Cell Division Flashcards
What is mitosis used for?
Growth
Repair
Asexual reproduction
What is meiosis used for?
Gamete production
Genetic variation
What does mitosis produce?
Two genetically identical diploid daughter cells
What does meiosis produce?
Four genetically unique haploid daughter cells
What does diploid mean?
Two copies of each chromosome
What does haploid mean?
One copy of each chromosome
How many chromosomes do humans have?
46 (23 pairs)
What sex chromosomes do males have?
XY
What sex chromosomes do females have?
XX
What is a pair of chromosomes called?
Homologous pair
What is the name of the stage in mitosis when the cell is not dividing?
Interphase
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is the division of cytoplasm called?
Cytokinesis
What happens at interphase?
DNA replicates
Organelles replicate
Centrioles replicate
Chromatin is uncoiled
What holds the homologous chromosomes together?
The centromere
What happens in prophase of mitosis?
Chromatin condenses to form chromosomes
Nuclear envelope breaks down
Replicated centrioles move to opposite poles
Spindle fibres (tubulin) begin to form at poles
What forms around the centromere and attaches to the spindle fibres during mitosis?
A protein complex called the kinetochore
What happens during metaphase of mitosis?
Kinetochores attach to spindle microtubules
Chromosomes line up along the equator
What happens in anaphase of mitosis?
Sister chromatids are pulled apart and now called chromosomes
Chromosomes move towards opposite poles of the cell
What makes the chromosomes move the opposite poles during anaphase?
The microtubules shortening my removing tubulin subunits, called depolymerising
What happens in telophase of mitosis?
Chromosomes have reached the poles and begin to decondense so nucleolus reforms
Nuclear envelope forms around chromosomes at each pole
Spindle breaks down
Process of cytokinesis in animal cells?
The cell membrane pinches in the middle to form a cleavage furrow The cytoskeleton (microfilaments) then continues to pull the membrane inwards
Process of cytokinesis in plant cells?
Cannot form cleave furrow due to cell wall
Golgi vesicles contain components needed for a new cell wall assemble across the equator (cell plate) and fuse to make a new membrane
New cell walls form on either side of the membrane
Where does meiosis take place in humans?
Ovaries or testes
Why do gametes have half the normal chromosome number?
To fuse with another gamete to produce a zygote with the normal number of chromosomes
How many times does the cell divide in mitosis?
Once
How many times does the cell divide in meiosis?
Twice
What addition processes happen in prophase 1 of meiosis compare to mitosis?
Members of homologous pairs find each other and lie close together (process called synapsis)
Non-sister chromatids become so close that they can overlap (called chiasmata) this can lead to crossing over of genetic material
What is different about metaphase 1 of meiosis compare to mitosis?
The chromosomes line up along the equator in homologous pairs
How does genetic variation happen through meiosis? (4)
Chiasmata and crossing over of genetic information
Which random arrangement of maternal/paternal chromosomes called independent assortment in metaphase 1
Orientation of each chromosome in metaphase 2
Random fusion of the gametes produced by meiosis
How is anaphase 1 in meiosis different to mitosis?
Sister chromatids are not separated as there is no division of the centromere
