Mod 6 Genetic Change

Question 1

What are the three types of mutagens?

Answer 1

• Biological - living organisms (includes viruses)
• Physical - highly-ionising radiatation
• Chemical - chemical agents

Question 2

What are examples of mutagens?

Answer 2

• Biological - virus, HPV, bacteria, fungi
• Physical - Gamma rays, X-rays
• Chemical - tar (tobacco), asbestos, benzene

Question 3

What is a mutation?

Answer 3

• The changing of the structure of a gene, resulting in a permanent variant form
• Most are harmful
• Some are ‘silent’
• Occassionally beneficial
• If a mutation is beneficial and able to be inherited, it will increase in frequency in the population

Question 4

What are two types of mutations?

Answer 4

• Germ-line: Gametes, affects whole organism (if inherited), can be passed on to offspring
• Somatic: Body cells, affect one part of the organism, cannot be passed on to offspring

Question 5

How are germ-line mutations passed on to offspring?

Answer 5

• Gamete contains mutated gene
• Forms a diploid zygote
• As the zygote’s cells replicate, every cell in the body will contain the mutation
• If the zygote is heterozygous, 50% of it’s gametes will contain the mutation

Question 6

What are the 4 types of point mutations?

Answer 6

• Frameshift - every amino acid that follows will be altered, caused by insertion/deletion
• Silent - codes for same amino acid, caused by substitution
• Missense - codes for different amino acid, caused by substitution
• Nonsense - codes for stop codon, caused by substitution

Question 7

What are the impacts of each type of point mutation?

Answer 7

• Frameshift - most harmful, every amino acid after insertion/deletion changes
• Silent - least harmful, doesn’t impact polypeptide chain
• Missense - likely causes less functional/incorrectly folded protein
• Nonsense - results in short polypeptide, likely a non-functional protein

Question 8

What are the types of chromosomal mutations?

Answer 8

• Deletion - part of a chromosome is lost
• Inversion - piece of chromosome detaches, rotates and rejoins
• Duplication - an extra piece of chromosome is added
• Translocation - a piece of chromosome 1 breaks off and joins chromosome 2 and vice versa

Question 9

What is aneuploidy?

Answer 9

• one or more extra copies of an entire chromosome or an entire missing chromosome
• abnormal number of chromosomes
• caused by non-disjunction, doesn’t pull apart homologous pairs
• failure of spindle fibres

Question 10

What is polyploidy?

Answer 10

• organism contains more than 2 complete sets of homologous chromosomes
• e.g. 3n fetus - 69 chromosomes

Question 11

What is the significance of introns in chromosomal mutations?

Answer 11

if a section of genes switches with another, the introns may ‘switch on/off’ the wrong gene

Question 12

Are mutations in exons or introns worse?

Answer 12

Exons - they code for an amino acid