24 terms

AP Biooo ch 12 (pt 2)

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RNA polymerase

enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription

Promotor

is a DNA segment that recognizes the enzyme RNA polymearse and thus promotes transcription

Terminator

A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

INtrons

a non-coding, intervening sequence within a eukaryotic gene

Exons

expressed sequence of DNA; codes for a protein

RNA Splicing

process by which the introns are removed from RNA transcripts and the remaining exons are joined together

tRNA

short-chain RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according

Anticodon

A sequence of three bases of a tRNA molecule that pairs with the complementary three-nucleotide codon of an mRNA molecule during protein synthesis.

Codon

a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

Ribosomes

small round structures that make proteins

rRNA

The most abundant type of RNA, which together with proteins froms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons; also called ribosomal RNA.

P Site

(peptide) site in the ribosome where peptide bonds are formed between adjoining amino acids on a growing polypeptide chain

Codon Recognition

first stage of elongation; tRNAs recognize through their anticodon and bring appropriate amino acid to the A site

Peptide Bond Formation

the polypeptide separates from the tRNA to which it was bound (the one in the P site) and attaches by a peptide bond to the amino acids carried by the tRNA in the A site. the ribosome catalyzes formation of the bond. thus, one more amino acid is added to the chain

Translocation

change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome

Stop Codon

UAG, UAA, or UGA; the codon that ends all RNA., A group of nucleotides that does not specify a particular amino acid, but instead serves to notify the ribosome that the protein being translated is complete. The stop codons are UAA, UGA, and UAG. They are also known as nonsense codons.

Mutation

(genetics) any event that changes genetic structure

Silent Mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

Missense Mutation

The most common type of mutation, a base-pair substitution in which the new codon makes sense in that it still codes for an amino acid.

Nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

Reading frame

the way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons

Mutagenesis

an event capable of causing a mutation