2.1.3 Nucleotides And Nucleic Acid

Question 1

Define DNA

Answer 1

Deoxyribonucleic acid is a polynucleotide containing genetic informartion
double helix with complementary bases, A-T,C-G
Sugar phosphate backbone that protects the bases
Antiparallel strands via H bonds,2 between adenine and thymine, 3 between cytosine and guanine

Question 2

State how many H bonds form between adenine and thymine on complementary strands of DNA

Answer 2

2 hydrogen bonds

Question 3

Describe the reaction that joins together 2 mononucleotide to form a dinucleotide

Answer 3

Condensation reaction
Occurs between the hydroxyl group on the phosphate of one nucleotide and pentose sugar of another nucleotide
Creates a covalent phosphodiester bond between nucleotides and releases a molecule of water

Question 4

Name the 3 components of a DNA nucleotide

Answer 4

Deoxyribose
Nitrogenous base
Phosphate grouo

Question 5

Define nucleotide

Answer 5

Monomers of DNA and RNA and are phosphate esters of pentose sugars
They can regulate or fuel metabolic pathways due to high energy phosphate bonds
Can from coenzymes such as NADP

Question 6

How many rings do guanine, adenine, cytosine and thymine have

Answer 6

Adenine and gunaine 2 carbon rings PURINES

Cytosine and thymine 1 carbon ring PYRI MIDINES

Question 7

Explain the function of ATP hydrolysis in the body and give 3 examples

Answer 7

ATP hydrolysis into ADP releases energy,used to fuel many processess in the body
Muscle contraction,active transport and secretion

Question 8

Outline the structural difference between the ATP and RNA nucleotides

Answer 8

ATP contains an adenine base,RNA nucletoides can be adenine, cytosine, uracil or guanije
ATP contains 3 phosphate groups whereas RNA nucleotides contain one

Question 9

Outline the process of DNA replicatio, explaining the importance of the enzymes DNA helicase and DNA polymerase

Answer 9

Strands of DNA are seperated by the enzyme DNA helicase, breaks the H bonds joining together the complemntary bases
Free nucleotide bind to their complementary bases, joined together via DNA polymerase, which forms phosphodiester bonds between each nucleotide

Question 10

Explain what is meant by the term ‘Semi conservative replication’

Answer 10

Production of 2 identical molecules of DNA from one DNA molecule
Each of the 2 new DNA molecules contains one strand from the parent molecule of DNA and one new strand made from free DNA nucleotide

Question 11

Define a gene and state it charachtersitics

Answer 11

Length of DNA coding for one polypeptide, shows which bases code for which amino acid
Degenearate- some AA is coded for by more than one triplet
Universal- same code in all organsims
Non overlapping- each base is only read once

Question 12

Explain what redundancy in the genetic code means

Answer 12

One amino acid is coded for by more than one triplet/ codon

Question 13

Describe which feature of the genetic code makes it possible for a gene to be transfered from one species to another

Answer 13

Genetic code universal

Codons in mRNA code for the same amino adid, irespective of the species

Question 14

Define transcription

Answer 14

Process where mRNA is prodcued from DNA

Question 15

Explain the process by which pre- mRNA is produced from DNA

Answer 15

Section of DNA molecule in the nucleus ‘unzips’ exposing the nucleotide bases of the 2 strands, RNA polymerase moves along the unzipped DNA segment using one of the strands as a tenplate,joining together the complementary RNA nucleotides to the template DNA strand via complementary base pairing

Question 16

Define translation

Answer 16

Process where mRNA is used to produce polypeptides

Question 17

Describe the sequence of events that occur during translation

Answer 17

mRNA strand moves out of the nucleus into the cytoplasm and attaches to a ribosome at the start codon
tRNA with its specfic AA,bind its anti codon to the complementary codon on mRNA as the riboosmes moves along the mRNA strand
PP is fomed as each successive AA specfied by the mRNA sequence binds together with peptide bonds and tRNA released
Synthesis of PP continues until ribosomes reaches a stop codon

Question 18

In translation,explain why the first 2 tRNA molecules must be side by side at the ribosome

Answer 18

First 2 AA in the PP chain must be held close in order for a peptide bond to form in condensation