Ch.16 (DNA Replication) Flashcards
To be a molecule considered as genetic material, it must have: (4)
- must contain info necessary to construct ENTIRE organism
- must be passed unaltered from parent to offspring
- must be copied since parents can produce more than 1 offspring
- significant phenotypic variability - genes must vary
DNA replication (traits of the reaction) (3)
synthesis
anabolic
requires energy
Where does DNA replication happen?
In multiple replication bubbles
DNA replication [traits] (4)
bidirectional
opposite replication
endergonic process (require energy)
requires numerous enzymes
What sort of bonds form in DNA replication?
Phosphodiester: between nucleotides of a daughter strand
What is a daughter strand complementary and antiparallel to?
Template strand
What is required for the newly synthesized daughter strand?
a free 3’ OH (otherwise a primer is needed)
In what direction is the daughter strand?
5’ to 3’
What direction is synthesis for DNA and RNA?
5’ to 3’
Replication fork [definition] (2)
Y shaped structure where synthesis of 2 daughter strands occurs almost simultaneously
primer needed
primer (RNA)
provides initial 3’ OH
Replication towards the fork
continuous leading strand
Replication away from fork
discontinuous lagging strand
lagging strand, or DNA segments are called?
Okasaki or Okazaki
Events of DNA replication (6) in order
- Unzipping parental strands : DNA helicase (also DNA topoisomerase reduces strain)
- SS DNA binding proteins prevent parental strands from re-zipping
- RNA primer: primase
- DNA synthesis: DNA polymerase III in 5’ to 3’
- RNA primers degrade, replaced by DNA: DNA polymerase I
- Okazaki fragments of lagging strands join: DNA ligase
What enzyme is involved in unzipping parental strands?
DNA helicase
What enzyme is involved in preventing supercoiling?
DNA topoisomerase
What protein is involved in keeping parental strands apart?
SS DNA binding proteins
What enzyme is involved in producing RNA primers?
Primase
What enzyme is involved in DNA synthesis?
DNA polymerase III
What enzyme is involved in catalyzing the degradation of RNA primers and its replacement by DNA?
DNA polymerase I
What enzyme is involved in sealing/joining Okazaki fragments?
DNA ligase
Difference for DNA replication in eukaryote and prokaryotes.
1)
- eukaryotes: occurs in S phase
- prokaryotes: ongoing and uncoupled from cytoplasmic division
2)
- eukaryotes: replication bubbles , multiple per chromo.
- prokaryotes: single
3)
- eukaryote - problems: linear chromo ends
- prokaryote - problems: improper segregation of chromo
Telomere
sequences at both ends of linear chromosomes that consist of hexanucleotide repeats
What is the telomere pattern?
AGGGTT
What enzyme adds telomere?
Telomerase
Do mammalian cells lose ability of maintaining telomere length?
Yes, at an early stage.
Telomere role
protect coding region of chromosomes from being lost
Hayflick limit
Cells stop diving if chromosomes reach a critical short length
Where is telomerase present? (4)
Germ cells, precursor cells, called stem cells and embryonic cells.
Which cells have high levels of telomerase activity?
Cancer cells
How many telomeres in one metaphase chromosome?
4
One linear chromosome =?
1 DNA molecule
How many strands in one DNA molecule?
2
How many telomeres in 1 DNA molecule?
2
