Q) Use a named example of a genetic disease to explain the effect of substitution mutation
Main points | |
Key idea: | Named example : Sickle cell anaemia – substitution mutation |
· Thymine nucleotide in the β-globin gene is substituted by adenine nucleotide. · After transcription, original codon (GAG) of mRNA coding for hydrophilic aa glutamic acid is changed to a new codon (GUG) coding for hydrophobic valine | |
Key idea: | Effect on specific conformation and function of polypeptide chain |
· After translation, the new aa seq (i.e. pri struc) alters folding of polypep chain into its specific conformation · Abnormal haemoglobin interact with each other - form fibre-like struc at low O2 level | |
Key idea: | Effect on red blood cells (rbc) + health of patient |
· RBC form sickle shapes instead of usual biconcave shapes · Blockage of bl capillaries, tissue damage, pain · Destruction of deformed rbc leads to anaemia | |
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Discuss the effect of base substitution mutation at the mRNA and protein level (v) Do not mix up the effect of changed DNA seq on (1) mRNA seq, (2) aa seq of β subunit of Hb, (3) specific shape of protein, and (4) shape of rbc (vi) Anaemia refers to the decrease in number of red blood cells or less than the normal quantity of haemoglobin in the blood. | |
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