Chapter 13 Flashcards
Chargaffs rules
How many hydrogen bonds form between base pairs
- DNA base composition varies between species
- Percentage of A=T and C=G
2 bonds with AT
3 bonds with CG
Origin of replication
Site of start of replication; short stretches of DNA that have specific sequence of nucleotides. PROTEINS RECOGNIZE THE SEQUENCE AND ATTACH AND START
Helicase
Enzyme that untwist the double helix at replication fork, separating the two strands
SSBP
Bind to unpaired DNA strands, keeping them from re-pairing
Topoisomerase
A protein that breaks, swivels and rejoins DNA strands to relive stress.
Primase
An enzyme that joins RNA nucleotides to make a primer during DNA replication using the parental DNA strands as a template.
DNA polymerase
Catalyze the synthesis of new DNA by adding nucleotides at the 3’ end of a pre existing strand
Leading strand
Lagging strand
The new complementary strand synthesized continuously towards replication fork in 5’-3’ direction.
A disdcontinually synthesized DNA strand the elongates by means of Okazaki fragments in 5’-3’ away from replication fork.
Okazaki fragments
Segments of 100-200 nucleotides long on lagging strand
DNA ligase
A linking enzyme essential for DNA replication; catalyze the covalent bonding of the 3’ end of one DNA fragment to the 5’ end of another.
Besides building what else does polymerase do?
Proof reads each nucleotide, if it’s wrong polymerase adds the correct one.
Mismatch repair
Enzymes that remove and replace
Nuclease
Enzyme that cuts DNA or RNA, either remaining one or a few bases or hydrolyzing DNA or RNA completely into its component nucleotides.
Nucleotide excision repair
A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.
Telomeres
Repetitive DNA at the end of a euk. Chromosome. These protect the genes from being eroded during successive rounds of replication.
Nucleoid
A non-membrane- enclosed region Im a prok. Cell where its chromosomes are located.
Heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
Euchromatin
Less condensed form of Euk. Chromatin that is available for transcription.
Histones
Small protein with a high proportion of positively charges amino acids that binds to the negatively charged DNA.
Nucleosome
Basic unit of DNA packing
Plasmids
Small circular DNA molecules that are replicated separately.
Gene cloning
Production of multiple copies of a gene
Polymerase chain reaction
Technique used for amplifying DNA in Vito by incubating it with specific primers, a heat resistant DNA polymerase and nucleotides.
DNA sequencing
Determining the order of nucleotide bases in a gene or fragment.
In bacteria where does the replication fork go
From both directions until it meets
How many origins of replication do eukaryotic chromosomes have?
Hundreds
Telomerase
Enzyme responsible for maintain of the length of telomeres by addition of guanine repetitive sequences
