Molecular genetics - Nucleic acids

DNA

deoxyribonucleic acid

what are nucleic acids?

chains of monomers called nucleotides joined by condensation reactions (polymerisation) (polymers)

what do viruses use as genetic material

RNA

What are the components of DNA?

• a phosphate group

• a nitrogenous base

• phosphate group (phosphorus and oxygen) (attached to the 5 carbon)

What bond do nucleotide units use

and where is it between

Convalent bonds between the phosphate group of the 5’ C of one sugar and the hydroxyl group of the 3' C of the next sugar.

phosphodiester linkages

what are purines and what is their structure

• they have two rings in their structure

• guanine

• adenine

what are pyrimidines and what is their structure?

• they have one ring in their structure

• thymine

• cytosine

• uracil

what base does RNA have that DNA doesn’t have

uracil instead of thymine

what is the structure of an RNA

Rna is composed of a ribose sugar, which means it has OH at the 2’ position.

• covalent bonds form between nucleotides of RNA to make a strand

• bonds between phosphate group of one 5’c and hydroxyl group on 3’C of another

what is the structure of dna nucleotides together called

• doulbe helix

• DNA polymer

what bonds are between the complementary bases?

• hydrogen bonds to stabilize

• adenine and thymine

• guanine and cytosine

what term describes the direction of DNA strands?

antiparallel

is RNA double or single stranded?

SINGLE!!!

what is evidence of the common ancestor?

DNA is conserved in all forms of life

what does complementary base pairing allow for?

• DNA retaining its sequence in replication stage of cell division

• it ensures that the same protein is produced every time a gene is expressed

why does DNA replication occur in a 5’ to 3’ direction?

• because DNA polymerase which catalyzes this reaction can only attached to the 3’ hydroxyl group

how do purines and pyrimidines stabilize the double helix

• their lengths balance each other out so the pair is always the same length (always 3 rings length)

• if mismatching occurs in replication it can be detected bc the pair is the wrong length

what is the name of the strand of DNA that links nucleosomes

• linker DNA

what are nucleosomes

units of eukaryotic chromatin supercoiled to from chromosomes

• DNA wrapped around 8 histone proteins and a special h1 protein

necessary form chromosomes to be properly sorted in mitosis and meisois

wen can DNA be accessed? (nucleosomes)

• when the DNA is uncoiled and histones are moved out of the so that the DNA can be copied or transcribed

what did the hershey chase experiment conclude?

that dna was the genetic material and not protein

explain the hershey chase experiment

• T2 bacteriophage used which inserts its genetic material (DNA) into bacterial cells but it’s protein coat stays on the outside

• they labelled the protein with radioactive sulfur and the DNA with radioactive phosphorus

• bacteriophages w radioactive phosphorus that infected other bacteria transmitted their radio-activeness

• bacteriophages with radioactive sulfur had their virus coats removed by a blender and no bacteria was infected

Chargaff’s Rule

• found that amounts of complementary base pairs were equal to each other

• used paper chromatography to seperate the DNA and measure concentrations

• falsified the tetranucleotide hypothsis (thought that DNA was single stranded with all 4 nucleotides equal)

when are nucleosomes held loosley/tightly

loose: normal activity

tight: cell division

why is DNA attracted to histones

• because DNA is negatively charged and histones are positively charged