Ap Biology Unit 6 topics 3 & 4

the process by which DNA directs the synethsis of proteins

the synthesis of RNA using info from DNA; DNA →RNA

the message of the DNA to be transcribed; occurs in the nucleus

synethesis of a polypeptide using info from RNA; RNA → polypeptide

ribosome; a nucleotide sequence becomes an amino acid sequence

mRNA is synthesized during transcription using a DNA template. mRNA carries info from the DNA ( in the nucleus) to the ribosomes in the cytoplasm

important for translation; each tRNA can carry a specific amino acid

an anticodon

tRNA; attachment of a complementary codon to mRNA

helps form ribosomes and links amino acids together

sequence of nucleotides: proteins

sequence that is read in groups of three

the template strand or non coding strand or minus strand or anti sense strand

anti parallel and complementary to the DNA nucleotides

codons

amino acids

64

61

more than one codon code for each amino acid

the codons on the mRNA must be read in the correct groupings during translation to synthesize the correct proteins

initiation: RNA polymerase molecules attaches to the promoter region of DNA; DO NOT NEED PRIMER

PROMOTER REGION; TATA BOX

and transcription factors help RNA polymerase bind

upstream of the desired gene to transcribe

rna polymerase can bind directly to promoter

rna polymerase; triplet code; template

moves in 3-5 direction and the mRNA transcript ELONGATES 5-3

rna polymerase moves downstream and only opens small sections of DNA at a time

then pairs complementary RNA nucleotides

the growing mRNA strand peels away from the DNA template strand

DNA DOUBLE HELIX THEN REFORMS

helps increase the amount of mRNA synethesis which increases protein production

rna polymerase transcribes a sequence of DNA called polyadenylation signal sequence

this codes of the polyadenylation signal and releases the pre mRNA from the DNA

MUST UNDERGO MODIFICATIONS BEFORE TRANSLATION

proceeds through termination sequence and causes a termination signal

RNA polymerase detatches and mRNA transcript is released and proceeds to translation

mRNA DOES NOT NEED modifications

5’ cap

poly a tail

RNA splicing

the 5’ end of the pre mRNA receives a modified GUANINE nucleotide cap

the 3’ end of the pre mRNA receives 50-250 adenine nucleotides

help the mature mRNA leave the nucleus

help protect the mRNA from degradation

help ribosomes attach to the 5’ end of the mRNA when it reaches the cytoplasm

sections of the pre-mrna, called INTRONS, are removed and then exons are joined together

DOES NOT code for amino acids, intervening sequence

expressed sections CODES FOR AMINO ACIDS

a single gene can code for more than one of polypeptide (alt splicing)

mature mRNA

all life comes from the same genetic code so there is a common ancestor. this shows how genes are passed on from generation to generation

- redundancy: more than one codon code for each amino acid
- it shows that codons are universal to all life
- it helps minimize mutations that could occur

the synethsis of a polypeptide using info from the mRNA (happens in ribosomes)

…amino acid sequence

tRNA translates mRNA to an amino acid sequence

complemntary and antiparallel to mRNA

tRNA carries the amino acid that the mRNA codon codes for

attaches amino acids to tRNA

charged

eu; small - 40s, large - 60s

pro; small - 30s, large - 40s

a site, p site, e site

holds the next tRNA carrying an amino acid

holds the tRNA carrying the growing polypeptide chain

exit site

initiation: begins when small ribosome subunits bind to mRNA and charged amino acids combine to the start codon

the first tRNA carrying met → to p site'

other tRNA → a site

elongation: mRNA moves through ribosomes, the ribosome reads mRNA transcript and tRNA bind via their anticodon, they carry amino acid which are linked together by peptide bonds

codon recognition: the appropriate anticodon of the next tRNA goes to the a site

peptide bond formation: peptide bonds are formed that transfer the polypeptide to the a site tRNA

translocation: the tRNA in the a site moves to the p site, the tRNA in the p site goes to the e site.

termination: stop codon reaches A site of ribosomes, polypeptides release and transitional units are dissasembled

linear chain of amino acids

coils and folds due to hydrogen bonds forming

side chain interactions

2+ polypeptide chains interacting

component of ribosome that functions to link acids together into larger protein chain

Part of ribosome that recognizes mRNA transcripts and initiates translation

the growing polypeptide chain begins to coil and fold

the final shape

chaperone proteins

RNA → DNA

uses enzyme reverse transcriptase

couples viral RNA to DNA and then the DNA becomes part of the RNA