biology unit 2 notes- Genetics

  • Created by: pegah
  • Created on: 22-02-14 15:27

Unit 2 biology





-Contains all genetic information

--> Instructions needed to grow and fertilise an egg


-Double helix structure (two separate strands coiled around each other )

-Strands are polynucleotides (lots of nucleotides joined together)

nucleotide structure:

-Phosphate group

-Deoxyribose sugar

-Bases- Adenine-Guanine-Thymine-Cytosine

Many nucleotides join together to form a polynucleotide.

Join together from the sugar of one and the phosphate group of another.

--> Creates a sugar-phosphate backbone

Specific base pairings:

Polynucleotides join together by hydrogen bonds between the bases

A-T always pair up

G-C always pair up

Double helix: very stable, doesn’t easily get damaged/break down

Long/coiled up: so a lot of genetic information can fit into a small space

Paired structure: so it can easily copy itself. (semi conservative replication)

Eukaryotic cells:

-Contain linear DNA molecules

-These exist as chromosomes

-Each chromosome is made up of one long molecule of DNA

-Molecule is wound around histone proteins

-Histone proteins help support the DNA

Prokaryotic cells:

-Carry DNA as chromosomes

-DNA molecules are short and circular

-DNA condenses to fit into the cell by supercoiling

-DNA floats around cytoplasm


 - Genes are sections of DNA.

-They’re found on chromosomes

- Genes code for proteins

Making proteins:

-Proteins are made from amino acids

-Each protein has it’s own number and order of amino acids

-The order of nucleotide bases determines the order of amino acids

-3 bases code each amino acid (triplet code)

-Different sequences of bases code for different amino acids

The code in DNA is…


No comments have yet been made