RNA and Protein Synthesis

RNA - ribonucleic acid

- has ribose
- singled strand
- uracil (instead of thymine)

Types of RNA

Messenger RNA (mRNA) - carries DNA instructions to the ribosomes

Ribosomal RNA (rRNA) - subunits of ribosomes

Transfer RNA (tRNA) - carries amino acids to the ribosomes

Central Dogma - DNA codes for RNA, which codes for protein

Transcription (DNA --> RNA)

Base pair rule ( Guanine to Cytosine; Adenine to Uracil)

One side of the DNA is the template

RNA polymerase builds a strand of RNA based on the template code

Example:

DNA: A T A C A G
RNA: U A U G U C

Promoter - region where RNA polymerase binds to mRNA and begins transcription

RNA Editing

Introns - pieces of RNA that are removed
Exons - remaining pieces are spliced together (and sent to ribosomes)

14.2 Ribosomes and Protein Synthesis

Polypeptides - chains of amino acids that form proteins

Genetic code

- three bases on mRNA, the codon
- codons determine a single amino acid
- RNA to protein is called TRANSLATION

How does RNA make a protein?

RNA tells the ribosomes what protein to build
Every three letters (AAA) specifies a single amino acid
Proteins are made of many amino acids, folding into a 3D shape

A codon chart is used to determine the amino acid

Start codon (MET) initiates translation
Stop codon - ends translation

Assignment: Protein Synthesis and Codons Practice

Translation

1. Begins at the start codon
2. Transfer RNA attaches to mRNA
3. Rivosome joins amino acids together
4. Chain grows until the stop codon

 

14.4 Mutations

- changes in the sequence of nucleotides
- changes in chromomes

Mutagens - agents in the environment that can cause mutations

Types of DNA Mutations

Substitution - change in a single base; which changes the amino acid

Silent mutations occur when the change in base does not change the amino acid

Insertion and Deletions - when a single base is added or lost; results in a frameshift

Chromosome mutations

Deletion - section is lost
Duplication - section is repeated
Inversion - section is flipped
Transloation - section moves to another chromosome

How Can a Single Mutation Cause Disease?

Hemoglobin is a protein that makes up blood cells

When a protein is made wrong (by the DNA code), it may become nonfunctional

Hemophilia - blood clotting proteins don't work
Sickle Cell Disease - blood cells are shaped wrong
Cystic Fibrosis - cell membrane doesn't move chloride ions

Assignment: DNA, Proteins, and Sickle Cell