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Biology 400 > P02 The Hereditary Material > Flashcards

P02 The Hereditary Material Flashcards

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1
Q

The history that lead to the discovery of the structure of the DNA molecule consisted of what 2 streams?

A
  1. Genetics: Genetics became so powerful that geneticists thought they could solve any problem by the means of genetics, could understand biochemical pathways by the means of genetics
  2. Physics: Especially X-ray crystallography. Study of large molecules by bounding x-rays off them
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2
Q

Double helix structure suggested its function

A
  1. The copying of genetic information (strand unwinding)

2. DNA could divide (two identical strand)

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3
Q

Who discovered DNA

A

Friedrich Miescher (watson and crick just discovered shape)

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4
Q

How did Friedrich Miescher discover DNA

A

isolated nuclei from pus and found a new kind of molecule; he called it ‘nuclein’
-nuclein had acidic and basic part (nucleic acid = acidic part, histones = basic part)

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5
Q

What did Friedrich Miescher think the function of nuclein was

A
  • thought it was involved in heredity

- knew the significance of nuclei in heredity

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6
Q

What did Albrecht Kossel do?

A
  • discovered the 5 kinds of bases in nucleic acids (G,C,A,T/U)
  • distinguished between DNA and RNA (Miescher didn’t do this)
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7
Q

Phoebus Aaeron Levene

A
  • explained the structure of nucleotides and differences in structure between DNA and RNA (deoxyribose and ribose)
  • tetra nucleotide hypothesis (made up of equal amounts of ACGT)
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8
Q

What did Levene suggest about the 4 base pairs of DNA

A
  • present in equal amounts (WRONG)

- bad

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9
Q

Levene’s history

A
  • Jewish

- Immigrated to US and worked as physician then burned out and became a biochemist

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10
Q

Alcaptonuria was studied by who?

A
  • Archibald Garrod

- soon after rediscovery of Mendel’s laws

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11
Q

What did he study to observe Alcoptonuria

A
  • family pedigrees

- showed that it is inherited as a mendelian recessive trait

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12
Q

Alcoptonuria symptoms

A
  • not able to get rid of homogentisic acid

- excreted in the urine, turns black upon exposure to air

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13
Q

What did Archibald guess about alleles

A
  • guessed that 2 recessive alleles produces 2 defective enzymes
  • concluded that a normal allele produced an enzyme for the metabolism of homogentisic acid
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14
Q

What did Franz Moewus study

A
  • genetics of sexuality of chlamydomonas eugametos (unicellular green algae) in 1930
  • associated mendellian mutation with an inability to produce sex hormones
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15
Q

Similarities between Franz Moewus and Archibald Garrod

A

-associated genes with biochemical functions

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16
Q

What happened with Franz Moewus work

A

He was caught making up data so his work was discounted

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17
Q

Who lead to the fusion of genetics and biochemistry?

A
  • Beadle and Tatum
  • Studied pathways that involved 3 genes. Knocking out one gene lead to a different pathway.
  • gene knockouts effected different parts of the same pathway.
  • specific mutants lacks specific enzyme
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18
Q

What was the first protein to be studied in structural and functional detail?

A

Haemoglobin

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19
Q

Who discovered sickle cell anemia

A

Linus Pauling and co workers

-sickle cell is inherited in simple mendelian fashion, also related to malformed protein

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20
Q

What is sickle cell anemai

A

-malformed version of protein haemoglobin

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21
Q

What book did Erwin Schrodinger write?

A

“What is Life” 1944

22
Q

What did Erwin Schroding study

A
  • physicist

- founder of wave mechanics

23
Q

What did “What is Life” explain

A
  • study of living matter might reveal unknown laws of physics
  • genes must be made up of a few hundred-few thousand atoms to account for genetic stability (any more would allow for too frequent gene destruction)
  • genes must be aperiodic crystals - every atom or group of atoms has a particular place and role in the gene
24
Q

What did Schroding give lectures about

A

-unknown laws of physics

25
Q

Aperiodic crystals

A

-arrangement of atoms in which every atom has a role in containing/transmitting information in gene

26
Q

sugar-coated microbe

A
  • Streptococcus pneumoniae

- model that showed that genes are made up of DNA

27
Q

2 strains of Streptococcus pneumoniae

A
  1. S (smooth) strain - causes pneumonia in mice; surrounded by a polysaccharide coat that renders it invisible to the mouse immune system
  2. R (rough) strain - harmless to mice; not surrounded by coat so the immune system deals with it
28
Q

What did Fred Griffith discover?

A

transformation of the R strain to the S strain

29
Q

What happens when heat-killed S cells are injected into mouse

A

mouse lives

30
Q

What happens when R cells are transferred into mouse

A

mouse lives

31
Q

What happens when heat killed S cells mixed with R cells are injected into mouse

A

mouse dies

-living S cells are found in blood sample from the dead mouse

32
Q

What do these mouse experiments suggest?

A

Perhaps a (genetic material) gene is transferred from the dead S cells to the living R cells enabling the R cells to make a protective polysaccharide coat (thus the R cells become S cells and kill mouse)

33
Q

What did Fred Griffith think this genetic material passed from S cell to R cell was

A
  • DNA

- a lot of people didn’t think that DNA was this material, a lot of people thought it was proteins

34
Q

Alfred Hershey and Martha Chase and T2 were involved in what

A

Phage genetics

35
Q

What are phages?

A
  • viruses of bacteria that inject their genes into a host bacterial cell
  • expresses their genes and makes more phage particles
  • when phages inject their genes the inject DNA not protein
36
Q

What was the Hershey Chase experiment

A

-mixed radioactively labelled phage with bacteria
-agitated in blender, separated phages outside the bacteria from the cells and their content
-centrifuged so bacteria form a pellet at the bottom of test tube
-measure the radioactivity in the pellet and the liquid
(Radioactivity is in the pellet so the T2 protein is outside the liquid. Therefore the DNA is what is in the cell)

37
Q

James Watson

A
  • did PhD on phage genetics

- but went to uni of Cambridge to work on X-ray crystallography of proteins

38
Q

Why did James Watson switch from Biology to physics?

A

to learn X-ray crystallography so he could explain the structure of DNA

39
Q

Francis Crick

A
  • was a physicist still working on his PhD in his mid-thirties
  • also at Cambridge working on X-ray crystallography of hemoglobin in same lab as Watson
40
Q

Who worked on mutations in WWII

A

Crick

41
Q

What did Linus Pauling discover?

A

found alpha helix (one of first macromolecules)

-structural theme in biology that Watson an Crick found interesting

42
Q

Linus Pauling and model building

A

-played with models, lead to a lot of his insights

43
Q

What were Chargaff’s rules

A

A=T, G=C

-Lavine thought that everything was equimolar, Chargaff showed that it was only At and Gc

44
Q

Rosalind Franklin and Maurice Wilkins

A

X-ray diffraction pictures of crystallized DNA

-Rosalind Franklin died before nobel prize was awarded

45
Q

What did Watson and Crick think?

A

thought that DNA –> RNA –> protein

-thought DNA was the most golden of molecules -people who thought proteins carried hereditary info were idiots

46
Q

Watson and crick used what from others

A

x-ray pictures of others

rosalind franklin

47
Q

What did Watson and Crick propose in 1951

A
  • triple helical model of DNA

- 3 polynucleotide strands and the bases pointing out

48
Q

Linus Paulings DNA triple helix

A
  • pauling prepared paper for publication (wrong)

- the race was on

49
Q

Wilkins showed watson what?

A

-Rosalind Franks picture of B-DNA took late in 1952

50
Q

What 2 models did Watson consider after seeing the picture

A

1) A-A, C-C, G-G, T-T

2) A-T and G-C pairs (noticed that this explains Charagraff’s rules)

51
Q

What does crick point out

A
  • the two strands must run in opposite (antiparallel) directions
  • polarity?

Biology 400 (13 decks)

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