2. [1 points]. Caenorhabditis elegans (the famous model organism used in biomedical research for which 3 Nobel prizes have been awarded) has 5 autosomes and an X chromosome. Hermaphrodites have two X chromosomes (XX) and males have only one (that is, males are XO, where the "O" stands for "no homolog for the X", or "nullo"). Draw mitosis and meiosis for a male and for a hermaphrodite. What is the total number of possible combinations of chromosomes in C. elegans male sperm due to independent assortment at Metaphase I of meiosis? [Another way to think about the question is, disregarding recombination/crossing-over, what is the total number of genetically different male gametes produced, assuming that homologous pairs are different in at least one locus?] [Hint: Males can produce gametes that are "nullo" (O) for the X, as well as gametes that have an X, because the X dyad only segregates to one of the two poles during meiosis I.] Explain your answer. 3. [1 point] During which phases of mitosis are chromosomes each composed of two chromatids? A. From the end of S phase through metaphase B. Through G1and anaphase C. From metaphase through telophase D. from anaphase through telophase E. in G0 only 4. [2 points] If there are 20 centromeres in a cell at anaaphase of mitosis, how many chromosomes are there in each daughter cell following cytokinesis? And how many chromosomes would there be in a
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elegans, a male has 5 autosomes and one X chromosome, while a hermaphrodite has 5 autosomes and two X chromosomes. Show more…
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1. Consider a diploid cell in a male frog that has three pairs of chromosomes designated as A A, B B and C C. Each pair of chromosomes has a maternal and paternal member (e.g. Am and AP) each originally derived from the frog’s mother and father respectively. Using these designations, demonstrate your understanding of mitosis and meiosis by answering the following questions. B) During meiosis, assuming no crossing over, draw the chromosomes with chromatids that would be present at Metaphase I. What combination would be present at the poles at the end of Anaphase I? Are there any other alignments other than what you have drawn? What are they? C) For your original drawing of Metaphase I and Anaphase I of part B, what would be the chromosome combinations found in Anaphase II, just before sperm formation in Telophase II? If there were other alignments in Metaphase I or combinations in Anaphase I, what would be the other resulting chromosome combinations be in the sperm for these cases? D) In question B above, assume that chromosomes C fail to disjoin (separate) in Anaphase I. What would be the combination of chromosomes in the sperm (Telophase II) be? If these sperm all fuse via fertilization with normal gametes (ovules) from a female frog, what proportion will be diploid? What will the others be?
Supreeta N.
1 a. How many chromosomes are found in a single cell during Metaphase II of Meiosis II (point A) of this diagram? Possible answers: 4, 2, 8, 16 1 b. How many chromosomes are found in a single cell during Anaphase II of Meiosis II (point B) of this diagram? Possible answer choices: 4, 8, 2, 16 1c. How is meiosis important for sexual reproduction in humans? All of these. It halves the number of chromosomes that would otherwise be passed onto offspring. It allows for the production of haploid gametes by only having one round of replication, followed by two rounds of division. It enhances the genetic variability that is important for the evolution of a species. None of these.
Evelyn D.
How does the segregation of traits result in different combinations of gametes at the end of meiosis? a. The chromosomes randomly align during metaphase I at the equator, and separation of homologous chromosomes occurs during anaphase I. Similarly separation of sister chromatids occurs at anaphase II of meiosis II. At the end of meiosis II, four different gametic combinations are produced, each containing a haploid set of chromosomes. b. The chromosomes randomly align during anaphase I at the equator. Separation of bivalent chromosomes occur during metaphase I of meiosis I. Similarly, separation of sister chromatids occurs at metaphase II of meiosis II. At the end of meiosis II, four different gametic combinations are produced, each containing a haploid set of chromosomes. c. The chromosomes randomly align during prophase I at the equator, and separation of sister chromatids occurs during metaphase I of meiosis I. Similarly separation of bivalent chromosomes occur at metaphase II of meiosis II. At the end of meiosis II, four different gametic combinations are produced, each containing a diploid set of chromosomes. d. The chromosomes randomly align during prophase I at the equator, and separation of bivalent chromosomes occur during anaphase I of meiosis I. Similarly, separation of homologous chromosomes occurs at metaphase II of meiosis II. At the end of meiosis II, four different gametic combinations are produced, each containing a diploid set of chromosomes.
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