Cell Division Flashcards
How is Genetic Variation Produced?
Independent Assortment of Bivalent in Metaphase I so homologous chromosnes have Different Alleles which produces a Larger n. of Allele Combinations
Mutations change the nucleotide sequence
**Crossing over ** of Chiasma at Prophase I so Chromatids have *new combonation * of alleles –> alleles swapped between non sister chromatids
Random Fertilisation hence there is a varitety of alleles so offspring have alleles from more than 1 parent
What are 3 roles of meiosis
Growth and repair of tissues
Asexual reproduction
Producing gametes from haploid cells
What is special in Metaphase I
Bivalents line up along equator
What is special in anaphase I
Whole chromosone with different allele combinations are pulled appart to opposite poles of cell thus each cell contains genetically different chromosones
What is special in Telophase I
Two haploid cells produce
What are homologous chromosones
One maternal and One paternal which carry genes *but different alleles *and form a bivalent
Why must genetic material of a cell replicate
Cells are genetically identical so both cells are able to recieve a full copy
What occurs in Prophase
Chromosones condense
Spindle fibres form
Nuclear envolope breaks down
Centrioles appear and move to oppsoite poles of cell
What occurs in metaphase
Chromosones line up along equator(center of cell) and attach to spindle
What occurs in Anaphase
Spindles contract –> pulling chromosnes to opposite ends of the cell
Waht occurs in telophase
Chromosones reach opposite poles of cell
Nuclear envolope reforms
What occurs in cytokensis
Cytoplasm divide
What occurs during Interphase
Genetic material copied
Protein Synthesis
Checking DNA for errors
What happens if dna is not checked for errors
Then daughter cell will not recieve identical info.
What are the 3 types of potentcy
Totipotency
Multipotenet
Pluripotent
What is totipotency
Stems cells that can differentiate into any cell and can form organisms
What is pluripotency
Comes from emberyos and can turn into almost any type of cell but cannot form whole organisms
What is Multipotentcy
Cells w/ limited potential to develop into many types—> ADULT STEM CELL
What are adaptations of erythocrytes
Bioconcave shape which increases SA over which O2 can be absorbed
No nucleus thus can store more space
Large SA:V Ratio
Flexible –> Squeeze through capillaries
What are adaptations of neurophils
**Flexible shape **to squeeze through cell junctions. Contains may lyzozymes which are hydrolytic enzymes to englulf bacteria
What are adaptations of sperm cells
Nucleus w/ half n. of chromosones
Acrosome in head containing digestive enzymes which break down outer layer of egg cell
Tail rotates –> propelling sperm cell foeard and allowing it to move towards egg cell
What are adaptations of Root Hair cells
Increases SA thus uptake by osmosis is greater
What are adaptations of cilliated epithillium
Contain cillia which *beat in rhythm to move mucus to top of trachea from lungs
What are adaptations of guard cells
THICKER inner cell wall
THINNER outer cell wall
which allows cell to bend whilst turgid
State the phases in cell cycle and what they are (G1 G2 S M)
S –> Cell replication
M –> Mitosis
G1 _> Cell checks chemicals nned for replication present
G2–> Checks whether all dna replicated
What is a stem cell
Undifferentiated type of cell which differentiates into all other cell types
What is the similarities and difference between Prophase I in Mitosis and Meiosis
Sim –> Chromosones condense and consists of 2 sister chromatids
Nuclear envolope breaks down & Spindle fibres form
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Differences (IN MEIOSIS)
Homologous chromosones form and form a bivalent
Crossing over occurs in chiamsa in prohase I
In prophase II –> Cells are genetically different
How is organisation of Homologous chromosones duirng metapahse I increase genetic variation
Independent assortment
H.C line up along the equator
H.C face opposite poles of the cell
Genetically different chromatids
How are xylem vessel elements produced from STEM cells
Differentiation
Cell Elongation
Lignification of Cell Wall
Why does meiosis need 2x as many stages as mitosis
To halve chromosome n.
As DNA has previously replicated
Why is mitosis and not meiosis used for asexual reproduction
-Mitosis produces genetically identical cells
-Maintains diploid n. of chromosones
