Lesson 2: DNA and Chromatin Key Terms

gene

region of DNA that is transcribed as a single unit and carries information for a discrete hereditary characteristic

deoxyribonucleic acid

polynucleotide formed from covalently linked deoxyribonucleotide units. The store of hereditary information within a cell and the carrier of this information

double helix

the 3D structure of DNA, in which two antiparallel DNA chains, held together by hydrogen-bonding between the bases, are wound into a helix

base pairs

a pair of complementary bases in a double-stranded nucleic acid molecule, consisting of a purine in one strand linked by HYDROGEN bonds to a pyridine in another (AT has 2 bonds, CG has 3) think: T for two, C and G rhyme with 3

antiparallel

describes the relative orientation of the two strands in a DNA double helix or two paired regions of a polypeptide chain; the chemical polarity of one strand is opposite to that of the other (5’ to 3’ and 3’ to 5’)

template

single strand of DNA or RNA whose nucleotide sequence acts as a guide for the synthesis of a complementary strand

genome

the totality of genetic information belonging to a cell or an organism

chromosome

structure composed of a very long DNA molecule and associated proteins that carries part (or all) of the hereditary information of an organism

homologous chromosome

the maternal and paternal copies of a particular chromosome in a diploid cell

exon

segment of a eukaryotic gene that consists of a sequence of nucleotides that will be represented in mRNA or in a final transfer, ribosomal, or other mature RNA molecule

intron

noncoding region of a eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing

cell cycle

reproductive cycle of a cell

replication origin

a location on a DNA molecule at which duplication of the DNA begins by the formation of replication forks

centromere

constricted region of a mitotic chromosome that holds sister chromatids together. This is also the site on the DNA where the kinetochore forms so as to capture microtubules from the mitotic spindle.

telomere

end of a chromosome, associated with a characteristic DNA sequence that is replicated in a special way. Counteracts the tendency of the chromosome otherwise to shorten with each round of replication

histone

one of a group of small abundant proteins, rich in arginine and lysine, that combine to form the nucleosome cores around which DNA is wrapped in eukaryotic chromosomes

chromatin

complex of DNA, histones, and non-histone proteins found in the nucleus of a eukaryotic cell. The material of which chromosomes are made

nucleosome

beadlike structure in eukaryotic chromatin, composed of a short length of DNA wrapped around an octameric core of histone proteins. The fundamental structural unit of chromatin

epigenetic inheritance

inheritance of phenotypic changes in a cell or organism that do not result from changes in the nucleotide sequence of DNA

heterochromatin

chromatin that is highly condensed even in interphase; generally transcriptionally inactive

euchromatin

chromatin that isn’t super condensed, generally transcriptionally active