57 terms

The Cell Cycle

cell theory
cells arise from preexisting cells
cell cycle
repeating pattern of growth, division, and possible differentiation
specific location on chromosome
compacted chromatin-contain 1000 genes
complex of proteins and DNA
located at ends of chromosome-essential for chromosomes stability
located at center of chromosome-attatchment site for microtubules for chromosome movement -control activity of chromosomes
diploid cells
contain homologous chromosome pairs-majority of cells EXCEPT sex cells-complete set of chromosomes present-#2N-somatic (body) cells-cells with paired chromosomes-created by mitosis
haploid cells
contain 1 chromosome of each type-sex cells-1/2 set of chromosomes until fertilization occurs-#N-gamete (sex) cells-cells with single chromosome-created by meiosis
somatic cells
diploid # 46-22 pairs of homologous chromosomes(also called autosomes)-pairs similar in appearance and size-1 pair of sex chromosomes
sex cells-sperm and egg-haloid # 23---22 unpaired chromosomes + 1 sex chromosome-become diploid after fertilization
2 homologous chromosomes join-2 pairs of sister chromatid line up side by side and joined by proteins-
All the genetic information in an organism; all of an organism's chromosomes.
assemblies of proteins that function in attaching the chromosomes to mitotic spindle
a type of tubulin protein responsible for formation of the mitotic spindle-move towards poles of cell
protein complexes responsible for moving chromosome during cell division
visible linkage site between sister chromatids-2 or 3 may form between homologues
chromosomes in humans
individually you have 46 chromosomes-22 sets are homologous chromosomes(which means 2 XX make 1 set of homologous chromosomes)(diploid pairs)-1 set is your sex chromosome(23)--22+23=46
stem cells
capable of dividing and differentiating-self renewable(divide for entire life of organism)-generate cells and tissues for transplant--research-differentiate into variety of cell types (EX: embryonic stem cells, somatic stem cells, ____ cells in bone marrow--->blood cells)
differentiated cells capable of dividing
can only divide for specific part (EX: liver cells-divide to become more liver cells only)
permanently differentiated cells
incapable of dividing after differentiation (EX: brain and heart cells)
asexual reproduction
offspring arise from single parent-offspring are identical to parent-complete set of genetic info passed from parent to offspring (ex; bacteria)-simple but no variation -all prokaryotes and few eukaryotes(unicellular)-involve period of growth and DNA replication-divide in binary fission
sexual reproduction
offspring arise from 2 parents-fusion of gametes-each gamete contains half of the parents genetic info-fusion results in 1 complete set of genetic info-more complex but variation can occur
binary fission
cell division in bacteria-parent organism divides & makes 2 genetically identical daughter cells-occurs rapidly
1.)chromosomes replication
2.)membrane elongates until cell is twice its normal size
3.)plasma membrane pinches inward
4.)cell wall forms between two daughter cells
sister chromatids are identical to each other-homologous chromosomes are not identical
what are the differences between sister chromatids vs. homologous chromosomes?
important note
cell division is required for organism reproduction
2.)(M) Mitotic phase & 1.)Interphase
2 stages of cell cycle
cell growth and copying of chromosomes in preparation for cell division(before mitosis and meiosis)-about 90% of cell cycle-divided into sub phases G1, S phase, and G2
G1 phase
1st phase in interphase-period before DNA replication-cell grows in size and receives internal and external signals to decide if it should divide-if positive, cell enters S phase to continue cell division(no turning back after this!)-if negative, cell will not divide-prevents too much cell division from happening
S phase
2nd phase in interphase-replication of DNA-chromosomes duplicate themselves-sister chromatids produced
G2 phase
3rd phase in interphase-period after DNA replication-continued cell growth-cell division occurs after this phase(mitosis and meiosos)
Mitotic (M) Phase
produces 2 daughter cells genetically identical to each other and parent cell-each contains 1 copy of parent chromosomes-division of genetic information between 2 daughter cells-occurs after interphase-4 phases: Prophase, Metaphase, Anaphase, Telophase
MITOSIS-Early Prophase: chromosomes condense and become visible-spindle microtubules form between centrioles-centrioles move towards poles of cell-Late Prophase: nucleolus and nuclear envelope disappear-centrioles at opposites poles-spindle microtubules capture chromosomes at kinetochore of centromere-polar microtubules elongate the cell
MITOSIS-microtubules lengthen and shorten-chromosomes line up on equator of the cell(metaphase plate)-sister chromatids face toward opposite poles
MITOSIS-sister chromatids separate-individual chromosomes move toward poles-each pole gets 1 copy of each parental chromosomes-cell continues to elongate
MITOSIS-spindle microtubules breakdown-nuclear envelope forms around chromosomes at each pole-nucleoli appear-chromatins uncoil
MITOSIS-often occurs during telophase-division of cytoplasm between daughter cells-plasma membrane pinches cell into 2 daughter cells
plant cell wall is too stiff for normal cytokinesis-carbohydrate filled vesicles line along equator of cell and fuse to form cell plate-cell plate merges with plasma membrane and form cell wall between daughter cells
How does cytokinesis in animal cells differ from cytokinesis in plant cells?
G1 to S phase: determines if DNA is intact and suitable for replication-G2 to M phase: determines if DNA was accurately replicating-Metaphase to Anaphase: determines if chromosomes are attached to spindle microtubules, aligned properly along cell equator
3 checkpoints of cell cycle (mitosis stops if checkpoint determines problem)
prerequisite for sexual reproduction-occurs in sex cells that produce gametes ((testes(sperm)and ovaries(egg))-end with 4 haploid daughter cells-each contains 1/2 of parents genetic info-NOT genetically identical to each other or parent-consits of: interphase, meiosis (nuclear division), cytokinesis
MEIOSIS-same to interphase before-G1-->S phase-->G2-duplication of chromosomes-->sister chromatids-sister chromatids attached at centromere
prophase 1
MEIOSIS-post crossing over-tetrads detach from nuclear envelope-nucleoli and nuclear envelope disappear-centrioles move towards poles-spindle microtubules form and attach to chromatid pairs of tetrads at kinetochores
metaphase 1
MEIOSIS-tetrads line up along equator of cell-1 homologue per tetrad faces pole-random orientation--->genetic variation-spindle microtubules attach at kinetochore
anaphase 1
MEIOSIS-homologous chromosomes in a tetrad separate from each other and move toward opposite poles-1 chromosome of each homologous pair at each pole
telophase 1
MEIOSIS-chromosomes arrive at poles and spindle microtubules disappear-each pole has haploid set, but each chromosome has two chromatids-nuclear envelope may reform
cytokinesis 1
MEIOSIS-cell divides into 2 haploid cells-chromosomes are duplicated-1 duplicated chromosome(2 chromatids)
prophase 2
BEGINNING OF MEIOSIS 2-chromosomes recondense-spindle microtubules form-attach to kinetochore-
metaphase 2
MEIOSIS 2-chromosomes line up along equator-chromatids face opposite poles
anaphase 2
MEIOSIS 2-chromatids separate-independent chromatids(unduplicated chromosomes) move toward opposite poles-1 chromatid from each chromosome at each pole
telophase 2
MEIOSIS 2-spindle microtubules disintegrate-nuclear envelopes reform at poles-nucleoli reappear
cytokinesis 2
MEIOSIS 2-4 haploid daughter cells-each daughter cell genetically different-each daughter cell contains 1/2 of parent DNA-1/2 original # of chromosomes(unduplicated)
crossing over of DNA
mutual exchange of DNA segments-occurs between chromatids at chiasmata-result: genetic variation
46 chromosomes
how many chromosomes are found in a human somatic cell during G2?
22 homologous pairs of chromosomes
how many homologous pairs of chromosomes are found in a human somatic (body) cell during G2?
92 chromatid
how many sister chromatids are found in a human somatic cell nucleus during G2?
crossing over-random alignment of homologous chromosomes at metaphase plate during metaphase 1-sexual reproduction-mutation in genes
what are some events that can lead to genetic variation?