BIOL-Exam 3A, Mitosis + Meiosis

Mitosis and Meiosis, BIOL 1020, Djibo Zanzot, Exam 3

unicellular organisms

division of one cell reproduces this entire organism

multicellular eukaryotes

depend on cell division for development from a fertilized cell, growth, and repair

cell cycle

life of a cell from formation to its own division

• cell division is essential to this

genome

all DNA in a cell

• single DNA molecule in prokaryotes

• number of DNA molecules in eukaryotes

chromosomes

package DNA molecule in a cell

# of chromosomes and complexity of an organism

there is no correlation between…

somatic cells (2n)

• non-reproductive (body) cells

  • any cell NOT sperm/egg

• diploid

gametes (n)

• reproductive cells

  • sperm/egg

• haploid

sister chromatid (img)

• DNA in a chromosome is copied

  • results in 2 exact copies

centromere (img)

narrow center that separates sister chromatids

• later with anaphase and kinetechores

cohesins

proteins linking sister chromatids

mitosis

the division of the genetic material in the nucleus (in eukaryotes)

cytokinesis

the division of cytoplasm (in eukaryotes)

interphase: G1 phase → S phase → G2 phase →

M phase: mitosis → cytokinesis

cell cycle order

prophase → metaphase → anaphase→ telophase → cytokinesis

mitosis cycle

binary fission

• cell division in prokaryotes

• chromosome replicates at origin of replication

• 2 daughter chromosomes actively move apart

• plasma membrane pinches inward dividing the cell in 2

prokaryotic cells

do NOT undergo mitosis

endogenous controls

signals to divide the cell from within

exogenous controls

signals to divide by chemical factors outside of the cell

cyclin + cyclin-dependent kinase (CDK)

2 types of regulatory proteins involved in cell cycle control

• form MPF (maturation-promoting factor)

MPF (maturation-promoting factor)

a cyclin + CDK complex triggers a cell’s passage past G2 and into M phase

anchorage dependent growth

cells will only divide if they are attached to a substrate

density-dependent inhibition

crowded cells will stop dividing

growth factors

released by certain cells, stimulate other cells to divide

• ex. PDFG (platelet-derived growth factor)

  • made by platelets

metastasis

process where cancerous cells or growth factors spread throughout the body

benign

abnormal cells remain only at the origin site

malignant

abnormal cells invade surrounding tissues & metastasize

cancer

breast > lung > prostate > colorectal

unchecked cell division

CDK (cyclin-dependent kinase)

has a consistent concentration in the cytoplasm

interphase (img)

G1: 1 diploid set of chromosome

S: DNA synthesis

G2: 2 diploid sets of chromosomes

prophase (img)

• chromatin condenses to chromosome

• nuclear envelope fragments

• mitotic spindle takes shape

metaphase (img)

• pairs of sister chromatids align at metaphase plate

• kinetochore microtubules are attached to pairs of sister chromatids

anaphase (img)

• cohesins are cleaved (proteins holding sister chromatids togethers)

• kinetochore microtubules pull chromosomes apart

telophase (img)

• each daughter cell receives 2n chromosomes

• nuclear envelope reforms

• chromosomes decondense into chromatin

• cleavage furrow pinches the cell into 2 daughter cells

• cytokinesis

chromosomes are not cells

chromosomes are not cells

2ⁿ or 2^ⁿ

# of combinations possible when chromosomes assort independently into gametes

Prophase 1

where crossing over of genes occurs

genetics

scientific study of heredity and variation

heredity

transmission of traints from one generation to the next

variation

demonstrated by the differences in appearance that offspring show from parents & siblings

genes

• units of heredity

• made of segments of DNA

• passed to next gen via gametes

loci/locus

specific location of a gene on a chromosome

aexual reproduction

single individual passes genes to offspring w/o the fusion of gametes

clone

group of genetically identical individuals from the same parent

karyotype

an ordered display of the pairs of chromosomes from a cell

homologous chromosomes

• 2 chromosomes in each pair (homologs)

• have same length, shape, and carry genes controlling the same inherited characteristics

autosomes

non-sex chromosomes (22/23 pairs)

fertilization

union of gametes (sperm + egg)

zygote

fertilized egg, has one set of chromosomes from each parent

• first diploid cell

• produces somatic cells by mitosis & develops into an adult

• not in fungus

Meiosis 1+2

• results in 4 daughter cells

• each daughter cell has only half as many chromosomes as the parent cell

meiosis I

reductional division

• homologs pair up and separate

• results in 2 haploid daughter cells w/ replicated chromosomes

meiosis II

equational division

• sister chromatids separate

• results in 4 haploid daughter cells

anaphase I

in meiosis where cells go diploid → haploid

synapsis

pairing of homologs during P1

mutations

• changes in an organism’s DNA

  • make alleles (dif. version of genes)

  • shuffling of allels produces genetic diversity

crossing over

• produces recombinant chromosomes which combine DNA from each parent

• homologous portions trade places on sister chromatids

independent assortment

each pair of chromosomes sorts maternal/paternal homologs into daughter cells independently of other pairs

• i.e. non-homologous chromosomes do not all sort by parentage

random fertilization

any sperm can fuse w/ any ovum (adds to genetic variation)

prophase 1 (img)

• chromatin condenses

• sister chromatids align w/ homologs (form tetrads)

• crossing over occurs here

metaphase 1 (img)

n sets of tetrads align at the metaphase plate

anaphase 1 (img)

• homologs separate daughter cells

• diploids are now haploids

telophase 1 (img)

2 daughter cells with n pairs of sister chromatids are formed

leads into interkinesis + meiosis II

metaphase II (img)

n sets of sister chromatids align at metaphase plate

anaphase II (img)

separates n sets of sister chromatids

telophase II (img)

results in 4 haploid daughter cells

hallmarks of cancer

• self-sufficiency in growth signals

• insensitivity to antigrowth signals

• evading apoptosis

• sustained angiogenesis

• tissue invasion & metastasis

• limitless replicative potential

self-sufficiency in growth signals

• “grow without go”

• stuck gas pedal

• oncogenes

insensitivity to antigrowth signals

• “failure to stop”

• no brakes

• tumor suppressor genes (BRCA 1 & BRCA 2)

evading apoptosis

• broken self-destruct

• lacking programmed cell death

• failed cell suicide

sustained angiogenesis

• “need to feed”

• makes new blood vessels for energy

• VEGF: vascular endothelial growth factor

tissue invasion and metastasis

• spread, growing bigger or new tissue

• growth factors affect dif. tissues

limitless replicative potential

cancer cells can divide endlessly instead of stopping after a set # of divisions like normal cells