GENE
- Molecular structure of a gene
- mainly two types based on function
- structural genes
- based on sequence
- Regulatory genes ( control genes )
- DNA
- Genic dna
- single of low copy number
- Extragenic dna
- highly repetitive DNA sequences
- B- extragenic DNA
- Tandemly repeated DNA sequences
- Satellite dna
- Minisatellite dna
- highly variable DNA sequences
- DNA finger printing
- Microsatellite dna
- Interspersed repetitive DNA sequence
- short
- long
- do not act as genes
- Junk dna
- Single copy genes
- Chain initiation
- chain termination
- Genetic code
- 3 bases of DNA ( 3 alphabets of DNA )
- codons
- each codon codes for a single amino acid
- triplet code
- initiation codon
- AUG
- termination codon
- UAA or UAG
- Transcription ( Copying )
- RNA polymerase binds to
- promoter region
- begins from 5' to 3 end
- synthesis of mRNA
- it is single stranded
- Structure of mRNA
- all sequences of structural genes are transcribed ( exons and introns )
- by process of SPLICING
- then introns are excised
- exons are joined to form mature RNA which is shorter
- It has two ends
- 5 end
- methylguanine cap
- 3' end
- poly (A) tail
- Translation
- mRNA
- Provides the coding sequence for ( बहुजीवर्थाणु / जीवार्थसूत्र - polypeptide chain)
- Ribosome
- tRNA
- Process
- initiation
- 5 cap of mRNA
- initiation complex formed by
- attachment of elongation factors
- then moves along the 3' end
- encounters AUG codon which is the start codon
- signals the start of
- elongation
- termination
- encounter of stop codon on mRNA
- release factor binds with ribosome
- mutation
- change occurs in structure of gene
- gene mutation or point mutation ( utparivartan )
Discussion