RNA and Protein Synthesis

RNA - ribonucleic acid

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

codon

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 ribosome

DNA → RNA → Protein

Proteins are made by the cell to perform tasks

Ex. Enzymes and hemoglobin

Central Dogma

Transcription

DNA → RNA

Base pair Rule

G – C
A -- U

One side of DNA is the template

Uses RNA polymerase

Transcription

DNA A T A C A G

RNA

DNA is used a
template to make
RNA

RNA has
URACIL instead
of thymine

* still uses the
base-pair rule

Promoter

- region where RNA polymerase binds
- begins transcription

Promoter

RNA Editing

-introns
pieces of RNA
that are
removed

-exons
remaining
pieces are
spliced

Quick Check:

1. Both RNA and DNA contain: a) thymine b) deoxyribose c) guanine
2. RNA is made from a DNA: a) template b) intron c) polymerase
3. RNA polymerase binds to the: a) exon b) promoter c) ribosome
4. How many types of RNA are there? a) 1 b) 2 c) 3

5. The process where RNA is made from DNA is called
a) splicing

b) transcription c) replication

14.2 Ribosomes and Protein Synthesis

Polypeptides
- chains of amino acids, form proteins

Genetic code

- three bases on mRNA - codon
- code for 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 3 letters (AAA)
specifies a single amino
acid.

Proteins are made of
many amino acids, folded
into a 3D shape

A codon chart is used
to determine the amino
acid

Amino acids are
abbreviated to 3 letter
words

Leu = leucine
Val = valine
Ser = serine

Codon wheels also show amino acids

For each codon,
determine the amino
acid:

A A G =

U C U =

G U C =

Start Codon (met) - initiates translation

Stop Codon - ends translation

Circle the start codon
and the stop codons.

DNA

A T A

C A T

A A A

G G A

RNA

Amino
Acid

DNA

C C G

T C A

T T A

A C T

RNA

Amino
Acid

Protein Synthesis and Codons Practice

Translation (Steps)

1. Begins at the start codon

2. Transfer RNA attaches to
mRNA

3. Ribosome joins amino
acids together

4. Chain grows until the
stop codon

Steps in
translation

Quick Recap

Transcription

- DNA is made into mRNA
- Occurs in the nucleus

Translation

- mRNA brings code to ribosomes
- amino acids form a protein

Quick Check

1. Transcription
2. Translation

3. mRNA
4. DNA
5. tRNA
6. Codon
7. Anticodon
8. Protein

14.4 - Mutations

- changes in the sequence
of nucleotides
- changes in chromosomes

Mutagens - agents in the
environment that can cause mutations

Polydactyl cat at Ernest Hemingway’s House

Point mutations

Substitution or change in
a single base
- can change amino acid
- may code for same
amino acid - (silent
mutation)

Insertions and Deletions

- result in frameshift
- all amino acids are wrong!
- big change in protein!

Chromosome Mutations - affect whole chromosome

Still confused, check out
this video:

Mutations in DNA by
Teacher’s Pet

1. Deletion - section is lost

2. Duplication - section is repeated

3. Inversion - section is flipped

4. Translocation - section moves to

another chromosome

Quick Check:

Identify the:

Inversion

Duplication

Deletion

How can a single mutation
cause a disease?

Hemoglobin is a protein that
makes up blood cells.

This cell
is shaped
wrong

What happens when you have a nonfunctional protein?

Hemophilia - blood clotting
proteins don’t work

Sickle Cell - blood cells are
shaped wrong. (Point Mutation)

Cystic Fibrosis - cell membrane
doesn’t move chloride ions

Sickle Cell Disease

Change (mutation) in a single nucleotide

Leads to wrong amino acid

Protein with the wrong shape

Task:

DNA, Proteins, and Sickle Cell

Synthesis - Explain why the mutant hemoglobin gene causes sickle cell disease.