DNA And Cell Division

4 Nitrogenous Bases

Adenine

Guanine

Cytosine

Thymine

How many bases in Human DNA

3 billion

Sequencing determines information

Base Pairings

A with T - Two hydrogen bonds
C with G - Three hydrogen bonds

Purines vs. Pyrimidines

Purines include Adenine and Guanine, which are bigger

Pyrimidines include Cytosine, Thymine, and Uracil, which are smaller

Purines have a cyclo hexane cyclo pentane double ring, pyrimidines have only hexane

Nucleotide components

A purine or pyrimidine with a sugar molecule and a phosphate

Where would we expect to see A and T?

At places where breakages are common (duplication sites)

Which way does DNA turn?

Spinning from your pinky to your thumb (right hand helix)

Structure of DNA

A-Dna

Credited to James Watson and Francis Crick (undeservingly)

Was actually Rosalind Franklin who spent years producing and calculating the image

Used X Ray Crystallography

Discovery of DNA

Central Dogma

DNA -> RNA -> tRNA -> Amino Acid -> Protein

RNA vs. DNA

DNA is deoxyribonucleic acid, RNA is ribonucleix acid

mRNA

RNA in single chains to go to cytosol

tRNA

Single chain of about 80 RNA in hairpin that binds to amino acids

rRNA

ball of RNA that creates the ribosomes

Replication

When DNA is copied Hydrogen bonds are broken by enzymes and DNA uncoils

Forks the dna (two stripes and one closed end)

Which enzyme unwinds the helix?

Helicase

Which enzyme forms new bonds?

DNA Polymerase

Which enzyme prepares the strand to be replicated?

Primase

Leading Vs. Lagging Strand

The leading strand can keep adding in the direction that helicase is separating the fragments in, meaning that it will end up as one single strand

The lagging strand is moving in the opposite direction of the helicase, meaning that it has to create short segments of DNA called Okazaki fragments and DNA ligases link these fragments together

Why is it called semi conserved?

Half of the dna is old, half of it is new

Another enzyme checks to make sure the things are correct

All enzymes and their functions

Ligase - Seals nicks made by DNA Polymerase I

Polymerase I - remove RNA primers

DNA Polymerase III - Adds base pairs

Primase - Adds RNA Primers - 10-15 nucleotides long

SSB - Single stranded binding protein (hydrophobic)

Ori - AT content very high for easy breakage and also repeats

Topoisomerase - Prevents supercoiling by acting like scissors (think headphones)

Meaning of 5' and 3'

5' is the fifth carbon where phosphate is
3' is the third carbon where alcohol is

Transcription Meaning

Dna to RNA

Translation Meaning

RNA to protein

Transcription Process

RNA polymerase finds the sequences that position the RNA (-35 and -10 elements)

Creates mRNA from DNA by using the many enzymes

Starts at the TATA box Continues until stop codon is found

Attaches to a ribosome eventually

RNA polymerase II walks and copies from 5' to 3' but subs in uracil

Types of Strands

Coding strand is not touched

Template strand is the one that is getting bonded with RNA

preRNA is almost identical to the coding strand

pre RNA to mRNa

5'cap is added to the beginning of the preRNA (Guanine)

3' poly-A trail is added to end (many Adenines)

Introns (internal and non-coding regions) are removed and the exons (other parts) are stuck back together

Translation and Phases

Methionine is actually on the protein - Stop codons only code to stop

tRNA has an anticodon on one end(binds to a codon) and the other end brings the amino acid

Phase 1 - Initiation Ribosome assembles around the mRNA and starts at the start codon

Phase 2 - Elongation Each codon adds a new amino acid

Phase 3 - Termination Stop codon triggers a separation of the chain and then the polypeptide is created

Ribosome Structure

made up of protein and rRNA
Large subunit and small subunit

Gene Mapping

Landmarks of chromosomes and also phenotypes that relate to specific DNA markers in the chromosome