module 6 - 19.1 gene mutations

Question 1

what are mutations?

Answer 1

• sudden, random changes in DNA of a cell and occur in all groups of living things
• occur through meiosis and mitosis

Question 2

what may a mutation be restricted to?

Answer 2

may be restricted to a single gene or may affect a number of chromosomes in a cell

Question 3

what is a somatic mutation?

Answer 3

mutations in an organisms non-reproductive cells, affects only this one organism and cant be inherited

Question 4

what can mutations lead to?

Answer 4

formation of new genes

Question 5

what happens if new genes have some form of selective advantage?

Answer 5

• they will become part of the genetic makeup of that species
• individuals with that gene are more likely to survive and pass on the gene to offspring who would inherit the characteristic

Question 6

what mutagenic agents can also produce mutations?

Answer 6

• viruses
• chemicals
• radiation

Question 7

what is sickle cell anaemia?

Answer 7

• inherited nutation of gene that codes for structure of haemoglobin
• makes red blood cells sickle shaped
• provided Africans resistance to severe malaria
• passed on through generations

Question 8

what are examples of gene mutations?

Answer 8

• deletions within base sequence
• substitutions within base sequence

Question 9

what do deletions/substitutions of a base within the DNA code do?

Answer 9

changes transcribed message in mRNA molecules whose codons determine the nature and sequence of amino acids

Question 10

what is also altered by a mutation?

Answer 10

• primary structure of genetic information slowing from DNA to ribosomes for protein synthesis
• active site of enzymes

Question 11

what happens if there is a damaging effect of different mutations?

Answer 11

• phenotype is affected negatively
• proteins are no longer synthesised or proteins synthesised are non-functional
• interferes with essential processes

Question 12

what is a point mutation?

Answer 12

• the change of a single nucleotide base pair in DNA
• one nucleotide is substituted with another which contains a different base (substitution)

Question 13

what does substitution often result in?

Answer 13

• errors during DNA replication
• single amino acid being changed for another at a specific position within the final polypeptide chain

Question 14

what is deletion?

Answer 14

• one nucleotide is lost all together
• alters the reading frame of the gene
• usually irreversible

Question 15

what is addition or insertion?

Answer 15

• one nucleotide is added or inserted
• caused by transposable elements or errors during replication of repeating elements
• alters joining of the mRNA
• causes shift in reading frame (frameshift)

Question 16

what does the deletion of 3 bases result in?

Answer 16

• doesn’t alter reading frame
• results in loss of amino acid from final polypeptide chain

Question 17

what is the effect of deletion on proteins?

Answer 17

generally have a much greater effect on structure of proteins and leads to formation of non-functional proteins