3.4.2 - DNA and protein synthesis

What is a codon?

3 bases on RNA that code for a specific amino acid

What is the genome?

The complete set of an organisms DNA in a cell

What is the proteome?

The full range of proteins that a cell is able to produce

Where is tRNA located?

In the cytoplasm

What is the structure of tRNA?

What holds the shape of tRNA together?

H bonds

What is an anticodon?

A triplet of RNA bases that are complementary to codons on the mRNA molecule

What is rRNA used for?

It combines with proteins to make ribosomes

Why is mRNA being shorter an advantage?

It is able to fit through nuclear pores

Describe the steps in transcription

• The H bonds between DNA bases break causing the double helix to unwind and separate leaving bases exposed

• Only one of the strands acts as a template and free nucleotides align to exposed bases due to complementary base pairing

• RNA polymerase then forms phosphodiester bonds between the RNA nucleotides

What is splicing?

When introns are removed for pre-mRNA

Describe the steps in translation

• The modified mRNA leaves the nucleus and mRNA attaches to a ribosome

• A tRNA molecule - with a specific amino acid -will bind to the complementary codon on mRNA via its anticodon

• The ribosome joins the amino acids together using a peptide bond

• ATP is needed for the joining of the amino acids and also to join the amino acid to the tRNA molecule

• The ribosome moves along the mRNA and the process repeats with new tRNA molecules binding and more amino acids joining together

• This continues until a stop codon is reached and the polypeptide is released from the ribosome