Molecular Genetics - Genetic Mutations

Question 1

Effect of mutations in somatic vs germ cells, introns vs exons

Answer 1

• Somatic cells: only effect production of proteins in that cell + daughter cells
• Germ cells (sperm/egg): can be inherited by offspring
• Introns: may not be noticed by organism (non-coding regions)
• Exons: noticed by organism

Question 2

Spontaneous mutation vs induced mutation

Answer 2

• Spontaneous: arise randomly due to errors during DNA replication
• Induced: caused by mutagenic agents such as various chemicals, viruses, + radiation (e.g. X-rays, gamma rays, UV radiation)

Question 3

What is a point mutation?

Answer 3

Just one nucleotide in DNA sequence is changed

Question 4

Substitutional point mutation vs frameshift point mutation

Answer 4

• Substitution mutation: one nucleotide is substituted for another
• Change in one or more codons
• Frameshift mutation: nucleotide is added or removed from sequence
• Causes shift in reading frame of mRNA, all codons following mutation will be different, resulting in a different amino acid sequence

Question 5

What are the 3 types of substitution mutations?

Answer 5

1. Silent mutation: even though second codon changed, amino acids stays the same
2. Missense mutation: codon change results in different amino acid
3. Nonsense mutation: changes codon to STOP codon

Question 6

What are the 2 types of frameshift mutations?

Answer 6

1. Insertion mutation: nucleotide is added
2. Deletion mutation: nucleotide is removed

Question 7

What is a chromosomal mutation?

Answer 7

Multiple nucleotides in DNA sequence changed

Question 8

What are the 4 types of chromosomal mutations?

Answer 8

1. Deletion: piece of chromosome is deleted
2. Duplication: section of chromosome is copied + appears 2 or more time in a row
3. Inversion: piece of chromosome breaks off, but reattaches in the opposite direction
4. Translocation: pieces of chromosome break off and join onto another (non-homologous) chromosome

Question 9

What are transposable elements?

Answer 9

• “Jumping genes”
• DNA fragments that can move around within a genome, from one chromosome to another
• Alters expression of these genes, causing them to be expressed at different times
• Example: variety of kernel colours in decorative corn