lec 4 cell division Flashcards
Why is cell divison nessecary?
-growth+development
-maintain+replace tissue
-pass genetic info
What are 2 broad stages of cell division? What happens?
Interphase: prepares cell for division
Mitosis OR miosis: cell divides
Where does mitosis occur?
cells that make up body but not involved in sexual reproduction
(ex skin cells)
Where does miosis occur?
cells that sexually reproduce
What is mitosis? What must be replicated and passed onto the divided cells?
2 things
parent cell divides into 2 identical daughter cell
FIRST it replicates DNA+organelles, then divides
each daughter cell must have;
-full compliment of DNA from parent
-same organelles as parent
What are the 3 major stages of interphase?
G1, S and G2
What does each stage of interphase do? In order
G1: particular proteins made+activated for S phase
S (synthesis): DNA replicated
G2: makes proteins to prepare cell for mitosis
Which of our cells are actively dividing?
Skin and intestinal
What phase do liver cells remain in?
G0 or resting phase for up to a year before undergoing division
What is a chromosome?
single strand of DNA
How does DNA fit in the nucleus? What is this called?
tightly wrapped around proteins
DNA+protien= chromatin
When is the only time we can see chromosomes fully?
When DNA fully packed, during mitosis
What must chromosomes do for mitosis to occur?
Replicate
How and when are chromosomes replicated?
how many phases
5 phases, before mitosis
What is a chromatid? How are they joined?
each half of replicated chromosome
2 chromatids held together by centromere
(x shape, like chromosome, but a copy)
What are the stages of mitosis?
Interphase, early prophase, late prophase, Anaphase, Telophase
What occurs in each stage of mitosis?
Interphase: DNA replicated
Early Prophase:
-first stage
-DNA condensed
-centrosomes move to opposite poles
Late prophase:
-nuclear envelope dissolves,
-spindle fibers attach to chromosomes
Anaphase:
-DNA segregation
-chromatids separated into single, daughter chromosomes by fibers
(chromatids–> new chromosomes)
(x shape ripped apart into 2 sticks)
Telophase: chromosomes arrive at spindle poles
Cytokenisis: cell divides
Why are centrosomes important?
spindle fibers (microtubules) grow outwards from centrosomes
What do spindle fibers do? where do they attach? where do they bring chromosomes?
attatch to each chromosome, and to each pole
-attatchment occurs at protein in centromere called kinetochore
-then, line up (single line, theyre on top of each other) chromosomes on metaphase plate (central equator of cell) during metaphase
What occurs in telophase, detailed.
Last stage of mitosis
-spindle fibers break down
-chromosomes less condensed
-nuclei start forming
What is the process called when cells PHYSICALLY divide, what forms?
Cytokinesis
in animal cells, cleave-furrow forms
-cell is pinched more and more until divided
What is another name for mitosis?
Nuclear division
What is the difference between mitosis in animals vs in plants?
same as mitosis, but cells dont pinch off
-vesicles carry cell wall components to central equator
-fuse together to create cell plate, then form cell wall
what are pairs of chromosomes called? How many do we have and where do they come from?
homolouges
23 pairs,
23 individual chromosomes from each father and mother
what are human gamates? what is important about gamates? how are they produced?
egg and sperm
gamates are HAPLOIDS, meaning they contain half of compliment of chromosomes
produced by MEIOSIS by diploid germ cells
what do diploid germ cells have? what do they do?
diploid= contains full compliment of chromosomes
go thru meiosis to produce sperm (gamate) which is haploid
what are haploids?
contain half of compliment of chromosomes
gamates are haploids
what is it called when two haploids fuse?
fertilization
what is a zygote?
result of fertilization
2 haploids=full compliment of DNA in zygote
how are gamates made?
first, halving # of chromosomes
happens in meiosis 1
what is meiosis 1 process of meiosis w/ respect to mitosis?
meiosis 1
same stages of mitosis, BUT each chromosome pairs with its homologue
what is it called when a chromosome pairs w/ it’s homologue to form a pair?
bivalent pair
function of each phase in meiosos
prophase 1: chromosomes pair
metaphase 1: spindle fibres attatch
anaphase 1: each bivalent pair seperated, not chromosomes ripped apart
telophase 1: nuclei with HALF the chromosomes
what do spindle fibers do during meiosis
chromosomes line up in pairs
spindle from each side connects to ONLY the pairs on their side
essentially, what is meiosis?
halving the chromosome number
what are the resulting daughter cells of meiosis considered as?
haploid
what happens after meiosis 1? what happens in anaphase 2?
meiosis 2: similar to mitosis
-haploid cells from meiosis 1 undergo second division
-chromatids seperate at anaphase 2
what is the result of meiosis 2?
4 haploid cells (gamates) w/ HALF the chromosome number
- NOW X shape into 2 peices
in very simple terms, what is a big difference b/w mitosis and meiosis
mitosis: chromosomes seperated into chromatids
meiosis: chromosomes NOT seperated (2 FULL chromosomes paired up, then pairs seperated)
very simply draw the dividing of chromosomes/pairs in mitosis and meiosis 1 and 2
MITOSIS
X —> I…….I
X —> I…….I
X —> I…….I
X —> I…….I
MEIOSIS 1
XX –> X ……….X
XX –> X ……….X
MEIOSIS 2
X ……X —> II……II
X …….X –> II……II
(dots are just spaces)
