short Section: of DNA to unwind
c
What is the role of the SRY gene in humans? A) It initiates the X inactivation process in females. B) It is located on the X chromosome and causes the X to pair with the Y chromosome during male meiosis. C) It is located on the Y chromosome and initiates the developmental pathway toward the male phenotype. D) It is located on an autosomal chromosome and represses expression of autosomal genes in order to balance their expression level with genes on the X chromosome. E) None of the above answers is correct.
b
What phase of Meiosis serves as a demonstration of Mendel's 2nd Law, The principle of Independent Assortment? a. Prophase I b. Anaphase I c. Prophase II d. Anaphase II
c
What type of synthesis occurs on the leading strand? A. Conservative B. Dispersive C. Continuous D. Discontinuous E. Recombination
a
Where are promoters usually located? A. Upstream of the transcriptional start site b. Downstream of the transcriptional start site C. Near the terminator sequence D. Near James Watson's house E. Downstream of the terminator
d
Whereas the nucleotide strand used for transcription is termed the _______, the nontranscribed strand is called the _________. A. promoter; terminator B. terminator; promoter C. transcription apparatus; TATA box D. template strand; nontemplate strand E. nontemplate strand; template strand
d
Which of the following chromosome constitutions would never lead to a viable human baby being born? A) XXX B) XYY C) XO (O = the absence of a second chromosome) D) YY E) XXY
d
Which of the following crosses would produce a 1:1 ratio of phenotypes in the next generation? a. AA×AA b. AA×aa c. Aa×Aa d. Aa×aa e. aa×aa
c
Which of the following crosses would produce a 3:1 ratio of phenotypes in the next generation? a. AA×AA b. AA×aa c. Aa×Aa d. Aa×aa e. aa×aa
d
Which of the following does NOT occur during the G2 phase of the cell cycle? a. The G2/M checkpoint is reached. b. DNA replication and error checking is completed. c. The cell completes preparation for mitosis. d. The cell divides.
c
Which of the following enzymes do NOT aid in unwinding of DNA for replication? A. Helicase B. Single-stranded binding proteins C. Primase D. Gyrase E. Topoisomerase
e
Which of the following is a characteristic exhibited by cytoplasmically inherited traits? A) Present in both males and females B) Usually inherited from one parent, typically the maternal parent C) Reciprocal crosses give different results D) Exhibit extensive phenotypic variation, even within a single family E) All of the above
e
Which of the following is a sequence of DNA where transcription is initiated? A. Hairpin loops B. Transcription factor C. Initiator Proteins D. 3' UTR on pre-mRNA E. Core Promoter
e
Which of the following is not a chemical or structural characteristic of RNA that is different from those of DNA? A. The RNA sugar is ribose instead of deoxyribose. B. RNA is usually a single-stranded molecule instead of a hydrogen-bonded double strand like DNA. C. The bases in RNA include uracil instead of thymine. D. RNA molecules are generally shorter in length than those of DNA macromolecules. E. The 2′ carbon of ribose has an H, unlike the OH in that position of deoxyribose.
c
Which of the following species is considered a model genetic organism? a. The plant, Linaria vulgaris b. The deer mouse, Peromyscus maniculatus c. The worm, Caenorhabditis elegans d. The frog, Hyla chrysoscelis e. The chimpanzee, Pan troglodytes
d
Which of the following statements about X inactivation in mammalian females is FALSE? A) Females that are heterozygous for an X-linked gene have patches of cells that express one allele and patches of cells that express the other. B) Some genes on the inactive X continue to be expressed after the chromosome is inactivated. C) X inactivation is random as to which X is inactivated and takes place early in embryonic development D) Inactivation is thought to be initiated by expression of the Xist gene on the X that will remain active. E) Once an X chromosome first becomes inactivated in a cell, that same X will remain inactivated in somatic cells that are descendants of this cell.
e
Which of the following statements is FALSE? A. Both DNA and RNA are synthesized in a 5′ to 3′ direction. B. During RNA synthesis, the DNA template strand is read in a 3′ to 5′ direction. C. During RNA synthesis, new nucleotides are added to the 3′ end of the growing RNA molecule. D. RNA polymerase has 5′ to 3′ polymerase activity. E. RNA molecules have the same 5′ to 3′ orientation as the DNA template strands to which they are complementary.
d
Which of the following statements is true? a. The genotype is the physical appearance of a trait. b. Alleles, genes, and loci are different names for the same thing. c. The phenotype of a dominant allele is never seen in the F1 progeny of a monohybrid cross. d. A testcross can be used to determine whether an individual is homozygous or heterozygous. e. All of these statements are true.
e
Which of the following statements is true? a. The probability of a woman giving birth to three girls in a row is 1/8. b. The chi-square test is used to determine if observed outcomes are consistent with expected outcomes. c. The probability of two or more independent events occurring together is calculated by multiplying their independent probabilities. d. Branched diagrams are used for determining probabilities of various phenotypes or genotypes for genetic crosses involving more than one gene pair. e. All of these statements are true.
b
Which of the following would serve the least well as a model for understanding basic mechanisms of inheritance? a. Fruit flies b. Humans c. Yeast d. Mice e. Zebrafish
a
Which one of the following research topics belongs to the discipline of transmission genetics? a. Inheritance pattern of gene alleles b. Mechanism of DNA Replication c. Gene expression patterns d. Evolution e. Chemical modification of nucleic acids
b
Which one of the following topics belongs to a different subdiscipline of genetics when compared to the rest? a. Mechanism of gene regulation b. Allele frequencies of certain gene in different environments c. Transcription d. Chemical alternation of chromosomes e. Mechanism of DNA repairs and maintenance
b
Why was the pea plant an ideal plant for Mendel to use? a. Generation time that is several years b. Simple traits that are easy to identify c. Low numbers of offspring produced d. Expensive and time-consuming to grow e. All of the answer choices are correct.
b
Within cells, genes are located on structures called a. genomes. b. chromosomes. c. phenotypes. d. genotypes. e. alleles.
b
Women with Turner syndrome (XO) and normal women (XX) are clearly different phenotypically. In addition, the vast majority of XO conceptions abort before birth. However, both XO and XX women have one active X chromosome since the X in XO women remains active and one might expect that they would therefore have similar phenotypes. What is the most reasonable explanation for their different phenotypes? A) XO women do not have a copy of the SRY gene. B) Some genes remain active on the inactive X chromosome and XX women will have two copies of these genes expressed and XO women only one copy. (concept= X-inactivation Escape) C) In XO women, the single X chromosome has no partner to pair with during mitosis so that each cell division is delayed by pairing problems with the single X not finding a pairing partner. D) XO women are missing a copy of the XIST gene so that they are forced to develop partway along the male pathway during embryogenesis. E) Both c and d are reasonable explanations.
d
You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However, the L allele is only 60% penetrant. You cross two heterozygous giraffes. What proportion of offspring would you expect to exhibit the short ossicone phenotype? Assume the penetrance of L applies equally to both homozygotes and heterozygotes. A) 0.25 B) 0.40 C) 0.45 D) 0.55 E) 0.60
c
You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a pure-breeding brown spider with a pure-breeding green spider. Predict the phenotype of the progeny. A) Half brown, half green B) Three-fourths brown, one-fourth green C) All brown D) All green E) All yellow
b
n a germ-line cell from a human male that is dividing, when do the X and Y chromosomes segregate? A) During mitosis B) During meiosis I, anaphase C) During meiosis II, anaphase D) They do not segregate; gametes contain a copy of X and a copy of Y.
