10.6-10.16 GENETIC

INFORMATION FROM DNA TO

RNA TO PROTEIN

1. DNA GENOTYPE =PROTEINS= PHENOTYPE=

The central concept in biology is:DNA determines what protein is made

RNA takes instructions from DNA

RNA programs the production of protein synthesis

Proteins determine the phenotype of the organism

Proteins are made into two main stagesTranscription-

the transfer on genetic info from DNA to RNA molecule

Translation- transfer of info in the RNA into a protein

DISCUSS W/ PARTNER: What is a protein? What protein have you eaten

today and/or yesterday? What role do proteins play in

your bodily functions?

2. GENETIC INFO

WRITTEN CODONS

mRNA Codon Chart

Genes are located on molecules of DNA

The language of DNA is the order (sequence) of nucleotides Ex: AAGCTT

The order of the nucleotides determine which genes are made

Transc

riptio

n & Tr

anslatio

n of c

odons

THE GENETIC CODE DNA’s instructions

are based on 3 nucleotides (triplet code)

The 3 nucleotide sequence (codon) are the genetic instructions from DNA to make amino acids; which together make polypeptide chains (proteins)

Each codon specifies for an amino acid

3. TRANSCRIPTION

A close-up view of transcription

During transcription:1. RNA polymerase (an enzyme)binds

to DNA on the promoter region & separates the DNA strands.

Promoter- Region of DNA (a codon) that allows transcription to begin

Terminator- Region of DNA that signals the end of a gene & transcription stops.

• There are 3 main types of RNA:• Messenger RNA (mRNA)– carry

copies instructions from genes for putting together amino acids into proteins. Carry “messages” from DNA to the rest of the cell.

• Ribosomal RNA (rRNA)- makes up a major part of the ribosome (proteins are put together here)

True shape of a functioning ribosome

• Transfer RNA (tRNA)- transfers each amino acid to the ribosome as it is specified by coded messages in mRNA.

4. RNA EDITING

• When RNA molecules are formed, introns and exons are copied from DNA.

• Introns- DNA sequences of nucleotides that do not code for a protein

• Exons- sequences that does code for a protein

• The introns are cut out of RNA molecules.

• The exons are then spliced together to form mRNA.

5. TRANSLATION

• Takes place on the ribosomes• Translation- the decoding of an mRNA

message into a polypeptide chain (protein)

1. Translation begins when an mRNA molecule attaches to a ribosome.

2. As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA.

3. In the ribosome, the amino acid is transferred to the growing polypeptide chain.

• In the process anticodons are formed• Anticodon- 3 unpaired bases of tRNA that are

complementary to mRNA•

RIBOSOMES Are made of rRNA Have a binding site for mRNA and three

binding sites for tRNA moleculesThe P site holds the tRNA carrying the growing

polypeptide chain

The A site carries the tRNA with the next amino acid

tRNAs leave the ribosome at the E site

STEPS OF TRANSLATION

1)Initiation brings together mRNA, with tRNA Special initiator tRNA carries and attaches to the

start codon

2)Elongation adds amino acids according to the mRNA codonsPeptide bond formation b/w a.a’s During translocation, the ribosome

moves the tRNA with the attached polypeptide from the A site to the P site

Elongation continues codon by codon to add amino acids until the polypeptide chain is completed

3)Termination occurs when one of the three stop codons reaches the A site

SUMMARY OF TRANSLATION

MUTATIONS Errors can occur during DNA

replication, DNA repair, or DNA recombination

These can lead to base-pair substitutions , insertions , or deletions

Can lead to frame shifts, which move the reading frame over slightly and change the primary structure of the polypeptide

MUTAGENS Are chemical or physical agents

that interact with DNA to cause mutations

Physical agents include high-energy radiation like X-rays and ultraviolet light

Chemical agents include carcinogens cause cancer