Nucleotides and nucleic acids

Question 1

what 3 components structure a nucleotide

Answer 1

a phosphate group, a pentose sugar and an organic base

Question 2

what are 2 polymers of nucleotides

Answer 2

DNA and RNA

Question 3

what is the structure of ATP (adenosine triphosphate)

Answer 3

one molecule of adenine, one ribose sugar and 3 phosphate groups

Question 4

what are the components of a DNA nucleotide

Answer 4

a deoxyribose sugar, a phosphate group and one of the 4 organic bases (adenine, guanine, cytosine or thymine)

Question 5

what is the structure of a DNA molecule

Answer 5

double stranded that twists into a double helix, the 2 strands are anti-parallel and therefore run in opposite directions, that 2 sugar - phosphate backbones are held in place by pairs of complimentary bases joined by hydrogen bonds

Question 6

what are the components of a RNA nucleotide

Answer 6

a ribose sugar, a phosphate group and one of the organic bases (adenine,guanine,cytosine or uracil)

Question 7

what is the structure of a RNA nucleotide

Answer 7

a relatively short molecule and single-stranded

Question 8

what bond is formed between 2 nucleotides due to a condensation reaction

Answer 8

phosphodiester bond/ester bond

Question 9

what is a phosphodiester bond

Answer 9

a phosphate group and 2 ester bonds

Question 10

what reaction breaks the phosphodiester bond

Answer 10

hydrolysis

Question 11

what 2 organic bases are purines

Answer 11

adenine and guanine

Question 12

what 2 organic bases are pyrimidines

Answer 12

cytosine and thymine

Question 13

how many hydrogen bonds from between the complimentary base pairs

Answer 13

cytosine+guanine=3 hydrogen bonds
adenine+thymine=2 hydrogen bonds

Question 14

what is the first stage of DNA replication

Answer 14

DNA helicase breaks the hydrogen bonds between the 2 polynucleotide DNA strands, the helix unzips to form 2 single strands

Question 15

what is the second stage of DNA replication

Answer 15

each original strand acts as a template for a new strand , free-floating DNA nucleotides join to the exposed bases on each original template strand by complimentary base pairing

Question 16

what is the third stage of DNA replication

Answer 16

the nucleotides of the new strand are joined together by DNA polymerase, forming the sugar-phospahte backbone, hydrogen bonds form between the bases on the original and new strand, this twists to form a double-helix

Question 17

what is the fourth stage of DNA replication

Answer 17

each new DNA molecule contains one strand from the original DNA molecule and one new strand

Question 18

what is semi-conservative replication

Answer 18

half of the strands from each molecule are from the original piece of DNA

Question 19

what is the first stage of transcription

Answer 19

DNA helicase breaks the hydrogen bonds which unzips and unwinds the section of DNA that contains the gene

Question 20

what are the 2 strands called and used for after being seperated by DNA helicase

Answer 20

one of the strands is a sense strand which contains the code for the protein to be synthesised it runes from 5’ to 3’, the anti-sense strand is a complimentary copy that doesn’t code for a protein and acts as a template strand

Question 21

what is the second stage of transcription

Answer 21

RNA polymerase moves along the DNA template strand and attaches free nucleotides to their complimentary bases on the DNA, phosphodiester bonds are formed

Question 22

what is the third stage of transcription

Answer 22

RNA polymerase continues making a strand of mRNA until a stop codon is reached

Question 23

what happens to the mRNA after it is produced through transcription

Answer 23

the mRNA detaches from the DNA template and leaves the nucleus via a nuclear pore, the DNA double helix reforms, mRNA then travels to a ribosome for translation

Question 24

what is splicing

Answer 24

when mature mRNA is formed by the introns (non-coding regions of genes) being removed from the pre - RNA molecule, and the exons (coding regions) joining together.

Question 25

what is the first stage of translation

Answer 25

rRNA (ribosomal RNA) makes up the ribosome that moves along the mRNA strand, and one end of the mRNA attaches to the ribosome

Question 26

what is the second stage of translation

Answer 26

a tRNA (transfer RNA) with a complimentary anticodon, carrying a specific amino acid moves to the ribosome and pairs with the first mRNA codon

Question 27

what is the third stage of translation

Answer 27

the ribosome moves along the mRNA to the next codon and again pairs up with a complementary tRNA, to bring the two amino acid-carrying tRNAs together

Question 28

what is the fourth stage of translation

Answer 28

energy released from ATP is used to form a peptide bond between the amino acids bought to the ribosome by tRNA

Question 29

what is the fifth stage of translation

Answer 29

the ribosome moves to the third mRNA codon, releasing the first tRNA and pairing up a third (only space for 2 tRNA at a time)

Question 30

what is the sixth stage of translation

Answer 30

this continues until the ribosome reaches a stop codon, then the polypeptide is complete and the mRNA and tRNAs are released from the ribosome

Question 31

the tRNA molecules released from the ribosome can't be reused true or false?

Answer 31

false they can be reused

Question 32

what does it mean that the genetic code is non-overlapping

Answer 32

each base triplet is read in sequence,seperate from the triplet before it and after it and the base triplets don't share their bases

Question 33

what does it mean that the genetic code is universal

Answer 33

the same base triplets code for the same amino acid in all living organisms/things

Question 34

what does it mean that the genetic code is degenerate

Answer 34

more combinations of base triplets than amino acids (20 amino acids but 64 possible base triplets), some amino acids are coded for by more than one base triplets

Question 35

what is the method for DNA purification

Answer 35

1- use a fruit or vegetable e.g. strawberries and break up the cells e.g. through use of a blender 2- make up a solution of detergent (dilute washing-up liquid), salt (sodium chloride) and distilled water 3- add broken cells to a beaker containing detergent solution, incubate the beaker in a water bath at 60 degrees for 15 minutes 4- once incubated put beaker in an ice bath to cool the mixture down, when its cooled filter the mixture e.g. pass through a mesh 5- add protease enzymes to the filtered mixture 6- slowly dribble some ice cold ethanol at a 45 degree angle to the solution, so it forms a layer on top of the DNA-detergent mixture 7- once left for a few minutes, the DNA will form a white precipitate (solid) which can be removed using a glass rod

Question 36

how is the detergent solution suited to make the method work

Answer 36

detergent- breaks down the cell membranes salt- binds to the DNA and causes it to clump together temperature- the temperature of the water bath should stop enzymes in the cells from working properly and breaking down the DNA

Question 37

how does the protease enzymes work

Answer 37

these will break down (hydrolyse) some proteins in the mixture

Question 38

what does adding the ethanol do to the DNA

Answer 38

causes it to precipitate