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).

DNA and Genomics - Have you wondered...

Q1) DNA is a polymer of deoxyribonucleotides (that contain either A/C/G/T as its nitrogenous bases). For the genetic code contained in DNA to be able to code for all 20 amino acids, the genetic code has to be a triplet code.

Given the above information, calculate (means workings must be shown) how many codons there are altogether. How many of these codons code for amino acids? Explain your answer. 

Q2) Given that there are XXX number of codons coding for amino acids, there should be the same XXX number of tRNA molecules available, as the anticodon on tRNA complementary base pairs to the codon on the mRNA.


However, this is not true. Explain why.