RNA-UNIT 6 CONT.

StructureTypes of RNATranscription

RNA =RiboNucleic Acid

STRUCTURE Polymer

Single stranded Monomers

Nucleotides

RNA NUCLEOTIDES Monomers made of 3 parts each:

Phosphate Group Ribose Sugar 1 of 4 nitrogen bases

C, A, G, and U! U = Uracil No Thymine!

URACIL Pyrimidine-why? Pairs with adenine

COMPARE RNA TO DNA

3 TYPES OF RNA1. Messenger RNA (mRNA)

“Records” information from the DNA in the nucleus and transports it out of the nucleus to the ribosomes

3 TYPES OF RNA2. Transfer RNA (tRNA)

Delivers amino acids to site of protein synthesis (ribosomes)

3. Ribosomal RNA (rRNA) Helps with ribosome structure; function not

entirely understood

We will not go into detail on these second 2 until next week!

WHY IS MRNA IMPORTANT? DNA is at risk of being damaged if it leaves the nucleus The info in DNA is copied into mRNA mRNA is able to leave nucleus and travel to ribosomes (site of protein synthesis)

WHY IS TRNA IMPORTANT? It brings amino acids to ribosomes to

form protein strand.

HOW DO WE GET MRNA FROM DNA? Transcription

4 Steps (similar to replication)

What is different between transcription and DNA replication?

STEPS OF TRANSCRIPTION1. DNA is “unzipped” (HELICASE)2. Match correct nucleotides according to base pair rules

*On only one side of the DNA (RNA POLYMERASE)*U’s not T’s!

STEPS OF TRANSCRIPTION3. Bonding-covalent bonds form between sugar and phosphates

*Why don’t the hydrogen bonds remain?

4. Transcription occurs until a “stop sign” is reached and the mRNA strand is complete

Transcription Animation

GENETIC CODE - TRANSLATION 3 Nitrogen bases represents 1 CODON = 1

AMINO ACID 64 possible codons

3 “stop” codons 61 code for amino acids (20 possibilities) 1 codes to start = AUG = methionine

Code is universal – codons represent the same amino acid in all organisms

CODON DECODER

CODON CHART Use your codon chart to answer the

following: 1. How many different codons code for valine?

2. The codon CGU is for which amino acid?

3. What are the codons for the three “stops”?

4. What are the first 3 amino acids for this strand of mRNA?