Exam 4 Definitions

Chromosome

Single, long piece of DNA that is associated with proteins in a condensed structure

Chromatin

DNA and protein complex

Histones

Any group of basic proteins found in chromatin

Nucleosome

First level of chromosomal organization

Euchromatin

Portions of chromosomes that exist in extended state

Heterochromatin

Highly condensed region of chromosome

Epigenetics

the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself

DNA Replication

Process of copying DNA during cell division

Replication Origins

Specific DNA sequence recognized by initiator proteins

Initiator Protein

Break hydrogen bonds between bases of two DNA strands

DNA Polymerase

Enzyme that catalyzes addition of new base pairs to template strand of DNA

RNA Primers

Short (10 nucleotides long) sequence of RNA added to DNA

Telomeres

Long, repetitive nucleotide sequences at the ends of chromosomes

Telomerase

Enzyme that contains RNA sequence to add repetitive DNA segments to lagging strand

Mutation

Alteration of DNA structure that influences protein expression

Depurination

Removal of a purine base from DNA

Deamination

Spontaneous loss of amino group from cytosine to create uracil

Thymine Dimers

UV radiation causes two thymine molecules in close proximity to bond together

Transcription

Conversion of DNA to RNA

Promoter

Specific sequence of DNA that lies immediately upstream of the starting point for RNA synthesis and requires activation to bind RNA polymerase

tRNA

Carries amino acids to ribosomes and recognizes codons of mRNA

Wobble

Flexible base pairing of anticodon on tRNA to mRNA codon

Initiator tRNA

Specialized tRNA that recognizes the AUG codon

Polyribosomes

Multiple ribosomes translate the same mRNA at one time

Genes

Segment of DNA that holds a nucleotide sequence that codes for a particular protein