3.1.5 nucleic acids

Question 1

What are the complimentary base pairs in DNA?

Answer 1

A and T
C and G

Question 2

What are the complimentary base pairs in RNA?

Answer 2

A and U
C and G

Question 3

How many hydrogen bonds are between A and T?

Answer 3

2

Question 4

How many hydrogen bonds are between C and G

Answer 4

3

Question 5

Which nitrogenous bases are purines

Answer 5

A and G
2 carbon rings

Question 6

WHich nitrogenous bases are pyramidines

Answer 6

T, C and U
1 carbon ring

Question 7

What does DNA stand for?

Answer 7

deoxyribose nucleic acid

Question 8

What are the three comoponents of a nucleotide

Answer 8

nucleotides make up DNA
- nitrogenouse base
- phosphate
- deoxyribose sugar

Question 9

How is a dinucleotide formed?

Answer 9

• condensation reaction
• bond is formed between C3 and phosphate
• phosphodiester bond

Question 10

Describe and explain the 4 adaptations of DNA?

Answer 10

• Stability, maintains the sequence of genetic info, needs to last the lifetime of the cell
• Hydrogen bonds- strength and stability on mass, allows strands to be seperated for protein synthesis or replication
• Large molecule - stores all the genetic info
• Base pairs are on the inside of the molecule- protects genetic code

Question 11

What are the uses of the two strands in DNA?

Answer 11

• Coding strand - order of nitrogenous bases on the coding strand codes the order of amino acids in the primary structure of a protein
• Non coding strand - provides two strands for DNA replication and protects the order of the bases

Question 12

What are the components of RNA?

Answer 12

• ribose
• phosphate group
• nitrogenous base- adenine, uracil (instead of thymine), guanine cyastine

Question 13

What are the three types of RNA?

Answer 13

1. messenger RNA - carries genetic information from the DNA to the ribosomes
2. transfer RNA - brings the amino acids to the ribosomes
3. ribosomal RNA - produced in the nucleolis, forms a part of ribosomes

Question 14

What are the differences between DNA and RNA?

Answer 14

• RNA is single stranded and DNA is double stranded
• RNA uses uracil in place of thymine
• RNA contains a ribose sugar and DNA contains a deoxyribose sugar

Question 15

What is the structure of mRNA?

Answer 15

• Single stranded molecule
• Contains unpaired bases
• bases are arranged in codons (groups of three)

Question 16

What is the structure of tRNA?

Answer 16

• single stranded molecule that folds into a specific shape
• Has anticodon region complimentary to the codons on mRNA
• attachment site for amino acids

Question 17

What can increase the occurence of mutations in DNA

Answer 17

• X rays
• UV light
• Benzine
• Tobacco tar

Question 18

How is DNA replicated

Answer 18

• semi conservative replication
• In each new DNA molecule, one polynucleotide strand is present from the original DNA molecule

Question 19

What are the three types of mutations

Answer 19

addition - frameshift to the right
deletion - frameshift to the left
substitution

Question 20

Why is the genetic code considered universal

Answer 20

• the same codons code for the same amino acids in all organisms

Question 21

What is an intron and exon?

Answer 21

INTRON:
- The section of genetic code that is removed from the pre-mRNA during splicing

EXON
- The section of genetic code that is not removed from the pre-mRNA during splicing

Question 22

Difference between bacterial DNA and eukaryotic

Answer 22

• Circular instead of helix
• no introns in bacteria
• no histones in bacteria
• binary fission instead of mitosis

Question 23

Transcription

Answer 23

Where one gene on the DNA is copied into mRNA

Question 24

Translation

Answer 24

Where the mRNA joins with a ribosome and tRNA molecules bring the specific amino acid that each codon codes for

Question 25

How does mRNA leave the nucleus

Answer 25

Nuclear pores

Question 26

Transcription step by step

Answer 26

- The DNA helix unwinds to expose the bases to act as a template - only one chain of the DNA acts as a templatelte, the coding strand - the breaking of the hydrogen bonds between the two DNA strands is catalysed by DNA helicase - mRNA nucleotides align opposite exposed complimentary base pairs on the DNA - RNA polymerase bonds together the RNA nucleotides via phosphodiester bonds to create the pre-mRNA strand

Question 27

Splicing

Answer 27

- the pre-mRNA strand contains intron and exons - Introns are not coded for but exons are - Splicing removes the intron form the pre-mRNA strand resulting in the mRNA strand

Question 28

Translation step by step

Answer 28

- modified RNA leaves the nucleus via nuclear pores and attaches to a ribosome in the cytoplasm - the ribosome attaches to the start codon and holds it in place for a tRNA molecule with a complimentary anti codon to attach - the tRNA molecule has a specific amino acid attached to the top - The ribosome will move along the mRNA chain so another tRNA can attach - the ribosome catalyses the formation of peptide bonds between adjacent amino acids, this requires ATP - the tRNA detaches and collects another amino acid

Question 29

When does DNA replication occur

Answer 29

interphase

Question 30

DNA replication step by step

Answer 30

- DNA helicase unwinds the double helix strand which runs anti parallel, by breaking the hydrogen bonds between the bases - Each polynucleotide strand acts as a template for the formation of a new strand, formed by nucleotides which are attracted to their complimentary base pairs - The new nucleotides are joined together by DNA polymerase which catalyses the condensation reaction of the phosphodiester bond - The original and new strand join together via hydrogen bonding between the base pairs - this is called semi conservative replication

Question 31

How does DNA polymerase work

Answer 31

- The bases of the free nucleoside triphosphates align withtheir complimentary base pairs on each of the template strands of the DNA - The enzyme DNA polymerase synthesises new DNA strands from the two template strands - It does this by catalysing the condensation reaction between the C3 of the deoxyribose sugar and the phosphate groups of the adjacent nucleotides - This creates the sugar phosphate backbone of the new DNA strands - DNA polymerase breaks off the two extra phosphates and uses the released energy to create the phosphodiester bonds

Question 32

What is semi conservative replication

Answer 32

- One strand from the original DNA is conserved - The other strand is synthesised by the cell - Half of the original DNA is conserved in order to create a new DNA molecule

Question 33

What is the importance of semi conservative replication of DNA

Answer 33

- It ensures that all the genetic material is inherited from its parent cell - Genetic continuity