Gene mutations

Question 1

What is a gene mutation?

Answer 1

• any change to the sequence of nucleotide bases can change the triplet code which means the amino acid sequence may be read wrong and a different polypeptide is produced
• deletion
• insertion
• substitution

Question 2

What is insertion?

Answer 2

• a nucleotide is inserted into the normal DNA sequence
• the amino acid sequence of the polypeptide is entirely different and so the polypeptide is unlikely to function correctly
• one new base causes the sequence to be read differently as they are usually read in triplets and the sequence will have shifted to the right

Question 3

What does degenerate mean?

Answer 3

-a single amino acid may be coded for by more than one codon

Question 4

What is substitution?

Answer 4

• a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base
• if a base is replaced by the same base it will be read the same

Question 5

What is deletion?

Answer 5

• a nucleotide is lost from the normal DNA sequence
• the amino acid sequence of the polypeptide is entirely different and so the polypeptide is unlikely to functions correctly
• one deleted base causes the sequence to be read differently as they are usually read in triplets and the sequence will have shifted to the left

Question 6

What are chromosome mutations?

Answer 6

-changes in the structure or number of whole chromosomes

Question 7

What is non disjunction?

Answer 7

• individual homologous chromosomes sometimes fail to separate during meiosis
• this results in changes to the number of individual chromosomes as it results in having either one more or one less chromosome
• downs syndrome

Question 8

What is polyploidy?

Answer 8

• when organisms have more three or more sets of chromosome
• this results in changes to whole set of chromosomes
• mostly occurs in plants

Question 9

When do mutations occur?

Answer 9

-mutations occur during the formation of gametes