Mutagenesis and Genetic Screens

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Description and Tags

inducing mutations with mutagens, screening mutant phenotypes, and mapping mutant phenotypes to mutant genotype

9 Terms

1

List some mutagens that induce mutations

  • chemical mutagens (EMS, TMP,ENU,Formaldehyde…)

  • Radiation (x-ray and radioactivity)

  • transposable elements (insertions)

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2

What is ethyl methanesulfonate (EMS)? What are the advantages and disadvantages?

A chemical mutagen that increases the rate of mutation by about 100-1000x higher than normal).

Pros and Cons:

  • mutations are random (you cannot target a sequence for mutation, therefore, a homozygous mutation is nearly impossible)

  • phenotypic mutations are rare (exons make up less than 5% of the genome, and most mutations do not effect genes)

  • mutations can be replicated

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3

Define haplosufficient genes

When one copy is sufficient to produce a normal phenotype, that is because the allele remaining can produce enough gene product (like protein) to maintain normal function in the organism

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4

What can be said about the majority of mutations?

Most mutations are haplosufficient and recessive.

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5

Define mutagenesis screening

A technique used to identify and study phenotypes by inducing mutations and observing their effects.

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6

mutagenesis screening requirement

animals → complex multicellular organisms with specialized tissues, therefore germline mutations must occur so mutation is heritable

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7

How do you look at the homozygous recessive phenotype of a mutation in plants?

M0 (EMS treatment, mutation created, heterzygotes crossed with wt) → M1 (two heterzygotes created) → M2 (homozygote created by selfing)

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8

mutagenesis screening in hermaphrodites

Hermaphrodite organisms allow F1s to be self-crossed to generate homozygous mutants

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9

Once phenotypes have been screened a particular gene can be located and studied (linkage), how?

Look at the resulting phenotypic ratios:

unlinked → 9:3:3:1

fully linked (0 m.u.) → 2:1:1:0

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