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unit 3 bio.odt

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BLG 311
Mc Grey

13. Match the events to the correct phase of meiosis. a) pairs of homologous chromosomes line up along the equator of the cell (metaphase I) b) synapsis occurs and the four chromatids form a tetrad (prophase I) c) replication of the genetic material (interphase I) d) one member of the homologous pair segregates from the other and begins to move to opposite sides (anaphase I) e) sister chromatids split at the centromere and move toward opposite poles (anaphase II) 14. List the differences between meiosis and mitosis. - mitosis occurs in all cells, meiosis occurs only in reproductive organs - mitosis results in two diploid cells, meiosis results in four haploid cells - in mitosis homologous chromosomes do not pair. - in meiosis homologous chromosomes do pair up. - in mitosis crossing over does not occur. - in meiosis crossing over occurs and increases genetic diversity 15. Define the following a) homologous pairs (b) sister chromatids (c) tetrad - homologous pairs: chromosomes come in pairs called homologous pairs. They are chromosomes that are similar, but not identical. Humans really have 23 pairs of chromosomes. There are two chromosome number 1s, two chromosome number 2s, etc. The homologous pairs are the maternal (inherited from the mother) and paternal (inherited from the father) versions of the same chromosome. EX: the homologous pair for eye colour are similar because they are for the same trait, but not identical. The alleles may be different, the allele passed on from the mother may be brown eye colour, and from the father blue eye colour. - sister chromatids: Each chromosome is made of two sister chromatids held together by a centromere. The two chromatids are identical copies of genetic information. -tetrad: the homologous pair which is made up of four chromatids, is called tetrad. 16. Do homologous chromosomes have the same number of genes? Do they have identical genes? Explain. As I just mentioned in the previous question, homologous chromosomes have the same number of genes, but they are similar, not identical. The genes could have different alleles. For ex: the gene for hair colour might be blonde from the mother and black from the father.Although the homologous chromosome is for the same trait (hair colour) the alleles are different. 17.Amuscle cell of a mouse has 40 chromosomes. Indicate the number of chromosomes you would expect to find in each of the following cells of the same mouse. a) daughter cell formed after mitosis (40) (b) skin cell (40) (c) egg cell (20) (d) fertilized egg (40) 18. Distinguish between haploid and diploid cells in humans.Apply them to the terms “somatic cell” and “sex cell”. Haploid cells, which are our sex cells, have half number of chromosomes. This is so that when the egg and sperm fertilize to produce a zygote, the zygote has 46 chromosomes. If each haploid cell contained the full number of chromosomes, each future generation would contain double the number of chromosomes than the previous one. Somatic cells are diploid cells, meaning they have a full set of chromosomes. In humans, haploid number is 23 (n=23), and diploid number is 46 (2n=46). 19. If a cell has a diploid number of 32, what would be the chromosome number of a cell in late prophase I of meiosis? The chromosome number of a cell in late prophase I of meiosis would be 32. 20. How many chromosomes would each daughter cell in the previous question have at the end of telophase II of meiosis? At the end of telophase II in meiosis, each daughter cell would have 16 chromosomes. 21. State some ways cells can become cancerous. Certain genes turn on cell division but are silent in their normal location. If these cells get transported to another location, they become active and cause cells to continue dividing at a rapid rate. These cells are called oncogenes and can lead to cancer. 22. Cancer cells are unusual in a variety of ways: they are immortal, they metastasize, don’t perform their normal function, and they can form tumors. Explain each of these behaviors. Cancers may be “immortal”. HeLa cells from a tumor were removed from a women in 1951, and these cells are still reproducing today. Normal cells tend to stick to similar cells, but cancer cells d
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