Guided Reading Questions Meiosis

Meiosis Guided Reading Questions Define and apply the terms: somatic cell, gamete, sister chromatid, homologous chromosomes, diploid, haploid. Contrast meiosis from mitosis in the stages and outcomes. Explain how meiosis creates such great variation. 1. In humans, we have 46 chromosomes in any somatic cell. Each of these is a pair. For example, you have two copies of chromosome number 1. You inherited one from your mother (in the egg cell) and one from your father (in the sperm cell). What do we call these pairs? ______Homologous chromosomes_____________. 2. Use the following words to describe the life cycle of humans. Make a concept map or diagram: diploid, haploid, egg, sperm, meiosis, zygote, fertilization, mitosis, adult 3. A diploid organism has 22 chromosomes in its somatic cells. How many chromosomes will be in the gametes? 23 5. Contrast the term diploid from haploid: Diploid organisms have cells containing two homologous sets of chromosomes, while haploid organisms reproduce sexually and contain a single set of chromosomes. 6. How many divisions take place in mitosis? ___1__ How many in meiosis? _2__ If a fruit fly cell has 8 chromosomes, how many chromosomes will be in the daughter cells after a cell goes through mitosis? __8_ How many chromosomes are present in daughter cells after meiosis in a fruit fly? _4__ 7. Crossing over takes place during prophase I. What does this mean exactly? Nonsister chromatids of each homologous pair of chromosomes exchange segments During anaphase I, what is being pulled apart? Tetrads. During anaphase II, what is being pulled apart? Centromere. 8. Are the cells produced just after meiosis I considered haploid or diploid and why? Why is another division needed after meiosis I? It produces two haploid cells. The crossing over maximizes scope for variations and evolution, so the organism can survive in its environment better. 9. Examine figure 8.14, what makes metaphase I different from metaphase of mitosis? The tetrads in Metaphase Ⅰ line up are the metaphase plate, while individual chromosomes line up are the metaphase plate in Metaphase. Why are the chromosomes colored red and blue in this figure? What does red or blue represent? Different colors enable to distinguishes the two chromosomes of each homologous pair. Red represents chromosomes from mother and blue represents chromosomes from father. 10. While mitosis produces cells that are identical to the parent, meiosis produces gametes that have half the genetic content as the parent cell and produces much variation. This variation “shuffles” up the genetic content, so that every gamete produced from a single person is unique. As this incredibly unique sperm randomly fertilizes an incredibly unique egg unique offspring. That is why you are the only YOU (aside from any identical twins in the class!) So where does the variation come from? Independent orientation and crossing over. Let’s explore the significance of these processes. Describe for yourself or draw (based on fig 8.15) why independent orientation of homologs at metaphase I produces variation. Independent assortment produces variation because it results different gametes depending on how they're arranged at the metaphase plate; occurs during metaphase 1 Explain why crossing over between homologous chromosomes produces variation. Crossing over produces variation because it creates new combinations of genes that were present in either parent Imagine a chromosome that has alleles “R” and “g” on it. The homologous chromosome has different versions of these genes and contains the “r” and “G” versions. What are the possible gamete combinations that can occur? Rr RG rg rG