Chapter 5- Genes and Proteins

Gene

A segment of DNA on a chromosome that codes for a specific trait

Transcription bubble

the region of locally unwound DNA that allows for transcription of mRNA

Template strand

The DNA strand that provides the pattern, or template, for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript.

Transcription

the organic process whereby the DNA sequence in a gene is copied into mRNA

Spliceosome

complex of enzymes that serves to splice out the introns of a pre-mRNA transcript

Coding strand

the strand of DNA that is not used for transcription

Promoter

region of DNA that indicates to an enzyme where to bind to make RNA

mRNA

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

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

rRNA

ribosomal RNA; type of RNA that makes up part of the ribosome

RNA polymerase

enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template

The Three steps of Transcription

initiation, elongation, termination

Initiation

RNA polymerase binds to promoter

Elongation

addition of amino acids to the polypeptide chain; continues until it reaches a stop codon

Termination

RNA polymerase reaches a terminator sequence (Stop codon) and detaches from the template

Introns

sequence of DNA that is not involved in coding for a protein

Exons

Coding segments of eukaryotic DNA.

aminoacyl-tRNA synthetase

An enzyme that joins each amino acid to the appropriate tRNA.

Translocation

The process in which a segment of a chromosome breaks off and attaches to another chromosome.

point mutation

gene mutation in which a single base pair in DNA has been changed

Chromosomal mutation

A change in the chromosome structure, resulting in new gene combinations.

Codon

a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

nonsense mutation

changes a normal codon into a stop codon

silent mutation

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

frameshift mutation

mutation that involves the insertion or deletion of a nucleotide in the DNA sequence