RNA & Protein Synthesis

Chapter 13

DNA

• A book of instructions that tells each individual what proteins to make for their needs.

• The path from genes to proteins has two steps:

1. Transcription—reading the DNA codes

2. Translation—actually translating the codes and making the protein

RNA• A single strand of nucleotides that codes

for the protein needed.

Major differences between DNA and RNA:

• Single strand vs. double strand

• Sugar is ribose (has O2)

• T is replaced with a U (uracil)

3 Types of RNA

• 1. Messenger RNA (mRNA) – carries the

message from the nucleus to the cytoplasm (codon-3 nucleotide sequence

2. Transfer RNA (tRNA) transfers the amino acids to the ribosomes to make the protein (anticodon-complementary to codon)

3. Ribosomal RNA (rRNA) is part of the structure of ribosomes (where proteins are made)

Transcription

• In simple terms, when the DNA is read, a strand of RNA is created from it.

Translation

• That strand of RNA is then translated by enzymes and the appropriate amino acids are sequenced to create the protein.

• That strand of RNA is then translated by enzymes and the appropriate amino acids are sequenced to create the protein.

•Protein Synthesis Animation

Protein Synthesis Animation #2

Mutations

• Any changes in the nucleotide sequence on a gene can result in a mutation. Some mutations are fatal or very harmful; others can actually benefit the organism (we will discuss this in upcoming chapters) but most have little to no effect at all.

Gene Mutations

• Mutations that affect a single gene– Point mutations: substitutions, insertions &

deletions. – Usually occur during replication

Chromosomal Mutations

• Changes in the number or structure of chromosomes.

• See figure 13-12 on page 374