AP BIO Vocab. MODS:33-34

Translation

process by which a molecule of mRNA is used to guide the synthesis of a protein

Ribosomes

consist of a small subunit and a large subunit; the site of protein synthesis in cells

ribosomal RNA (rRNA)

Bind to and “read” the sequence of nucleotides in mRNA

Codons

nonoverlapping group of three nucleotides which code for a single amino acid in the polypeptide chain

Reading frames

the different ways of pairing the string of letters into three letter words

Transfer RNA (tRNA)

a small RNA molecule consisting of 70-90 nucleotides

Aminoacyl tRNA synthetases

The amino acids are attached to tRNA’s by enzymes

In prokaryotes

translation occurs as soon as the mRNA comes off the DNA template; smaller ribosomes.

Operons

a group of genes located in a row along the DNA and are transcribed as a single unit from one promoter

In Eukaryotes:

transcription occurs in the nucleus and translation occurs in the cytoplasm; larger ribosomes

Genetic code

The relationship between the three nucleotides in codon & the amino acid it specifies

Initiation Codon or Start Codon.

The codon at which translation begins;is coded as AUG, specifies the amino acid methionine (Met)

Stop Codons, Termination Codons or Nonsense Codons:

UAA, UAG, and UGA do  not code for any amino acids but rather signal where translation terminates and the protein is released from the ribosome

Translation initiation

the initiator AUG codon is recognized and Met is established as the first amino acid in the new polypeptide chain

Translation elongation:

successive amino acids are added one by one to the growing chain

Translation termination:

the addition of amino acids stops and the completed polypeptide chain is released from the ribosome

Anit Condon

A three-base sequence on tRNA

Template Strand

used as a model for the synthesis of an RNA transcript

RNA Polymerase

an enzyme that RNA molecule is synthesized by

Nontemplate Strand

The DNA strand that is not used as the templete for transcription

(1st stage of Transcription);Initiation

RNA polymerse and other protiens bind double-stranded DNA

2nd stage:Elogation

successivee nucleotides are added to the 3´ end of the growing RNA transcript as the RNA polymerse proceeds along the template strand

3rd Stage;Termination

in which RNA polymerse encounters a sequence in the template strand that causes trancription to stop and the RNA transcript to be released

Terminators

are sequence where transription terminates

Promoters

Regions of typically a few 100 base pairs where RNA polymerse and associated proteins bind to the DNA molecule to initiate transcription

TATA box

promoter includes the sequence 5´-TATAAA-3´ or something simular

Primary Transcript

contains the complement of every base that was transcribed from the DNA temple strand

Messenger RNA (mRNA)

carries the genetic ¨message¨from the DNA to the ribosome

RNA processing

a process in which the primary transcript undergos a series of chemical modifications that convert the primary transcript into mRNA

GTP cap

5´ cap consists of a modification nucleotide called 7-methylguanosine

Poly(A) trail

2nd modificationis the additon of a string of about 250 consecutive adenine nucleotides to the 3´ end

Exons

expressed protiens

introns

interspersed with exons and not as expressed protiens

RNA splicing

a prosses in which exons are stiched together and introns are remove

alternative splicing

the presence of multiple introns in most genes allows for this process, in which primary transcription from same gene can bespilced in different ways

Ribosomal RNA (rRNA)

makes up the bulk of ribosomes and is essential in translation

Transfer RNA(tRNA)

carries individual Amino acids for the use in translation