Haemoglobin structure and function Flashcards Preview

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Flashcards in Haemoglobin structure and function Deck (20)
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1
Q

Describe the structure of haemoglobin

A

Made up of 2 alpha and 2 beta chains, each globin cahin is associated polyphyrin ring - haem group and iron in the centre

2
Q

Where does the polyphyrin ring bind to?

A

The histidine residues on E7 and F8

Oxygen lies between E7 histidine and iron atom

3
Q

HbA?

A

alpha 2 beta 2

4
Q

HbA2?

A

alpha 2 delta 2

5
Q

HbF?

A

alpha 2 gamma 2

6
Q

Hb Portland?

A

zeta 2 gamma 2

7
Q

Hb Gower 1?

A

zeta 2 epsilon 2

8
Q

Hb Gower 2?

A

alpha 2 epsilon 2

9
Q

Hb Barts?

A

gamma 4

10
Q

HbH?

A

Beta 4

11
Q

On which chromosomes can you find the alpha genes?

A

chromosome 16

12
Q

On which chromosome are the beta genes?

A

chromosome 11

13
Q

How does gene transcription occur?

A

It occurs in a temporal fashion in relation to the distance from 5’ end

14
Q

How are the genes for globin chains structured?

A

all 3 exons 2 introns

15
Q

What is the molecular pathology in thalassemias?

A

Nonsense mutations - coding of an aa changes to a stop codon
Frameshift - deletion of 2 adjacent bases leading to shift of transcription window
Promotor/polyA mutation - decreased mrna production
defective mRNA splicing - splice junction mutations - translation of introns
cryptic mutations - mutations in an intron which causes splicing at an different splice site

16
Q

What are the molecular pathologies associated with alpha thalassemia?

A

Deletions are more common

17
Q

What is the locus control region?

A

They move sequentially along to express different genes at different stages

18
Q

How do promotors and enhancers work?

A

They promote the gene in cis as they are 5’ to the gene they control
Enhancers works at a distance and can be either 5’ or 3’ to the gene

19
Q

How does the chromatin structure and histone modification work?

A

Histone acetyl transferase promote chromatin by opening and closing the gene
open - euchromatin is ready for transcription
methylation inhibits transcription
Acetylation of the histone promotes transcription

20
Q

Describe the alpha and beta globin gene clusters

A

(5’ to 3’)

  • Alpha cluster: HS-40, zeta, alpha 2, and alpha 1 genes
  • Beta cluster: LCR, epsilon, Ggamma, Agamma, delta and beta genes