Page 2 st4 lowa University-Depwtmeen of Bok&Chemi-try; BIO 100-General Biology O
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Page 2 st4 lowa University-Depwtmeen of Bok&Chemi-try; BIO 100-General Biology Online Course processes in cells. When it comes to basic cell biology, researchers have lea about human diseases by studying these simple eukaryotes. Yeast have a somewhat unusual ability to reproduce either sexually using meiosis, or asexually using mitosis, depending on the environment in which they are living Preparation Task 1) Describe the mechanisms by which meiosis would introduce genetic variability in a population. Ifone diploid yeast cell was heterozygous for an allele with a Dominant mutation on it, what proportion of its offspring could be expected to carry that dominant mutation after mating? (Assume it mates with a cell that is homozygous for the normal, recessive allele.) Interestingly. yeast switch to sexual reproduction when they are under conditions of stress! assume yeast populations follow this simplified rule: When For the purposes of this task, yeast are reproducing sexually, they will be found as diploid cells that can go through meiosis (or mitosis), while populations that are producing asexually will include only haploid cells undergoing mitosis. Remember that chromosomes can be counted using karyotypes as seen in your text Fig 9.3. 1N Haploid 2N Mitosis) Fusion Mitosis Environmental Haploid Types Non Stressful i Stressful ) Meiosis Asexual Reproduction Sexual Reproduction A Simplified Model of Yeast Reproduction Preparation Task 2) Explain why sexual reproduction could be advantageous to a population under stressful conditions. Relate this to the process of natural selection Preparation Task 3) Consider the differences between mitosis and meiosis "and identif Upper hows University Departmnt of Bigy& Chemistry Bio 100-Generl Biekgy Online CourseExplanation / Answer
Ans 1) The process of meiosis in the yeasts helps them to gametes with half number of chromosome and when they fuse it forms new individuals. The process of genetic variability often leads to many mutations. There is mechanism like crossing over and independent assortment which leads the yeast to induce genetic variability. If yeast that is diploid and is heterozygous dominant for a mutation, the chances of the offspring to get it is around 50%.
Ans 2) The yeast cells switch over to sexual reproduction when they are under stress conditions. It is because when they are stressed it might lead to death of the offspring. When they retort to sexual reproduction, the offspring tends to get some variations which helps in its survival even through extreme conditions.
Ans 3) The yeast cells undergo asexual reproduction under normal conditions but when there is stressed condition, it use sexual reproduction. The asexual reproduction or mitosis that are haploid and in case of sexual reproduction the gametes are diploid.
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