Lecture 12

Question 1

Chromosomal theory of inheritance

Answer 1

chromosomes bear genetic information

this was discovered because when bits of chromosomes were taken away there were effects on physical appearance and visible differences

Question 2

What do chromosomes contain

Answer 2

DNA and proteins (histones)

Question 3

Proteins

Answer 3

polymers of amino acids

Question 4

How many amino acids are there

Answer 4

20+

Question 5

Virulence

Answer 5

the severity or harmfulness of a disease or poison

Question 6

Griffiths

Answer 6

isolated two strains of Streptococcus pneumonia

this bacterium has. mutant form that couldn’t produce a polysaccharide capsule (R strain)
this is virulent

Question 7

Avery, Macleod and McCarty experiment

Answer 7

got the two strains of Griffiths experiment and cultured the S bacteria in a mouse and heated it to get its individual components
- polysaccharide hydrolysis
- protein extraction
- DNA extraction

they mixed them separately with R strain

Question 8

Alfred Hershey and Martha Chase

Answer 8

repeated the Avery, Macleod and McCarty experiment but with machinery rather than purifying each component manually, this is unreliable

Question 9

Phages

Answer 9

Phages are a protein capsule filled with DNA

you infect a growing bacteria culture with a phage then inject genetic material used to multiple the phage inside the bacterium, they eventually burst open the bacterium killing it.

Question 10

Radioactive labelling

Answer 10

they grew bacteria using amino acids labelled with radioactive sulphur

supplemented with a nucleotide labelled with radioactive phosphorus

radioactive phages are injected into bacteria with no radioactive material

Question 11

What biologists knew at the beginning of the quest for DNA structure

Answer 11

DNA is genetic material: structure must allow copying

structure of nucleotides and their polymer structure known

Chargaff’s rules- AT, CG

Question 12

X-ray crystallography

Answer 12

technique pioneered by Lawrence Bragg who used it to solve the structure of several materials

used by Rosalind Franklin to study DNA

Question 13

Watson and Crick

Answer 13

were relying on theoretical considerations of DNA structure until they saw Franklins crystallography and used it to determine the antiparallel double helix structure of DNA

Question 14

Base pairing- Franklins

Answer 14

franklins work also revealed purine and pyrimidines bases

two purine bases would’ve been too wide and two pyrimidines would’ve been too narrow

Question 15

Purines

Answer 15

Adenine and guanine

Question 16

Pyramidine

Answer 16

Cytosine and thymine

Question 17

Why crystallography explained antiparellel strands

Answer 17

so that the spacing between turns would fit the deduced nucleotide per turn (10)

Question 18

Elements of the double helix

Answer 18

nucleotide polymer with phosphodiester bonds

two antiparallel strands

complementary base pairing

helical structure

polymerisation biochemistry

replication mechanism

RNA secondary structure

interaction with proteins

Question 19

RNA primary structure

Answer 19

nucleotide polymer with phosphodiester bonds and base pairing

polymerisation

RNA much less stable chemically

RNA has more secondary and tertiary structural possibilities

Question 20

Heteroduplex

Answer 20

Hybrid between DNA and RNA