FIGURE 17-30 The segregating chromosomes of a reciprocal- translocation heterozygote form a cross-shaped pairing configuration. The two most commonly encountered segregation pattems that result are the often inviable "adjacent-1" and the viable "alternate." N, and N2, normal The two main chromosome-segregation patterns in a reciprocal-translocation heterozygote Translocation heterozygote Original position of translocated segments nonhomologous chromosomes; T, and T2, translocated chromosomes. Normal Translocated Up and Down designate the opposite poles to which homologs migrate in anaphase I. O LounchPad ANIMATED ART: Chromosome rearangements: reciprocal transocation Pairing configuration N, Two types of segregations: Adjacent-1 Final meiotic products Often inviable Up T, +N2 Duplication of purple, deletion of yellow translocated segment Duplication of yellow, deletion of purple translocated segment Down N, + T2 Alternate Up Translocation genotype Down N+N Normal Both complete and viable

FIGURE 17-30 The segregating chromosomes of a reciprocal- translocation heterozygote form a cross-shaped pairing configuration. The two most commonly encountered segregation pattems that result are the often inviable "adjacent-1" and the viable "alternate." N, and N2, normal The two main chromosome-segregation patterns in a reciprocal-translocation heterozygote Translocation heterozygote Original position of translocated segments nonhomologous chromosomes; T, and T2, translocated chromosomes. Normal Translocated Up and Down designate the opposite poles to which homologs migrate in anaphase I. O LounchPad ANIMATED ART: Chromosome rearangements: reciprocal transocation Pairing configuration N, Two types of segregations: Adjacent-1 Final meiotic products Often inviable Up T, +N2 Duplication of purple, deletion of yellow translocated segment Duplication of yellow, deletion of purple translocated segment Down N, + T2 Alternate Up Translocation genotype Down N+N Normal Both complete and viable

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter6: Cytogenetics: Karyotypes And Chromosome Aberrations

Section: Chapter Questions

Problem 1QP: Analyzing Karyotypes 1. Originally, karyotypic analysis relied only on size and centromere placement...

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Analyzing Karyotypes 1. Originally, karyotypic analysis relied only on size and centromere placement to identify chromosomes. Because many chromosomes are similar in size and centromere placement, the identification of individual chromosomes was difficult, and chromosomes were placed into eight groups, identified by the letters A to G. Today, each human chromosome can be readily identified. a. What technical advances led to this improvement in chromosome identification? b. List two ways this improvement can be implemented. c. What clinical information does a karyotype provide?
On Neurospora chromosome 4, the leu3 gene is just to theleft of the centromere and always segregates at the firstdivision, whereas the cys2 gene is to the right of the centromere and shows a second-division segregation frequency of 16 percent. In a cross between a leu3 strain anda cys2 strain, calculate the predicted frequencies of thefollowing seven classes of linear tetrads where l = leu3 andc = cys2. (Ignore double and other multiple crossovers.)
. Chromosome 3 of corn carries three loci (b for plant-color booster, v for virescent, and lg for liguleless). A testcross of triple recessives with F1 plants heterozygous forthe three genes yields progeny having the followinggenotypes: 305 + v lg, 275 b + +, 128 b + lg, 112 + v +,74 + + lg, 66 b v +, 22 + + +, and 18 b v lg. Give the genesequence on the chromosome, the map distances between genes, and the coefficient of coincidence.
An individual is heterozygous for a reciprocal translocation, with the following chromosomes: A • B C D E F A • B C V W X R ST • U D E F R ST • U V W X Q. Draw the products of alternate, adjacent-1, and adjacent-2 segregations.
A woman who sought genetic counseling is found to be heterozygousfor a chromosomal rearrangement between the second andthird chromosomes. Her chromosomes, compared to those in anormal karyotype, are diagrammed on the next page:(a) What kind of chromosomal aberration is shown?
During ascus formation in Neurospora, any ascosporewith a chromosomal deletion dies and appears whitein color. How many of the eight ascospores in theascus would be white if the octad came from a crossof a wild-type strain with a strain of the oppositemating type carrying:a. a paracentric inversion, and no crossovers occurredbetween normal and inverted chromosomes?b. a pericentric inversion, and a single crossoveroccurred in the inversion loop?c. a paracentric inversion, and a single crossoveroccurred outside the inversion loop?d. a reciprocal translocation, and an adjacent-1segregation occurred with no crossovers betweentranslocated chromosomes?e. a reciprocal translocation, and alternate segregationoccurred with no crossovers between translocatedchromosomes?f. a reciprocal translocation, and alternate segregation occurred with one crossover between translocated chromosomes (but not between thetranslocation breakpoint and the centromereof any chromosome)?
The a, b, and c loci are all on different chromosomesin yeast. When a b+ yeast were crossed to a+ b yeastand the resultant tetrads analyzed, it was found thatthe number of nonparental ditype tetrads was equal tothe number of parental ditypes, but there were no tetratype asci at all. On the other hand, many tetratypeasci were seen in the tetrads formed after a c+ wascrossed with a+ c, and after b c+ was crossed withb+ c. Explain these results.
Progeny of triploid tomato plants often contain parts of an extra chromosome, in addition to the normal complement of 24 chromosomes . Mutantswith a part of an extra chromosome are referred to as secondaries. James and Margaret Lesley observed that secondaries arise from triploid (3 n), trisomic (3 n + 1), and double trisomic (3 n + 1 + 1) parents, but never from diploids (2 n). Give one or more possible reasons that secondaries arise from parents that have unpaired chromosomes but not from parents that are normal diploids.
Rice has a chromosome number of 2n = 24. If different euploids and anaeuploids are available in rice, identifythe chromosomal mutation, chromosome configuration, chromosome number, and/or type of gametes in each of the mutations below. Complete the table. Example: for 10B, the answer is "10 II + 2 I"
An individual heterozygous for a reciprocal translocation possesses the following chromosomes: A B • C D E F G A B • C D V W X R S • T U E F G R S • T U V W X Q. Give the products that result from alternate, adjacent-1, and adjacent-2 segregation.
why The chromatids formedby recombination within the inversion loop of a paracentric inversionheterozygote containtwo centromeres or none, instead of the normal one ?
A heterozygous reciprocal translocation involving 2 non-homologous chromosomes resulted to a new sequence ABCDXYZ and TUVWEFG. Illustrate the chromosomes before and after translocation and the pachytene configuration of the chromosome after translocation.