PresentationNEWOF REPLICATION ANDTRANSCRIPTION.pptx

IN THIS PPT WE DISCUSSED ABOUT THE THE REPLICATION PROCESS OF DNA AND THEN THE PROCESS OF TRANSCRIPTION OF THE DNA(DEOXYRIBOSE NUCLIC ACID)

1. DNA REPLICATION AND TRANSCRIPTION

2. THINK ABOUT IT Before a cell divides, its DNA must first be copied. How might the double-helix structure of DNA make that possible?

3. Enzymes in DNA replication Helicase unwinds parental double helix Binding proteins stabilize separate strands DNA polymerase III binds nucleotides to form new strands Ligase joins Okazaki fragments and seals other nicks in sugar-phosphate backbone Primase adds short primer to template strand DNA polymerase I (Exonuclease) removes RNA primer and inserts the correct bases

4. DNA replication The parent molecule unwinds, and two new daughter strands are built based on base-pairing rules (a) The parent molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding with its specific partner, A with T and G with C. (b) The first step in replication is separation of the two DNA strands. (c) Each parental strand now serves as a template that determines the order of nucleotides along a new, complementary strand. (d) The nucleotides are connected to form the sugar-phosphate backbones of the new strands. Each “daughter” DNA molecule consists of one parental strand and one new strand. A C T A G A C T A G A C T A G A C T A G T G A T C T G A T C A C T A G A C T A G T G A T C T G A T C T G A T C T G A T C

5. DNA transcription is the process of creating a complimentary RNA molecule, called messenger RNA (mRNA), from a DNA template. Stages of Transcription Transcription proceeds in enzymatically catalysed steps Initiation Elongation Termination Transcription

6. Initiation: RNA polymerase (RNAP) recruits to the DNA template. RNAP reads the DNA template and positions itself at the binding site. RNAP begins to unwind the DNA double helix. Elongation: RNAP adds nucleotides to the growing RNA chain, in a complementary manner to the DNA template. Nucleotides are added in a 5' to 3' direction, opposite to the direction of DNA replication. RNAP moves along the DNA template as nucleotides are added, synthesizing the RNA molecule. Termination: When RNAP reaches the end of the DNA template, it releases the RNA molecule and dissociates from the DNA. The RNA molecule is then transported out of the nucleus and into the cytoplasm for translation.