C19 - Genetics

Question 1

What is a mutation?

Answer 1

Change in the sequence of bases in DNA which may affect the phenotype of the organisms

Question 2

What is a mutagen?

Answer 2

Chemical or physical agents which cause a mutation

Question 3

Examples of mutagens

Answer 3

Ionisation radiation (X-Rays)
Deaminating agents
Alkylating agents
Base analogs
Viruses

Question 4

What are the types of mutations?

Answer 4

Substitution / deletion / insertion of one or more nucleotides within a gene

Question 5

What are point mutations?

Answer 5

When only one nucleotide is affected by mutation

Question 6

What is substitution?

Answer 6

Mutation where one or more nucleotides are substituted for another in a DNA strand

Question 7

What is insertion?

Answer 7

Mutation where one or more extra nucleotides are inserted into a DNA strand

Question 8

What is deletion?

Answer 8

Mutation where one or more nucleotides are deleted and lost from the DNA strand

Question 9

What is a frameshift mutation?

Answer 9

Caused by insertion or deletion of a nucleotide
It causes the reading frame to move (read in triplets)
If a multiple of 3 added or deleted

Question 10

What effects can mutations have?

Answer 10

No effect - doesn’t change phenotype BC normally function proteins still synthesised
Damaging - changes phenotype negatively BC proteins no longer synthesised or are non-functional
Beneficial - rare

Question 11

What is a chromosome mutation?

Answer 11

Affects whole chromosomes / a number of chromosomes in a cell

Question 12

Types of chromosome mutations?

Answer 12

Deletion - section of chromosome breaks off and is lost within cell
Duplication - sections are duplicated on a chromosome
Translocation - section of a chromosome breaks off and joins another non-homologous chromosome
Inversion - section of chromosome breaks off, is reversed, joins back onto chromosome

Question 13

What is a silent mutation?

Answer 13

Does not change any proteins or the structure of proteins synthesised
Could change primary structure, not overall
Have no effect on the phenotype
Occur in non-coding regions of DNA / code for same amino acid (degenerate code)

Question 14

What are non-sense mutations?

Answer 14

Cause codon to become stop codon rather than amino acid
Shortens protein
Usually make it non-functional
Usually have negative/harmful phenotypes

Question 15

What are missense mutations?

Answer 15

Cause incorporation of incorrect amino acid into primary structure when protein is synthesised
Mutation could be silent, beneficial or harmful

Question 16

What is a conservative mutation?

Answer 16

Occurs when new amino acid has similar properties to original

Question 17

What is a non-conservative mutation?

Answer 17

Occur when new amino acid has different properties to original so more likely to have effect on protein structure