2.1.3 Nucleotides and nucleic acids

Question 1

What elements do nucleotides contain?

Answer 1

C,H,O,N,P

Question 2

Structure of a nucleotide

Answer 2

phosphate group, pentose sugar, nitrogenous base

Question 3

Structure of DNA nucleotide

Answer 3

Deoxyribose sugar, phosphate group, nitrogenous base (A,G,C,T)

Question 4

Structure of an RNA nucleotide

Answer 4

Ribose sugar, phosphate group, nitrogenous base (A,G,C,U)

Question 5

What are the two different structural forms of nitrogenous bases?

Answer 5

Pyramidines and purines

Question 6

List the purines found in DNA

Answer 6

adenine and Guanine

Question 7

List the pyrimidines found in DNA

Answer 7

Cytosine, Thymine, Uracil

Question 8

Structure of purines.

Answer 8

double ring

Question 9

structure of pyrimidines

Answer 9

single ring

Question 10

Explain sugar phosphate backbone

Answer 10

DNA molecules are made up of two polynucleotide strands lying side by side running in opposite directions. The sugar links with the parallel phosphate by a phosphodiester bond.

Question 11

What type of bond joins nucleotides together?

Answer 11

Phosphodiester bond

Question 12

Why are fruits such as kiwi’s and strawberries good for DNA purification?

Answer 12

They have large amounts of DNA in their cells.

Question 13

Explain the method for DNA purification.

Answer 13

-Cut up fruit into small pieces.

-Add washing up liquid to water in a beaker.

-Add some of the fruit into the beaker.

-Place the beaker in a water bath for 15 minutes.

-Move the beaker into an ice cold water bath and stir.

-Using filter paper, filter the mixture into another beaker.

-Pour the filtrate into a test tube and add 2-3 drops of protease enzyme.

-Carefully trickle ice cold ethanol down the side of the test tube and sit until the DNA precipitate forms.

Question 14

Why do you have to place the beaker in a water bath in DNA purification?

Answer 14

Disrupts phospholipid bilayer of fruit cell membrane and nuclear membrane so DNA is released.

Question 15

Why do you add detergent in DNA purification?

Answer 15

Disrupts phospholipid bilayer.

Question 16

Why do you have to cool the mixture in an ice cold water bath during DNA purification?

Answer 16

Stops the DNA itself from breaking down.

Question 17

Why do you have to filter the mixture during DNA purification?

Answer 17

Removes cell debris.

Question 18

Why do you have to add protease enzyme during DNA purification?

Answer 18

Denatures and removes the proteins just leaving DNA.

Question 19

What is semi-conservative DNA replication?

Answer 19

One parental DNA splits to make 2 brand new DNA, each with a parent strand & daughter strand

Question 20

Positive of semi conservative DNA replication.

Answer 20

Ensures genetic continuity.

Question 21

How does semi conservative replication occur?

Answer 21

• DNA helicase enzyme breaks hydrogen bonds by unwinding the double helix. This forms two strands.

-Each new strand acts as a template to form two new polynucleotide strands.

-The new strands are joined by DNA polymerase enzyme.

-Original DNA strand and new strand join together via hydrogen bonds.

Question 22

Why is the genetic code described as being degenerate?

Answer 22

More than one codon codes for one amino acid which reduces the risk of mutations.

Question 23

What are the two stages of protein synthesis?

Answer 23

Transcription and translation

Question 24

What is transcription?

Answer 24

The process of DNA being transcribed and producing an mRNA molecule.

Question 25

What is translation?

Answer 25

The translation of an mRNA molecule and the formation of an amino acid sequence.

Question 26

Where does transcription occur?

Answer 26

Nucleus of cell .

Question 27

Where does translation occur?

Answer 27

ribosome

Question 28

Explain transcription.

Answer 28

-Part of a DNA molecule unwinds by the enzyme DNA helicase and the exposed gene can be translation into a single stranded mRNA molecule.

-Free RNA nucleotides pair up with their now exposed complementary bases on the template strand of the unzipped molecule.

-The sugar phosphate groups of these RNA nucleotides are bonded together by DNA polymerase to form the sugar phosphate backbone.

-When the gene has been transcribed, the hydrogen bonds break between the DNA and mRNA molecule and the mRNA leaves via a pore in the nuclear envelope.

Question 29

Explain translation.

Answer 29

-After leaving the nucleus, mRNA attaches to a ribosome.

-In the cytoplasm there are free molecules of tRNA which have a triplet of unpaired based at one end and a region where an amino acid can join to at the other.

-the tRNA molecules bind with their specific amino acids and bring them to the mRNA molecule.

-The triplet of bases on each mRNA molecule pairs with a complementary triplet in the mRNA molecule.

-Peptide binds form between the amino acid chains until a stop codon is reached.