transcription and translation

DNA characterisitics

sugar: deoxyribose

double stranded

base: thymine

main single form

RNA characterisitics

sugar: ribose

single stranded

base: uracil

3 main forms: mRNA, rRNA, tRNA

What types of RNA do not encode proteins?

rRNA and tRNA

rRNA

Ribosomal RNA

Makes up ribosome – joins amino acids together by peptide bonds to make proteins

tRNA

Transfer RNA

tRNA molecules carrie amino acids to ribosomes during protein synthesis

One tRNA for every amino acid

mRNA

Messenger RNA

mRNAs are translated by ribosomes to make proteins

encodes proteins

transcription

when DNA unwinds and RNA polymerase binds to a promoter near the start of a gene

• mRNA is synthesized in the 5’ > 3’ direction using DNA as a template

what is an antibiotic that targets transcription

rifamycin

what does rifamycin do

Inhibit synthesis of mRNA by targeting RNA polymerase

penetrates tissues

what are side effects of rifamycin

Red urine, saliva, sweat, or tears

codons

group of three nucleotides on mRNA

• Start codon--AUG→formylmethionine

anticodons

• Complementary sequence on the tRNA (to codon on mRNA)

for anticodons, the codon sequence determines what

which amino acid is brought to the ribosome

what “machine” carries out translation

ribosomes

translation order

• Ribosome binds mRNA

• mRNA codons determine which tRNA (each carry a different amino acid) “docks” in the ribosome

• tRNA leaves amino acid for the forming polypeptide

process of translation step 1

components needed to begin translation come together

process of translation step 2

on the assembled ribosome a tRNA carrying the forst amino acid is paired with the start codon on the mRNA. the place where this first tRNA sits is called the P site. a tRNA carrying the second amino acid approaches

process of translation step 3

the second codon of the mRNA pairs with a tRNA carrying the second amino acid at the A site. The first amino acid joins to the second by a peptide bond. this attaches the polypeptide to the tRNA in the P site

process of translation step 4

the ribosome moves along the mRNA until the second tRNA is in the P site . the next codon to be translated is brought into the A site. The first tRNA now occupies the E site

process of translation step 5

the second amino acid joins to the third by another peptide bond, and the first tRNA is released from the E site

process of translation step 6

The ribosome continues to move along the mRNA and the new amino acids are added to the polypeptide

process of translation step 7

when the ribosomes reaches a stop codon, the polypeptide is released

process of translation step 8

the last tRNA is released and the ribosome comes apart. the released polypeptide forms a new protein

A site

attachment site for a tRNA

P site

polymerization site where peptide bonds are formed between amino acids

E site

exit site for tRNA molecules

what are Aminoglycosides effective against

gram - bacteria

what can Aminoglycosides cause damage to

auditory nerve and kidney function

examples of Aminoglycosides

streptomycin and gentamicin

what are Tetracylines used for

Broad-spectrum (gram positive and gram negative)

what is a characterisitc of Tetracylines

long retention in body and penetration

what is Tetracylines used in

animal feed – becoming more of a concern

side effects of tetracylines

Discolor teeth in children and not given to pregnant women (liver damage)

Chloramphenicol – simple structure used for

Broad–spectrum but toxicity problems

Chloramphenicol characterisitcs

Inexpensive – used in low cost situations

Ready diffusion

what can chloramphenicol cause

aplastic anemia

what is macrolides effective agaisnt

gram positive bacteria (not very effective against gram negative bacteria)

how is macrolides taken

Oral antibiotic for children

example of macrolides

erythromycin

how does the coupling of transcription and translation help prokaryotes grow quickly

Ribosomes can immediately begin the process of protein translation as mRNA molecules are by transcribed by RNA polymerase.

polyribosomes

multiple ribosomes can bind mRNAs and translate proteins simultaneously

polysomes

complex of multiple ribosomes simultaneously translating a single messenger RNA (mRNA) molecule into proteins