20.1 - Gene Expression

Question 1

What is a mutation

Answer 1

Any change to the quantity or the structure of the DNA of an organism, or any change to one or more nucleotide bases or their arrangement

Question 2

Name the three main types of base substitution consequences

Answer 2

1. Formation of a stop codon (premature termination)
2. Formation of a codon for a different amino acid (missense)
3. Formation of a codon for the same amino acid (silent)

Question 3

What is a frame shift mutation, and which two types of mutation typically cause it

Answer 3

A shift in the reading frame of the DNA, caused by the addition or deletion of a single base, which alters every subsequent triplet and changes the amino acid sequence

Question 4

How does an inversion of bases mutation differ from a deletion or addition

Answer 4

A group of bases is separated from the sequence, reversed (put int he inverse order), and reinserted at the same position

Question 5

What human disease is given as an example of a consequence of a base substitution mutation

Answer 5

Sickle cell anaemia, caused by a change in the protein structure that effects its shape and function

Question 6

Name the two general categories of factors that cause mutations

Answer 6

1. Spontaneous mutations (occurs during DNA replication)
2. Induced mutations (caused by outside factors/mutagens)

Question 7

Name two types of mutagenic agents (mutagens)

Answer 7

1. High energy ionising radiation (e.g X rays, UV light)
2. Chemicals (e.g Benzopyrene in tobacco smoke)

Question 8

What is the main benefit of mutations

Answer 8

They produce the genetic diversity necessary for natural selection and speciation

Question 9

What happens when a mutation occurs in a body cell (somatic cell) rather than in a gamete

Answer 9

It can disrupt normal cellular activities like cell division, which can lead to diseases such as cancer

Question 10

Why is the formation of a different codon for the same amino acid known as a silent mutation

Answer 10

Because the genetic code is degenerate, and the resulting polypeptide is unaffected