LEC 15 Flashcards
Mitosis & Meiosis
Parts of Mitotic Phase (2)
- “mitosis” (process of nuclear division)
- “cytokinesis” (cytoplasm division)
Mitotic Phase end result
2 new daughter cells
Mitosis Phases (4)
- Prophase
- Metaphase
- Anaphase
- Telophase
Mitosis time frame
60 min
Mitosis def
process by which a single parent cell divides to make two new daughter cells in 4 phases
What happens to centrioles during prophase?
centrioles move to opposite poles of cell
What happens to nuclear membrane during prophase?
disappears
What happens to centromeres during prophase?
Centromeres on the sister chromatids develop into two separate structures – one for each duplicated DNA molecule
What happens to the microtubule portion of cytoskeleton during prophase? (2)
comes apart and reforms a mitotic spindle which lengthens between centrioles
What happens to the mitotic spindle during prophase? (2)
reforms and lengthens between centrioles
crosses through the middle of the cell after nuclear membrane disappears
Prophase in order (5)
- Centrioles move to opposite poles of cell
- Microtubule portion of cytoskeleton comes apart
- Reforms a mitotic spindle which lengthens between centrioles
- The nuclear membrane disappears
- Mitotic spindle now crosses through the middle of the cell
- Centromeres on the sister chromatids develop into two separate structures – one for each duplicated DNA molecule
Metaphase is called the:
position-changing phase
Metaphase time frame (2)
20 minutes and cell appears to rest
Metaphase in order (2)
- Duplicated chromosomes align across the centre of the cell (“metaphasic plate”)
- Mitotic spindle attaches to the two portions of the centromeres
Anaphase is called the:
apart phase
metaphasic plate
Centre of the cell where the duplicated chromosomes align
Anaphase time frame
1 minute
Anaphase end result
two complete & separate sets of identical chromosomes at opposite sides of the cell
Anaphase in order (2)
- Centromeres split, detaching the sister chromatids from each other
- Sister chromatids (now called daughter chromosomes) move to opposite poles as the mitotic spindle contracts and pulls
Anaphase needs _____ in the form of _____ and contractile proteins that act as “_____”
- energy
- ATP
- motors
Telophase is called the:
end phase
Telophase begins when:
the two sets of chromosomes arrive at poles of cell
Telophase is the _______ of prophase.
reverse
Telophase in order (3)
- The mitotic spindle comes apart
- Nuclear membranes form around chromosomes
- Chromosomes uncoil and revert back to non-visible form (chromatin)
Cytokinesis steps (4)
- Cytoplasm divides
- Contractile ring of protein filaments (remainders of the cytoskeleton) forms just inside the plasma membrane
- The contractile ring tightens and forms a cleavage furrow
- Cell gets “pinched” into two
“daughter cells”
“daughter cells” def
Are identical to each other and their parent cell
Daughter cells produced through mitosis are ________
DIPLOID
46 chromosomes = ______ pairs of chromosomes
23
All human cells (except sperm and egg) have:
46 chromosomes
“diploid” literal meaning
“diploos” meaning “two fold”
23 chromosomes have: (2)
22 pairs of autosomes (chromosomes other than sex chromosomes)
1 pair of sex chromosomes (X & Y)
why does mitosis & cytokinesis happen? (2)
happens constantly in some areas of the body for growth and repair of tissues
where does mitosis & cytokinesis happen? (3)
- Epithelial cells
Dead cells constantly worn away, need to be replaced - Stomach lining
Gastric juices are harsh, constantly wear away the lining - Red bone marrow
RBC have lifespan of 120 days
Rate of 2 million new RBC are produced per second
Abnormal cell division def
Malignant cancer cells
- Uncontrolled cell division
- Keep dividing and tend to spread
Abnormal cell division causes
Mutations caused by carcinogens or viruses
What can mutations lead to?
change in cell function
Abnormal cell division treatment (2)
Removal of the malignant cells – radiation
Stop cell division - chemotherapy
Meiosis is aka
Reduction-Division
daughter cells of meiosis (2)
- gametes or mature sex cells
- haploid
Meiosis def (2)
- two successive nuclear & cell divisions
- reduces the number of chromosomes by half in each daughter cell)
What does meiosis create in males?
Sperm
Occurs in the testicles – men
Process of spermatogenesis
Where does meiosis happen in males?
testicles
What is the process of meiosis called in males?
spermatogenesis
What does meiosis create in females?
ova (egg)
Where does meiosis happen in females?
ovaries
What is the process of meiosis called in females?
oogenesis
Ova & sperm have a __________ number of chromosomes
haploid
After _______ (when the two gametes join), the new individual () will have the number of chromosomes
- fertilization
- zygote
- diploid
Prior to meiosis starting, cell goes through the ___________
normal S-phase
What happens in the S-phase? (2)
- DNA replicates
- Sister chromatids held together by centromere
Stages of Meiosis: (2)
- Meiosis I (Prophase I, Metaphase I, Anaphase I,
Telophase I) - Meiosis II (Prophase II, Metaphase II, Anaphase II,
Telophase II)
Meiosis I – Prophase I VS Mitosis Prophase
Same except crossing over occurs in meiosis
Meiosis I – Prophase I crossing over (3)
- Duplicated homologous chromosomes pair up and form a tetrad
- The duplicated homologous chromosomes of each tetrad then “swap” sections of DNA (this is the “crossing over”)
- The result is a “re-shuffled genes” to give the homologous chromosomes a “recombination” of the parental genes
Meiosis I – Metaphase I
Each tetrad (homologous pairs) line up along the equator of the cell, independent of the other tetrads
Meiosis I – Anaphase I
Homologous pairs separate and move to opposite poles as the spindle fibres contract
The result is a random combination of maternal and paternal chromosomes
Meiosis I – Telophase I
Cytokinesis occur
Cell cleaves and splits into two
Meiosis I – End Result
- Two NON - IDENTICAL daughter cells
- Cells IMMEDIATELY enter into Meiosis II (DNA is NOT replicated before starting Meiosis II)
Meiosis I – End Result Daughter cells
Each one has haploid number (23) of chromosomes, each consisting of two sister chromatids
Is DNA is replicated after Meiosis 1 and before starting Meiosis II?
No
Meiosis II
- Proceeds just like mitosis
- Sister chromatids separate
End of result of MEIOSIS II
4 non-identical daughter cells
Meiosis II – End Result Daughter cells (2)
- Each cell has haploid number (23 total) of chromosomes
- Daughter cells are NOT genetically identical to the original parent cells
Differentiation
Cell becomes different from its parent or sister cell
Differentiation why?
Due to certain genes being expressed
Differentiation where and when?
At any point during the lifespan of the cell/organism
Genes are __________ by ____________ factors around the cell
- influenced
- environmental
zygote
slide 34
compactation stage
slide 34
morula
slide 34
blastocyst
slide 34
Factors affecting fetal development
Embryo may not survive or may have abnormalities if affected at the right time in the right concentration by external sources
Factors affecting fetal development - External Sources: (7)
- Cigarettes – Increased cancer risk in offspring
- Alcohol – Fetal alcohol syndrome
- Legal Drugs – Thalidomide, marijuana etc.
- Illegal Drugs – Heroin, cocaine, etc.
- Chemical exposures – DDT, formaldehyde, PCB’s, lead, etc.
- Radiation – Ionizing and non-ionizing
- Intrauterine infections – HIV, syphilis, rubella (German measles)
