Page 15 - CH6 (1)

● Salient features of genetic code:
○ Codon is triplet. 4​= 64 (61 codons code for amino acids while 3

3​
are stop codons)
○ One codon codes for a single specific amino acid. Codons are

unambiguous.
○ Codons are degenerate since some amino acids are coded by
more than one codon.

○ Genetic code is universal. 1 codon codes for same amino acid in
all species.

○ Codons are read continuous. They lack punctuations.
○ AUG has dual functions − Codes for Methionine and acts as a

start codon

Effects of Mutations on Genetic Code

● Mutations include insertions, deletions, and rearrangements.
● Mutation results in changed phenotype and diseases such as sickle cell

anaemia. (Change Glu ​​Val in gene coding for beta globin chain of
→

j
.
haemoglobin) Such mutations are called ​oint mutations​
● Insertion or deletion of a single base pair disturbs the entire reading
.
r

f
frame in mRNA. Such mutations are called ​ameshift mutations​
● Frameshift mutations hold the proof of the fact that codon is triplet