genetic - Chapter 5

A linkage group can be defined as genes that may be so far apart on a chromosome that they cannot be shown to be linked directly but they can be shown to be on the same chromosome due to their linkage with other genes. A: TRUE B: FALSE

A

Another name for a chromosome is a _______, since it contains genes that are often inherited together. A. linkage group B. crossing over group C. genetic recombinant D. bivalent

A

Chiasmata can be seen through a light microscope and are sites of recombination. A: TRUE B: FALSE

A

Genes that are not syntenic are not linked. A: TRUE B: FALSE

A

If an individual is heterozygous at two loci (Ab/aB) which are on the same chromosome arm with the A locus closest the centromere under what conditions would a crossover in a somatic cell generate a twin spot? A. The crossover would have to occur between the A locus and the centromere locus and involve two homologous (non-sister) chromatids. B. The crossover would have to occur between the A locus and the B locus and involve two homologous (non-sister) chromatids. C. The crossover would have to occur between the B locus and the end of the chromosome locus and involve two homologous (non-sister) chromatids. D. A double crossover would have to occur, with one crossover between the A locus and the centromere and a second crossover between the A and B loci locus and both crossovers would have to involve two homologous (non-sister) chromatids. E. No crossover in a somatic cell could generate a twin spot.

A

If the p value corresponding to a given X^2 value and number of degrees of freedom exceeds 0.05, then the null hypothesis is rejected and it is predicted that the two genes being evaluated are not linked. A: TRUE B: FALSE

A

In an ordered octad, every spore is adjacent to at least one spore that is genetically identical to itself. A: TRUE B: FALSE

A

Sturtevant's detailed mapping studies of the X chromosome of Drosophila established what genetic principle? A. That genes are arranged in a linear order on the chromosomes. B. That genes are carried on chromosomes. C. That sex determination is controlled by the X and Y chromosomes. D. That segregation of an allelic gene pair is accompanied by disjunction of homologous chromosomes. E. That different pairs of chromosomes assort independently.

A

Suppose an individual is heterozygous for a pair of alleles (e.g., A/a). Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells homozygous for a? (Pick the most precise answer.) A. The crossover would have to occur between the A locus and the centromere and involve two homologous (non-sister) chromatids. B. The crossover would have to occur between the A locus and the end of the chromosome and involve two homologous (non-sister) chromatids. C. The crossover would have to occur on the same chromosome arm as the A locus and involve two homologous (non-sister) chromatids. D. The crossover would have to occur on the same chromosome as the A locus and involve two homologous (non-sister) chromatids. E. The crossover would have to occur between the A locus and the centromere and involve two sister chromatids (not homologous) chromatids.

A

The R/r and S/s genes are linked and 10 map units apart. In the cross Rs/rS X rs/rs what fraction of the progeny will be RS/rs? A. 5% B. 10% C. 25% D. 40% E. 45%

A

The cross Lpq / lPQ X lpq / lpq is carried out and the L gene is found to be in the middle. What would be the genotypes of the double crossover gametes in this cross? A. LPQ and lpq B. LpQ and lPq C. lpQ and LPq D. Lpq and lPQ E. cannot be determined

A

The hypothesis that predicts no linkage between genes is known as the null hypothesis. A: TRUE B: FALSE

A

The length of an entire linkage group or chromosome may exceed 50 mu because the map distance is calculated from the addition of the distance between many gene pairs. A: TRUE B: FALSE

A

What is the p value from this test? (Pick the most accurate choice.) A: p > 0.5 B: 0.1 < p < 0.5 C: p < 0.1 D: p < 0.05 E: p < 0.01

A

Chiasmata are structures of cross over between sister chromatids of homologous chromosomes. A: TRUE B: FALSE

B

In Drosophila, the genes b, c, and sp are linked and arranged as shown below: b——30 mu——c——20 mu——sp This region exhibits 90% interference. How many double crossovers would be recovered in a three-point cross involving b, c, and sp out of 1000 progeny? A. 3 B. 6 C. 54 D. 60 E. 600

B

Large sectors suggest a mitotic recombination event late in the growth of a yeast colony. A: TRUE B: FALSE

B

Suppose a three-point testcross was conducted involving the genes X, Y, and Z. If the most abundant classes are XYz and xyZ and the rarest classes are xYZ and Xyz, which gene is in the middle? A. X B. Y C. Z D. cannot be determined

B

Suppose the L and M genes are on the same chromosome but separated by 100 map units. What fraction of the progeny from the cross LM/lm X lm/lm would be Lm/lm? A. 10% B. 25% C. 50% D. 75% E. 100%

B

Tetrad analysis shows that crossing over occurs at the four-strand stage (i.e., after replication) because, when two genes are linked, A. NPD > T. B. T > NPD. C. T > PD. D. PD > NPD. E. PD > T.

B

The Q gene locus is 10 map units from the R gene locus which is 40 map units from the S gene locus: Q——10 mu——R——40 mu——S Which interval would likely show the higher ratio of double to single chiasmata? A. Q-R B. R-S C. The ratios would be the same in the two intervals. D. Two chiasmata never occur in the same interval.

B

The pairwise map distances for four linked genes are as follows: A-B = 22 m.u., B-C = 7 m.u., C-D = 9 m.u., B-D = 2 m.u., A-D = 20 m.u., A-C = 29 m.u. What is the order of these four genes? A: ABCD B: ADBC C: ABDC D: BADC E: CADB

B

Twin spotting provides evidence of what genetic event? A. Meiotic recombination B. Mitotic recombination C. Linkage D. Mutation E. Biological evolution

B

Two genes are considered linked when F2 progeny more commonly show the recombinant genotype. A: TRUE B: FALSE

B

43. What happens physically during the process of crossing over? A. Two homologous chromatids break and rejoin at random sites along the chromosome. B. The genetic information on one chromatid is replaced by copying genetic information from a homologous chromatid without there being any physical exchange between the chromosomes. C. Two homologous chromatids break and rejoin at precisely the same site along the chromosome so that there is no loss or gain of material on either product. D. It is not known what occurs during crossing over.

C

A dihybrid test cross is made between genes H and I. Four categories of offspring are produced: HI, Hi, hI, and hi. You wish to use the X2 test to test the hypothesis that the H and I genes are unlinked. How many degrees of freedom would there be in this test? A. 1 B. 2 C. 3 D. 4 E. 0

C

Crossing over takes place in paired bivalents consisting of ______ chromatids, and involves _______ of the chromatids. A. 2, 2 B. 2, 4 C. 4, 2 D. 4, 4 E. 8, 4

C

If the map distance between genes A and B is 10 map units and the map distance between genes B and C is 25 map units, what is the map distance between genes A and C? A: 15 map units B: 35 map units C: either 15 map units or 35 map units, depending on the order of the genes D: The map distance between A and C can not be predicted from these data.

C

In Drosophila, singed bristles (sn) and carnation eyes (car) are both caused by recessive X-linked alleles. The wild-type alleles (sn+ and car+) are responsible for straight bristles and red eyes, respectively. A sn car female is mated to a sn+ car+ male and the F1 progeny are interbred. The F2 are distributed as follows sn car 55 sn car+ 45 sn+ car 45 sn+ car+ 55 20 0 What is the X^2 value for a test of the null hypothesis? A. 0.5 B. 1.0 C. 2.0 D. 0.4 E. 20

C

In Drosophila, singed bristles (sn) and cut wings (ct) are both caused by recessive, X-linked alleles. The wild type alleles (sn+ and ct+) are responsible for straight bristles and intact wings, respectively. A female homozygous for sn and ct+ is crossed to a sn+ct male. The F1 flies are interbred. The F2 males are distributed as follows sn ct 13 sn ct+ 36 sn+ ct 39 sn+ ct+ 12 What is the map distance between sn and ct? A. 12 m.u. B. 13 m.u. C. 25 m.u. D. 50 m.u. E. 75 m.u.

C

In tetrad analysis, second-division segregations result from A. single crossovers between linked genes. B. double crossovers between linked genes. C. single crossovers between a gene and a centromere. D. independent assortment of unlinked genes. E. nondisjunction of homologs.

C

The zipper-like connection between paired homologs in early prophase is known as a A: spindle fiber. B: synaptic junction. C: synaptonemal complex. D: chiasma. E: none of the choices are correct.

C

Which of the following types of tetrads contain two recombinant and two parental asci? A. PD only B. PD and NPD C. T only D. PD and T E. NPD and T

C

In humans, the genes for red-green color blindness (R = normal, r = color-blind) and hemophilia A (H = normal, h = hemophilia) are both X-linked and only 3 map units apart. 48. Suppose a woman has four sons, and two are colorblind but have normal blood clotting and two have hemophilia but normal color vision. What is the probable genotype of the woman? A. HR / hr B. Hr / hr C. hr / hR D. Hr / hR E. HR / Hr

D

Recombination frequencies near 50% suggest that A. two genes are on different chromosomes. B. two genes lie very close together on the same chromosome. C. two genes are on the same chromosome but lie very far apart. D. two genes are on different chromosomes, or two genes are on the same chromosome but lie very far apart. E. none of the choices are correct.

D

Some of the larger human chromosomes typically contain multiple chiasmata during meiotic prophase. If you were to carefully study the distribution of these chiasmata, what would you find? A. Chiasmata are randomly distributed along chromosomes. B. All chromosome pairs have the same number of chiasmata. C. A single chromosome pair always has the same number of chiasmata in every meiotic cell. D. Chiasmata are spaced along a chromosome arm more regularly than would be expected by chance. E. Chiasmata are spaced more irregularly along a chromosome arm than would be expected by chance.

D

Suppose the map for a particular human chromosome interval is: a——1 mu——b——1 mu——c——1 mu——d——1 mu——e——1 mu——f In a man heterozygous for all six genes, what fraction of his sperm would be recombinant in the a-f interval? A. 0% B. 1% C. 2.5% D. 5% E. Cannot be determined

D

The map of a chromosome interval is: A——10 mu——B——40 mu——C From the cross Abc / aBC X abc / abc, how many double crossovers would be expected out of 1000 progeny? A. 5 B. 10 C. 20 D. 40 E. 80

D

Which of the following processes can generate recombinant gametes? A. Segregation of alleles in a heterozygote. B. Crossing over between two linked heterozygous loci. C. Independent assortment of two unlinked heterozygous loci. D. Crossing over between two linked heterozygous loci and independent assortment of two unlinked heterozygous loci E. Segregation of alleles in a heterozygote, crossing over between two linked heterozygous loci and independent assortment of two unlinked heterozygous loci

D

Which statement(s) below apply to the concept of gene linkage? A. The different alleles of two or more genes that are on a chromosome are inherited in an manner inconsistent with Mendel's Second law B. Recombination between homologous chromosomes during meiosis results in different combinations of alleles for different genes C. Recombination between sister chromatids during meiosis results in different combinations of alleles for different genes A: A only B: B only C: C only D: A and B E: A, B, and C

D

A woman whose mother is colorblind and whose father has hemophilia A is pregnant with a boy and what is the probability that the baby will have normal vision and blood clotting? A. 0.03 B. 0.15 C. 0.485 D. 0.47 E. 0.015

E

Genes Q and R are 20 map units apart. If a plant of genotype QR / qr is selfed, what percentage of the progeny will be qr in phenotype? A. 4% B. 10% C. 16% D. 20% E. 40%

E

Individuals heterozygous for the RB+ and RB- alleles can develop tumors as a result of A. a mitotic crossover that leads to homozygosity for both RB+ and RB-. B. a somatic mutation in the RB+ allele that leads to homozygosity for RB-. C. a somatic mutation in the RB- allele that leads to homozygosity for RB+. D. the fact that RB- is dominant to RB+. E. a mitotic crossover that leads to homozygosity for both RB+ and RB- and a somatic mutation in the RB+ allele that leads to homozygosity for RB-.

E

The R/r and S/s genes are linked and 10 map units apart. In the cross Rs / rS X rs / rs what percentage of the progeny will be Rs / rs? A. 5% B. 10% C. 25% D. 40% E. 45%

E

The measured distance between genes D and E in a two point test cross is 50 map units. What does this mean in physical terms? A. D and E are on different pairs of chromosomes. B. D and E are linked and exactly 50 map units apart. C. D and E are linked and at least 50 map units apart. D. Either D and E are on different pairs of chromosomes or D and E are linked and exactly 50 map units apart E. either D and E are on different pairs of chromosomes or D and E are linked and at least 50 map units apart

E