Understanding Protein Synthesis

Differences between DNA and RNA:

RNA’s JOB= Make Proteins!!

1. messenger RNA (mRNA)

Types of RNA

2. transfer RNA (tRNA)

3. ribosomal

Types of RNA

1) messenger RNA (mRNA)- carries instructions from the DNA

Types of RNA

2) ribosomal RNA (rRNA)- combines with proteins to form

Protein Synthesis Overview

There are two steps to making proteins (protein synthesis):
1)

Transcription

1) Transcription begins when the enzyme RNA polymerase binds to

Transcription

3) RNA polymerase pairs up free floating RNA nucleotides with DNA

Transcription

5) mRNA editing occurs in the nucleus*
*RNA Editing: Before the mRNA

RNA Editing (even better pic in your textbook p. 302)

Transcription

Nucleus

Transcription vs. Replication

The main difference: transcription results in the formation of

The Genetic Code

Proteins (polypeptides) are long chains of amino acids that

The Genetic Code

A codon consists of three consecutive nucleotides that specify

The Codon Table

Sixty-four combinations are possible when a sequence of three

Some codons do not code for amino acids; they provide instructions

All organisms use the same genetic code (A,T,C,G).
This provides evidence that

Cracking the Code

This picture shows the amino acid to which each

Translation

Translation takes place on ribosomes, in the cytoplasm.

The cell

Messenger RNA (mRNA)

1) The mRNA that was transcribed from DNA during

Transfer RNA(tRNA)

2) The mRNA enters the cytoplasm and attaches to

The Polypeptide “Assembly Line”

5) The ribosome moves along the mRNA and