bio 7.1.2 Protein Synthesis

Whole presentation done

Central dogma of biology

DNA gets transcribed into RNA which is translated into proteins

What direction is the DNA template strand?

3’ to 5’

DNA template strand definition

The strand that RNA will be complementary to

mRNA direction if DNA is 3’ to 5’?

5’ to 3’

codons definition

mRNA base triplets

What is RNA synthesis catalyzed by?

RNA polymerase

what does RNA polymerase do?

It seperates DNA strands and hooks together RNA nucleotides

DNA sequence where RNA polymerase attaches

promoter

sequence signaling the end of RNA transcription

terminator

stretch of DNA that is transcribed

transcription unit

3 steps of transcription (and translation)

initiation, elongation, termination

Initiation (transcription)

After RNA polymerase binds to the promoter, the DNA strands unwind, the polymerase initates RNA synthesis at the start point on the template strand

Elongation (transcription)

The polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5´ to 3´. After, DNA strands re-form a double helix

Termination (transcription)

the RNA transcript is released and the polymerase detaches from the DNA

noncoding regions

introns

Intron long form

intervening sequences

Expressed regions short

exons

what does RNA splicing do

removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

What is RNA splicing carried out by sometimes?

spliceosomes

What do spliceosomes consist of?

a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites

Ribozymes definition

catalytic RNA molecules that function as enzymes and can splice RNA

Alternative RNA splicing definition

process that allows a single gene to code for multiple proteins

what does tRNA do?

it transfers amino acids to the growing polypeptide in a ribosome

What do ribosomes facilitate?

specific coupling of tRNA anticodons with mRNA codons in protein synthesis

What are the two ribosomal units made out of?

proteins and ribosomal RNA

Are bacterial and eukaryotic ribosomes the same?

no

3 binding sites of a ribosomes

E, P, A

A-site description/function

binding site, holds the tRNA that carries the next amino acid to be added to the chain

P-site description/function

holds the tRNA that carres the growing polypeptide chain

E-site description/function

exit site, where discharged tRNAs leave the ribosome

Initiation (translation) (what does it bring together?)

a mRNA, a tRNA with the first amino acid, and two ribosomal subunits

Initiation (translation) steps

A small ribosomal subunit binds with mRNA and a special initiator tRNA, then the small subunit moves along the mRNA until it reaches the start codon, then initiation factors bring in the large subunit that completes the translation initiation complex

Elongation (translation)

amino acids are added one by one at the C-terminus of the growing chain, involves elongation factors

elongation (translation) steps of each addition

codon recognition, peptide bond formation, and translocation

termination (translation)

when a stop codon in mRNA reaches the A site of the ribosome

termination (translation) steps

A site accepts a release factor, it causes the addition of a water molecule instead of an amino acid, this reaction releases the polypeptide, the translation assembly comes apart

polyribosome

when multiple ribosomes translate a single mRNA simultaneuosly

types of point mutations

substitution, addition, deletion

silent mutation

change in mRNA codon but amino acid coded is the same

missense mutation

codes for a different amino acid

non sense mutation

codes for a stop codon

frame-shift mutation

creates change in number of nucleotides and amino acids produced

how many codons are there?

64

of the 64 triplets how many code for different things?

61 code for amino acids, 3 are stop codons

Genetic code properties (3) + brief description

universality (same for all living organisms), redundancy (more than one codon may specify a particular amino acid), unambiguousness (no codon may specify more than one amino acid)

redundancy genetic code explanation

more than one codon may specify a particular amino acid