Concept explainers
Researchers have discovered that some regions of chromosomes are much more likely than others to cross over. We might call such a region a “hot spot” for crossing over. Let’s suppose that two genes, gene A and gene B, are
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Genetics: Analysis and Principles
- Two phenotypically normal parents produce a phenotypically abnormal child in which chromosome 5 is missing part of its long arm but has a piece of chromosome 7 attached to it. The child also has one normal copy of chromosome 5 and two normal copies of chromosome 7. With regard to chromosomes 5 and 7, what do you think are the chromosomal compositions of the parents? Would it most likely be reciprocal translocation? It wouldn't be simple translocation because then the child would have the entirety of one chromosome and only some of the other, but in this case, there is only partial chromosome 5 and chromosome 7?arrow_forwardIn humans, chromosome 16 sometimes has a heavily stained area near the centromere. This feature can be seen in a microscope, but otherwise has no effect on the phenotype of the person carrying it. When such a “blob" exists on a given copy of chromosome 16, it is a constant feature of that chromosome and is inherited. A couple conceived a child, but the fetus had multiple abnormalities and was miscarried. e.g., The fetus had three copies of chromosome 16, where 2 of the 3 copies of chromosome 16 had large blobs. Both of the mother's copies of chromosome 16 lacked blobs, but the father was heterozygous for blobs. The fetus was formed from a fertilization event that included a gamete produced by the in which nondisjunction occurred during the meiotic division. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a mother; first. mother; second. father; first. C Your answer d father; second. E3 Fullso L e Insufficient information is provided…arrow_forwardA cytogeneticist has collected tissue samples from members of a certain butterfly species. Some of the butterflies were located in Canada, and others were found in Mexico. Through karyotyping, the cytogeneticist discovered that chromosome 5 of the Canadian butterflies has a large inversion compared with chromosome 5 of the Mexican butterflies. The Canadian butterflies were inversion homozygotes, whereas the Mexican butterflies had two normal copies of chromosome 5. 1) Would a cross between Mexican and Canadian butterflies produce phenotypically normal offspring? and 2) Would the offspring of the cross (so F2 generation) be fertile?arrow_forward
- In humans, chromosome 16 sometimes has a heavily stained area in the long arm near the centromere. This feature can be seen through the microscope but has no effect on the phenotype of the person carrying it. When such a “blob” exists on a particular copy of chromosome 16, it is a constant feature of that chromosome and is inherited. A couple conceived a child, but the fetus had multiple abnormalities and was miscarried. When the chromosomes of the fetus were studied, it was discovered that it had three copies of chromosome 16 (it was trisomic for chromosome 16), and that two of the three chromosome 16s had large blobs. Both chromosome 16 homologs in the mother lacked blobs, but the father was heterozygous for blobs. Which parent experienced nondisjunction, and in which meiotic division did it occur?arrow_forwardThe karyotype of a young girl who is affected with Down syndrome revealed that she has 46 chromosomes. Her phenotypically normal older brother's karyotype revealed that he has 45 chromosomes. (a) Propose an explanantion for the chromosome number in both children (b) What would you expect the chromosome number of the parents of these two children?arrow_forwardIn corn, the genes v (virescent seedlings), pr (red aleurone), and bm (brown midrib) are all on chromosome 5, but not necessarily in the order given. The cross: v+ pr bm/ v pr+ bm+ with v pr bm/ v pr bm produces 1000 progeny with the following phenotypes: v+ pr bm 226 v pr+ bm+ 229 v+ pr bm+ 153 v pr+ bm 185 v+ pr+ bm 59 v pr bm+ 71 v+ pr+ bm+ 36 v pr bm 41 What is the gene order, and the (b) genetic map of these three genes?arrow_forward
- In a human genetic study, a family with five phenotypicallynormal children was investigated. Two children were “homozygous”for a Robertsonian translocation between chromosomes19 and 20 (they contained two identical copies of the fusedchromosome). They have only 44 chromosomes but a completegenetic complement. Three of the children were “heterozygous”for the translocation and contained 45 chromosomes,with one translocated chromosome plus a normal copy of bothchromosomes 19 and 20. Two other pregnancies resulted instillbirths. It was later discovered that the parents were firstcousins. Based on this information, determine the chromosomecompositions of the parents. What led to the stillbirths? Whywas the discovery that the parents were first cousins a key pieceof information in understanding the genetics of this family?arrow_forwardThe genes that codes for the creation of certain blood groups are located on chromosome "XGp22.3", chromosome "12p12.3", chromosome "2q14.3", and so on. What is this chromosome terminology? What does it mean?arrow_forwardIn a college genetics laboratory course, a healthy student constructs a karyotype from a cell from inside her cheek. She finds only one chromosome 3 and one chromosome 21, plus two unusual chromosomes that do not seem to have matching partners. a. What type of chromosomal abnormality does she have? b. Why doesn’t she have any symptoms? c. Would you expect any of her relatives to have particular medical problems?arrow_forward
- Mitotic recombination can occasionally produce a twin spot.Let’s suppose an animal species is heterozygous for two genesthat govern fur color and length: one gene affects pigmentation,with dark pigmentation (A) dominant to albino (a); the other geneaffects hair length, with long hair (L) dominant to short hair (l).The two genes are linked on the same chromosome. Let’s assume ananimal of this species is AaLl; A is linked to l, and a is linked to L.Draw the chromosomes labeled with these alleles, and explainhow mitotic recombination could produce a twin spot with onespot having albino pigmentation and long fur and the other havingdark pigmentation and short fur.arrow_forwardA wild-type chromosome has the following segments: A B C • D E F G H I Researchers have found individuals that are heterozygous for each of the following chromosome mutations. For each mutation, sketch how the wild-type and mutated chromosomes would pair in prophase I of meiosis, showing all chromosome strands. a. A B C • D E F D E F G H I b. A B C • D H I c. A B C • D G F E H I d. A B E D • C F G H Iarrow_forwardA cytogeneticist has collected tissue samples from members of acertain butterfly species. Some of the butterflies were located inCanada, and others were found in Mexico. Through karyotyping,the cytogeneticist discovered that chromosome 5 of the Canadianbutterflies had a large inversion compared with chromosome 5 ofthe Mexican butterflies. The Canadian butterflies were inversionhomozygotes, whereas the Mexican butterflies had two normalcopies of chromosome 5.Explain whether a mating between Canadian and Mexicanbutterflies would produce phenotypically normal offspring?arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning