2. ( Of all the chromosomal disorders, abnormalities in chromosome number are the most easily identifiable from a karyotype (chromosome smear). While most of the time, meiosis occurs "correctly", occasionally pairs of homologous chromosomes fail to separate during meiosis. This is called nondisjunction. The risk of nondisjunction increases with the age of the parents. Nondisjunction can occur at meiosis I or meiosis II 1. For a diploid cell with n= two chromosomes (so the cell has 2n=4 chromosomes), draw pictures, label the stages, and explain the outcome if nondisjunction occurs at meiosis I or meiosis II. 2. In each case, indicate the percent of gametes that have the normal complement of chromosomes, one extra, and one too few. 3. Give an example of a disease or syndrome that is the result of nondisjunction. Indicate the chromosome involved.

4. Interpret the following images (hint: first describe each as _n=________chromosomes.) A B a. Indicate which diagram shows the following: C one daughter nucleus after telophase of mitosis? one daughter nucleus after telophase of meiosis I? one daughter nucleus after telophase of meiosis II? one nucleus during prophase of mitosis? 88 P b. Which of these diagrams does not fit with the others? D n= n= n= _n= E _1_x Indicate how much DNA is in each compared to its respective gamete which has 1x amount of DNA. In what way is it different? X

2. The amount of DNA in a Drosophila melanogaster somatic cell equals 8 during G1 of interphase, how much DNA is present in the cell during each phase of mitosis and meiosis? Amount of G2 Phase Prophase Metaphase Anaphase Telophase DNA in: Mitosis 8. Meiosis I 8. Meiosis II 4

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1. Based on type, which of the following human cells are diploid? Select all that apply. intestine stomach female sex cell bone ☐male sex cell

Having extra sex chromosome can have less serious negative effects than having an extra autosome and some of the individuals can function within a normal range. However, for some of them is very difficult to expect normal life. Make some comparison between 45, X women and 45, Y.

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c. Draw a cell with n=2 during metaphase of meiosis I. Use two colors to show that crossing over and independent assortment have occurred. d. Draw cells with n=2 during metaphase of to show that crossing over and independent assortment have occurred. eiosis Use two color

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