MBG 1000 Lecture Notes - Lecture 5: Reading Frame, Nonsense Mutation, Silent Mutation

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purplecattle88

24 Jan 2017

School

University of Guelph

Department

Molecular Biology and Genetics

Course

MBG 1000

Professor

Georgevander Merwe

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Document Summary

A change in the nucleotide sequence of dna: source of genetic variation. Outcome can be neutral (no effect), beneficial, or detrimental: origin. Changes in the nucleotide sequence as a result of errors in dna replication: dna polymerase replicates dna. Native proof-reading activity can correct its errors. 1-12 gametes out of a million human gametes will have a mutation in some gene. Chance dna cannot correct mutations in high risk people (cancer survivors) Environmental impact: free radical damage (metabolism, environmental impact (uv: lying i the sun, chemical) Age because of the free radicals in our bodies. Involves multiple genes; often large fragments of dna: deletion, duplication. Involves the substitution of one nucleotide base for another. Silent mutation: dna change results in a new mrna codon that specifies the same amino acid. Missense mutation: dna change results in a new mrna codon that specifies a different amino acid.

Related Questions

1).Which of the following demonstrates the importance of mutation?

A.Mutation is the ultimate source of genetic variation and thus is the foundation of why people are interested in genetics in the first place.

B.Mutation will remove variation from the population.

C.Mutations are always beneficial and thus allow organisms to adapt.

D.Mutation is detrimental to the population and thus is important only because we need to get rid of mechanisms that induce mutations.

E.Mutation is not important.

2).While the SOS repair pathway can repair devastating pyrimidine dimers, it comes at a cost. Which of the following best explains the cost of repairing DNA via the SOS repair pathway?

A.The other strand of DNA is used as a template to repair the damaged strand of DNA.

B.A nucleotide is removed so that DNA polymerase III can move past the pyrimidine dimer.

C.SOS will help DNA replication bypass pyrimidine dimers but will do so by using random nucleotides in place of the lesion.

D.The SOS repair pathway uses analogs in place of nucleotides when repairing damaged DNA.

3.Suppose you have two species of corn. One has sweet kernels and the other has large ears. Both have 20 chromosomes, each of which is homologous in both species. Suppose you want to create a hybrid that has both characteristics of sweet kernels and large ears, so you cross individuals from the two species. The initial hybrid you obtain has 20 chromosomes, but then you establish a viable tetraploid (4n) individual with 40 chromosomes. Which of the following could best explain this observation?

A.		Nondisjunction of a single chromosome caused the doubling of the genome.
		B.The initial F1 hybrid was unable to produce normal haploid gametes and instead produced diploid gametes. As a result, self-fertilization created progeny with 40 chromosomes.
		C.The original F1 hybrid was able to produce normal gametes, thus, the tetraploid was formed by fusing one normal haploid gametes with an abnormal diploid gamete.
		D.Nondisjunction of a random set of chromosomes produced abnormal gametes, and thus the 40 chromosomes represent a random assortment of chromosomes from the two parents.
		E.None of the above can explain the phenomenon.

E.There is no consequence to SOS repair and the damaged DNA is repaired precisely back to the wild-type allele.

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MBG 1000 Lecture Notes - Lecture 5: Reading Frame, Nonsense Mutation, Silent Mutation

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