Genetics Final Notecards
The F, G, and H loci are linked in the order written. There are 30 map units between F and G, and 30 map units between G and H. If a plant F G H/f g h is testcrossed, what proportion of progeny plants will be f g h/f g h if there is no interference?
0.245
The mouse autosomal genes B and S are linked and 38 map units apart. Genotypes B S/B S and b s/b s are intercrossed and the F1 is testcrossed to b s/b s. The proportion of B-S- progeny will be: 
0.31
The replisome contains a protein subunit responsible for attaching free ends of DNA on the newly formed strand. This subunit/enzyme is named:
ligase
In swine, when a pure-breeding red is crossed to a pure-breeding white, the F1 are all red. However, the F2 shows 9/16 red, 1/16 white, and 6/16 as a new color, sandy. A particular red individual (Parent 1) is crossed to a particular sandy individual (Parent 2), and the progeny is comprised of four sandy, three red, and one white piglets. What are the most likely genotypes of the two parents?
A/a; b/b and A/a; B/b
A male mouse of genotype A/a . B/b is testcrossed multiple times. Overall, these testcrosses produce 11 mice of phenotype A B, 81 A b, 77 a B, and 14 a b. Based on these data, the genotypes of the male mouse's parents are most likely:
Ab/Ab and aB/aB.
Ascospores from a cross a X b c (all auxotrophic markers) are analyzed. If genes a and b are linked, 10 map units apart, but gene c is located on a different chromosome, what proportion of ascospores is expected to be a+b+c+?
About 22.5%
A corn plant known to be hybrid for three linked genes is testcrossed. The progeny phenotypes and frequencies are: The coefficient of coincidence in this genomic region is: +++ 74 abc 70 a++ 44 +bc 50 ++c 4 ab+ 2 a+c 368 +b+ 388
0.40
In Drosophila, the genes crossveinless-c and Stubble are linked, about 7 map units apart on chromosome 3. cv-c is a recessive mutant allele of crossveinless-c (cv-c+ is wild type), while Sb is a dominant mutant allele of Stubble (Sb+ is wild type). A dihybrid female Drosophila with genotype cv-c Sb+/cv-c+Sb is testcrossed. The proportion of phenotypically wild-type individuals in the progeny of the testcross will be:
0.465
A mutation occurs in a germ cell of a pure-breeding, wild-type male mouse prior to DNA replication. The mutation is not corrected, and the cell undergoes DNA replication and a normal meiosis producing four gametes. How many of these gametes will carry the mutation?
2
Two pure-breeding mutant plants were crossed: One had small leaves (wild-type leaves are large) and the other made pink flowers (wild-type flowers are purple). All F1 individuals had small leaves and purple flowers. Assuming independent assortment, what proportion of the F2 individuals are expected to be phenotypically wild-type?
3/16
Two pure lines obtained from Mendel's experiments are crossed to each other. The first line makes green smooth seeds (peas), and the second line has white flowers. All F1 individuals have purple flowers and produce yellow wrinkled seeds. What proportion of the F2 plants should have purple flowers and make green wrinkled seeds?
3/36
A leucine-requiring mutant strain of haploid yeast is crossed to a cysteine-requiring mutant strain. Assuming independent assortment, what proportion of the spores produced will be mutant?
3/4
In a cross in which there is a mean crossover frequency of 0.9 between two marker loci, the recombinant frequency for those loci will be:
30%
A corn plant of genotype A/a;B/B;C/c;D/d;E/e;f/f;G/g is selfed. How many different completely homozygous genotypes could be produced?
32
If an individual has 10 gene pairs, how many different gametes can be formed if 5 of the gene pairs are homozygous and the remaining 5 gene pairs are heterozygous?
32
If two mice of genotype F/f;G/g;H/h;I/i;J/j are repeatedly mated, how many different phenotypes will be found in the progeny? (Assume complete dominance for all genes.)
32
Complete medium (contains all amino acids, vitamins, and a variety of carbon sources) 347 Minimal medium (glucose as a carbon source) 261 Minimal medium + ampicillin (an antibiotic) 51 Minimal medium +methionine (an amino acid) 303 Minimal medium +arginine (an amino acid) 301 Minimal medium +methionine+ampicillin 57 Minimal medium + arginine+ampicillin 64 Reference: Ref 9-1 Based on the data presented in the table above, how many colonies are met- arg+AmpS?
36
A dihybrid plant is selfed, and the offspring shows a 13:3 phenotypic ratio for flower color. If the same dihybrid plant was testcrossed instead of being selfed, what would be the expected phenotypic ratio in the offspring?
3:1
A wild-type strain of haploid yeast is crossed to a mutant strain with phenotype d. What phenotypic ratios will be observed in the progeny?
50% wild-type and 50% mutant (d)
Two genes, A and B, are linked. An individual of genotype A b/A b is crossed to one that is a B/a B. The F1 is selfed and an F2 is obtained. Which of the following ratios most likely represents the phenotypic ratio observed in this F2?
51:24:24:1
A dihybrid in cis is crossed to a dihybrid in trans (the two genes of interest, A and B, are linked). What proportion of the progeny is expected to be homozygous recessive with respect to the two genes of interest?
6.25%
Of the three key building blocks of DNA, which type(s) of building block stabilizes the structure via weak van der Waals interactions (through stacking), and regular hydrogen bonds?
Nitrogeneouse bases
Beside DNA, which of the following are major components of chromatin?
Proteins
The most commonly used phage characters in the study of phage inheritance are:
plaque morphology and host range
A strain of E. coli with the genotype arg-bio-gal-TetR is able to grow on minimal medium (containing glucose as a carbon source) supplemented with:
the amino acid arginine and the vitamin biotin.
If two bacterial genes are very closely linked (less than one map unit apart), then their frequency of co-transduction will be:
very high, almost 100%
Mendel identified evidence for the location of genes on separate structures (chromosomes) through his:
identification of independent assortment of distinct genes during meiosis.
Which of the following are characteristics of an E. coli strain of genotype F- gal+ lac- pur+ ile- strr?
its auxotropic for lactose
A plant of genotype C/C . d/d is crossed to c/c . D/D, and the F1 is testcrossed. If the genes in question are linked, the percentage of double homozygous recessive individuals in the offspring of the testcross will be:
less than 25%
Alfred Hershey and Martha Chase examined transformation using bacteriophage (bacterial DNA virus) and bacterial cells. Sulfur was used to label cellular components in this experiment because of its presence in the amino acid(s)
methionine and cysteiene
If a met-thr- Hfr strain is mated with an F- of genotype leu-thi-, prototrophic recombinants can be detected by plating the mixture on:
minimal medium
Two bacterial strains were obtained with the following genotypes: Hfr: ala-leu+aziSStrS F-: ala+leu-aziRStrR After an uninterrupted conjugation, you want to select F- recombinants that are ala+leu+. Which of the following media would you use for this selection?
minimal medium containing streptomycin
A bacterium that is unable to grow on minimal medium is said to be:
auxotrophic
To demonstrate transformation of bacteria one could:
extract DNA from arg+ cells and add it to arg- cells.
Wild cats (Felis silvestris) and common mice (Mus musculus) are diploid. In wild cats 2n = 38, while in common mice 2n = 40. Based on this information, we can conclude that wild cat cells have
fewer DNA molecules than common mouse cells.
In Labrador retrievers, black color coat (B/-) is dominant to brown color coat (b/b). A breeder crosses two black individuals who have previously produced some brown puppies. If the cross produces six puppies: a) What is the probability that the first born will be brown? b) What is the probability that four of them will be brown and two will be black? c) What is the probability that at least one of them will be brown?
(a) Both parents must be heterozygotes B/b because they have previously produced brown puppies. The probability that they produce a brown puppy is therefore  . (b) Each pup has  chance of being black and  chance of being brown. The order in which the brown and black puppies are born does not matter, so there are 15 different permutations of 4 brown+2 black (5!). Hence, the probability is: 15((1/4)(1/4)(1/4)(1/4)(3/4)(3/4))=135/4096=3.3% (c) In this case, the only instance that does not satisfy the condition is the case in which all puppies are black. The probability of this event Modify Remove is (3/4)6 = 729/4096 = 17.8%. Therefore, the probability of obtaining at least one brow puppy is 1 - (729/4096) = 82.2%.
Consider the following pedigree of a rare autosomal recessive disease. Assume all people marrying into the pedigree do not carry the abnormal allele. (a) If individuals A and B have a child, what is the probability that the child will have the disease? (b) If individuals C and D have a child, what is the probability that the child will have the disease? (c) If the first child of C * D is normal, what is the probability that their second child will have the disease? (d) If the first child of C * D has the disease, what is the probability that their second child will have the disease?
(a) Choosing M for unaffected and m for the disorder, male B must be M/m, and female A has a 2/3 chance of being M/m. The overall chance of an affected child is 1 * 2/3 * 1/4 = 1/6. (b) If C's mother A is heterozygous, C stands a 1/2 chance of being heterozygous. D's mother must be heterozygous, and D stands a 1/2 chance of inheriting that heterozygosity. The overall chance of an affected child is 2/3 * 1/2 * 1 * 1/2 * 1/4 = 1/24. (c) The probability is still 1/24. (d) Now that we know individuals C and D must both be M/m, the chance of the second child being m/m is 1/4.
In a particular species of plants, flower color is dimorphic: Some individuals have red flowers, whereas others have yellow flowers. If flower color is controlled by a single gene with two alleles (cred and cyellow): (a) What would be the simplest way to determine which allele is dominant? (b) What will be the genotypic ratio in the offspring of a cross between a monohybrid and a pure-breeding individual?
(a) Crossing a pure-breeding red to a pure-breeding yellow individual, and assessing the phenotype of the monohybrid produced. If it makes red flowers, then cred is dominant, if it makes yellow flowers, then cyellow is dominant. (b) 1:1; half of the offspring will be heterozygous and half will be homozygous like the pure-breeding parent.
Suppose that red flower color (RR or Rr) is dominant to white flower color (rr) in Petunia. A friend has a Petunia plant with red flowers and wants to determine whether the plant is RR or Rr. (a) What cross could you perform to help your friend determine the genotype of his Petunia plant? (b) How will this cross help you determine the genotype of your friend's red flowered petunia? That is, how will the results from this cross differ if the red-flowered petunia is RR vs. Rr?
(a) Perform a testcross (test the red Petunia to a genotypically rr Petunia) (b) You will observe different segregation in the testcross progeny, depending on the genotype of the red petunia. If the red petunia is RR, then all testcross progeny will be red; If the red petunia is Rr, then  of the testcross progeny will be red (Rr) and  will be white (rr).
In maize, the genes W and D are so tightly linked that virtually no crossovers occur between them. A dihybrid W d/w D is testcrossed to w d/w d. The percent of progeny with W-/D- phenotype will be:
0
Mendel's Y/y; R/r dihybrid pea plants were the F1 of the cross between a double homozygous dominant and a double homozygous recessive. If we testcrossed these dihybrids, what proportion of the offspring would be recombinant and phenotypically resemble the F1 dihybrid?
0%
In maize, two plants that are both heterozygous for the recessive alleles a and b are crossed. What frequency of double-mutant progeny will appear if a and b are 7.2 map units apart, and both parents carry a and b in repulsion (trans)?
0.001296
A corn plant of genotype A/a;B/B;C/c;D/d;E/e;f/f;G/g is selfed. What is the probability of producing a completely homozygous individual out of all possible offspring?
0.031
The maize genes sh and bz are linked, 40 map units apart. If a plant sh+bz/sh bz+ is selfed, what proportion of the progeny will be sh bz/sh bz?
0.04
The linkage relationships among the four mouse genes, A, B, C, and D, are shown in the map below. A   30mu  B C 15mu D
0.064
Ascospores from a cross leu-2 X ad-7 met-3 (all auxotrophic markers) are plated on minimal medium (no adenine, leucine, or methionine). If the three genes are unlinked, what proportion of ascospores is expected to grow into a colony on this medium?
0.125
In a haploid organism, the loci leu and arg are linked, 30 map units apart. In a cross: leu+arg X leu arg+, what proportion of progeny will be leu arg?
0.15
Out of 800 progeny of a three-point testcross, there were 16 double crossover recombinants, whereas 80 had been expected on the basis of no interference. The interference is:
0.155
An E. coli culture is growing in (rich) liquid medium. A representative sample of this culture is plated on solid rich medium, and 950 colonies grow on this medium. A sample of bacteria from each of these colonies is then plated on minimal medium, and only 108 of these samples grow into a colony. What proportion of the bacteria in the original liquid culture are auxotroph?
0.886
What is the maximum number of heterozygous genotypes that could be produced by monohybrid self?
1
In the purple penguin, an allelic series occurs at the p locus on an autosome. All alleles affect the color of feathers: pd = dark-purple, pm = medium- purple, pl = light-purple, and pvl = very pale purple. The order of dominance is pd > pm > pl > pvl. If a pl/pvl female is crossed to a pd/pmmale, the ratio of phenotypes expected among the baby penguins would be:
1 dark:1 medium.
In a diploid invertebrate, genes D and E are closely linked. Single crossovers between these two genes occurs only in one out of 40 meioses, and multiple crossovers are never observed. If an individual has the genotype D e/d E, what percentage of its gametes are expected to be recombinant (either DE or de)?
1.25%
in Drosophila, the recessive alleles for brown and scarlet eyes (of two independent genes) interact so that bw/bw; st/st is white. If a pure-breeding brown is crossed to a pure-breeding scarlet, what proportion of the F2 will be white?
1/16
A laboratory mouse homozygous for an RFLP marker is mated to a wild mouse that is heterozygous for that marker. One of the heterozygous individuals resulting from this cross is mated back to the wild parent. What proportion of the offspring will have the same RFLP pattern as the original laboratory mouse?
1/2
In a haploid fungus similar to Neurospora, a red-colored mutant is crossed to an alanine-requiring mutant. Assuming independent assortment, what proportion of the spores produced will be alanine-requiring?
1/2
Mendel crossed Y/Y;R/R (yellow wrinkled) peas with y/y;r/r (green smooth) peas and selfed the F1 to obtain an F2. What proportion of the F2 individuals were pure-breeding?
1/4
The wild-type eye color in the fruitfly Drosophila melanogaster is dark red, as a result of a mixture of bright red and brown pigments. "Enzyme A" is encoded by the "a" gene, and is required to synthesize the bright red pigment. Lack of red pigment results in a somewhat brown eye color. You cross two fruitflies who are heterozygous for a recessive mutation that completely inactivates the "a" gene. What proportion of their offspring will have a recessive eye color phenotype?
1/4
Mendel crossed Y/Y;R/R (yellow wrinkled) peas with y/y;r/r (green smooth) peas and selfed the F1 to obtain an F2. In the F2 what proportion of the yellow wrinkled individuals were pure-breeding?
1/9
The pedigree below shows the inheritance patterns of two extremely rare, independent genetic conditions (represented with black and grey symbols, respectively). If individuals A and B have a child, what is the probability that it will have both conditions?
1/9
In a fungal cross A B X a b (the loci are linked), in meiosis in which there has been a four-strand double crossover between the loci, the percentage of meiotic products that will be recombinant for A and B for that ascus is:
100
A male Drosophila melanogaster has the genotype A/a; B/b; C/c; XD/Y. How many different sperm genotypes can it produce through meiosis of one single pre-gametic (2n) cell?
2
In a flowering plant, gene "A" encodes an enzyme responsible for the presence of dots on the flowers' petals. A1, A2, and A3 are the three known alleles of this gene; A1 is the wild type, A2 is a null allele, while A3 has a mutation in the promoter region of the gene, which results in the synthesis of very little gene product. If the "A" gene is haploinsufficient, what is the predicted phenotypic ratio in the F1 of a cross between a wild-type and a A2/A3 heterozygous?
100% of the F1 plants will have flowers with no dots.
Drosophila eyes are normally red. Several purple-eyed strains have been isolated as spontaneous mutants, and the purple phenotype has been shown to be inherited as a Mendelian autosomal recessive in each case. To investigate allelism between these different purple mutations, two purple-eyed pure strains were crossed. Reference: Ref 6-2 Modify Remove If the purple mutations are in the same gene (i.e., they are allelic), the phenotypic ratios in the F1 are expected to be
100% purple
Drosophila eyes are normally red. Several purple-eyed strains have been isolated as spontaneous mutants, and the purple phenotype has been shown to be inherited as a Mendelian autosomal recessive in each case. To investigate allelism between these different purple mutations, two purple-eyed pure strains were crossed. Modify Remove Reference: Ref 6-2 If the purple mutations are in different genes (i.e., they are not allelic), the phenotypic ratios in the F1 are expected to be
100% red
In Drosophila, the two genes w and sn are X-linked and 25 map units apart. A female fly of genotype w+sn+/w sn is crossed to a male from a wild-type line. What percent of male progeny will be w+sn?
12.5%
An A/a; B/b dihybrid is test-crossed, and about  of the progeny phenotypically resembles the dihybrid parent, while  resembles the tester parent. If the dihybrid parent was selfed, what would be the expected phenotypic ratio in the progeny?
15:1
Meiosis I is about to start in a cell of a plant in which 2n = 18. At this stage, the cell has
18 chromosomes, and a total of 36 chromatids.
A cross is made between an Hfr strain that is StrSa+b+d+ in genotype and an F- strain that is StrRa-b-d- in genotype. Interrupted-mating studies show that b+ enters the recipient strain last, and that the Str locus is very far away from b+, so it never enters the recipient strain. The b+ recombinants are then tested for the presence of the a+ and d+ alleles. The following data were obtained: a+ b+ d+ a- b+ d+ a+ b+ d- a- b+ d- 326 2 14 58 400 what's the map distance between markers d and b?
19 map units
"Dumpy" is a commonly used mutant phenotype in the nematode worm C. elegans. Two "Dumpy" individuals are crossed to each other and this cross produces 210 "Dumpy" and 68 wild-type individuals. If one of the "Dumpy" individuals used in this cross was mated with a wild-type, what ratio of "Dumpy": wild-type would we observe in the offspring?
1:1
When selfed, a particular plant always produces an F1 with a phenotypic ratio of 2:1. If this plant is test-crossed, what is the expected phenotypic ratio in the progeny?
1:1
Crosses between two ducks with spread-out tail phenotype always produce ducklings with spread-out, normal, and pointy tails in a 2:1:1 ratio. In addition, normal-tailed ducks crossed to short-tailed ducks always produce only normal-tailed individuals, while crosses between pointy-tailed and short-tailed individuals always produce only pointy-tailed ducklings. If the tail shape phenotype is controlled by a single locus, what is the expected phenotypic ratio in the progeny of the cross spread-out tail × short tail?
1:1 of normal : pointy.
If genes assort independently, a testcrossed dihybrid characteristically produces progeny phenotypes in the ratio:
1:1:1:1
Two genes, A and B, are linked. An individual of genotype A b/A b is crossed to one that is a B/a B. The F1 is testcrossed. Which of the following ratios most likely represents the phenotypic ratio observed in the progeny of this testcross?
1:4:4:1
The diagram below shows a simplified version of the biochemical pathway responsible for fruit color in peppers. Assume that Enzyme 1 is encoded by gene A (a is a null allele), Enzyme 2 is encoded by gene B (b is a null allele), and Enzyme 3, which breaks down the chlorophyll present in the fruit, is encoded by gene C (c is a null allele). In the absence of Enzyme 3, the fruit takes a brown color in the presence of red pigment, but remains green in the absence of red pigment. Enzyme 1 Enzyme 2 Colorless precursor → Yellow pigment → Red pigment Enzyme 3 Chlorophyll (green) → Absence of chlorophyllA pepper plant that produces red fruits was selfed, and the progeny obtained consisted of 176 plants that made red fruits, 78 that made colorless fruits, and 62 that made yellow fruits. If the original red fruit-producing plant was crossed to a tester of genotype a/a; b/b; c/c, what would be the expected phenotypic ratio in the offspring?
2 colorless : 1 red : 1 yellow
In Neurospora, a, b, and c are auxotrophic mutants (require particular compounds for growth). The mating a b+ X a+b gives 5% prototrophs (grown on unsupplemented medium). The mating b+c X b c+ gives 2.5% prototrophs, and the mating a+c X a c+ gives 2.5% prototrophs. Assuming complete interference prevails in the chromosome segment in question, what percentage of prototrophs would you expect in the mating a+b c+ X a b+c? (The order of mutations is not necessarily a,b,c: It can be determined on the basis of the two-point crosses above.)
2.5%
In chickens, the dominant allele Cr produces the creeper phenotype (having extremely short legs). However, the creeper allele is lethal in the homozygous condition. If two creepers are mated, what proportion of the living progeny will be creepers?
2/3
Medium Number of colonies that grew Complete medium (contains all amino acids, vitamins, and a variety of carbon sources) 347 Minimal medium (glucose as a carbon source) 261 Minimal medium + ampicillin (an antibiotic) 51 Minimal medium +methionine (an amino acid) 303 Minimal medium +arginine (an amino acid) 301 Minimal medium +methionine+ampicillin 57 Minimal medium + arginine+ampicillin 64 Reference: Ref 9-1 Based on the data presented above, how many colonies are wild type (met+ arg+AmpS)?
210
In a plant in which 2n = 24, what is the total number of chromosomes present at the end of interphase?
24
A phenotypically normal woman is heterozygous for the recessive Mendelian allele causing phenylketonuria, a disease caused by the inability to process phenylalanine in food. She is also heterozygous for a recessive X-linked allele causing red-green colorblindness. What percentage of her eggs will carry the dominant allele that allows normal processing of phenylalanine and the X-linked recessive allele that causes colorblindness?
25%
For a (fictitious) haploid fungus, the starting point in the biosynthesis of the amino acid arginine is Compound X, which is always present in, and absorbed from the environment. The arginine biosynthetic pathway is: A mutant strain of genotype a- (lacking enzyme A) is crossed to a mutant strain of genotype c- (lacking enzyme C). What proportion of the progeny is expected to grow on medium supplemented with Compound Y?
25%
In the offspring of a dihybrid self, what percentage of the individuals are themselves dihybrid?
25%
A trihybrid cross is a cross between two individuals who are heterozygous for three genes. Assuming independent assortment and complete dominance, what phenotypic ratios would be observed in F1?
27:9:9:9:3:3:3:1
In a certain breed of dog, the alleles B and b determine black and brown coats, respectively. However, the allele Q of an unlinked gene is epistatic to the B and b color alleles, resulting in a gray coat (q has no effect on color). If animals of genotype B/b; Q/q are intercrossed, what phenotypic ratio is expected in the progeny?
3 black, 12, gray, 1 brown
The diagram below shows a simplified version of the biochemical pathway responsible for fruit color in peppers. Assume that Enzyme 1 is encoded by gene A (a is a null allele), Enzyme 2 is encoded by gene B (b is a null allele), and Enzyme 3, which breaks down the chlorophyll present in the fruit, is encoded by gene C (c is a null allele). In the absence of Enzyme 3, the fruit takes a brown color in the presence of red pigment, but remains green in the absence of red pigment. Enzyme 1 Enzyme 2 Colorless precursor → Yellow pigment → Red pigment Enzyme 3 Chlorophyll (green) → Absence of chlorophyll
3 brown : 1 green : 9 red : 3 yellow
Complete medium (contains all amino acids, vitamins, and a variety of carbon sources) 347 Minimal medium (glucose as a carbon source) 261 Minimal medium + ampicillin (an antibiotic) 51 Minimal medium +methionine (an amino acid) 303 Minimal medium +arginine (an amino acid) 301 Minimal medium +methionine+ampicillin 57 Minimal medium + arginine+ampicillin 64 Reference: Ref 9-1 Based on the data presented in the table above, how many colonies are met- arg-?
4
If a plant of genotype A/a;B/b;C/c;D/d is selfed and the genes assort independently, how many different genotypes will be found among the progeny?
4
In mountain rabbits, the EL-1 gene is located on chromosome 3. Four alleles of this gene have been identified in the population. With respect to EL-1, what is the maximum number of genotypes in the progeny of a single cross between two mountain rabbits?
4
A pure line of Guinea pigs with genotype A/A; b/b is crossed to a pure line with genotype a/a; B/B. The F1 male and female Guinea pigs are crossed to each other to generate the F2. What proportion of the F2 individuals are the result of a recombinant egg being fertilized by a recombinant sperm?
4/16
A double infection experiment is conducted to determine the distance between two markers in the bacteriophage RB49, a phage similar to T2 and T4. A mutation in the first marker (F13-) results in the inability to grow on E. coli strain B178, while a mutation in the second marker (P6-) prevents the phage from growing at high temperature. A permissive E. coli strain is infected with both F13- and P6- phages, and the lysate is analyzed. 1002 plaques were formed on a lawn of permissive E. coli at 37oC, and out of these 1002, 49 also formed plaques on E. coli B178 at high temperature. What is the predicted frequency of phages with genotype F13+P6- in the lysate?
45%
A couple are both heterozygous for the autosomal recessive disease cystic fibrosis (CF). What is the probability that their first child will either be a boy or have CF?
5/8
If a plant of genotype A/a is selfed, and numerous offsprings are scored, what proportion of the progeny is expected to have homozygous genotypes?
50%
A fish of genotype a/a; B/b is crossed to a fish whose genotype is A/a; B/b. What proportion of the progeny will be heterozygous for at least one of the genes? (Assume independent assortment.)
6/8
How many different DNA molecules eight nucleotide pairs long are theoretically possible?
65,536 (4^8)
In certain breeds of rabbits, the t/t genotype results in a specific malformation of the teeth. However, in any given rabbit population, only about 75% of the individuals with a t/t genotype actually have the teeth malformation. What is the penetrance of the t mutant allele?
75%
A plant is heterozygous at three loci. How many different gamete genotypes can it theoretically produce with respect to these three loci?
8
In a trihybrid, how many different gamete genotypes can be produced with respect to the three genes of interest?
8
Mice (Mus musculus) have 40 chromosomes per diploid cell (2n=40). How many double- stranded DNA molecules, and how many chromosomes are there in a mouse cell that is in the G2 stage of the cell cycle?
80 DNA molecules and 40 chromosomes
The three genes, D, E, and F, are closely linked as indicated on the map below. In this region of the genome, there is no interference (the coefficient of coincidence is 1). D 5mu E 10mu F If a trihybrid with genotype ABC/abc is testcrossed, what is the expected percentage of "parentals" within the progeny?
85.5%
Two new mutant lines of a flowering plant have been obtained; one breeds true for blue flower color and the other breeds true for red flower color (wild-type flower color is purple). Consider the following crosses: 1. blue × purple → F1 all purple → F2 75% purple; 25% blue 2. red × purple → F1 all purple → F2 75% purple; 25% red 3. red × blue → F1 all purple If the purple flower color results from the mixture of red and blue pigments, and all the intermediate products in the pigment pathways are colorless, what phenotypic ratios do you expect in the F2 of cross 3?
9 purple : 3 blue : 3 red : 1 white (colorless)
Two new mutant lines of a flowering plant have been obtained; one breeds true for blue flower color and the other breeds true for red flower color (wild-type flower color is purple). Consider the following crosses: 1. blue × purple → F1 all purple → F2 75% purple; 25% blue 2. red × purple → F1 all purple → F2 75% purple; 25% red 3. red × blue → F1 all purple If the red pigment is a precursor of the purple pigment, the blue pigment is a precursor of the red pigment, and a colorless compound is the precursor of the blue pigment in a linear biosynthetic pathway controlling flower color, what phenotypic ratios do you expect in the F2 of cross 3?
9 purple : 4 blue : 3 red
Cystic fibrosis is an autosomal recessive condition. If the parents of a boy with cystic fibrosis have two more children, what is the probability that both of these children will be unaffected?
9/16
In the cross between a female A/a;B/b;c/c;D/d;e/e and male A/a;b/b;C/c;D/d;e/e, what proportion of the progeny will be phenotypically identical to the female parent? (Assume independent assortment of all genes and complete dominance.)
9/64
From one F+ strain, three distinct Hfr strains were derived. The first three markers transferred during an Hfr X F- cross (different for each of the three Hfr) are: Hfr 1: . . . D A F→ Hfr 2: . . . E B F→ Hfr 3: . . . E C D→ Which of the following must be the order of the genes on the bacterial chromosomal circle? (A is shown at both ends to represent circularity. Assume that the Hfr picks up all intermediates between any two represented genes.)
A D C E B F A
To demonstrate linkage of two markers A and B by transformation, one needs to demonstrate that the frequency of transformation by:
A and B is greater than the product of their individual transformation frequencies.
In loppins (small, diploid invertebrates), chocolate-dependent problem-solving ability is an autosomal recessive trait. You have been hired to map the position of the gene controlling this phenotype (called "lu") using two SSLP markers (called "A" and "B"). You first cross two pure-breeding loppins: lu+A[3 repeats] B[5 repeats]/lu-A[3 repeats] B[5 repeats] X lu- A[6 repeats] B[8 repeats]/lu-A[6 repeats] B[8 repeats]. The F1 is then crossed back to the lu-/lu- parent. Which of the following results would indicate that the lu gene is much closer to SSLP "A" than to SSLP "B"?
A higher proportion of lu+A[6 repeats]/lu-A[6 repeats] than lu+B[8 repeats]/lu-B[8 repeats] individuals
In hogs, a dominant allele B results in a white belt around the body. At a separate locus the dominant allele S causes fusion of the two parts of the normally cloven hoof resulting in a condition known as syndactyly. A belted syndactylous sow was crossed to an unbelted cloven-hoofed boar, and in the litter there were: 25% belted syndactylous25% belted cloven. The genotypes of the parents can best be represented as:
B/b;S/s * b/b;s/s
The following is known about the inheritance of size and fur color in Holland lop rabbits: • Crosses between large individuals only produce large individuals. • Crosses between dwarf individuals produce both large and dwarf rabbits in a ratio of 1:2. Such crosses also produce some very small kits (baby rabbits) that generally die within a few days. • Crosses between brown rabbits only produce brown kits. • Some crosses between black rabbits produce only black kits, whereas others produce both black and brown kits. • The size and fur-color phenotypes segregate independently. Based on the information above, what are the expected phenotypes in the F1 of a cross between a dwarf rabbit that breeds true for brown fur color and a large rabbit that breeds true for black fur color?
Black dwarf only
Of the three key building blocks of DNA, which type(s) of building block is/are structurally different in RNA molecules?
Both deoxyribose and nitrogenous bases
In sweet peas, the allele C is needed for color expression (c results in white). The precise color expressed is determined by the alleles R (red) and r (blue). A cross between certain red and blue plants resulted in progeny as follows: 3/8 red, 3/8 blue, 1/4 white. What were the genotypes of the plants crossed?
C/c; R/r × C/c; r/r
The diagram below shows a simplified version of the biochemical pathway responsible for fruit color in peppers. Assume that Enzyme 1 is encoded by gene A (a is a null allele), Enzyme 2 is encoded by gene B (b is a null allele), and Enzyme 3, which breaks down the chlorophyll present in the fruit, is encoded by gene C (c is a null allele). In the absence of Enzyme 3, the fruit takes a brown color in the presence of red pigment, but remains green in the absence of red pigment. Enzyme 1 Enzyme 2 Colorless precursor → Yellow pigment → Red pigment Enzyme 3 Chlorophyll (green) → Absence of chlorophyll Consider two genotypically different pure lines that make colorless peppers. If these two plants are crossed, what phenotypes should be observed in the F1?
Colorless only
Two new pure-breeding strains of mouse (strain 1 and strain 2) have been obtained. Crosses between strain 1 and wild type, as well as crosses between strain 2 and wild type and between strain 1 and strain 2 always produce 100% wild-type mice. What kind(s) of interactions can be deduced from these results show?
Complementation and dominance
Oswald Avery and colleagues strengthened scientific support that DNA was the transforming factor by replicating the Griffith experiment with some important differences in experimental design. They found that the enzyme ______________ was effective at destroying the transforming capacity of S strain biomolecules.
DNase (DNA destruction
A rare, curly winged mutant of Drosophila was found in nature. A mating of this fly with a true-breeding, normal laboratory stock produced progeny in the ratio 1 curly winged to 1 normal (both sexes had the same ratio). All curly winged progeny of this cross, mated with normal progeny of the same cross, again yielded 1 curly winged to 1 normal fly. When mated with one another, the curly winged progeny of the first cross yield a progeny of 623 curly: 323 normal. This ratio strongly suggests which of the following:
Flies homozygous for the curly allele are lethal and never survive.
Using molecular techniques, researchers have knocked out both copies of gene "G" in a series of genetically identical mouse embryos. These mice develop normally, except for their forelimbs, which are missing several small bones. What can be concluded from the results of this experiment?
Gene "G" is necessary for proper development of forelimbs' small bones in mice.
A sweet pea plant of genotype A/A . B/B is crossed to one that is a/a . b/b to produce a dihybrid F1. One cell of one F1 individual (genotype A/a . B/b) goes through meiosis and produces four gametes of the following genotypes: A.b, A.b, a.B and a.B. What can be concluded regarding the linkage relationship between the two genes?
Genes A and B could be linked or unlinked; the result is not indicative of either as in both cases it's possible to obtain 100% recombinant gametes form one meiosis.
A diploid plant is a trihybrid for flower color (gene "F"), leaf size (gene "L") and seed weight (gene "S"); its phenotype includes red flowers, large leaves, and heavy seeds. This plant is crossed to a tester plant (which has white flowers, small leaves, and light seeds). The progeny is as follows: 23 Red, heavy, large 232 White, heavy, large 25 Red, heavy, small 228 White, heavy, small 230 Red, light, large 25 White, light, large 235 Red, light, small 26 White, light, small What can be concluded about the linkage relationships of the three genes in question?
Genes F and S are linked, while L assorts independently.
In pet rabbits, brown coat color is recessive to black coat color. A black female rabbit gives birth to four black-coated and three brown-coated baby rabbits. What can be deduced about the genotype of the baby rabbits' father?
He could be heterozygous black/brown or homozygous brown.
Topoisomerase and helicase have distinct functions that include which of the following?
Helicase is responsible for unwinding the double helix (separating strands).
You have come across a dog (named Cindy) that does not have a tail. Interestingly, all the puppies produced by this dog don't have a tail either. If the lack of tail is caused by a genetic mutation, where has this mutation most likely taken place?
In Cindy's gametes
Which of the following is true with respect to haploid and diploid cells?
In diploid cells, meiosis I results in the formation of two haploid cells.
Pet rabbits can have a variety of coat colors. Below are the results of a series of crosses performed with black-, blue-, and brown-coated pure lines. Cross 1. 2. 3. Phenotypes of parents Black × blue Black × brown Blue × brown F1 phenotypes All black All black All black If the F1 of cross number 3 is selfed, what is the expected proportion of black kits (baby rabbits) in the offspring?
More than 50%, but less than 75%
In a wild-type fungus, protein E (encoded by the haplosufficient gene "E") normally homodimerizes, and the E-E dimer catalyzes a biochemical reaction necessary for the production of a dark pigment. ED represents a mutant, dominant negative allele of gene E. What is the predicted phenotype of a fungus cell of genotype E+/ED, and why?
Mutant (no pigment production), as the mutant allele ED is dominant.
In loppins (fictitious diploid invertebrates), ear shape is controlled by two genes with two alleles each; upright ears (F) is dominant to floppy ears (f), and double-pointed ears (P) is dominant to single-pointed ears (p). Moreover, due to genetic interactions, floppy ears are always single-pointed. A loppin with floppy ears is crossed to a loppin with upright single-pointed ears, and the phenotypic ratios in the offspring are 2 floppy : 1 double- pointed upright : 1 single-pointed upright. What are the genotypes of the parents?
P/p; f/f and p/p; F/f
Of the three key building blocks of DNA, which type(s) of building block is/are negatively charged and oriented on the outside of the double helical structure?
Phosphate
What is the mechanism that ensures Mendel's First Law of segregation?
Segregation of homologous chromosomes during meiosis I
Chargaff's rules do not hold for which of the following genome types?
Single-stranded DNA virus
A plant with small red flowers is crossed to a plant with large white flowers. The resulting F1 is comprised of 75 plants with small red flowers and 72 plants with small white flowers. If flower color and flower size are controlled by a single gene each, what can be concluded from these results?
Small size is dominant to large size, but we can't determine which color is dominant.
Alfred Hershey and Martha Chase examined transformation using bacteriophage (bacterial DNA virus) and bacterial cells. In these experiments, they used radioactivity to label nucleic acids (in this case DNA) proteins. What do radioactive sulfur and phosphate specifically label?
Sulfur labels protein, and phosphate labels DNA.
Suppose that a single gene controls fruit color in mango. Yellow fruit (Y-) is dominant to red fruit (yy). Suppose a true breeding yellow mango plant was crossed with a red-fruited plant and the resulting F1 was selfed. The F2 segregated as expected. If one of the yellow-fruited plants was randomly selected and selfed, what is the probability that its progeny would segregate for fruit color? Explain your logic.
The F2 consists of  YY:  Yy :  yy. Thus, the yellow-fruited plant that was randomly picked could be either YY or Yy. There is a chance that it was YY and  chance that it was Yy. If a YY plant was selected and selfed, the progeny would not segregate for fruit color. If a Yy plant was selected, the progeny would segregate for fruit color.
What process occurring during meiosis ensures independent assortment?
The arrangement of homologous chromosomes on the metaphase plate
Alfred Hershey and Martha Chase examined transformation using bacteriophage (bacterial DNA virus) and bacterial cells. In this experiment, how is transformation (altered phenotype) is displayed?
The bacteria are transformed (by phage DNA) into virus synthesizing cells.
The three bacterial markers a, b, and c are linked, but their order is unknown. A co-transduction experiment is performed and the following results are obtained: - markers a and b are co-transduced at a frequency of 2%; - markers a and c are co-transduced at a frequency of 20%; - markers b and c are co-transduced at a frequency of 65%. What can be concluded about the arrangement of the three markers on the bacterial chromosome?
The order is a-c-b, and c is closer to b than to a.
The nuclear genome of a mouse nerve cell is compared to that of a mouse skin cell. What differences can we expect to see between these two cells' nuclear genomes?
The two cells have the same genome; there will be no differences.
A female Drosophila with singed bristles is crossed to a male with sepia (dark brown) eyes. In the F1, all females are wild-type and all males have singed bristles. F1 males and females are crossed together, and the following F2 phenotypic ratios are obtained: 748 wild-type females 753 wild-type males 742 singed females 747 singed males 249 sepia females 250 sepia males 244 singed, sepia females 246 singed, sepia males If sn and se represent the mutant alleles of the singed and sepia gene, respectively, and sn+ and se+ are their wild-type counterparts, what are the most likely genotypes of the original parents?
Xsn/Xsn; se+/se+ and Xsn+/Y; se/se
If two markers are closely linked, they will show:
a low frequency of recombination and a high frequency of co-transformation.
In laboratory mice, the "short tail" phenotype is dominant to the wild-type ("long tail") phenotype. However, crosses between any two short-tailed mice always produce mixtures of short- and long-tailed offspring. Assuming that tail length is controlled by a single locus, a likely explanation for these results is that the "short tail" allele is:
a recessive lethal allele
Telomerase activity relies upon ________________ for appropriate priming.
a short, telomeric RNA sequence that is carried within its structure
A permissive bacterial strain is simultaneously infected with two strains of T4-like phage. One phage strain has the genotype a-b+, while the other is a+b-. If the map distance between markers a and b is about 10 map units, what proportion of the progeny phages are expected to have the genotype a+b+?
about 1/20
A plant of genotype C/C;d/d is crossed to c/c;D/D, and the F1 is testcrossed. If the genes in question are unlinked, the percentage of double homozygous recessive individuals in the offspring of the testcross will be:
about 25%
Initiation of replication occurs at an origin of replication site that typically includes an AT-rich region. Initiation benefits from these AT-rich regions because
adenine-thymine pairs are held together by two H-bonds, making them easier to separate during unwinding.
An E. coli colony grew on minimal medium supplemented with arginine and leucine. However, bacteria from this colony are unable to grow and form colonies on minimal medium supplemented with arginine and methionine. What is the genotype of the bacteria in this E. coli colony?
arg+leu-met+
A bacterial strain is able to grow on rich medium (which contains all the amino acids, vitamins, and a variety of carbon sources) but not on minimal medium or on minimal medium supplemented with leucine. What could be the genotype(s) of this bacterial strain with respect to the arg and leu loci?
arg-leu- or arg-leu+ 
The complexity of lagging strand replication is necessary because:
as polymerization occurs only in the 5' to 3' direction, the lagging strand must be synthesized in consecutive small fragments.
Remember that, in Labrador retrievers, B (black coat) is dominant to b (brown coat) and homozygosity for the recessive epistatic allele e always results in a yellow coat. A brown female is crossed to a yellow male, and their progeny consists of six black puppies. Interestingly, when one of the F1 females is crossed to her yellow father, she gives birth to seven puppies: three yellow, three black, and one brown. What are the most likely genotypes of the original brown female and yellow male?
b/b; E/E (female) and B/b; e/e (male).
If Escherichia coli, grown for a period of time in 15N, is transferred to 14N for one generation of DNA replication, the resulting DNA should have 14N added to all new DNA. If conservative replication is occurring, the 14N-containing new DNA will compose _________________.
both strands of DNA in half of all bacterial chromosomes
A female rabbit of phenotype c' is crossed to a male rabbit of c^ch. The F1 is comprised of 5 rabbits with a c' phenotype, two with c^ch phenotype, and 3 with c phenotype. Of the phenotypically c rabbits, two are females and are backcrossed to their father. This cross produces only rabbits with c^ch phenotype. These results suggest that:
c is recessive to both c' and c^ch.
A StrR mutant:
can grow in the presence of streptomycin
A gal- mutant
can utilize galactose as a carbon source
In eukaryotic DNA replication, re-association of histones with newly formed DNA is accomplished by:
chromatin assembly factor 1 (CAF-1) and histones binding to the sliding clamp structure.
The gene "C" codes for the membrane-associated protein C, responsible for signal transduction. A mutant allele of this gene, Cm, encodes a malfunctioning C protein, which has the same size as the wild type, associates with the plasma membrane like the wild type, but has no function in signal. With respect to the expression of the C proteins, the wild-type allele is
codominant to the Cm allele.
When comparing the three key models of DNA replication, the model that included the synthesis of a brand new double stranded DNA molecule from an original molecule was named:
conservative replication
A cross is made between an Hfr strain that is StrSa+b+d+ in genotype and an F- strain that is StrRa-b-d- in genotype. Interrupted-mating studies show that b+ enters the recipient strain last, and that the Str locus is very far away from b+, so it never enters the recipient strain. The b+ recombinants are then tested for the presence of the a+ and d+ alleles. The following data were obtained: a+ b+ d+ a- b+ d+ a+ b+ d- a- b+ d- What is the gene order?
d a b str
The Meselson-Stahl experiment made clear predictions regarding experimental outcomes if dispersive, conservative, or semiconservative DNA replication was occurring in their Escherichia coli cells. This experiment enables the detection of new and old DNA by assessing the _______________ of DNA molecules in the cells.
density
In an experimental plant, the genes t and q are linked. A pure breeding t/t individual is crossed to a pure breeding q/q individual to obtain a dihybrid F1. Genotypically, the F1 individuals can be described as:
dihybrids in trans
In the fruitfly Drosophila melanogaster, red and yellow eye pigments are synthesized through the pterin pathway. These, plus the brown pigment synthesized through the ommochrome pathway, produce the dark red Drosophila eye color. A part of the pterin pathway (simplified) is shown below. Modify Remove 3 of 11 Consider the genes encoding Enzyme 1 ("e1"), Enzyme 2 ("e2") and Enzyme 3 ("e3"), respectively. What are their predicted genetic interactions?
e1 is recessively epistatic to e2 and to e3.
The Meselson-Stahl experiment made clear predictions regarding experimental outcomes if dispersive, conservative, or semiconservative DNA replication was occurring in their Escherichia coli cells. To begin the experiment, cells were grown for a period of time in media containing __________ to label the chromosome.
heavy nitrogen
The replisome contains a protein subunit responsible for unwinding the double helix to enable DNA replication. This subunit/enzyme is named:
helicase
In the nematode C. elegans, homozygosity for the "e" mutant allele causes an extreme "uncoordinated" phenotype, where the worm completely loses its ability to move. Examination of 100 individuals with genotype e/e reveals that 58 of them can't move at all, 45 a show very reduced ability to move, and the remaining 17 seem to have a completely wild-type phenotype with respect to movement ability. These observations suggest that e has:
incomplete penetrance and variable expressivity.
Evidence of transformation of R strain cells by biomolecules from S strain cells includes:
isolation of smooth-looking cells from animals infected with "R strain" cells that had been incubated with heat-killed "S strain" cells.the transformed R strain cells gain the ability to kill mice.
When replicating the end of a chromosome, the lagging strand cannot copy the last ~10 nucleotides at the end of the chromosome. As a result, chromosomes contain telomere sequences at their ends, which are defined as:
non-coding, repetitive sequences that can be copied independent of the replisome.
Cell cycle progress enables the initiation of genome replication by:
providing Cdc6 and Cdt1, which aid assembly of initiation components at the origin of replication.
A female Drosophila with the mutant phenotype a is crossed to a male who has the mutant phenotype b. In the resulting F1 generation all females are wild-type and all males have the a mutant phenotype. Based on these results, we can conclude that the mode of inheritance of the phenotypes of interest is:
recessive for both a and b.
When comparing the three key models of DNA replication, the model that included the separation of the two strands of the original DNA (template) and using those strands as templates to synthesize two new DNA strands is called:
semiconservative replication
An interrupted conjugation experiment is conducted using the following strains: Hfr StrSx+y+z+ and F- StrRx-y-z-. Samples of exconjugants are tested at regular intervals for their ability to grow on minimal medium (MM) containing streptomycin plus compound X, Y, or Z. The table below summarizes the number of colonies obtained on the different media when conjugation was interrupted after 10, 15, 20, or 25 minutes. Media used Time of interruption MM+Str+X MM+Str+Y MM+Str+Z 10min 0 0 0 15min 0 10 0 20 min 15 250 0 25 min 250 250 10 Based on these results, what is the order of entry of the four markers in question?
str y x z
An Hfr strain of E. coli with the genotype gly+aziR StrS is mated with an F- strain of E. coli of genotype gly-aziSStrR. Gly refers to the amino acid glycine, azi refers to sodium azide, and Str refers to the antibiotic streptomycin. Conjugation occurs and the progeny are screened on a selective medium to detect recombinants. If you wanted to select for the F- recombinant genotype gly+aziR StrR, you should use a minimal medium containing:
streptomycin and sodium azide
A strain of E. coli has the genotype (and phenotype) leu- lac-. This notation means that this strain if bacteria is unable to:
synthesize the amino acid leucine and utilize the sugar lactose.
Oswald Avery and colleagues strengthened scientific support that DNA was the transforming factor by replicating the Griffith experiment with some important differences in experimental design. The key difference was:
systematically eliminating the impact of classes of "S strain" biomolecules using enzymatic digestion before mixing with "R strain" live cells.
The spontaneous (though infrequent) change of a nitrogenous base to a slightly distinct form is called
tautomerization
Alfred Hershey and Martha Chase examined transformation using bacteriophage (bacterial DNA virus) and bacterial cells. If phage are labeled with radioactive sulfur and allowed to infect bacterial cells, the radioactive sulfur will be localized to:
the outside of infected cells (in phage ghosts).
Smooth (S) and rough (R) strains of Streptococcus pneumonia are distinct because of their ability to cause illness (death in rodents). This trait is controlled by genes that regulate:
the production of a protective polysaccharide coat (capsule) around each cell
A bacterial chromosome has four markers, A, B, C, and D, evenly spaced throughout the circle. A generalized transducing phage will:
transduce any of the markers by different transduction events.
In the classic experiment by Griffith, evidence of the action of a hereditary biomolecule was identified by:
transformation (phenotypic change) of the "R strain" by "S strain" biomolecules.
