Genetic Mutations Flashcards

1
Q

What is a gene mutation

A

A change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

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2
Q

How often do mutations occur

A

Continuously and spontaneously within a population

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3
Q

How can a mutation in a gene lead to a change in the polypeptide it codes for

A

The DNA base sequence determines the the sequence of amino acids that make up a protein. Therefore, mutations in genes can occasionally change the polypeptide.

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4
Q

Why do most mutations not alter the polypeptide

A

The genetic code is degenerate

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5
Q

What does it mean if a genetic code is degenerate

A

Multiple codons can code for the same amino acid

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6
Q

What are the different ways that a mutation in the DNA base sequence can occur

A

Deletion, Insertion or Substitution

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7
Q

What is similar about insertion and deletion of nucleotides

A

Both change the amino acids that would have been coded for

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8
Q

What happens during a substitution mutation of nucleotides

A

A base in the DNA sequence is randomly swapped for a different base

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9
Q

What are the 3 forms of substitution mutation

A

Silent mutations, Missense mutations, Nonsense Mutations

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10
Q

What occurs during a silent substitution mutation

A

This mutation does not alter amino acid sequence of the polypeptide (this is because certain codons may code for the same amino acid as the genetic code is degenerate)​

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11
Q

What occurs during a missense substitution mutation

A

Alters a single amino acid in the polypeptide chain

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12
Q

What occurs during a nonsense substitution mutation

A

Creates a premature stop codon (signal for the cell to stop translation of the mRNA molecule into an amino acid sequence) causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function

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13
Q

What is a deletion mutation

A

A mutation that occurs when a nucleotide (and therefore its base) is randomly deleted from the DNA sequence.

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14
Q

What generally happens after mutations

A

Most mutations do not alter the polypeptide or only alter it slightly so that its appearance or function is not changed

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15
Q

What type of mutations are insertion + deletion known as

A

Frameshift Mutations

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16
Q

What does a deletion mutation do further down the chain

A

Like an insertion mutation, deletion has a knock on effect by changing the groups of 3 bases further on in the DNA sequence

17
Q

What do a small number of mutations do

A

code for a significantly altered polypeptide with a different shape​

18
Q

What can happen as a result of a mutation that codes for an altered polypeptide with a different shape

A

This may affect the ability of the protein to perform its function. E.g. If the shape of the active site on an enzyme changes, the substrate may no longer be able to bind to the active site​

19
Q

How do natural mechanisms within cells ensure the accuracy of DNA replication

A

By proofreading and repairing damaged DNA​

20
Q

How do you know when the natural mechanisms within cells that ensure the accuracy of DNA replication​ have become ineffective

A

When the mutation rate of a cell rises to above a normal (usually low) rate

21
Q

What are mutagenic agents

A

environmental factors that increase the mutation rate of cells​

22
Q

Give examples of mutagenic agents

A

High-energy radiation such as UV light​

Ionising radiation such as X rays​

Toxic chemicals such as peroxides​

23
Q

What is non - disjunction and how does it occur

A

when chromosomes fail to separate during meiosis​. This occurs spontaneously

24
Q

Give an example of how non - disjunction may occur

A

The gametes may end up with one extra copy of a particular chromosome or no copies of a particular chromosome​. Therefore, will have a different number of chromosomes to normal haploid number.

25
Q

What happens if abnormal gametes (which suffered from non -disjunction) take part in fertilisation

A

A chromosome mutation occurs as the diploid cell will have the incorrect number of chromosomes​. Chromosome mutations involve a change in the number of chromosomes​.

26
Q

Give an example of a chromosome mutation

A

own’s syndrome: Individuals with this syndrome have a total of 47 chromosomes in their genome as they have three copies of chromosome 21​

27
Q

What occurs during an insertion mutation

A

A nucleotide (with a new base) is randomly inserted into the DNA sequence, changing the amino acid that would have been coded for by the original base triplet and having a knock on effect by changing the triplets further on in the DNA sequence.