Bio exam 4 vocab

RNA polymerase

An enzyme that catalyzes the formation of phosophodiester linkages between ribonucleotides, forming an RNA product that is complementary to the sequences of bases in a DNA template.

Template strand

The strand in a DNA double helix that is “read” by RNA polymerase during transcription.

Non-template strand (coding strand)

The strand in a DNA double helix that matches the sequence of bases in the RNA product of transcription, except that the DNA contains thymine (T) and the RNA contains uracil (U).

Anticodon

A sequence of three bases found at one end of a tRNA that binds to a codon in mRNA during translation via complementary base pairing.

Release factor

A protein that fits into the A site of a ribosome, binds to a stop codon, and interacts with the ribosome to terminate translation.

Reading frame

The sets of three-base codons in RNA or DNA that specify the primary sequence of amino acids in a protein; is set by the start codon, and identifies the subsequent sequence of codons.

Ribozyme

An RNA molecule that catalyzes a chemical reaction, analogous to enzymes, which are protein catalysts.

Promotor

The regulatory sequence in a gene or operon where RNA polymerase initiates transcription

Genetic code

The set of relationships between the 64 possible codons in mRNA and the amino acids that are added to a newly synthesized protein.

Codon

A group of three bases in an mRNA that codes for an amino acid

Start codon

The codon that signals where translation and thus protein synthesis begins. Usually AUG and also codes for the amino acid methionine (Met).

Stop codon

A codon that signals where translation and thus protein synthesis ends. Usually UAA, UAG, and UGA.

Gene expression

The entire set of processes that results in using the information stored in a gene.

Positive control (over gene expression)

Mechanisms that increase the amount of active gene product available.

Negative control (over gene expression)

Mechanisms that decrease the amount of active gene product available.

Operon

A sequence of structural gene sequences whose products have related functions and that are under the control of the same promoter and other regulatory sequences, meaning that they are transcribed as a unit.

Transcription factors

Proteins that regulate transcription, often by binding to regulatory sequences in DNA.

Exons

In eukaryotic genes, sections of the coding sequence code for amino acids found in a protein product.

Introns

In eukaryotic genes, sections of the coding sequence that are transcribed but later removed before an mRNA is translated into a protein product.

Chromatin

The complex of DNA and histones that makes up a chromosome.

Nucleosome

A group of four histone proteins that has DNA wrapped around it.

Histone proteins

Proteins that have an abundance of positively charged lysines and arginines in their primary structure, which interact with negative charges on the sugar-phosphate backbone of DNA to form nucleosomes. 

5′ cap

A modified form of the nucleotide guanine (G) that is added to the 5′ end of a pre-mRNA in eukaryotes, during RNA processing that occurs prior to export from the nucleus.

Intron splicing

Removing introns from pre-mRNAs and rejoining exons into a continuous strand, during RNA processing that occurs prior to export from the nucleus.

Poly-A tail

A long series of adenine (A) nucleotides that is added to the 3′ end of a pre-mRNA in eukaryotes, during RNA processing that occurs prior to export from the nucleus.

Protein phosphorylation

The addition of a phosphate group or ATP to a protein.

Kinase

An enzyme that adds a phosphate group to other proteins.