L7 - DNA as genetic material Flashcards
name the experiments that are evidence for DNA being responsible for genetic transmission
- griffith
- avery et al
- hershey & chase
explain Griffith’s experiment that provides evidence for DNA being responsible for genetic transmission
he had two strains of pneumonia
smooth (S) - virulent
rough (R) - non virulent
- injected S into mouse - died
- injected R into mouse - lived
- heated S then injected - lived
- mixed heat killed S with R strain - died
- living S strain was recovered
concluded that there was a transforming principle that could turn R into S
explain Avery et al’s experiment that provides evidence for DNA being responsible for genetic transmission
1. extracted cytosol from S and treated trypsin (protein
breakdown)
----> form still virulent
2. treated with DNAase
----> no longer virulent
concluded DNA was transforming principle
explain Hershey & chase experiment that provides evidence for DNA being responsible for genetic transmission
- radiolabel phage protein with S35 , or phage DNA with P32 and infect bacterial cell
- put mixture in blender to separate phage particles from cells
- centrifuge so cells separate from capsules (cells at bottom capsules at top)
- can see what parts are radioactive
when DNA labelled - radioactivity in cell
when protein labelled - radioactivity in supernatant
what handed is the DNA helix
right handed
how many H bonds between
C - G
T - A
C-G three H bonds
T-A two H bonds
what carbon has lost an O in deoxyribose?
C2
what is the importance of the minor and major groove of DNA helix?
base pairs have chemically different profile in the major and minor groove
accessory factors recognise these
define pitch of helix
length of one complete turn
what is the pitch of DNA helix
3.4nm
how many base pairs per turn of helix
10
what is the distance between base pairs of DNA helix
0.34nm
what is the diameter of DNA helix
2nm
what is nucleoside
sugar + base
what is nucleoside triphosphate
base + sugar + triphosphate
