1
Q
What is a genetic aberration?
A
- a chromosome abnormality
2
Q
How are genetic aberrations caused?
A
- by mutations
3
Q
What is a mutation?
A
- any alteration in the genetic makeup of an organism
4
Q
What are factors that lead to genetic changes (changes in the sequence of nucleotides) during a lifetime?
A
- One or more nucleotides being damaged or lost by chance:
- crossing over of paternal and maternal chromosomes in meiosis
- replication of DNA
- transcription of DNA to RNA - Breakdown of DNA by mutagens:
- environmental factors such as sunlight, radiation, and smoking
- mutagenic chemicals ( formaldehyde, benzene, carbon tetrachloride)
- viruses and micro-organisms
5
Q
What is a mutagen?
A
- a physical or chemical agent that induces and speeds up mutations in DNA
6
Q
What are gene mutations?
A
- small, localised changes in the structure of DNA strands
7
Q
What are point mutations?
A
- changes that involve a single nucleotide
8
Q
How can point mutations occur?
A
- Substitution: where one nucleotide is exchanged for another
- Insertions: where one one or more extra nucleotides are added to the DNA molecule
- Deletions: where one or more nucleotides are removed from the DNA molecule
9
Q
What happens when the sequence of nucleotides is altered?
A
- individual codons are affected
- this alters the mRNA transcribed from the mutated DNA
- this causes the absence of, or incorrect for of protein for which that gene codes
