Genes are coded DNA instructions that control the production of proteins within the cell.1- Decoding the genetic messages by copying part of the nucleotide

2- RNA molecules contain coded information for making proteins.

RNA consist of a long chain of nucleotides

Sugar in RNA is reboseGenerally is single- strandedContains Uracil in place of thymine.

RNA MoleculesIs a disposable copy of a segment of DNA.

Is a working copy of a single geneThe ability to copy a single DNA sequence into RNA makes it possible for a single gene to produce hundreds of RNA molecules.

Types of RNAThey have a lot of functions but most of them are in charge of protein synthesis.

It controls the assembly of amino acids into proteins.

There are 3 main types:Messenger RNARibosomal RNATransfer RNA

3 types of RNA

Messenger RNAThey serve as a messenger from DNA (inside the nucleus) to the rest of the cell.

Ribosomal RNAProteins are assembled on ribosomes.

They are made up of several dozen proteins.

Transfer RNARNA molecule transfers each amino acid to the ribosome as it is specified by coded messages in mRNA.

TranscriptionCopying part of the nucleotide

sequence of DNA into complementary sequence in RNA.

RNA polymeraseEnzyme required to open DNA

During transcription, RNA polymerase binds DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.

How does RNA polymerase “knows” where to start and stop

making an RNA copy of DNA?RNA polymerase does not bind to DNA just anywhere.

Promoter – region of DNA that indicates to the enzyme where to bind to make RNA. (Where to start and where to stop)

Promoters

A G C A G C A G C STOP

Section of DNA

RNA EditingDNA of eukaryotic genes contains sequence

of nucleotides called:Introns –there are not involves in coding for

proteins.Exons – Sequence that codes the synthesis

of proteins.

Exon Intron Exon Intron Exon

RNA EditingWhen RNA molecules are formed, both introns

and exons are copied from DNA.

Introns are cut out of RNA molecules while in nucleus.

The remaining exons spliced back together.

Exon Intron Exon Intron Exon

ExonIntron

ExonIntron

Exon

Exon Exon Exon

Scientist don’t know yet why RNA molecules have to throw away information?Evolution???

The Genetic CodeProteins are made by joining amino acids into long chains called polypeptides

Polypeptides contain a combination of some or all 20 amino acids.

The properties of proteins are determine by the order in which amino acids are joined.

19 10 5 11 5 4 1612 5 14 17 7!!!!

7 22 25 18 16!!!

RNA contains 4 different bases:

The genetic code reads 3 letters at a time. So each 3 bases represents a “word”

A

U

G

C

CODONConsists of 3 consecutive nucleotides that specify a single amino acid that is added to the polypeptide.

RNA sequence:UCGCACGGU

Sequence in three basesUCG – CAC - GGU

Codon represents the different amino acids:

UCG – CAC - GGUSerine – Histidenie- Glycine

GAUACCCAG

UUACCUACU

There are 4 different bases, there are 64 possible three- base codons. (4 X 4 X 4 = 64)

- Some amino acids are specified by more than one codon.

Important AUG – Codon that specifies on Methionine

and serves as the initiation or “start” codon for protein synthesis.

There are also three stops:UAAUAGUGA

Promoters

A G C A G C A G C STOP

Methionine

AUG

UAAUAGUGA

TranslationThe sequence of nucleotides bases in an mRNA molecule serves as instructions for the order in which amino acids should be joined together to produce polypeptides.

TranslationThe cell uses information from messenger RNA to produce proteins.

mRNA is transcribed from DNA in the nucleus and then leaves.

Translation starts when an mRNA attaches to a ribosomal and then moves through it.

The amino acid is them brought into the ribosome by tRNA and then transfer it to the polypeptide.

tRNAEach tRNA carries only one kind of

amino acidMethionine, serine, etc

Each one has three unpaired bases called anticodon that are complementary to one mRNA codon.

Codons and Anticodons

A

A

U

U C

G

mRNA

tRNA

It assembles codon by codon.A peptide bond forms between the amino acids.

The ribosomes release the first tRNA and continue with the next.

The polypeptide continues to grow until the stop codon, on the mRNA. Then releases the polypeptide

The Roles of RNA and DNADNA – Master planRNA – Blue prints

Genes and ProteinsMost genes contains more than

instructions for assembling proteins.Proteins have to do with: color of a

flower, shape of a leaf, human blood type, or sex of a new born baby.

Proteins are enzymes that catalyze and regulates chemical reactions.

There are genes for every characteristic.