BIOL 2301 Ch. 10

nature of genetic material must:

contain complex info

replicate faithfully

encode the phenotype

have the capacity to vary

Kossel

found 4 nitrogenous bases

chargaff’s rule

A always = T

G always = C

proposes that they come paired, doesn’t know how

griffith’s experiments

demonstrated transformation in bacteria

something in bacteria that passes info (makes mice sick)

Rnase

destroys RNA

Dnase

destroys DNA

Protease

destroys proteins

Avery, MacLeod, and McCarty

experiments revealed transformation factor of bacteria

its DNA

Hershey and Chase

designed experiment to know whether protein or DNA phage transmits

used isotopes of phosphorous and sulfur

DNA only has phosphorous

protein only has sulfur

DNA is genetic material of phages

x-ray diffraction

provides info ab structures of molecules

learn ab cells by refracting light off of clear things

limit how close two things can be distinguished as 200 nm

rosalind franklin

published image of DNA

thinks DNA is a symmetrical triple helix

watson and crick

develop double helix model from franklin’s photo

not symmetrical

DNA has a backbone of sugar

diff sugars on backbones

ribose

OH on 2’ carbon

deoxyribose

only H on 2’ carbon

DNA structure

bases connected at 1’

phosphates and sugars connected at 3’

purine

9 member ring

A and G

extra N, NH, C

pryidimine

6 member ring

C, T, U

nucleoside

nitrogenous bases connected to pentose sugar

nucleotide

phosphate is fundamental component

4 nucleotides

phosphates bound on both sides (phosphodiester)

hydrogen bonds

link bases tg

weak compared to bonds that hold backbone

C-G stronger bc it has 3 bonds rather than 2

always purine-pyridimine

grooves in DNA

major

minor

polymerase uses major to know they’re correctly pairing

B-DNA

most stable

right-handed helix

clockwise spiral

no unusual base sequences

slim and elongated

10 bp’s per 360 degree rotation

“normal” rep

plenty of water around molecule

A-DNA

less water present

right-handed

shorter and wider

looks squished

Z-DNA

left-handed

backbone zigs and zags

particular base sequences

may play a role in gene expression

how some of the bases are

hydrophobic

base paris

hydrophilic

backbone

central dogma

genetic info passes from DNA to RNA to protein in a 1-way path

oversimplification

DNA and RNA = long linear polymers called nucleic acids

nucleic acids carry info in a form that can be passed torugh generations

hairpin

forms when DNA is single stranded *during replication or transcription)

common secondary structure in single strands of nucleotides

forms when sequences of nucleotides on same strand are inverted complements

paired bases = stem

intervening unpaired bases = loop

H-DNA

triplex structure

some DNA unwinds and single polynucleotide strand pairs with a double-stranded DNA from another part of the molecule

often occurs in long sequences

only purine or only pyridimine

natural conditions

DNA methylation

methyl groups are added in certain positions on nitrogenous bases

happens often to bacterial DNA to distinguish it

in eukaryotic cells, related to gene expression

low levels of transcription

A and C in bacteria often methylated