2.7 DNA replication, transcription and translation

Question 1

What type of process is DNA replication?

Answer 1

Semi-conservative

Question 2

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

Answer 2

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

Question 3

Why does DNA replication occur as a semi conservative process?

Answer 3

Because each nitrogenous base can only pair with its complementary partner

Question 4

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

Answer 4

Identical to the original strand separated from the template

Question 5

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

Answer 5

An identical base sequence to the original molecule

Question 6

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

Answer 6

Conservative model
Semi conservative model
Dispersive model

Question 7

What is the conservative model?

Answer 7

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

Question 8

What is the semi conservative model?

Answer 8

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

Question 9

What is the dispersive model?

Answer 9

New molecules are made of segments of new and old DNA

Question 10

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

Answer 10

Radioactive isotopes of nitrogen

Question 11

What did the results of Meselson and Stahl support?

Answer 11

Semi conservative model

Question 12

How did Meselson and Stahl use nitrogen in their experiments?

Answer 12

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

Question 13

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

Answer 13

Conservative model as both lighter and heavier nitrogen were found

Question 14

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

Answer 14

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

Question 15

What does pre existing strands do in DNA replication?

Answer 15

Act as templates for newly synthesised strands

Question 16

What are the two enzymes that coordinate DNA replication?

Answer 16

Helicase and DNA polymerase

Question 17

What does helicase do?

Answer 17

Unwinds the double helix and separates the two polynucleotide strands

Question 18

How does helicase do what it does?

Answer 18

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

Question 19

What happens to the two newly separated polynucleotide strands?

Answer 19

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

Question 20

What does DNA polymerase synthesise?

Answer 20

New strands from the two parental template strands

Question 21

What do free deoxynucleoside triphosphates do?

Answer 21

Align opposite their complementary base partner

Question 22

What does DNA polymerase do?

Answer 22

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

Question 23

What is PCR?

Answer 23

An artificial method of replicating DNA in lab conditions

Question 24

What is PCR used for?

Answer 24

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

Question 25

What does each reaction in PCR do?

Answer 25

Doubles the amount of DNA

Question 26

What does PCR stand for?

Answer 26

Polymerase Chain Reaction

Question 27

What does 30 cycles of a standard PCR sequence create?

Answer 27

Over 1 billion copies of DNA

Question 28

Where does the PCR occur?

Answer 28

In a thermal cycler

Question 29

What is used to control DNA replication in PCR?

Answer 29

variations in temperature

Question 30

What are the three steps of PCR?

Answer 30

Denaturation Annealing Elongation

Question 31

What is the temperature used during denaturation?

Answer 31

90ºC

Question 32

What is the temperature used during annealing?

Answer 32

55ºC

Question 33

What is the temperature used during elongation?

Answer 33

75ºC

Question 34

What happens during denaturation?

Answer 34

DNA sample is heated to separate the two strands

Question 35

What happens during annealing?

Answer 35

Sample is cooled to allow primers to anneal

Question 36

What happens during elongation?

Answer 36

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

Question 37

What enzyme is used during PCR?

Answer 37

Taq polymerase

Question 38

Why can taq polymerase function in PCR without denaturing?

Answer 38

As the enzymes optimal temperature is 75ºC

Question 39

What does taq polymerase do?

Answer 39

Extends the nucleotide chain from the primers

Question 40

In PCR what are primers used for?

Answer 40

To select the sequence to be copied

Question 41

What is transcription?

Answer 41

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

Question 42

During transcription, what does RNA polymerase separate?

Answer 42

The DNA strands

Question 43

During transcription, what does RNA synthesise?

Answer 43

A complementary RNA copy from one of the DNA strands

Question 44

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

Answer 44

Ribonucleoside triphosphates align opposite their exposed complementary base partner

Question 45

During transcription, what does RNA polymerase remove?

Answer 45

The additional phosphate groups

Question 46

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

Answer 46

To covalently join the nucleotide to the growing sequence

Question 47

What happens once the RNA sequence has been synthesised?

Answer 47

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

Question 48

What is a gene?

Answer 48

The sequence of DNA that is transcribed into RNA

Question 49

What is the antisense strand?

Answer 49

The strand of DNA that is transcribed

Question 50

What is the antisense strand complementary to?

Answer 50

The RNA sequence

Question 51

What is the sense strand?

Answer 51

The strand of DNA that is not transcribed

Question 52

What is the sense strand identical to?

Answer 52

The RNA sequence with T instead of U

Question 53

Where does transcription of genes occur?

Answer 53

In the nucleus

Question 54

Where does the RNA move to and why?

Answer 54

To the cytoplasm for translation

Question 55

What encodes the production of a polypeptide?

Answer 55

The base sequence of an mRNA molecule

Question 56

What reads the mRNA sequence?

Answer 56

The ribosome in triplets of bases called codons

Question 57

What does each codon code for?

Answer 57

One amino acid with a polypeptide chain

Question 58

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

Answer 58

The order of amino acids in a polypeptide chain

Question 59

What is the genetic code?

Answer 59

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

Question 60

What does the genetic code identify?

Answer 60

The corresponding amino acid for each codon combination

Question 61

How many codon possibilities are there?

Answer 61

64

Question 62

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

Answer 62

A start codon and an end codon

Question 63

What is translation?

Answer 63

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

Question 64

During translation, what do ribosomes bind to and where?

Answer 64

To mRNA in the cytoplasm

Question 65

During translation, how does ribosomes move along the molecule?

Answer 65

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

Question 66

During translation, what does anticodons on tRNA molecules do?

Answer 66

Align opposite appropriate codons according to complementary base pairing

Question 67

During translation, what does each tRNA molecule carry?

Answer 67

A specific amino acid

Question 68

During translation, what does ribosomes catalyse?

Answer 68

The formation of peptide bonds between adjacent amino acids

Question 69

During translation, what does the ribosome synthesise?

Answer 69

A polypeptide chain

Question 70

During translation, when does the ribosome stop synthesising?

Answer 70

When it reaches a stop codon

Question 71

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

Answer 71

Translation stops and the polypeptide chain is released

Question 72

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

Answer 72

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

Question 73

What is universal?

Answer 73

The genetic code

Question 74

How is the genetic code universal?

Answer 74

Almost every living organism uses the same code

Question 75

Why is genetic information transferrable between species?

Answer 75

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

Question 76

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

Answer 76

Produce human insulin in bacteria

Question 77

What are the four steps to extract insulin?

Answer 77

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

Question 78

What is mRNA?

Answer 78

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

Question 79

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

Answer 79

Cytosine is replaced with guanine and vice versa Uracil is replaced with Adenine Adenine is replaced with Thymine