EXAM 3 - DNA organization and replication

chromatin

DNA and its associated proteins

histones

proteins that DNA wraps around

nucleosome

a section of DNA wrapped around histone proteins. looks like a bead on a string

scaffold proteins

proteins that help organize and support DNA’s structure

chromatid

one of the condensed structures that makes up a replicated chromosome

CTCF

an anchor protein that brings different parts of the same DNA molecule together to form loops

DNA replication

process of copying DNA before a cell divides

semiconservative means each new DNA molecule contains

• one original (parental) strand

• one newly made strand

step 1 of DNA replication

two parental DNA strands separate

step 2 of DNA replication

each original strand acts as a template, or guide, for building a new strand

step 3 of DNA replication

new bases pair with the template: A with T, and G with C

step 4 of DNA replication

new strands form complete sugar-phosphate backbonesh

helicase

unzips DNA by separating the two trands

binding proteins

keep the separated strand apart

primase

makes a short RNA primer to start DNA synthesis

DNA polymerase

adds DNA nucleotides to build a new strand and checks for mistakes

ligase

joins DNA fragments and seals gaps in the backbone

RNA primer

short piece of RNA that gives DNA polymerase a starting point

replication fork

y-shaped area where DNA strands separate and are copied

leading strand

built continuously in the 5’ to 3’ direction

lagging strand

built in short pieces called okazaki fragments

proofreading

DNA polymerase checks for incorrect bases and replaces them

primer removal

enzymes remove the RNA primers, and the gaps are filled with DNA. ligase joins the pieces together

replication bubble

an area where DNA has opened and is being copied

telomeres

repeated DNA sequences at the ends of linear eukaryotic chromosomes, help protect chromosome ends

senescence

when a cell stops dividing

telomerase

an enzyme that extends telomeres by adding repeated DNA sequences. it uses an RNA template and repeats a binding extension, and movement cycle

PCR

lab technique used to make millions or billions of copies of a specific DNA sequence

target DNa

the DNA section being copied

primers

short sequences that bind to opposite ends of the target

free nucleotides

building blocks for new DNA

taq polymerase

heat-resistant DNA polymerase that works during repeated heating and cooling

denaturation - heat

DNA strands separate

annealing/ hybridization - cool

primers bind to complementary sequences on the DNA

extension - DNA is built

taq polymerase adds nucleotides to make new DNA strands

RT-PCR (reverse transcription PCR)

used when starting material is RNA

DNA sequencing

dtermining the order of bases in a DNA molecule

sanger sequencing

used to sequence individual genes or check a selected DNA region

next-generation sequencing (NGS)

reads millions of DNA fragments in parallel