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17 Terms

1
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What is an accepted point mutation?

The replacement of one amino acid for another, accepted by natural selection.

2
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What are the two processes resulting in accepted point mutations?

Occurrence of mutation in the gene template and acceptance of the mutation by the species.

3
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Why must the new amino acid must function similarly to the old one?

Because it must have similar physiochemical properties to be accepted.

4
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What is the basis for the assumptions made about amino acid replacement in mutations?

The likelihood of amino acid X replacing Y is the same as Y replacing X, based on their frequencies and chemical similarity.

5
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How many amino acid exchanges were observed in the study?

1572 exchanges.

6
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Which amino acids had the most exchanges according to the study?

Asp and Glu.

7
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Approximately what percent of amino acid interchanges involved codons differing by more than one nucleotide?

About 20%.

8
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What is relative mutability?

The probability that each amino acid will change in a given small evolutionary interval.

9
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How is relative mutability calculated?

By dividing the number of changes of each amino acid by its occurrence in sequences subject to mutation.

10
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Which amino acids are the most mutable?

Asn, Ser, Asp, and Glu.

11
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Which amino acids are the least mutable?

Trp and Cys.

12
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What does the mutation probability matrix represent?

A distance-dependent matrix that combines individual kinds of mutation and relative mutability of amino acids.

13
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How are the nondiagonal elements of the mutation probability matrix calculated?

By using the formula $M_{ij} = \frac{\lambda m_j A_{ij}}{\sum_i A_{ij}}$.

14
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What do the columns of the mutation probability matrix represent?

The original amino acid and the probability that it will change.

15
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What is the formula to calculate the percentage of amino acids that will change on average?

$100(1-\sum_i f_i M_{ii})$.

16
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What do scores greater than 1 in the relatedness odds matrix indicate?

That the amino acids replace each other more often in related sequences than in random sequences.

17
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Why do hydrophobic and aromatic amino acids tend to replace one another more often?

Due to natural selection and genetic code constraints reflecting similarities in function.