A level notes - DNA & RNA basics

Question 1

DNA & RNA are?

Needed to make ?

Answer 1

Nucleic acids

Proteins

Question 2

DNA & RNA function (in protein making)

Ribosomes role

Answer 2

DNA: stores genetic info
RNA : transfers genetic info to the ribosomes ( proteins are made in the ribosomes - Well some are!)

The ribosomes read the RNA to make the polypeptides (what proteins are made of)

Question 3

Translation
VS
Transcription

Answer 3

How new proteins are synthesised from mRNA
- the code in the MRNA is converted into an AA sequence in a protein

How mRNA is synthesised from DNA
- the code in the DNA is transferred to a complementary RNA code

Question 4

DNA & RNA are polymers oF MONONUCLEOITIDES ?
What are they

Structure of both :

How they are different etc
(3)

How do they Bond?

Answer 4

Basic biological molecule that consists of 3 parts

1. PENTOSE Sugar
2. Phosphate Group
3. Nitrogen containing organic BASE (0rganic means it contains carbon )

Differences : SUGAR

DNA : deoxy ribose sugar
RNA : ribose sugaR

• BASE groups
  DNA : adenine , cytosine , guanine , thymine

RNA : URACIL replaces thymine

-MONONUCLEOTIDES
DNA : 2 polynucleotide strands - parallel & anti parallel - twist & form DOUBLE HELIX
RNA : only 1

Bond?
HB between bases : A-T/U (2HB)
C-G: (3HB)

Question 5

Amino acid structure :

Answer 5

amino group : NH2
carboxyl group : COOH
R group that contains carbon

Question 6

Different types of RNA

Answer 6

mRNA - acts as a messenger between DNA & protein synthesis
Feature: made in nucleus during transcription (from DNA)
- carries genetic info out of nucleus to cytoplasm where it is then used to make a protein during translation

tRNA : transfer RNA : carries AA to the ribosomes for protein synthesis
Features : found in cytoplasm
- 2 binding sites : AA & sequence of 3 bases ie ANTICODON

Question 7

Protein synthesis

Answer 7

Transcription :

• RNA polymerase attaches to the DNA double helix
• breaks HB & DNA unwinds
• RNA mononucleotides pair up with specific bases
• RNA polymerase then joins these paired mononucleotides & forms RNA molecules
• RNA polymerase passes the DNA STRANDS separating them while assembling the mRNA strand
• BUT once passes the DNA strands start to link up again - HB REFORM
• once stop codon is released by ? MRNA : stops making mRNA & detatches from DNA
• mRNA leaves nucleus enters cytoplasm and transfers genetic material to make new protein during translation

Question 8

Step 2 TRANSLATION

Answer 8

Translation :

• mRNA molecule travels to ribosomes ( mRNA is a copy of DNA & this will contain codons - base pairs etc)
• tRNA molecules transport AA to the ribosome
• tRNA molecule with an anticodon complementary to the codon on th mRNA attaches itself to the ribosome
• process repeats
• 2 AA form a peptide bond
• tRNA molecule leaves
• 3rd tRNA molecule attaches to ribosome (codon & anti codon rules etc)
• AA joins original peptide bond
• 2nd tRNA molecule leaves
• process repeats itself
• once stop codon is reached, AA which have for,med a polypeptide chain break away from ribosome

Question 9

DNA replication

Answer 9

DNA replicates by : SEMI - CONSERVATIVE REPLICATION

DNA Replicates itself before cell division
Each replicated DNA strand contains an original & new strand hence semi conservatives

Process:
- DNA strands broken down by DNA helicase ( helicase enzymes unpackage organisms genes )
- complementary base pairing occurs : each strand has bases ie FREE FLOATING DNA NUCLEOTIDES like A,T & wants to pair
-A&T , C&G
- join by condensation reactions forming HB’s ?
This reaction is catalysed by DNA polymerase
- each DNA molecule contains an old & new strand