Key area 4- Genes & proteins in health & disease

Question 1

What is a single gene mutation?

Answer 1

.They involve the alteration of a DNA nucleotide sequence (as a result of substitution, insertion or deletion of nucleotides)

Question 2

What are the single gene mutations?

Answer 2

.Substitution
.Insertion
.Deletion

Question 3

What are the nucleotide substitutions?

Answer 3

.Missense
.Nonsense
.Splice site
.They bring about only minor changes as only one nucleotide, therefore one different amino acid, so sometimes the organism is affected only slightly or not at all

Question 4

What is missense?

Answer 4

.This results in one amino acid being changed for another
.This may result in a non-functioning protein or have little effect on the protein
.For example, sickle-cell disease, PKU

Question 5

What is nonsense?

Answer 5

.This results in a premature stop codon (UAA, UAG, UGA) being produced
.This results in a shorter protein
.For example, duchenne muscular dystrophy (DMD)

Question 6

What is splice site?

Answer 6

.This results in some introns being retained and/or some exons not being included in the mature transcript
.For example, Beta Thalassemia

Question 7

What are frame-shift mutations?

Answer 7

.Nucleotide insertions and deletions
.They cause all of the codons and all of the amino acids after the mutation to be changed.
.This has a major effect on the structure of the protein produced

Question 8

What is an example of nucleotide insertion?

Answer 8

.For example, Tay-Sachs syndrome
.Another Guanine is inserted

Question 9

What is an example of nucleotide deletion?

Answer 9

.For example, Cystic fibrosis
.A cytosine is deleted

Question 10

What is a chromosome structure mutation?

Answer 10

.Duplication
.Deletion
.Inversion
.Translocation
.The substantial changes in chromosome mutations often make them lethal

Question 11

What is duplication?

Answer 11

.A section of a chromosome is added from its homologous partner

Question 12

What is deletion?

Answer 12

.A section of a chromosome is removed
.For example, Cri-du-chat syndrome

Question 13

What is inversion?

Answer 13

.A section of a chromosome is reversed
.For example, Haemophilia A

Question 14

What is translocation?

Answer 14

.A section of a chromosome is added to a chromosome which is not its homologous partner
.For example, chronic myeloid leukaemia (CML)