Flashcards in Exam 2 Deck (44):
M phase consists of what two distinct events?
1. Mitosis-the division of the replicated chromosomes
2. Cytokinesis- the division of the cytoplasm
What happens during M phase?
What happens during Prophase?
1. Chromosomes condense
2. Breakdown of micotubles which are replaced by mitotic asters
- The mitotic asters pull them apart in late mitosis
What happens in Prometaphase?
1. Nuclear envelope breaks down
2. Microtubles attach to chromosomes at the kinetochore
3.Chromosomes captures and brought to the spindle equator
What happens in Metaphase ?
1. chromsomes align at the metaphase plate
2. Sister chromatid are attached by opposite poles by microtubles attached to kinetchore.
What happens during anaphase A?
-Chromosomes move to poles
-Creats 2 sets of chromosomes
What happends during Anaphase B?
-Spindle pole separation
What happens during Telophase and Cytokinesis?
-Contracting ring forms(animals)
-the cytoplasm divides to form two daughter cells
What are Sister Chromatids?
-Chromatids attached at the centromere
-They are still considered a single chromosome
What are microtubules?
Long, hollow cylinders mad up of the protein tubulin
What is the miotic spindle?
Macromolecular machine that separates sister chromatids
What is a Chromsome?
What are 4 key elements ?
-DNA is compounded into chromosomes
What is a centromere?
the region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division
What is the spindle aparatus?
The spindle aparatus is made of microtubules
What is the Kinetocore?
Where the microtubules of the spindle attach
Identical copies of a chromsome
How many chromosomes do you have?
46 separate chromosomes
How many pairs of chromosomes do you have
What is MTOC?
-Microtuble Organizing Center
What does it mean when DNA is antiparallel?
One strands runs 3'-5' and the other runs 5'-3'
What is semiconservative replication?
Parental strands seperate, each is a template for a new strand.
What is conservative replicaiton?
-The parental molecule serves as a template for an entirely new molecule
-One daughter has both old strands; the other has both new strands
What is dispersive replication?
-Parent molecules is cut into sections.
-each daughter has old & new DNA intersperesed
What is DNA polymerase?
An enzyme that catalyzes DNA synthesis
What direction can DNA polymerase only go?
It can only add D-nucleotides to the 3' end
-The 3' OH of the previous nucleotide
Which direction does DNA synthesis go in?
From 5' to 3'
What enzyme catalyzes the replication fork?
What is a replication fork?
-There is a leading strand and a lagging strand
-Where the DNA starts to seperate
-DNA double helix must unwine and seperate so that DNA polymerase can use each strand as a template.
What do dNTP's do?
-They are monomers
-They have energy because of closely packed phosphate groups
-They have enough P. Energy to make formation of phosphodiester bonds which are exergonic
Where does DNA replication start?
The replication origin
What does DNA helicase do?
What does it look like?
-Catalyzes by breaking down hydrogen bonds between 2 DNA strands
-It looks like a ring
What do Single-strand DNA binding proteins do? (SSBPs)
-Attach to the separated strands to prevent them from closing
What are the 3 stages of DNA Replication?
How does DNA polymerase Proofread?
-Mismatched bases have a distinct shape
-Will only add nucleotide if previous pair is correct
-It removed mismatched base
What does RNA Primase do/
What does Repair polymerase do?
What does ligase do?
Enzyme that seals remaining nicks
What is the problem at the end of replication?
-Single strand DNA is left at the end of the lagging strand
-single strand DNA is degraded by shortening the chromosome over time and linear chromosomes would vanish
-The problem is the degredation
How does Telomerase solve the end replication problem
1.The 3' end of the lagging strand forms a single-stranded "overhang"
2. Telomerase binds to the overhang uses the RNA that it carries as a template for DNA synthesis
3.Telomerase continues to move down the new strand, adding more short DNA seuqences to the end
4. Once the overhang is long enough, normal DNA synthesis can occur.
What does telomerase do?
It's an enzyme that replicationes telomers, using an RNA template.
WHEN does DNA replicate?
Name the steps of DNA replication?
1. Helicase from repliation origin unzips DNA making 2 seperate strandds
2. SSBP's bind to the seperate strands to keep them apart
3. Primase creates RNA primers on both strands
4.DNA polymerase is behind the primers and adds bases and creates new DNA
How does the leading strand replicate?
DNA Polymerase just adds nucleotides down the molecule