Cell Division (4) Flashcards
What process do prokaryotes such as bacteria and archaebacteria divide by?
Binary fussion
What are the basic genetic material of a bacterial cell?
- F-plasmid
- R-plasmids
- Chromosomal DNA
Plasmid DNA (def)
- extrachromosomal circular DNA molecules
- each contain an orgin or replication, and genes or enzymes
Orgin of replication in plasmids (def)
specific region recognized by DNA replication enzymes
R-plasmids (def)
contain antibotic resistance genes that allow some malicious bacteria to develop resistance to common antibiotics
F-plasmids (def)
fertility plasmids containing genes for making F-pili (reproductive part to transmit DNA during bacterial mating)
transmitted through sexual mating
replicate individually of the bacterial cell division
C-factors (def)
colicinogenic (can cause cancer) factors contain genes coding for toxins
important for the survival of the bacterial
Chromosomal DNA (3 facts)
circular chromosomal DNA, DNA is in the nucleoid region
each cell contains a single orgin of replication and is bound to plasma membrane
chromosomal DNA replicates once per cell division
Binary fission (def)
once a bacterium cell replicates its chromosomal DNA and sufficient number of plasmid DNA, the plasma membrane grows inwards to divide, and new cell wall is formed between
Mitosis
Process by which eukaryotic cells replicates their DNA into 2 identical copies and divided into two identical cells
- all somatic and vegetative cells (cells of multicellular organisms) divide by mitosis
Genetic elements of eukaryotic cells
- linear chromosomes organized into chromatin
Chromatin
DNA and protein loosely dispersed in the nucleus
Nucleosomes
small beads of DNA and histones
When and how are chromosomes formed in cell division?
During the metaphase stage
chromosomal dna -> nucleosomes -> chromatin -> chromosomes
- chromosomal DNA is bound to histone group of proteins (DNA bound around histones to form nucleosomes)
- comdensed nuclesomes form looped domains of chromatin
- looped domains condense to form chromosomes
Reproductive cells of eukaryotes’ name and number of chromosomes?
name: gametes
number: half the number of somatic cells
chloroplasts and mitochondria contain their own …
chromosomes similar to prokaryotic chromosomes (circular DNA)
chloroplasts and mitochondria replicate by …
their own binary fission
sister chromatids
a replicated chromosome that created two strands attached at the ceter
. not double stranded
centromere
central region of the attachment of sister chromatids
telomeres
ends of the chromosomes of sister chromatids
How many origins of replication do eukaryotic chromosomes have?
multiple origins of replication because the chromosomes are large
What are the two major phases of the cell cycle?
interphase, and mitotic (M) phase
What are the phases of the Interphase?
G1, S, G2,
What are the phases of the Mitotic (M) phase (mitosis + cytokinesis) ?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
- cytokinesis
G1 (gap 1) phase:
- rapid growth and metabolic activity
- centrioles repliate in the middle of the MTOC (in plants) or centrioles (in animals) with microtubules coming out from the center
S-phase (DNA Synthesis) phase:
chromosomes replicate along with their proteins, but still loosely disperesed as chromatic
replicated DNA is identical to parental chromosome
G2 (Gap 2) phase:
- growth and final preparation phase
- all organelles and membranes are duplicated
- chloroplasts and mitochondria have replicated by binary fission
Prophase:
- all the preparation for cell division occur
- nucleolus disappears
-chromatin forms chromatids - the 2 pairs of centrioles/asters move to opposite sides
- and mitotic spindle from from MTOC or centrioles
Prometaphase:
- nuclear envelope disappears
- microtubules of spindle fibers attached somewhere
Kinetochore:
microtubes of spindle fibers are connected to chromosomes at these places
I think it is the centromere of sister chromatids
Kinetochore fibers:
Fibers attached at the kinetochore
Non-kinetochore fibers:
Fibers not attached at the kinetochore
Metaphase:
- sister chromatids of replicated chromosomes are aligned in the middle of cell creating the metaphase plate
- final preparation before chromatids separate
Anaphase:
- centromere of each chromosome divides
- after separation each of the daughter chromatids are called a chromosome
- this creates 2 single stranded chromosomes
- chromosemes are able to move apart due to depolymeryzation of microtubules (NO ATP USED)
Telophase:
- polar fibers stretch more by polymerization using ATP to expand the cell more
- nuclei form and nucleoli reappear
- chromosomes loosen to chromatin again
Cytokinesis
Cytoplasm furrows inwards making a cleavage furrow or a cell plate (in plant cells) to divide the cells
- each new cell will have a nucleus, chromosomes, organelles, etc.
- cells will enter interphase again to grow and develop or divide again
- resulting cells are identical in DNA content and # of chromosomes
Proteins and the genes coding for such proteins control
…
- checkpoints
- rate
- sequence
What other things also influence the divisions of cell?
- nutritional status
- growth factors
- hormones
- cell density
- environmental
factors
What are animal cells grown on to conduct experiments?
On a monolayer or in suspensions
What is the critical stage/restriction point to control cell division?
- G1 phase from which cells go to G0 (no more division as in nerve cells or muscle cells)
or
- S-phase (synthetic),
- G2 phase
- M phase
Cells divide based on
cytoplasmic volume to DNA ration
What regulates the main process of cell division in eukaryotic cells?
Proteins
- Maturation-promoting factor (MPF)
Maturation-promoting factor (MPF)
Protein, combination of CDK (cyclin-dependent kinase) and cyclin to promote DNA synthesis and mitosis
Types of Cyclin:
S-cyclin: promotes S-phase
M-cyclin: promotes M-Phase
- Depending on the level of cyclin concentration, it binds to CDK
-
What can cyclin do?:
- Cyclin binding to CDC-2 stimulates autophosphorylation of CDK (kinase) and phosphorylation of other proteins involved in cell division
- Some of those proteins are proteases that can degrate cyclin to bring the levels down to regulate the cycle
DNA synthesis or mitosis occurs depending on the p…
phosphorylation status of S-MPF, M-MPF
Meiosis (where and why):
In sex cells to generate reproductive cells called gametes with 1/2 number of chromosomes that are different but from both parents
Sexual reproduction:
- meiosis known as reduction division needed for sexual reproduction
- individual gametes from two parents combine to form a new zygote cell to develop a new organism
Ploidy level:
indicates how many sets of chromosomes (N) are present in a cell
Haploid (1N)
single set of chromosomes
ex.) sperm cell, egg cell
Diploid (2N)
Two sets of chromosomes
ex.) body cells
Tetraploid (4N)
Four sets of chromosomes
ex.) plants, tobacco
Polyploid (many N)
several sets of chromosomes
ex.) sugarcane
How many chromosomes (individually and in pairs and in sets) do human cells have?
46 chromosomes
or
23 pairs
or
2 sets
Human cell chromosomes:
- 22 of the chromosomes are autosomes
-2 (X and Y) are sex chromosomes
- in each pair of chromosomes, one is paternal and one is maternal
Homologous chromosomes:
Pair of chromosomes where one is from the mother and one is from the father
they are similar but not identical
have equivalent copies of a gene
Alleles
the two forms of a gene from homologous chromosomes where each chromosome has equivalent copies of a gene
What happens to chromosome # ___ during meiosis?
Chromosome 46 in the diploid cell is halved into 23 chromosomes in the gametes
Meiosis 1 Overview:
Diploid cell (2N) -> Interphase 1 (DNA replication) -> Prophase 1 -> Metaphase 1 -> Anaphase 1 -> Telophase 1 -> Cytokinesis 1 -> 2 daughter cells (recomnined hologs separated but sister chromatids still attached)
Meiosis 2 Overview:
Interpase 2 (No DNA replication) -> Prophase 2 -> Metaphase 2 -> Anaphase 2 -> Telophase 2 -> Cytokinesis 2 -> 4 haploid (1N) daughter cells (sister chromatids separated)
Meiosis 1 what happens?
The chromosomes replicate and homologous chromosomes cross over to exchange genetic material, and the homologs separate
Meiosis Interphase 1:
Chromosomes replicate into two identical sister chromatids attached at the centromere.
Centrioles and other organelles also duplicate
Meiosis Prophase 1:
- Most important stage of meiosis
- Longest phase
- condensed chromosome is attached to the nuclear envelope
- the homologous chromosomes align themselves and come together to from bivalents or tetrads (four chromatids)
- synapsis happens
- sister chromatids are still attached
- later, the nuclear membrane disappears, centrioles move apart, and spindle fibers form
Synapsis (meiosis prophase 1)
the homologous chromosomes align themselvs and come togehter to form four chromatids
and each gene is brought closer to its counterpart (allele) in the other chromatids
sections of homologous chromosomes are exchanged (DNA from one homolog is cut and joined with another homolog after getting an equivalent portion)
What is “crossing over”? (meiosis prophase 1)
the overlapping of homologous chromosmes duing meiosis prophase 1
What is “recombination”? (meiosis prophase 1)
DNA exchange during meiosis prophase 1
The x-shaped regions of crossing over are called CHIASMATA
Chiasmata causes genetic exchange between the maternal and paternal chromosomes
Meiosis Metaphase 1:
Bivalent chromosomes (tetrads) align themselves along the middle of the cell along with the metaphase plate
During this alignment there is a random assortment of homologous chromosomes that contribute to gentic variation.
Meiosis Anaphase 1:
Individual pairs of sister chromatids separate from each other and go to opposite poles while the sister chromatids are still attached to each other.
Meiosis Telophase and Cytokinesis 1:
Chromatids move to opposite poles, nuclear envelope may form, and the cleavage furrow deepens or cell plate forms to divide the cells.
Meiosis Interphase 2:
Interphase or interkinesis can be seen, but no DNA is replicated
Meiosis 2:
Sister chromatids separate
Meiosis Prophase 2:
If ther is an nucleous or nucleolus present they disappear and spindle fibers appear
Meiosis Metaphase 2:
Sister chromatids align onthe metaphase plate, there are kinetochore fibers pointing to opposite poles attached at the centromere
Meiosis Anaphase 2:
Centromeres on sister chromatids separate and individual chromosomes (1N) move towards opposite ends.
Meiosis Telophase 2 and Cytokinesis 2:
Nuclei begin to form around chromosomes
Cleavage furrow or cell plate separates the new daughter cells.
Mitosis (7 facts)
- Chromosome # does not change
- Daughter cell is genetically identical
- No synapsis, tetrands or crossign over
- Sister chromatids and homologs separate during anaphase
- One major division
- DNA replicate before each division
- 2 Daughter cells
Meiosis (7 facts)
- Chromosome # is reduced to half
- Daughter cells are related but different (1N)
- Synapsis of tetrads leads to crossing over and recombination
- Homologs separate during anaphase 1 and sister chromatids separate in anaphase
two - Two major divisions
- DNA replicate before Meiosis 1, but not again before Meiosis 2
- Four daughter cells
What are the 3 major sources of variation in sexual reproduction?
- Crossing over during prophase 1
- Independent assortment of chromosomes in metaphase 1
- Random fertilization
