AP Bio - Unit 6 (Part 1)

Prokaryote DNA

usually 1 circular chromosome

plasmids w/ horizontal transfer

smaller genome

no organelles

Eukaryote DNA

several linear chromosomes

limited plasmids (fungi, etc,)

larger genome

mitochondrial/chloroplast DNA

nucleotide

repeating unit that gets linked together to form DNA and RNA

made up of:

• sugar (ribose or deoxyribose)

• phosphate

• nitrogenous base

purine

nitrogenous base with a double ring structure

includes adenine and guanine in both DNA and RNA

nitrogenous bases are hydrophobic

pyrimidine

nitrogenous base with a single ring structure

cytosine and thymine found in DNA

cytosine anf uracil are found in RNA

complementary base pairs

specific pairing of nitrogenous bases

C - G

A - T (DNA)

A - U (RNA)

one purine and one pyrimidine per pair

hyrogen bonds

weak bonds that hold together base pairs

C - G form 3 bonds

A - T form 2 bonds

sugar-phosphate backbone

chain of alternating phosphates and sugar molecules

held together by strong phosphodiester bonds

phosphate group

group of 1 phosphorus and 4 oxygen atoms in the backbone

the PO₄ has a negative charge and is hydrophilic

deoxyribose sugar

a 5 carbon sugar in the backbone of DNA

3’ end and 5’ end

the orientation of the sugars can be identified from their location of their carbon atoms

5’ to 3’ end is the running strand

semiconservative replication

each new strand contains one old and one new strand

helicase enzyme

“unzips” the DNA

breaks hydrogen bonds

why are primers necessary?

DNA polymerase needs a “starting point”

it can only build by attaching bases to the 3’ end of an existing nucleotide because that is where the OH group is

leading strand

the strand growing the same direction as helicase is the leading strand

topoisomerase

relieves DNA supercoiling that occurs due to the torsional stress caused by unzipping

single stranded binding proteins

prevent the strands from reannealing

RNA polymerase

crates and attaches an RNA primer (10-15bp) to each strand

this is neccessary because DNA polymerase III needs a starting point to build a strand of DNA

DNA Polymerase III

builds a new strand of DNA by adding nucleotides to the 3’ end of the growing strand

DNA Polymerase I

replaces the RNA primers with DNA fragments

ligase

attaches the fragments together

PCR

artificial process that mimics natural DNA replication

amplifies a specific region of DNA

taq polymerase

links together nucleotides to build a new strand of DNA