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IB Biology > 2.7 DNA replication, transcription and translation > Flashcards

2.7 DNA replication, transcription and translation Flashcards

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1
Q

What type of process is DNA replication?

A

Semi-conservative

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2
Q

When a new double stranded DNA molecule is formed, what will each strand be?

A

One will be from the original template molecule
One will be newly synthesised

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3
Q

Why does DNA replication occur as a semi conservative process?

A

Because each nitrogenous base can only pair with its complementary partner

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4
Q

What is each new strand of DNA when it is replicated by the combined action of helicase and DNA polymerase?

A

Identical to the original strand separated from the template

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5
Q

when DNA is replicated by the combined action of helicase and DNA polymerase, what will the two semi conservative molecules have?

A

An identical base sequence to the original molecule

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6
Q

What are the three models proposed for the method of DNA replication?

A

Conservative model
Semi conservative model
Dispersive model

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7
Q

What is the conservative model?

A

A whole new molecule is synthesised from a DNA template which will remain unchanged

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8
Q

What is the semi conservative model?

A

Each new model has one new synthesised strand and one template strand

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9
Q

What is the dispersive model?

A

New molecules are made of segments of new and old DNA

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10
Q

What did Meselson and Stahl use to test the validity of the three hypothesis?

A

Radioactive isotopes of nitrogen

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11
Q

What did the results of Meselson and Stahl support?

A

Semi conservative model

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12
Q

How did Meselson and Stahl use nitrogen in their experiments?

A

DNA molecules were prepared using heavier nitrogen and then induced to replicate in the presence of the lighter nitrogen

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13
Q

In meselson and stahls experiment what was disproved after one division and why?

A

Conservative model as both lighter and heavier nitrogen were found

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14
Q

In meselson and stahls experiment what was disproved after two divisions and why?

A

The dispersive model as some DNA molecules had only the lighter nitrogen

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15
Q

What does pre existing strands do in DNA replication?

A

Act as templates for newly synthesised strands

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16
Q

What are the two enzymes that coordinate DNA replication?

A

Helicase and DNA polymerase

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17
Q

What does helicase do?

A

Unwinds the double helix and separates the two polynucleotide strands

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18
Q

How does helicase do what it does?

A

By breaking the hydrogen bonds that exist between the complimentary base pairs

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19
Q

What happens to the two newly separated polynucleotide strands?

A

they will act as templates for the synthesis of new complementary strands

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20
Q

What does DNA polymerase synthesise?

A

New strands from the two parental template strands

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21
Q

What do free deoxynucleoside triphosphates do?

A

Align opposite their complementary base partner

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22
Q

What does DNA polymerase do?

A

Cleaves the two excess phosphates and uses the energy released to link the nucleotide to the new strand

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23
Q

What is PCR?

A

An artificial method of replicating DNA in lab conditions

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24
Q

What is PCR used for?

A

To amplify large quantities of a specific sequence of DNA from an initial small sample

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25
Q

What does each reaction in PCR do?

A

Doubles the amount of DNA

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26
Q

What does PCR stand for?

A

Polymerase Chain Reaction

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27
Q

What does 30 cycles of a standard PCR sequence create?

A

Over 1 billion copies of DNA

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28
Q

Where does the PCR occur?

A

In a thermal cycler

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29
Q

What is used to control DNA replication in PCR?

A

variations in temperature

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30
Q

What are the three steps of PCR?

A

Denaturation
Annealing
Elongation

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31
Q

What is the temperature used during denaturation?

A

90ºC

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32
Q

What is the temperature used during annealing?

A

55ºC

33
Q

What is the temperature used during elongation?

A

75ºC

34
Q

What happens during denaturation?

A

DNA sample is heated to separate the two strands

35
Q

What happens during annealing?

A

Sample is cooled to allow primers to anneal

36
Q

What happens during elongation?

A

Sample is heated to optimal temperature for a heat tolerant polymerase to function

37
Q

What enzyme is used during PCR?

A

Taq polymerase

38
Q

Why can taq polymerase function in PCR without denaturing?

A

As the enzymes optimal temperature is 75ºC

39
Q

What does taq polymerase do?

A

Extends the nucleotide chain from the primers

40
Q

In PCR what are primers used for?

A

To select the sequence to be copied

41
Q

What is transcription?

A

The process where an RNA sequence is produced from a DNA template

42
Q

During transcription, what does RNA polymerase separate?

A

The DNA strands

43
Q

During transcription, what does RNA synthesise?

A

A complementary RNA copy from one of the DNA strands

44
Q

During transcription, what happens when the DNA strands are separated?

A

Ribonucleoside triphosphates align opposite their exposed complementary base partner

45
Q

During transcription, what does RNA polymerase remove?

A

The additional phosphate groups

46
Q

During transcription, what does RNA polymerase use the energy for?

A

To covalently join the nucleotide to the growing sequence

47
Q

What happens once the RNA sequence has been synthesised?

A

RNA polymerase detaches from the DNA molecule and the double helix reforms

48
Q

What is a gene?

A

The sequence of DNA that is transcribed into RNA

49
Q

What is the antisense strand?

A

The strand of DNA that is transcribed

50
Q

What is the antisense strand complementary to?

A

The RNA sequence

51
Q

What is the sense strand?

A

The strand of DNA that is not transcribed

52
Q

What is the sense strand identical to?

A

The RNA sequence with T instead of U

53
Q

Where does transcription of genes occur?

A

In the nucleus

54
Q

Where does the RNA move to and why?

A

To the cytoplasm for translation

55
Q

What encodes the production of a polypeptide?

A

The base sequence of an mRNA molecule

56
Q

What reads the mRNA sequence?

A

The ribosome in triplets of bases called codons

57
Q

What does each codon code for?

A

One amino acid with a polypeptide chain

58
Q

What does the order of the codons in an mRNA sequence determine?

A

The order of amino acids in a polypeptide chain

59
Q

What is the genetic code?

A

Set of rules where information encoded within mRNA sequence is converted into amino acid sequences by living cells

60
Q

What does the genetic code identify?

A

The corresponding amino acid for each codon combination

61
Q

How many codon possibilities are there?

A

64

62
Q

What does the coding region of an mRNA sequence always begins with and end with?

A

A start codon and an end codon

63
Q

What is translation?

A

The process of protein synthesis where genetic information encoded in mRNA is translated into a sequence of amino acids on a polypeptide chain

64
Q

During translation, what do ribosomes bind to and where?

A

To mRNA in the cytoplasm

65
Q

During translation, how does ribosomes move along the molecule?

A

In a 5’ to 3’ direction until it reaches a start codon

66
Q

During translation, what does anticodons on tRNA molecules do?

A

Align opposite appropriate codons according to complementary base pairing

67
Q

During translation, what does each tRNA molecule carry?

A

A specific amino acid

68
Q

During translation, what does ribosomes catalyse?

A

The formation of peptide bonds between adjacent amino acids

69
Q

During translation, what does the ribosome synthesise?

A

A polypeptide chain

70
Q

During translation, when does the ribosome stop synthesising?

A

When it reaches a stop codon

71
Q

During translation, what happens when the ribosome reaches a stop codon?

A

Translation stops and the polypeptide chain is released

72
Q

What are the eight key components of translation?
(Mr cat app)

A

Messenger RNA
Ribosome
Codons
Anticodons
Transfer RNA
Amino acids
Peptide bonds
Polypeptides

73
Q

What is universal?

A

The genetic code

74
Q

How is the genetic code universal?

A

Almost every living organism uses the same code

75
Q

Why is genetic information transferrable between species?

A

As the same codons code for the same amino acids in all living things

76
Q

What has the ability to transfer genes been utilised to do?

A

Produce human insulin in bacteria

77
Q

What are the four steps to extract insulin?

A

The gene responsible for insulin production is extracted from a human cell

It is spliced into a plasmid vector before being inserted into a bacterial cell

The transgenic bacteria are then selected and cultures in a fermentation tank

The bacteria now produces human insulin which is harvested purified and packaged for human use

78
Q

What is mRNA?

A

mRNA is a complementary copy of a gene and is used to deduce the gene sequence

79
Q

When converting a sequence from mRNA to the original DNA code, what rules must be applied?

A

Cytosine is replaced with guanine and vice versa

Uracil is replaced with Adenine

Adenine is replaced with Thymine

IB Biology (57 decks)

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