Nucleic Acids

RNA

What are RNA?

• Nucleic acid polymer of nucleotide monomers

• Plays role in translation of genetic information from DNA to protein products

• Acts as messenger between DNA and Protein synthesis complexes (ribosomes)

• Forms vital portions of ribosomes• Carrier molecule for amino acids to be

used in protein synthesis

What does she look like?

• Ribose and phosphate backbone bonded by phosphodiesters

• 4 different bases-A, G, C and U

• Uracil replaces Thymine

• usually a single strand, not a helix

• 5 carbon sugar-ribose

**hydroxyl groups make the RNA less stable than DNA

..hot

characteristic DNA RNA

length DNA is longer than RNA, because it stores all the genetic information.

RNA is short because it carries one gene at a time.

Number of strands

two one

location in cell Nucleus - it is too big to go through the nuclear membrane.

Nucleus and cytoplasm; can travel any where

Characteristic DNA RNA

Nitrogenous bases

A, T, C, G A, U, C, G

Sugars Deoxyribose Ribose

How is it made DNA replication Transcription

Mirror mirror on the wall……..

Protein synthesis

Process Site Major Components

Notes

Transcription Nucleus DNA geneRNA polymerase

Gene is activated.A copy of the code is made from RNA (m-RNA)m-RNA leaves the nucleus, goes to cytoplasm.

Protein synthesis

Process Site Major components

Notes

Translation In the cytoplasm, on the ribosomes

m-RNARibosomesPeptidyl transferase enzyme Transfer RNAs

Ribosome decodes the m-RNA and makes the correct protein

What’s cooking?

• The main copy of the genes is in the nucleus to protects it from damage.

• During protein synthesis, the DNA code is transferred into a working copy made of messenger RNA (transcription)

-DNA double helix is unwound• Genes are transcribed one at a time • The m-RNA leaves the nucleus and translation

takes place in the cytoplasm, on the ribosome

• The enzymes progress along the template strand in the 3’-5’ direction synthesizing a complementary RNA molecule with elongation in the 5’-3’ direction

• Some RNA-dependent RNA polymerases use RNA as their template for synthesis of the new RNA strand e.g. poliovirus (RNA virus)

….still cooking RNA

3 Types of RNA are Involved in Protein Synthesis

Messenger RNA m-RNA •An RNA copy of a gene •Carries information from the DNA to the ribosomes.

Ribosomal RNA r-RNA  catalytic components of the ribosomes; also includes the enzyme peptidyl transferase (makes peptide bonds)

4 diff RNA-18S, 5.8S,28S,5S

rRNA

• Make up 80% of the RNA molecules• In the cytoplasm, rRNA and Protein

combine to form a nucleoprotein-Ribosome• Ribosome binds mRNA and carries out

protein synthesis.• Non-coding RNA are RNA genes that

encode RNA not translated to proteins e.g. tRNA and rRNA both involved in translation

Transfer RNA

About 74-95 nucleotides

t-RNA •Transfer amino acids to ribosome to form a polypeptide chain

•have anticodons which match the m-RNA codons.

• The transcribed code is carried from the nucleus to the ribosomes by messenger RNA (m-RNA)

• The ribosomes contain ribosomal RNA (r-RNA). This type is structural and also acts as an enzyme when the protein is lengthened

• Transfer RNA (t-RNA) carries amino acids to the ribosomes: there must be at least 20 types of t-RNA

• Decoding (translation) occurs on the ribosome

• Ribosomes are constructed of a special RNA (r-RNA) and protein

• They have 2 sub-units which come together to form a decoding machine

• Some ribosomes attached to membranes (rough endoplasmic reticulum), others not attached (free ribosomes)

Teach teacher…. Um no! TRANSLATE to amino acids

• m-RNA leaves the nucleus and looks for a Ribosome

• RNA leaves the nucleus and carries the code into the cytoplasm, then attaches to a ribosome

De-coding

• The RNA Code is Translated into Protein

• Ribosome finds start codon (AUG), then decodes the message, 3 bases at a time

• When the ribosome reaches the stop codon the protein is released and the decoding can start over to make another protein

• In Translation Amino Acids are Carried to the Ribosomes by Transfer RNA

• There are at least 20 kinds of t-RNA because there are 20 different amino acids

• Each transfer RNA has a site that attaches to a specific amino acid, and a site with 3 nucleotide bases (anticodon) that must match up with the RNA code letter for that amino acid

• Amino acids attach to the new protein only if the t-RNA anticodon matches (is complementary to) the m-RNA codon

• Proteins are Finished Off in the Endoplasmic Reticulum & Golgi Apparatus

• Most new proteins are not immediately functional- they must be finished off

• In the endoplasmic reticulum and Golgi apparatus they are folded into the proper shape and sometimes chemical groups are added or clipped off

• Some are routed to the cytoplasm, others to the mitochondria, etc.

…………..recap

start 1st codon 2nd codon

3rd codon

DNA code

TAC AGT CGG GCT

m-RNA AUG GCC CGA

t-RNA anticodon

UAC AGU CGG

Amino acid

Methionine

Serine Alanine Arginine

• DNA synthesizes RNA which in turn makes Protein

Many Hormones Act by Turning on Genes• certain hormones e.g. sex hormones, cortisone,

aldosterone, thyroxine) pass through the cell membrane and enter the nucleus

• In the nucleus they bind to receptors which turn on genes

Reverse TranscriptionReverse Transcription

• RNA viruses– Some viruses use RNA instead of DNA as

genetic material – One group of RNA viruses, termed

retroviruses, convert RNA back to DNA. – RNA viruses make numerous mistakes in

replicating genetic information. This means that some viruses like HIV (causes AIDS) changes very rapidly making it difficult to make a vaccine.