Flashcards · Biology · Reproduction, Meiosis and Variation
Mutations and Genetic Variation
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What is a mutation?
A random change in the base sequence of DNA.
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Where do new alleles come from?
Mutations.
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Name two things that increase the rate of mutation.
Ionising radiation (such as X-rays, UV) and certain chemicals.
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When do most mutations occur?
When DNA is copied before cell division.
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Do mutations happen at random?
Yes. They are spontaneous and unpredictable.
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Do most mutations affect the phenotype?
No. Most have no effect.
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Why do many mutations have no effect?
Much DNA is non-coding, and several triplets can code for the same amino acid.
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What size of effect do some mutations have?
A small effect, such as a slightly different protein.
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Can a single mutation have a large effect?
Yes, but rarely.
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Is a mutation in a skin cell passed to children?
No.
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Is a mutation in a gamete passed to children?
Yes.
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Why is there usually a lot of genetic variation in a population?
Mutations have occurred over many generations and produced many alleles.
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Why are mutations important to evolution?
They produce new alleles, which are the variation natural selection acts on.
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Give an example of a beneficial mutation.
A bacterium becoming resistant to an antibiotic.
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Why do bacteria develop mutations in large numbers?
They reproduce rapidly and there are millions in a population.
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What is the mistake in saying "mutations are always harmful"?
Most have no effect, and a few can be beneficial.