DNA structures and replication one pager

How does cell divsion start

begins with DNA replication

DNA replication

An exact copy of all the cells DNA must be made. includes Copying all 46 chromosomes

DNA is a what

Nucleic acid

Dna does what

Stores cellular information needed to build and maintain a cell

What is DNA composed of

nucleotide monomers

Nucleotide includes

Nitrogenous base

Sugar molecules (deoxyribose)

Phosphate group

Nitrogenous Bases

Adenine, Thymine, Cytosine, Guanine

Bonds in DNA

DNA exists as 2 strands are held together by interactions between nitrogenous bases (Hydrogen bonds)

2 groups for nitrogenous bases

Purine

Pyrimidines

Purines

Two rings (A and G)

Pyrimides

One ring, T and C

Bonds and nitrogenous bases

2 hydrogen bonds between A and T

3 hydrogen bonds between C and G

Anti Parallel

Two strands run in opposite directios

5’ end

3’ end

5’ prime

has a phosphate group

3’ prime

has an OH group where dehydration reactions take place

RNA

single stranded

U instead of T

contains ribose

Semi conservative replication

One of the original strands is conserved in the new double stranded DNA molecule

DNA replication steps

1. Two strands of orginal DNA are seperated

2. Each stand is used as a template to build a new DNA strand

3 basic ideas of DNA replication

1. First step is to unwind and seperate 2 strands of DNA

2. New DNA nucleotides are added in the 5’ to 3’ direction

3. One strand is built continuously (leading) while the other strand is made in segments (lagging)

Orgins of replication

DNA replication occurs at these regions along DNA simultaneously

Bubble

DNA helicase

unzips the DNA by breaking the hydrogen bonds between the two strands and produces a replication fork

Tapoisomerase

An enzye that unwinds the DNA just before the replication fork to ensure smooth unzipping

Single strand binding protiens

Prevent the unzipped DNA from re-zipping

Primase

An enzyme that adds termpoary RNA nucleotides to the unzippled DNA strands (5’ to 3’ direction)

RNA primer

RNA nucleotides which provide a starting point to add a new DNA nucleotide

• Provides an OH group that DNA nucleotides need to be attached to

DNA polymerase III

Enzyme responsabile for the addition of the DNA nucleotides for the new strands

Leading strand

Easy to make becayse it grows in the direction of the replication fork (5’ to 3’)

Lagging strand

Built in the direction away from replication fork

requires strand to be made in segments instead of continuously

Lagging strand Steps

1. RNA primers are added, however they are spaced out

2. RNA polymerase III can add new DNA nucleotides between the primers

3. RNA primers are removed and gaps are filled in by DNA polymerase I

4. DNA backbone (phosphate and sugars) are attached by DNA ligase

is DNA replication accurate

YES EXTREMELY

Terms to know

this important pic