“Go Sally Go! Make Children!”
Can be divided into 2 stages:
- G1 Growth phase 1.
- S Synthetic phase.
- G2 Growth phase2.
- M Mitosis/Meiosis.
- C Cytokinesis.
Chromatin shows 2 types of coiling behavior:
Chromatin is made of DNA and histone proteins, in the ratio 1:1.
Histone proteins are basic proteins, rich in Lysine and Arginine.
Chromatin consists of repeating units called Nucleosomes.
It occurs in the nucleus during the G1 & G2 stage of the cell cycle.
Of the two strands of DNA only one strand called the template strand takes part in transcription.
A transcription unit in DNA consists of three regions:
Structural gene is the part of DNA from which RNA is formed.
Transcription occurs with the help of DNA dependent RNA polymerase.
Polymerization occurs in 5′ → 3′ direction.
All reference points while defining the transcription unit are made with the coding strand.
Lying towards 5′ end (upstream) of the structural gene is the promoter. It is the binding site for RNA polymerase for transcription to start.
Lying towards 3′ end (downstream) of the structural gene is the terminator, where transcription ends.
Proband or Propositus is an individual from which a pedigree is initiated.
Female are represented in circles.
Male are represented in squares.
Individuals carrying the character to be studied are shaded. or
It helps us to find out whether the gene is dominant or recessive and autosomal or sex-linked. And the chances of expressing itself in the coming generations.
Amino-acyl tRNA synthetase and ATP, activate amino acids.It reacts with its specific tRNA to form amino-acyl tRNA.
RNA is a polymer of ribonucleotides, formed from DNA by transcription. And it translates to protein to perform specific functions of cell. Types of RNA are:
|Sequence of base pairs in the genome where DNA replication begins. A Nick is created.|
|Helps in unwinding the two strands by breaking hydrogen bonds.|
|Helps in relieving tension caused due to unwinding.|
Single stranded binding proteins
|Prevents reannealing of the two strands.|
|Y-shaped fork formed due to the separation of the two strands.|
|forms the RNA primer at the ORI.|
|Short strand of RNA formed at ORI as DNA polymerase III requires a free OH group at 3′ end to add nucleotides.|
|The nucleotides are high energy compounds present in triphosphate form, they act as the substrate for the new strand and also provide energy to form hydrogen bonds between nitrogenous bases.|
|Addition of nucleotides and it always occurs in 5′→3′ direction.|
DNA polymerase III
|Needed to form the new strand. Shows polymerization in 5′→3′ direction and exonuclease activity in 3′→5′ direction.|
Leading and Lagging strands
|3′→5′ strand is the leading strand as the new strand starts forming as the two strands separate. 5′→3′ strand is lagging strands as the new strand starts forming only after a short part of DNA has opened up.|
Continuous and Discontinuous
|The new strand is formed in a continuous manner in the leading strand and in a discontinuous manner in the lagging strand.|
|Short fragments formed on the lagging strand.|
DNA polymerase I
|Shows exonuclease and polymerization activity. Removes RNA primer and adds deoxyribonucleotides in its place.|
|Helps in joining of Okazaki fragments.|