MITOSIS MEIOSIS Flashcards
Increase cell growth
Increase in number of cytoplasmic structure
Mitochondria number and cytoskeletal structure Doubling in number of centrosomes
Preparation for mitosis
Some cells carry the destined cell
G1
DNA synthesis in interphase
S phase
biochemical preparation of the onset of mitsosis
G2
normal stage, will not enter mitosis, nerve cells, muscle cells
G0
Structure made of microtubules that controls the chromosome movement during mitosis
Mitotic spindle
Radical array of short microtubules, Extend from each centrosome
Aster
centrosomes + spindle microtubules + asters = ?
Spindle
Protein complexes associated with centromeres
Kinetochores
Cell division of prokaryotes
Binary Fission
Transmission of traits from one generation to the next
Heredity
Exhibited by the differences in appearance that offspring show from parents and siblings
Variation
Single individual passes all of its genes to its offspring without fusion of gametes
Asexual reproduction
2 parents give rise to offspring that have unique combinations of genes inherited from the parents
Sexual reproduction
Human somatic cells have ___ pairs of chromosomes
23
An ordered display of the pairs of chromosomes from a cell
Karyotype
2 chromosomes in a pair. These chromosomes are of the same length and shape. Carry genes controlling the same inherited characters
homologous chromosomes
Determines the gender of the individual, X or Y
Sex chromosomes
XX
Human females Sex chromosomes
XY
Human males Sex chromosomes
The remaining 22 pairs of chromosomes
Autosomes
2 sets of chromosomes
2n
Humans: 2n=46
Diploid cell
Gametes contain single set of chromosomes
n
Humans: n=23
Haploid cell
Union of gametes
Fertilization
Fertilized egg
Produces somatic cells by mitosis
Develops into an adult
Zygote
when does the ovaries and testes produce haploid gametes
sexual maturity
Gametes are only
produced through
meiosis
results in one set of chromosomes in
each gametes
Reduces the number of chromosome set from diploid to haploid Preceded by the replication of chromosomes
Takes place in 2 consecutive cell divisions
Meiosis
Results in 4 daughter cells, instead of 2 daughter cells like in mitosis
Meiosis I
Meiosis II
Each daughter cell has only _____ as many chromosomes as the parent cell
half
Each chromosome pairs with its homolog and crossing over occurs
Prophase I
X-shaped regions
Site of crossover
in prophase I
Chiasmata
Pair of homologs line up at the metaphase plate and each chromosomes face opposite poles
Microtubules from 1 pole are attached to the kinetochore of 1 chromosomes of each tetrad
Metaphase I
Pair of homologous chromosomes separate
One chromosome of each pair moves towards the opposite poles,
guided by the spindle apparatus Sister chromatids remain attached at the centromere and move as one unit toward the pole
Anaphase I
Each half of the cell has a haploid set of chromosomes
Each chromosomes still made up of two sister chromatids
_____ occurs simultaneously
Forms 2 haploid daughter cells
Telophase I and cytokinesis
Formation of spindle apparatus, chromosomes move toward the metaphase plate. no crossover, no pairing
Prophase II
Sister chromatids are arranged in the metaphase plate
Due to the crossing over in meiosis I, the sister chromatids are no longer genetically identical
Kinetochores of the sister chromatids attach to microtubules extending from opposite poles
Metaphase II
Sister chromatids separate
Move toward the opposite poles as 2 newly individual chromosomes
Anaphase II
Chromosomes arrive at the opposite poles
Formation of nuclei
Chromosomes begin decondensing
Telophase II
Each homologous pair undergoes synapsis and crossing over between nonsister chromatids with the subsequent appearance of chiasmata.
Prophase I
Chromosomes line up as homologous pairs on the metaphase plate.
Metaphase I
Homologs separate from each other; sister chromatids remain joined at the centromere
Anaphase I
Behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation
Genetic Variation
3 mechanisms contribute to genetic variation
Independent assortment of chromosome Crossing over
Random fertilization
Homologous chromosomes orient randomly at Metaphase I
each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs
Independent Assortment of Chromosome
produces recombinant chromosomes, which combine DNA inherited from each parent
contributes to genetic variation by combining DNA from two parents into a single chromosome
In humans, it occurs an average of one to three per chromosome
Crossing over
adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg)
The fusion of two gametes produces a zygote with any of about 70 trillion diploid combinations
Random Fertilization
Directs the sequential events of the cell cycle Regulated both by internal and external controls
Has specific checkpoints
Cycle stops until a go-ahead signal is received
Cell Cycle Control System
2 regulatory proteins
Cyclin
Cyclin-dependent kinase
Activity of Cdk rises and falls with changes in concentration of its cyclin partner
Cyclin-dependent kinase
Cyclin-Cdk complex that triggers a cell’s passage past the G2
checkpoint into the M phase
Maturation-promoting factor
most important checkpoint
G1 checkpoint
Released by certain cells
Stimulate other cells to divide
Growth factors
Crowded cells will stop dividing
Density-dependent inhibition
Do not respond to body’s control mechanisms Do not need growth factors to grow and divide
They make their own growth factor
They may convey a growth factor’s signal without the presence of the growth factor
They may have an abnormal cell cycle control system
Cancer Cells
Process where normal cell is converted into cancerous cell
Transformation
Cancer cells that are not eliminated by the immune system
Masses of abnormal cells within normal tissue
Tumors
Abnormal cells remain only at the original site
Benign tumor
Invade surrounding tissues and can metastasize
Export cancer cells to other parts of the body
Malignant tumor
