3.2.7 Mutation

Question 1

What are Mutations

Answer 1

Mutations are rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome

Question 2

Mutations occur, what?

Answer 2

continuously

Question 3

As the DNA base sequence determines the sequence of amino acids that make up a protein, what can mutations in a gene can sometimes lead to?

Answer 3

to a change in the protein that the gene codes for

Question 4

Most mutations do not alter, what?

Answer 4

the protein or only alter it slightly so that its appearance or function is not changed

Question 5

What is an Insertion

Answer 5

A new base is randomly inserted into the DNA sequence

Question 6

What do Insertions do?

Answer 6

An insertion mutation changes the amino acid that would have been coded for by the group of three bases in which the mutation occurs

• Remember - every group of three bases in a DNA sequence codes for an amino acid

Question 7

An insertion mutation also has an effect, what is that effect?

Answer 7

knock-on effect by changing the groups of three bases further on in the DNA sequence

Question 8

What is a deletion

Answer 8

A base is randomly deleted from the DNA sequence

Question 9

What do deletions do?

Answer 9

Like an insertion mutation, a deletion mutation changes the amino acid that would have been coded for by the group of three bases in which the mutation occurs

Question 10

A deletion has an effect similar to an insertion mutation, what is it?

Answer 10

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

Question 11

What is a Substitutions

Answer 11

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

Question 12

What do Substitutions do?

Answer 12

Unlike an insertion or deletion mutation, a substitution mutation will only change the amino acid for the group of three bases in which the mutation occurs; it will not have a knock-on effect

Question 13

a small number of mutations code for a significantly altered protein with a different shape, what does this affect?

Answer 13

This may affect the ability of the protein to perform its function

• If the shape of the active site on an enzyme changes, the substrate may no longer be able to bind to the active site
• A structural protein (like collagen) may lose its strength if its shape changes

Question 14

On rare occasions mutations lead to the development of, what?

Answer 14

new alleles and so new phenotypes

Question 15

Occasionally, the new allele (and its resulting phenotype) gives the individual a survival advantage over other members of the species, give an example

Answer 15

• A bird develops a mutation leading to a change in feather colours
• This makes it more attractive to birds of the opposite sex
• Which causes the bird to breed more frequently and have more chances of passing on the mutated phenotype to the next generation

Question 16

Mutations can also lead to harmful changes that can have dramatic effects on the body, give 1 example

Answer 16

sickle cell anaemia in humans

Question 17

What is sickle cell anaemia

Answer 17

Sickle cell anaemia was the first genetic disease to be described in terms of a gene mutation

Question 18

What is a gene mutation

Answer 18

A gene mutation is a change in the base sequence of DNA

Question 19

What does the mutation change?

Answer 19

The mutation changes the molecule haemoglobin, causing the red blood cells (RBC’s) to become stiff and sometimes sickle-shaped when they release oxygen to the body tissues

Question 20

The sickled cells tend to, what?

Answer 20

get stuck in narrow blood vessels, blocking the flow of blood

Question 21

those with sickle cell disease suffer, with what?

Answer 21

those with sickle cell disease suffer painful “crises” in their joints and bones

• They may suffer strokes, blindness, or damage to the lungs, kidneys, or heart. They must often be hospitalized for blood transfusions and are at risk for a life-threatening complication called acute chest syndrome

Question 22

Although many sufferers of sickle cell disease die before the age, what?

Answer 22

of 20

Question 23

modern medical treatments can sometimes prolong these individuals’ lives with sickle cell disease to what age?

Answer 23

into their 40s and 50s

Question 24

Mutations happen spontaneously and continuously but their frequency can be increased by exposure to the following, what?

Answer 24

1. Gamma rays, x – rays and ultraviolet rays – all types of ionising radiation which can damage bonds and cause changes in base sequences

Question 25

Increased rates of mutation can cause cells to become, what?

Answer 25

cancerous, which is why the above are linked to increased incidence of different types of cancer