Cell Division Flashcards
What is cell division?
Process by which parent cell ÷ into 2/ more daughter cells
Why is cell division important?
- required to replace cell loss
- repair tissue damage
- reproduce the organism
What are the 2 types of cell division?
- Mitosis
- Meiosis
What are the 4 phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What is INTERPHASE?
- gap btwn. the 2 cell divisions
How does the cell prepare itself in interphase?
- Size growth
- obtaining nutrients
- duplicating cell organelles
- copying DNA
- duplicating centrioles
What occurs in prophase?
- chromosomes : coil … thick + short
- chromosomes contain 2 chromatids joined @ centromere
- centrioles separate; move to opposite poles in cell
- microtubules formed + extend btwn. 2 centrioles - spindle formation
- Nucleolus DISAPPEARS
- nuclear envelope disappears + chromosomes released to cytoplasm
What occurs in metaphase ?
- spindles occupy center of cell
- chromosomes move towards equator + arrange in a line
- microtubules attached to centromere of chromo
What occurs in anaphase ?
- centromeres divide + sister chromatids separate into individual chromosomes.
- spindle fibers contract ; chromosomes pulled to opposite poles of cell
- cleavage furrow forms @ equator
What occurs in telophase?
- chromosomes gather @ opposite ends + nuclear membrane reformed
- spindle disintegrates
- deep cleavage furrow + divides cell into 2
Where does meiosis occur?
- testes + ovary during production of sperm + ovum
What are the 2 steps in meiosis?
- meiosis 1 + meiosis 2
How many daughter cells are produced @ end of meiosis ?
4 daughter cells
In prophase 1pf meiosis, what are the 5 sub stages ?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
What occurs in LEPTOTENE?
- chromosomes = individual threads;
- attached @ 1 end to nuclear envelope;
- show bead through length
What occurs in ZYGOTENE?
- homologous chromosomes together
- pair point to point - BIVALENTS
- held together by FIBRILLAR BAND called SYNAPTONEMAL COMPLEX
What occurs in PACHYTENE?
- shortening + thinking of chromosomes
- two chromatids of chromosomes = visible
- 4 chromatids of 2 chromo = TETRAD
- exchange of DNA (breaking + rejoining) = CROSSING OVER
What occurs in DIPLOTENE?
- short & thick chromosomes
- separate except where crossing over occurred
- crossing points become visible
What occurs in DIAKINESIS?
- chromosomes = short , thick and separated but HC lie together
During meiosis 2 what does not occur?
DNA replication
What is Down syndrome?
Trigsonomy 21- extra chromosome on a person I.e. on chromosome 21
What syndrome results from being born with an extra copy of X chromo?
Klinefelter syndrome
What condition most affects females when one of X chromosome is missing?
Turner syndrome ( monosomy X)
