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A-level Biology > (2.3) Nucleic Acids > Flashcards

(2.3) Nucleic Acids Flashcards

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1
Q

What is a nucleotide?

A

A monomer of DNA

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2
Q

What are the different parts of a nucleotide?

A
  • Phosphate group
  • Pentose sugar
  • Nitrogenous base
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3
Q

What are the two types of pentose sugars?

A
  • Deoxyribose
  • Ribose
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4
Q

How is deoxyribose different from ribose?

A

Deoxyribose contains a H group rather than an OH group

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5
Q

What are purines?

A

Double ringed structures (contain a pentagon shape with a hexagon shape)

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6
Q

What are the purines called?

A

Adenine and Guanine

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7
Q

What are pyrimidines?

A

Single ringes structures (a hexagon shape)

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8
Q

What are the pyrimidines called?

A

Cytosine, Thymine and Uracil (in RNA)

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9
Q

Why do pyrimidines and purines always join together in the double helix structure?

A

So the rungs of DNA are always the same length

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10
Q

What do DNA rungs contain?

A

Base pairs

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11
Q

What does it mean by a 5” to 3” and a 3” to 5” direction?

A

It refers to where the nucleotides join to and which carbons in the pentose sugar

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12
Q

What is the reason for the phosphate backbone running in different directions?

A

The two different sides run in an anti-parallel fashion and it mens the double helix is twisted

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13
Q

What is the role of DNA gyrase?

A

It untwists the Double helix structure

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14
Q

What is the role of DNA helicase?

A

It unzips the helix by breaking the hydrogen bonds between the nitrogenous bases

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15
Q

What is the role of single stranded binding proteins?

A

Prevents the two strands from reannealing after DNA helicase has done its job

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16
Q

What does reannealing mean?

A

Binding back together

17
Q

Which direction does DNA polymerase travel in?

A

5 prime to 3 prime direction

18
Q

What is the role of DNA polymerase?

A

It binds to the leading strand and forms covalent bonds between nucleotides by joining the phosphate backbone by forming phosphodiester bond

19
Q

How is the lagging strand synthesised in DNA replication?

A

Discontinuosly which creates okazhaki fragments

20
Q

What is the role of DNA ligase?

A

Sticks together the okazhaki fragments

21
Q

What experiment means semi-conservative replication is evidential?

A

Meselton Stahl experiment

22
Q

What was the Meselton Stahl experiment?

A
  • heavy nitrogen in 2 test tubes
  • grew bacteria and isolated DNA
  • found as generations went on the new DNA was less dense
23
Q

How is DNA semi-conservative?

A

Because one new strand and one old strand in the new DNA helix

24
Q

Describe DNA replication

A
  • DNA gyrase untwists the helix
  • DNA helicase unzips the helix by breaking hydrogen bonds
  • Single stranded binding proteins attach to stop reannealing
  • DNA polymerase binds to the leading strand forming covalent bonds between complementary nucleotides
  • The lagging strand is synthesised discontinuosly
  • DNA ligase sticks together the Okazhaki fragments
  • Eventually replication forks join together and create new DNA helixes
25
Q

What is translation?

A

The process of creating mRNA as DNA is too large to leave the nucleus. It involves a template strand and a coding strand

26
Q

What is a coding strand?

A

It is the same as the mRNA leaving the nucleus

27
Q

What is the template strand?

A

It is complementary to the mRNA

28
Q

What is the role of RNA polymerase?

A

It temporarily pulls apart DNA and joins the backbone of the mRNA strand

29
Q

How does mRNA leave the nucleus?

A

Through nuclear pores in the nuclear envelope

30
Q

How many codon combinations are there?

A

64

31
Q

What does it mean by codons are universal?

A

Every living organism has the same codes

32
Q

What does it mean by codons being degenerate?

A

Means there is more than one codon for a single amino acid

33
Q

What are the 2 subunits of ribosomes?

A
  • Small
  • Large
34
Q

What is the role of tRNA?

A

Helps code of mRNA to be read

A-level Biology (23 decks)

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