Sickle Cell anaemia Flashcards
1
Q
What is the cause of sickle cell?
A
- missense mutation in the HBB gene.
- this results in an abnormal beta subunit in haemoglobin due to glutamate amino acid being replaced by valine amino acid on position 6 of the beta subunit.
- phenylalanine and leucine are also found on the amino acid , they form sticky ends with valine because valine is hydrophobic. This results in polymerisation of a the molecule.
- now known as HBS.
2
Q
On what chromosome does the missense mutation of the HBB gene occurs?
A
- chromosome 11
- on the p arm of the chromosome (11p15.5)
- sickle cell mutation is a single base substitution of Adenine to thymine ( GAG - GTG).
3
Q
Why when testing for sickle cell , we cannot use red blood cells?
A
- because red blood cells do not have a nucleus so they do not contain DNA.
- so we cannot test for the HBB gene single base substitution
4
Q
Why can we not use isolated RNA to test for sickle cell ?
A
- because PCR does not work on RNA due to taq polymerase not recognising RNA. Only DNA. So In this case we will need to use reverse transcriptase to create a double stranded DNA - then use PCR.
5
Q
What is the main method we use to test for sickle cell ?
A
PCR
6
Q
What is destroyed as a result on the sick cell mutation ?
A
- destroys the mst11 restriction site so restriction endonucleuse can no longer recognise this site.
7
Q
Sickle cell anaemia is an autosomal ……. trait
A
Recessive
8
Q
Sickle cell trait
A
A person who is heterozygous for sickle cell
- they will have a very low concentration of sickle celled red blood cells but will not exhibit sickle cell phenotypically
