Chapter 11 Flashcards
what is cell division?
The process by which cells make more
cells
why does cell division occur?
- Growth
- Cell replacement
- Healing
- Reproduction
what are the important requirements that must be satisfied by cell division?
- Each daughter cells receives full genetic
complement parent cell - Parent cell large enough to divide in two (enough cytoplasmic components)
What are the 4 main events that must occur for cell division?
- Reproductive signal to initiate cell division
- Replication of DNA
- Segregation distribution of the DNA into the two new cells
- Cytokinesis separation of the two new cells
how does prokaryotic cell division occur?
Through binary fission
How many cells are produced through binary fission?
2 cells
What are the external factors that initiate prokaryotic cell division?
- nutrient concentration
- environmental conditions
What can accelerate the division cycle in Prokaryotic cell division?
Abundance of food
Explain binary fission. Diagram
the difference in mitotic cell division between eukaryotes and prokaryotes
what are the 2 main phases in the eukaryotic cell cycle?
M phase (mitosis & cytokinesis) Interphase (everything else)
what happens in interphase?
- lasts about 10−14 hours
- Cell makes many preparations for division
o Replication of the DNA in the nucleus
o Increase in the cell size (daughter cells require enough cytoplasm and membrane)
name the stages of interphase
- G1 phase
- S phase
- G2 phase
- G0 phase
what happens in G1 phase?
size and protein content of the cell increase (prepping for S phase)
what happens in S phase?
all DNA in nucleus is replicated
what happens in G2 phase?
cell prepares for mitosis and
cytokinesis
what happens in G0 phase?
cell types that are not actively dividing
(e.g - liver, nerve)
During mitosis and meiosis what happens to chromatin?
coiled and condensed ever more tightly
until the chromatids move apart
how many pair of chromosomes are in eukaryotes?
23, 22+ 1 sex chromosome
name of the process that segregates the chromosome
mitosis
disadvantages of interphase
specific chromosomes cannot be
distinguished
•DNA is loose, uncoiled
•gene expression
What are the 5 stages of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
what happens as cells move from G2 to start of mitosis?
- chromosomes condense
- visible
What happens in prophase?
•Chromatids visible
•Kinetochores develop (centromeres)
•Centrosomes = mitotic centers or poles; microtubules form between poles
to make spindle
what happens in prometaphase?
- Nuclear envelope and nucleoli disappear
- Chromosomes gradually pushed to equatorial plate
what is Kinetochore?
complex of proteins associated with centromere
what are the two types of microtubules?
- Polar microtubules — form spindle; overlap in center
- Kinetochore microtubules — attach to kinetochores on chromatids
what happens during metaphase?
•all centromeres have arrived at the equatorial plate.
what happens during anaphase?
- sister chromatids separate
- move to opposite ends of the spindle (now daughter chromosomes)
how does sister chromatids seperate?
- Cohesin is hydrolyzed by separase
- Separase inactive before this point (bound to securing, an inhibitory subunit)
- When all chromatids connected to spindle
- securin is hydrolyzed
- separase breaks down the cohesion
- spindle checkpoint
what happens during telophase?
Telophase:
•Spindle breaks down
•Chromosomes uncoil
•Nuclear envelope and nucleoli are reformed
•Two daughter nuclei are formed with identical genetic information
how are daughter cells formed?
Daughter cells are formed via cleavage of the cytoplasm following nuclear division.
cytokinesis in animal vs plant
what is the function of Phragmoplast?
cell plate partition , partition the cytoplasm and separate the two daughter nuclei of the dividing cell.
what are the overall functions of meiosis?
- Reduce chromosome number from diploid to haploid.
- Ensure that each product has a full set of chromosomes.
- Promote genetic diversity among the products.
how is meisois different from mitosis?
In meiosis I
- homologous chromosome pairs come together
- pair along their entire lengths
After metaphase I
- homologous pairs segregate
- sister chromatids remain together (after Metaphase II)
what are the stages of meiosis?
- Meiosis I preceded by an S phase (DNA is replicated)
- Each chromosome consists of two sister chromatids (cohesion)
- During Prophase I, the homologous chromosomes pair (synapsis)
- Joining at telomeres
- mediated by recognition of homologous DNA sequences
- Synaptonemal complex
- protein scaffold
- joins the homologous chromosomes.
what is crossing over? Also known as chiasmata
what meisois phase takes long time?
Prophase 1
time duration for human males for prophase 1 and meiotic cycle
1 week for prophase I and 1 month for entire meiotic cycle
time duration for human female for prophase 1 and meiotic cycle
prophase I begins before birth and completes up to decades later during the monthly ovarian cycle
what happens in prometaphase I ?
•nuclear envelope and nucleoli disappear.
•Spindle forms
•kinetochores of both chromatids of a
chromosome attach to the same half-spindle
what happens during metaphase I?
•chromosomes are at the equatorial plate; homologous pairs held together by chiasmata.
what happens during anaphase I?
•homologous chromosomes separate
•daughter nuclei contain only one set of
chromosomes
•each chromosome consists of two chromatids.
what happens during telophase I?
- Some organisms:
- nuclear envelope reaggregates
- followed by an interphase called interkinesis
- Other organisms:
- Meiosis II begins immediately
Differences between meiosis II and mitosis
- DNA does not replicate before meiosis II
- Meiosis II, the sister chromatids may not be identical (crossing over)
- Number of chromosomes at equatorial plate in meiosis II is half number as in mitosis
Overview of meiosis II
compare mitosis and meiosis diagram
Explain cytoplasmic division in females
- Unequal cytoplasmic division in females
- Leads to polar bodies (nonfunctional)
- 4 products of meiosis
- Only one becomes functional gamete (oocyte)
Explain cytoplasmic division in males
- Cytoplasmic division is rather equal
- All 4 become functional gametes (sperm)
summary of cell division
