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RNA and Protein RNA and Protein Synthesis Synthesis

RNA and Protein Synthesis From Genes to PRoteins

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RNA and Protein RNA and Protein SynthesisSynthesis

From Genes to PRoteins

All of the 100 trillion cells in your body came from one original cell: the fertilized eggfertilized egg that grew into YOU!

So how come there are so many different kinds of cells in your body? How did they get so specialized?

And all of those 100 trillion cells have exactly the same DNA in them.

The answer is… Different genes are turned on in different types of cells.

Each gene carries the instructions for making a protein, which does the work of the cell. Different cells make different proteins. For example, liver cells make different proteins than nerve cells, or eye cells, or stomach cells.

DNADNA is the “boss” or manager of each cell. It’s the DNA that has the instructions for making the proteins.

So what are the “workers” of the cells? The answer: RNA

Here’s what happens…

DNADNA RNARNA

transcription

ProteinProtein

translation

TraitTrait

RNA contains the sugar ribose instead of deoxyribose

RNA has the base uracil (U) instead of thymine (T).

RNA is very similar in structure to DNA with 3 main differences.

RNARNA

RNA Is Single-Stranded instead of Double-Stranded like DNA

Recently, a new class of RNA, microRNA,microRNA, has been shown to regulate gene expression.

There are Different RNAs with Different Functions

Messenger RNA (mRNA)

Transfer RNA (tRNA)

Ribosomal RNA (rRNA)

DNA/RNA

DNADNA RNARNA

name

sugar

shape

nitrogen bases

location

# types

function

deoxyribonucleic acid ribonucleic acid

deoxyribose ribose

double-helix (twisted ladder) one-sided ladder

adenine adenine

cytosine cytosine

guanine guanine

thymine uracil

Nucleus, mitochondria, chloroplast

travels between nucleus & cytoplasm

1 type3 types: mRNA tRNA, rRNA

forms genetic code that specifies what proteins are produced by a cell

mRNA:carries genetic code from nucleus to the ribosomes; tRNA brings amino acids to ribosomes for protein assembly

makes an RNA copy of DNA

The enzyme RNA polymeraseRNA polymerase opens the DNA strands and makes an RNA copy of one of the DNA strands.

RNA polymerase acts here

TranscriptionTranscription

The Genetic Language Uses 4 Letters Written The Genetic Language Uses 4 Letters Written Into 3-Letter WordsInto 3-Letter Words

Two examples

There are 20 different amino acids

Amino acids are the building blocks of proteins. A protein is made up of many amino acids bonded together. It’s the proteins that carry out every function in all your cells. It’s the proteins that give an organism its traits.

Amino Acids – What the Genetic Code Specifies

The 4 nitrogen bases (A, C, G, T) are read in groups of threegroups of three.

Each group of 3 bases is called a codoncodon..

Each codon stands for 1 of the 20 amino acids.

Since there are 64 possible combinations of 3 and only 20 amino acids, some amino acids have more than one codon. For example, AAAAAA and AAGAAG both code for lysinelysine.

There are also codes for ““StartStart”” and ““StopStop””..

Ribosomes are located in two places:

attached to the ERattached to the ER (Endoplasmic Reticulum), or floating in the floating in the cytoplasmcytoplasm.

RibosomesRibosomes are Complicated

Protein-Synthesizing

Machines

1.1. DNADNA molecule unzips and makes a single-stranded copy of gene (mRNA)(mRNA)

2.2. mRNAmRNA leaves the nucleus and attaches to a ribosomeribosome.

33.. RibosomeRibosome moves along the mRNAmRNA and “reads” it.

44.. tRNAtRNA brings amino acids to ribosome and attaches them to the protein chainprotein chain.

55.. The ribosomeribosome releases the proteinprotein..

1

2

3

5

4

Protein Synthesis

Protein Synthesis

Protein SynthesisProtein Synthesis

Protein SynthesisProtein Synthesis

Protein synthesis

(mRNA)(mRNA)

(tRNA(tRNA))

Protein SynthesisProtein Synthesis

Protein SynthesisProtein SynthesisProtein SynthesisProtein Synthesis

A U G G G C U U A A A G C A G U G C A C G U U

This is a molecule of messenger RNAmessenger RNA.It was made in the nucleus by

transcription from a DNA molecule.

mRNA moleculemRNA molecule

codoncodon

A U G G G C U U A A A G C A G U G C A C G U U

A ribosome on the rough E.R. attaches to the mRNA molecule.

ribosome

A U G G G C U U A A A G C A G U G C A C G U U

•It brings an amino acid to the first three bases (codon) on the mRNA.

Amino acid

tRNA molecule

anticodon

U A C

•A transfer RNA molecule arrives.

•The three unpaired bases (anticodonanticodon)) on the tRNA link up with the codoncodon.

A U G G G C U U A A A G C A G U G C A C G U U

•Another tRNA molecule comes into place, bringing a second amino acid.

U A C C C G

•Its anticodon links up with the second codon on the mRNA.

A U G G G C U U A A A G C A G U G C A C G U U

•A peptide bond (chemical bond) forms between the two amino acids.

Peptide bond

C C G U A C

A U G G G C U U A A A G C A G U G C A C G U U

•The first tRNA molecule releases its amino acid and moves off into the cytoplasm.

C C G U A C

A U G G G C U U A A A G C A G U G C A C G U U C C G

•The ribosome moves along the mRNA to the next codon.

A U G G G C U U A A A G C A G U G C A C G U U

•Another tRNA molecule brings the next amino acid into place.

C C G

A A U

A U G G G C U U A A A G C A G U G C A C G U U

•A peptide bond joins the second and third amino acids to form a polypeptide (protein) chain.

C C G C C G

A U G G G C U U A A A G C A G U G C A C G U U

•The polypeptide (protein) chain gets longer.

G U C

A C G

•The process continues.

•This continues until a termination (stop) codon is reached.

A U G G G C U U A A A G C A G U G C A C G U U

•The polypeptide (protein) chain gets longer.

G U C A C G

•The process continues.

•This continues until a termination (stop) codon is reached.

A U G G G C U U A A A G C A G U G C A C G U U

•The polypeptide (protein) is then complete, and is released from the ribosome.