Genetic Aberrations

Question 1

What is a genetic aberration?

Answer 1

• a chromosome abnormality

Question 2

How are genetic aberrations caused?

Answer 2

• by mutations

Question 3

What is a mutation?

Answer 3

• any alteration in the genetic makeup of an organism

Question 4

What are factors that lead to genetic changes (changes in the sequence of nucleotides) during a lifetime?

Answer 4

1. 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
2. Breakdown of DNA by mutagens:
   - environmental factors such as sunlight, radiation, and smoking
   - mutagenic chemicals ( formaldehyde, benzene, carbon tetrachloride)
   - viruses and micro-organisms

Question 5

What is a mutagen?

Answer 5

• a physical or chemical agent that induces and speeds up mutations in DNA

Question 6

What are gene mutations?

Answer 6

• small, localised changes in the structure of DNA strands

Question 7

What are point mutations?

Answer 7

• changes that involve a single nucleotide

Question 8

How can point mutations occur?

Answer 8

1. Substitution: where one nucleotide is exchanged for another
2. Insertions: where one one or more extra nucleotides are added to the DNA molecule
3. Deletions: where one or more nucleotides are removed from the DNA molecule

Question 9

What happens when the sequence of nucleotides is altered?

Answer 9

• 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