Describe normal embryo formation and two mechanisms of nondisjunction represented in the figure and identify the consequences of these chromosomal anomalies
What will be an ideal response?
The figure represents uniparental disomy, which can be produced by several mechanisms involving nondisjunction. (a) Normal chromosomal configuration where gametes contain one copy of each chromosome and fertilization produces a zygote carrying two copies of a chromosome—one derived from each parent. (b) Nondisjunction in both parents, in which one gamete carries both copies of a chromosome and the other gamete is missing a copy of that chromosome. Fertilization produces a diploid zygote, but both copies of one chromosome are inherited from a single parent. (c) Nondisjunction in one parent, resulting in the loss of a chromosome. This gamete fuses with a normal gamete to produce a zygote monosomic for a chromosome. An error in the first mitotic division results in duplication of the monosomic chromosome, producing uniparental disomy.
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10. One of the two major distinguishing characteristics of mollusks is
(a) the presence of three body regions. (b) the mantle. (c) segmentation of the body. (d) jointed appendages.
Which of the following is a component of the spore—or zygote—wall (in mosses, ferns, gymnosperms, and angiosperms) and helps prevent the desiccation of these structures?
A. sporangium B. sporopollenin C. chitin D. peptidoglycan E. sporangia
All of the genes in a population comprise its
A) genotype. B) gene pool. C) gene reservoir. D) genome.
Staphylococcus aureus produces the enzyme ________, which causes blood plasma to clot.
Fill in the blank(s) with the appropriate word(s).