A1.2 Nucleic Acids

DNA + diagram

Deoxyribonucleic Acid

RNA + diagram + mnemonic to remember order

Ribonucleic acid

GUACA (MOLE)

4 majoir types of biological molecules

• Carbohydrates

• Proteins

• Lipids

• Nucleic acids

Functions of nucleic acids

• Pass info between generations

• Code for protein production

Components of a nucleotide

• Phosphate group

• Nitrogenous base

• Pentose sugar

How are nucleotides linked together

By covalent bonds between the phosphate of one nucleotide and the sugar of another

When drawing covalent bonds, use:

Solid lines

When drawing hydrogen bonds, use:

Dashed lines

Bases in DNA

• Adenine

• Thymine

• Cytosine

• Guanine

Bases in RNA

• Adenine

• Uracil

• Guanine

• Cytosine

Purines

• Adenine

• Guanine

Pyrimidines

• Cytosine

• Uracil

• Thymine

Condensation reactions

Removal of water to create a covalent bond

Similarities of DNA and RNA

• Both are polymers of nucleotides

• Cytosine pairs with guanine

Differences between DNA and RNA

DNA	RNA
Double-stranded	Single-stranded
Deoxyribose	Ribose sugar
Adenine pairs with thymine	Adenine pairs with uracil

Sketch of ribose and deoxyribose

(draw and label)

Examples of nucleic acids

• DNA

• RNA

• tRNA

• mRNA

Semiconservative

Each resulting copy is made of one parent strand and one new strand

What is complementarity based on

Hydrogen bonding

Gene expression

Using DNA code for protein synthesis

Simple steps of gene expression

• DNA is used as a template to make RNA

• RNA is “translated” into a protein

• DNA to RNA follows rules of CBP

Complementary base pairing during transcription

• RNA polymerase builds an RNA strand

• Reads the DNA template

• Adds complementary RNA nucleotide

Complementary base pairing during translation

• Ribosome builds polypeptide by reading mRNA template

• Binds coded amino acid to polypeptide chain

Outline why there are limitless diversity of DNA base sequences

There are four nitrogenous bases in DNA (A, T, C and G). These 4 bases are components of nucleotides that can form a DNA molecule in any order and of any length

Directionality of RNA and DNA

• 5’ with a phosphate

• 3’ with a pentose

• DNA has antiparallel directionality

  • 5’ to 3’ on one side

  • 3’ to 5’ on other side

What do complentary pairs consist of

• One purine

• One pyrimidine

Nucleosome + diagram

DNA wrapped twice around a core of 8 histone proteins

Structure of nucleosomes

• DNA molecule wrapped

• 8 histone proteins

• Additional histone protein

• Linker DNA attached

Hershey–Chase experiment blurt

This was an experiment in the 1950s, Hershey-Chase knew chromosomes were made of DNA and protein and that they carried genetic info, but didn’t know which one was responsible for transmitting hereditary information: DNA or Protein?!

Viruses were made up of DNA and protein, so they grew two different groups of bacteriophage viruses in different radioactive mediums; Sulphur, Phosphorous and allowed each of these to infect others, they spun them through a centrifuge, this separates things based on weight, heavier things goes down

A pellet; the cell’s genetic material at the bottom of the centrifuge. The ones that were grown in radioactive sulphur was the supernatant  and in phosphorus, it was the pellet. They concluded that it was DNA that carried the genetic material NOT the protein!!

Tetranucleotide hypothesis

DNA consisted of a repeating sequence of 4 nucleotides in equal amounts and proteins were the genetic material

Falsification of the tetranucleotide hypothesis

Through Chargaff’s data

• Table shows that organisms infact DO NOT have equal amounts of A, T, G, and Cs