bio 4.2

Messenger RNA mRNA

long chain of nucleotides that carries genetic instruction for making proteins from the DNA in the nucleus to the ribosome out in the cytoplasm

Transfer RNA tRNA

chain of nucleotides folded into a hairpin structure with amino acid attachment site at top and 3-letter anticodon at bottom that transports and transfers amino acids to the ribosome.

Ribosomal RNA rRNA

chain of nucleotides that is folded into a globular shape, shorter small subunit and longer large subunit which has three sites, A, P, E which come together to form functional ribosome that is able to follow genetic instructions to make proteins.

transcription

1. The process of making a molecule of mRNA from a gene in DNA

gene

A sequence of DNA that codes for a particular protein

RNA polymerase

The major enzyme responsible involved in transcription

Nucleus

Location of the cell containing DNA that controls cell activities

Codon

Three-letter sequence of mRNA that specifies for a particular amino acid

Genetic code

The chart that correlates codons and amino acids

Translation

The process of making a protein from a sequence of mRNA

Ribosome

Organelle that builds proteins

Amino acid

The building blocks of proteins

Protein

Biological macromolecule made from amino acids, performs most cell functions

Mutation

a change in the sequence of DNA nucleotides.

how mutations could occur within cells

through errors made by DNA polymerase during DNA replication or can be caused by environmental factors, mutagens, such as UV radiation and carcinogens. 

Substitution mutation

a switch of a single nucleotide, and they affect just the one codon in which they appear.

Frameshift mutation

caused by the addition or deletion of a nucleotide which causes a shift or change in all of the codons “downstream” from that mutation causing a shift or change in the reading frame of triplets by the ribosome.

Missense substitution mutation

changes the codon to the codon of a different amino acid 

Nonsense subsistution mutation

changes the codon to a stop codon, prematurely ending the amino acid sequence.

Insertion

adds a nucleotide into the sequence.

Deletion

removes a nucleotide from the sequence.

initiation transcription

the enzyme RNA polymerase (RNA pol) finds the promoter region on the DNA and begins separating the DNA stands.

Elongation transcription

RNA pol follows the base-pair rules to match RNA nucleotides with the complementary DNA nucleotides to build the primary transcript.

Termination transcription

RNA pol finds the termination sequence releasing the primary mRNA transcript. 

Translation

occurs in the cytoplasm involving mRNA, tRNA, and the ribosome.

Transcription

occurs in the nucleus of eukaryotic cells occurring in three steps.

Initiation Translation

the small ribosomal subunit and the initiator tRNA (carrying MET) find the start (AUG) codon on the mRNA and then the large subunit binds with the tRNA carrying MET in the P-site.

Elongation translation

tRNA molecules enter into the A-site where the ribosome checks for proper tRNA anticodon and mRNA codon match (complementary base pairing), the ribosome shifts over one codon, moving the tRNA that was in the P-site into the E-site and the tRNA that was in the A-site into the P-site. In the P-site the tRNA molecule transfers its amino acid to the growing polypeptide (protein) chain and it is connected by forming a peptide bond.This cycle continues until the entire mRNA molecule has been “read” by the ribosome and the amino acid sequence is complete.

Termination translation

occurs when a stop codon (UGA, UAA, UAG) arrives in the A-site and a release factor binds causing the disassembly and release of the completed protein, small, and large subunits of the ribosome.