I’m trying to study for my Biology course and I need some help to understand this question.

Week 5 Discussion

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“Apoptosis, Crossover, and Tumor-suppressor genes”

This week’s discussion is focused mechanisms that cells use to keep cell division under control, to prevent cancer, and to function well. For your primary post, respond to one of the following three topics. Also, please reply to at least one fellow student on any topic.

Topic 1 : Apoptosis. Watch the Khan Academy video about apoptosis (1)*, then answer the following questions in your own words:

  • (a) What is the difference between apoptosis and necrosis?
  • (b) What is the role of apoptosis in the normal, healthy development of animals?

Topic 2 [article]: Crossover. Read the article from the University of Rochester on a gene that influences crossover rates in fruit flies. Then address the following:

  • (a) Explain the relationship between crossover, genetic diversity, and natural selection.
  • (b) Summarize the findings regarding a gene that influences crossover.

Topic 3 [research]: Tumor-suppressor genes versus Proto-oncogenes. This is a library-research topic in which you are required to provide your sources. Mutations in tumor suppressor genes can contribute to or cause cancer, just as mutations in proto-oncogenes can also contribute to or cause cancer. However, tumor suppressor genes are very different from proto-oncogenes.

  • (a) Explain why a gain-of-function mutation to a proto-oncogene (or its promoter) may be associated with increased risk of cancer.
  • (b) Explain why a loss-of-function mutation to a tumor suppressor gene may be associated with increased risk of cancer.

References:

  1. Khan Academy, No date given. Apoptosis , https://www.khanacademy.org/science/biology/cellular-molecular-biology/stem-cells-and-cancer/v/apoptosis
  2. Lindsey Valich, April 19, 2018. Scientists discover gene controlling genetic recombination rates. http://www.rochester.edu/newscenter/genetic-recombination-selfish-dna-may-help-explain-differences-in-fruit-flies-312422/

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Sylve

RE: Week 5 Discussion

COLLAPSE

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Good evening Classmate and Professor

Topic 2: Crossover

(a) Explain the relationship between crossover, genetic diversity, and natural selection.
The exchange of genetic material by crossing over is important to natural selection. The
rates of genetic crossovers have evolved to strike a balance between the benefits of crossing over
and the risks of selfish DNAs. When there is a wide range of genotypes to work on, natural
selection will work excellently. Mixing up different combinations of alleles by crossover or
recombination brings about the diversity which controls the process of natural selection (Valich,
2018).

(b) Summarize the findings regarding a gene that influences crossover.
The gene that influences crossover in fruit flies is the MEI-208 gene. This gene controls
the recombination rate. The gene controls the differences in the rate of crossing over between
species and the evolutionary forces involved. It is the first known gene, which scientists have
shown to be accountable for the evolution of the rates of recombination. The two fruit flies
species that were researched were the Drosophila melanogaster and the Drosophila mauritiana.
The sequences of the DNA in the two species were very different. The D. mauritiana species

has more crossing over to about 1.5 times of the D. melanogaster species (Valich, 2018).



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