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Introduction to Evolution and Genetics > DNA replication > Flashcards

DNA replication Flashcards

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1
Q

What is DNA?

A

DNA is a polymer

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2
Q

What does it mean by “dna is a polymer”

A

meaning it consists of repeated subunits – molecules – in this case nucleotides

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3
Q

What bonds connect nucleotides together?

A

phosphodiester bonds.

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4
Q

How is the DNA polymer chain formed?

A

the DNA polymer chain is formed by the sugar part of one nucleotide being covalently bonded to the phosphate group of the next nucleotide (phosphodiester bond) – and so on…

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5
Q

How are dna strands held together?

A

DNA strands are held together by hydrogen bonds between the nucleotides.

These bonds are formed between the sugar and phosphate molecules of adjacent nucleotides, creating a double helix structure.

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6
Q

What does DNA consist of?

A

Polymerised dNTPs

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7
Q

What are the bases of DNA?

A

The bases are nitogen-containing ring compounds, either pyrimidines or purines.

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8
Q

What bases are pyrimidines?

A

uracil, cytosine, thymine

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9
Q

What bases are purines?

A

Adenine, guanine

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10
Q

How many rings does a pyrimidine have?

A

1 ring

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11
Q

How many rings does a purine have?

A

2 rings

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12
Q

How are nucleotides added to a growing chain of DNA?

A

nucleotides are added on to a growing chain of DNA by the release of pyrophosphate (PPi) after the addition of a nucleotide – the remaining phosphate group then forms a phosphodiester bond.

so adjacent nucleotides on a DNA strand are joined by covalent bonds on the sugar phosphate backbone

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13
Q

Adjacent nucleotides on a DNA strand are joined by…

A

covalent bonds on the sugar phosphate backbone

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14
Q

What does a nucleotide consist of?

A

Base [nitrogenous]
Phosphate group
Sugar

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15
Q

Nucleotides are the subunits of…

A

nucleic acids.

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16
Q

What are the subunits of nucleic acids?

A

nucleotides.

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17
Q

DNA is a polymer of nucleotides consisting of…

A

…adenine (A), cytosine (C), guanine (G) and thymine (T)

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18
Q

How many strands in a DNA molecule?

A

DNA molecules are double-stranded

19
Q

How do the two strands in a DNA molecule pair together?

A

the two strands ‘pair’ together with complementary sequences forming the pairs

20
Q

What are the two types of groove in DNA molecule?

A

Minor groove
Major groove

21
Q

What bonds hold the bases together?

A

Hydrogen bonds

eg: hydrogen bond between G and C

22
Q

What direction does DNA run in?

A

5 prime to 3 prime

On left, 5 down to 3
On right 5 up to 3.

23
Q

In double stranded DNA, how do bases pair together?

A

in double stranded DNA A always pairs with T and C always pairs with G.

the two strands are paired because of hydrogen bonds (H bonds)

24
Q

How many hydrogen bonds between A and T?

A

2 H bonds

25
Q

In a molecule of water…

A

…an oxygen (O) atom shares electrons with 2 hydrogen (H) atoms

26
Q

Do oxygen or hydrogen atoms pull electrons toward their nucleus more strongly?

A

oxygen atoms pull electrons towards their nucleus more strongly than hydrogen atoms - more electronegative

27
Q

Oxygen atoms are more […] than hydrogen atoms.

A

Oxygen atoms are more electronegative the hydrogen atoms.

28
Q

Due to oxygen atoms pulling electrons towards their nucleus more strongly than hydrogen atoms (being more electronegative the hydrogen), what has happened to the charge of the overall water molecule?

A

because of this the water molecule has a charge difference across the molecule

29
Q

Why is there a charge difference across water molecules?

A

Oxygen atoms more electronegative than hydrogen atoms.

30
Q

because the atoms within water molecules have a net charge difference…

A

…adjacent molecules attract one another and hydrogen bonds form between the H atom of one molecule and the O atom of an adjacent molecule - intermolecular forces

31
Q

you can think of the bonding in DNA as …

A

…analogous to the simple case in water

32
Q

define adjacent

A

next to or near to something. eg: a neighbour.

33
Q

Where are covalent bonds located in relation to bases?

A

Covalent bonds are located between adjacent bases within a single strand in the dna molecule.
Hydrogen bonds are between bases which connect the TWO strands together within dna molecule.

34
Q

What happens to electrons in covalent bonds?

A

electrons shared.

35
Q

What are the strength level of covalent bonds?

A

strong bonds.

36
Q

What are the strength level of hydrogen bonds?

A

weak bonds

37
Q

unwinding of the double helix makes…

A

…two single strands

38
Q

polymerisation depends upon…

A

…the presence of a template strand.

39
Q

What does unwinding of the dna double helix and polymerisation require?

A

requires dNTPs, a polymerase, Mg2+ and a free 3’ OH end

40
Q

For any cell to reproduce it first must?

A

copy its genetic material.

41
Q

What does the genetic material of a cell contain?

A

the genetic material contains the blueprint for making all the proteins a cell needs - without it the daughter cells cannot function

42
Q

How does dna replicate?

A

DNA replicates by copying itself – each strand of the double helix contains the information to make a duplicate strand – because DNA molecules pair by complementary base pairing.

this is called semi-conservative replication

43
Q

Describe DNA polymerisation:

A

DNA is polymerised by a complex of proteins at the replication fork:
1 – DNA polymerase – catalyses the addition of bases to the 3’ end
2 – Topoisomerase – unwinds the helix to prevent torsion
3 - Helicase – melts the double stranded molecule
4 - DNA primase – makes short RNA primers (gives a free 3’ end)
5 - Single stranded binding proteins – prevents premature annealing
6 - DNA ligase – joins Okazaki fragments on the lagging strand

Introduction to Evolution and Genetics (18 decks)

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