Ch 4 4.3 Flashcards
Stages of DNA replication
- Unwinding
- Unzipping
- Synthesis
What happens in the unwinding stage of DNA replication?
DNA unwinds from histones
What happens in the unzipping stage of DNA replication?
DNA helicase breaks hydrogen bonds and makes replication fork (each strand runs in a different direction because of phosphodiester backbone)
Five prime end of DNA strand is which group?
Phosphate
Three prime end of DNA strand is which group?
Sugar group
What happens during Synthesis stage of DNA replication?
DNA polymerase uses template strand to synthesize new strand via complementary base pairing.
In which direction does the DNA polymerase add bases on a new strand?
5’ to 3’
In which direction does DNA polymerase move down the old DNA strand (template)?
3’ to 5’
What is the continuous strand during DNA replication?
The strand on which DNA polymerase can continuously synthesize because it is in the correct orientation
What is the lagging strand in DNA replication?
The strand on which DNA polymerase Hass to keep jumping around because it is in the opposite direction; has gaps in the strand. Each fragment called Okazaki fragment
Okazaki fragments
The fragments which DNA polymerase synthesizes on the lagging strand
What does DNA ligase do in DNA replication?
Repairs and seals gaps between Okazaki fragments on lagging strand
DNA polymerase synthesizes the new strand by adding bases in which direction?
Five prime to three prime
What is a semi conservative method of DNA replication?
Breaking apart the parental strand using each individual strand as template and then copying it to make two new molecules
Mutations in DNA replication
DNA polymerase can make mistakes which can lead to mutations; can correct itself
Why are some mutations in DNA replication not bad?
Proteins Come from a three base pair sequence of amino acids; there are a variety of combos for each amino acid so sometimes it doesn’t change the sequence and don’t see the error but it’s still a mutation
When is a DNA replication Mutation a bad thing?
When a different amino acid is placed, it can change the protein in structure which changes its function and synthesis ex: cancer cells
Phases of the cell cycle
Interphase
G1
S
G2
Mitosis
Prophase
Metaphase
Anaphase
Telophase and Cytokinesis
What happens during interphase G1?
 normal growth and metabolism of cell; Checkpoint one: moves to S or goes to G0
What happens during synthesis?
DNA replication; divide or apoptosis
What happens during G2?
Prep for mitosis
Repair DNA mutations (or apoptosis)
Synthesize needed enzymes
How many DNA molecules are there in G1 phase? After S phase? How many chromosomes?
G1:46 DNA molecules, 23 different kinds, 46 chromosomes
S: 92 DNA molecules, 23 different kinds, 46 chromosomes (sister chromatids)
Three functions of mitosis:
- Growth of all tissues and organs after birth
- Replacement of cells that die
3. Repair damaged tissues
What happens during prophase?
-Densely coiled chromosomes (46 chromosomes, 92 DNA molecules)
– nuclear envelope disintegrates
– centrioles move to different poles
– development of spindle fibers
What happens during metaphase?
-Chromosomes align on metaphase plate
-Spindle fibers complete mitotic spindles, attach to kinetochores
Asters
Starlight projection made of centriole in spindle fibers extending
What happens during anaphase?
-Sister chromatids split
-Single stranded daughter chromosomes migrate to each pole from spindle fibers for track
What happens during telophase?
-Chromosomes cluster on opposite sides and uncoil into chromatin
-rough ER makes new nuclear envelope around Cummington
– mitotic spindles disintegrate
-Nucleus forms
When does cytokinesis happen? What happens during cytokinesis?
Telophase;
– division of cytoplasm
– cleavage furrow
When does cell division occur?
- Enough cytoplasm for two cells
2. DNA replicated - Adequate supply of nutrients
- Stimulated by growth factors
5. Neighboring cells die opening up space
When do cells stop dividing?
- Snuggly contact neighboring cells
- Nutrients or growth factors are withdrawn
3. Contact inhibition
What is contact inhibition?
When a cell contacts with neighboring cells and has a plethora of cells= stop dividing
What are cyclins and when do they form?
Regulatory proteins for cell division that form during interphase
Cyclin–dependent kinases (CDK’s)
Enzymes activated by cyclins that allow cell to move from one checkpoint to another
G1 checkpoint Kolin when and what?
Between G1 and S phases; commitment stage: G0 ( don’t divide) or Synthesis. Apoptosis can happen at this point
G2/M checkpoint
Mitosis or apoptosis
What is meiosis? How is it different from mitosis?
-Division of sex cells (sperm and egg).
-Mitosis: two genetically identical daughter cells
-Meiosis: four or two genetically DIFFERENT Daughter cells (Only have one of each chromosome instead of two like in mitosis)
