Zoology Module Five

DNA

genetic material withing chromosomes, two long chains in double helix form, polymer of nucleotides consisting of a nitrogenous base, a sugar, and a phosphate group

Nucleotides

four kinds of chemical building blocks for DNA, adenine, thymine, guanine, cytosine

Meiosis

accurate replication of DNA prior to cell division

Semiconservative model of replication

after replication each daughter molecule will have one old strand and one new strand

Origins of replication

where two DNA strands are seperated, opens up replication bubble

Replication fork

at each end of replication bubble, Y-shaped region where parental DNA strands are being unwound

Topoisomerase

relieves strand of twisting of double helix by breaking, swiveling, and rejoining DNA strands

Primer

DNA polymeres need a primer that they can add nucleotides to, five to ten nucleotides long

Primase

enzyme that makes RNA primer

DNA polymerases

catalyze synthesis of new DNA at replication fork, need primer and DNA template strand

Okazaki fragments

lagging strand synthesized by these that are joined together by DNA ligase

Helicase

unwinds parental double helix at replication fork

Single-strand binding protein

binds to and stabalizes single-stranded DNA until it’s used as a template

DNA pol III

using parental DNA as template synthesises new DNA strand by adding nucleotides to RNA primer or pre-existing DNA strand

DNA pol I

removes RNA nucleotides of primer from five prime end and replaces them with DNA nucleotides added to three prime end of adjacent fragment

DNA ligase

joins Okazaki fragments of lagging strand, on the leading strand joins three prime end of DNA that replaces primer to rest of leading strand DNA

Mismatch repair

repair enzymes replace incorrectly paired nucleotides that have evaded proofreading

Telomeres

nucleotides sequences at the end of eukaryotic DNA molecules, postpones erosion of ends of DNA molecules

Chromosome

DNA molecule packed together with proteins

Chromatin

in eukaryotic cell this is the protein that combines with DNA

Histones

proteins responsible for main level of DNA packing in interphase chromatin

Nucleosome

the beads on a string in an unfolded chromatin fiber

Euchromatin

loosely packed chromatin

Heterochromatin

during interphase centromeres and telomeres of chromatin are highly condensed