Unit 8 - Gene Expression

Question 1

Gene Mutation

Answer 1

• Permanent changes in the DNA sequence that makes up a gene
• Specifically, changes in the sequence of nucleotides in a DNA molecule

Question 2

What is the difference between mutations in Gametes and Body Cells?

Answer 2

• Mutations in body cells can disrupt normal functions e.g. cell division potentially causing cancer
• Mutations in gametes can be inherited by offspring but can’t be in body cells

Question 3

Mutagens

Answer 3

Any substance that increases the rate of mutation occurring

Question 4

Examples of Mutagens

Answer 4

• Ionising radiation (e.g. X-rays): breaks down DNA strands or alters its structure
• Chemical mutagens (e.g. benzopyrene in cigarette smoke): modify DNA bases or interfere with DNA metabolism
• Spontaneous errors in DNA replication

Question 5

Substitution Mutations

Answer 5

A DNA base is swapped with a different base within a gene’s sequence

Question 6

Types of Substitution Mutations

Answer 6

• Silent Point Mutation
• Missense Point Mutation
• Nonsense Point Mutation

Question 7

Silent Point Mutation

Answer 7

• A substitution that results in the same amino acid being coded for
• Doesn’t impact the final protein made due the the degenerate nature of the genetic code

Question 8

Missense Point Mutation

Answer 8

• A substitution that results in a different amino acid being coded for
• A different protein with a different tertiary structure and therefore a different function is coded for

Question 9

Nonsense Point Mutation

Answer 9

• A substitution that results in a stop codon being coded for
• Results in a non-functional protein being coded for