Section 7.3 DNA and Genomics Lecture notes (ERROR)

7.3.1  Sickle Cell anaemia

·         On chromosome 11, the 17th nucleotide of the gene that codes for the beta chain of haemoglobin is changed from an 'A' to a 'T'.  (GAG to GTG) à WRONG!!!

·         This changes the mRNA codon from 'CUC' to 'CAC' à WRONG!!!, resulting in the 6th amino acid of the chain being changed from glutamic acid to valine. The R side chain of glutamic acid is a polar whereas that of valine is hydrophobic. The mutant haemoglobin is known as Haemoglobin S (HbS).

·         This substitution of one single base in the beta globin gene alters the quaternary structure of haemoglobin, which has a profound influence on the physiology and wellbeing of the individual.

To change the above to:

7.3.1  Sickle Cell anaemia

·         On chromosome 11, the 17th nucleotide of the gene that codes for the beta chain of haemoglobin is changed from an 'T' to a 'A'. (template 3’ CTT 5’ to 3’ CAT 5’) à CORRECT

·         This changes the mRNA codon from 5' GAA 3' to 5’ GUA 3' à CORRECT, resulting in the 6th amino acid of the chain being changed from glutamic acid to valine. The R side chain of glutamic acid is a polar whereas that of valine is hydrophobic. The mutant haemoglobin is known as Haemoglobin S (HbS).

Chromatin remodeling

 

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Organisation of Pro and Eu genome tutorial Q5 essay [8 marks]

1. Are non-coding DNA sequences that are bound by transcription factors

2. involved in regulating gene expression

3. 3 types of control elements include: promoter, enhancers and silencers.   

4. Promoter serves as recognition site for transcription factors and RNA polymerase

5. [more details ..] -  TATA box within promoter (consisting of 5’-TATAAA-3’) is recognized and bound by general transcription factors to recruit RNA polymerase to the promoter region

6. [relate back to how transcription is influenced] -  binding only produces basal / low levels of transcription 

7. Enhancers are distal control elements bound by activators.

8. a looping mechanism brings the bound activator to interact with the RNA polymerase  and transcription factors at the TATA site

9. [relate back to how transcription is influenced] -  Interaction of activators with RNA polymerase and/or general transcription factors increases the transcription of a gene.                                           

10. Silencers are distal control elements bound by repressors, 

11. [relate back to how transcription is influenced] -  Interaction inhibit transcription / gene expression

11. [Extra: some examples by which repressors work] - 

·          binding of repressor to DNA control elements mask the binding site of activators; OR

·         Binding of repressor to silencer and a certain transcription factor prevents further assembly of general transcription factors

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(Diagram --> Ignore the coactivators)