DNA : the material of inheritance Flashcards

Lecture 2 - Mari Knight

1
Q

“living thing”

A

a living thing should have

  1. metabolism
  2. hereditary replication
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2
Q

metabolism

A

a coordinated system of chemical reactions contributing to its maintanence system, a system that imports energy to maintain order

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3
Q

hereditary replication

A

a system of copying in which the new structure resembles the old

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4
Q

discovery of DNA

A

Miescher 1869
- discover ‘nuclein’ (component of cell)

Griffith 1928
- bacterial transformation

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5
Q

Griffith’s experiment : transformation

A
  • s strain and r strain
  • tested on a mouse
  • bacteria are capable of transferring genetic information through a process known as transformation
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6
Q

Chargaff’s Rule

A

Adenine = Thymine
Guanune = Cytosine
A + T ≠ G + C

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7
Q

DNA is a double helix

A

James Watson & Francis Crick (1953)

  • had potential to encode for amino acids, the building blocks of proteins
  • mutations could bring about significant differences in proteins
  • could be easily copied due to the complemantary nature of the 2 strands
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8
Q

DNA : basic structure

A
Nucelotide = phosphate + sugar + base 
DNA = phospate + deoxyribose sugar + nitrogenous base

bases:

  • Thymine
  • Cytosine
  • Guanine
  • Adenine

A always binds with T ( 2 hydrogen bonds )
G always binds with C ( 3 hydrogen bonds )

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9
Q

Pyrimidines

A

Cytosine and Thymine
( 6 carbon ring )

to remember : py : cy : thy

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10
Q

Purines

A

Guanine and Adenine

6 carbon ring + 5 carbon ring

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11
Q

DNA : anti-parallel structure

A

2 strands of DNA running anti-parallel to each other

one strand runs in a 5’ to 3’ direction and the other runs in a 3’ to 5’ direction.

  • 5 prime end = free phosphate
  • 3 prime end = free sugar

each strand is complimentary to the other

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12
Q

semiconservitive replication

A

DNA replication is semiconservative

produce two copies that each contained one of the original strands of DNA and one new strand

Each strand of the original molecule remains intact and serves as the template for the synthesis of a complementary strand

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13
Q

DNA : replication

A

occurs simultaneously at several points along the DNA strand ( replication bubbles )

DNA replication mediated by:

  • helicase
  • RNA primase
  • DNA polymerase
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14
Q

Replication Bubbles

A

an unwound and open region of DNA where DNA replication occurs

  • eventually will join up
  • rapid replication
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15
Q

DNA : properties

A

to sustain life DNA must be able to :

  • be replicated
    A) for cell generation : Mitosis
    B) for reproduction : Meiosis
  • be repaired
  • be expressed and regulated
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16
Q

Mutagens

A

a natural or human-made agent (physical or chemical) which can alter the structure or sequence of DNA

e.g. UV light, nitrous acid, ethidium bromide

17
Q

replication errors

A

size of the average eukaryotic genome is 10^9 - 10^10 bases – error rate of initial DNA polymerase during replication is ~ 1 per 10^5 bases.

the final error rate in replication is < 1 per billion nucelotides

18
Q

DNA proofreading

A

Corrects errors during replication
Orientation to the hydroxyl group is incorrect
Decreases error rate to ~ 1 per 10^7

19
Q

Mismatch repair

A

corrects errors after replication is complete
deformity in secondary struvcture recognised
decreases error rate to ~ 1 per 10^9

20
Q

primary structure ( proteins )

A

the sequence of a chain of amino acids

21
Q

secondry structure ( proteins )

A

occurs when the sequence of amino acids are linked by hydrogen bonds

alpha helix
beta pleated sheet

22
Q

tertiary structure

A

coiled/folded further. more bonds form between different parts, including hydrogen bonds and ionic bonds. disulfide bridges form when two cysteine

23
Q

quaternary structure ( proteins )

A

protein consisting of ore than one amino acid chain