Measured mutation rate would be 7 mutations31 cell

  • No School
  • AA 1
  • 31

This preview shows page 7 - 13 out of 31 pages.

Measured mutation rate would be 7 mutations/31 cell divisions or 0.226 mutations/cell division (unrealistically high example!).
Image of page 7
When and Where Mutations Happen In eukaryotes, mutations that occur in the somatic cells (somatic mutations) are not inherited; mutations that occur any time in the germ line are inherited. We usually measure the rate in mutations per gamete somatic mutation germ line mutation Germ line Soma
Image of page 8
Mutation Rates Mutations are stochastic events (unpredictable, random): we can never predict exactly when a mutation will occur or what kind of mutation will occur. We can measure the rate at which a given kind of mutation will occur. The rate is the probability that it will occur in a unit of time. Orders of magnitude: animals and plants 10 -6 - 10 -4 muts per gene per gamete 10 -10 - 10 -8 muts per bp per year ( from evolution rates) 10 -9 muts/bp year 3 10 9 bp > 1 new mutation in each gamete (we are all mutants!) Drosophila : u = 8.4 10 -9 muts/bp year U = 1.2 detrimental mutations/2N genome bacteria 10 -10 - 10 -6 muts per gene per cell division How to write rates so they can be used in dimensional analysis: 10 -9 muts per bp per year 10 -9 muts/bp year NOT 10 -9 muts/bp/yearbecause that is 10 -9 muts year /bp Mutagenesis increases the rate (probability) but the mutations are still stochastic.
Image of page 9
Mutation Rates A given mutagen increases the rate of some kinds of mutations but not others. In other words, it biases the probabilities, like weighting a coin. e.g. Ionizing radiation induces (increases the probability of) chromosome breaks and hence of large-scale “chromosome mutations” or rearrangements such as deletions or translocations. Acridines induce deletion or insertion frameshifts. Ethyl methan sulfonate (EMS) induces chemical changes in bases, mainly changing guanine to O 6 -ethylguanine which mispairs, resulting in changing GC pairs to AT. 5-bromouracil (Bu) is an analogue of thymine and is most often incorporated into DNA in place of thymine. It then pairs with G at the next replication, so that an AT pair is replaced by a GC pair. Less commonly it causes a GC pair to be replaced by AT. Modern genetic engineering can reduce or eliminate the stochasticity of mutation, allowing us to change a specific base in a specific gene in vitro , then put it back in the organism. Knockout mutations can be made in specific genes in vivo .
Image of page 10
Phenotypic Effects of Mutations in Exons Review code properties: Degenerate Triplet Commaless Start codon Stop codon(s)
Image of page 11
Phenotypic Effects of Mutations Useful terms for phenotypes of mutations: Amorph = nullimorph = null = knockout mutations: mutant allele is completely inactive (not transcribed, or translated, or encodes inactive protein or RNA). e.g. white eye mutant in Drosophila melanogaster Hypomorph: mutant allele has reduce activity (reduced rate of transcription or translation, or encodes protein or RNA with reduced activity).
Image of page 12
Image of page 13

You've reached the end of your free preview.

Want to read all 31 pages?

  • Fall '19
  • Mutation, transposable elements, Leu

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors