2.6 Cell Division Flashcards
Why do we need new cells ?
For growth and repair.
What are the stages of mitosis ?
(Interphase), Prophase, Metaphase, Anaphase, Telophase, (Cytokinesis).
What is a period of cell division called ?
M Phase, which involves mitosis and cytokinesis.
What is interphase divided into ?
G1, S, G2.
What is the cell cycle regulated by ?
Regulated by checkpoints, which occur at key points to make sure the process is ok to continue.
What occurs at interphase ?
-Cell prepares to divide.
-DNA is unravelled and replicated.
-Organelles replicate.
-More ATP content for mitosis to happen.
What is the centromere ?
Point where 2 chromatids join to form a chromosome.
What are chromatids ?
Separate strands of chromosome.
What are sister chromatids ?
Two strands on the same chromosome are known as sister chromatids.
Why are there 2 chromatids (strands) on each chromosome ?
Two strands because each strand is an identical copy of itself.
What occurs in prophase ?
-Chromosome condenses (shorter + fatter).
-Spindle fibres form.
-Nuclear envelope breaks down and chromosomes lie free in the cytoplasm.
What are centrioles ?
Tiny bundles of protein that move to opposite ends of cell forming spindle fibres.
What occurs in metaphase ?
-Chromosomes line up in the middle at the spindle equator and become attached by centromere.
-Checkpoint checks all chromosomes are attached to spindle.
What occurs at anaphase ?
-Centromere divides, separating sister chromatids.
-Spindle fibres contract, pulling chromatids to opposite ends of cell, centromere first.
What occurs at telophase ?
Chromatids reach opposite poles on the spindle. They uncoil and become long and thin and are now called chromosomes again.
Nuclear envelope forms around each group of chromosomes.
What occurs at cytokinesis ?
Cytoplasm divides and cleavage furrow forms to divide cells and produce 2 genetically identical daughter cells.
When does cytokinesis start and end ?
Starts at anaphase and ends at telophase and is separate to mitosis.
How does cytokinesis occur in animal cells ?
Occurs by furrowing of cytoplasm.
How does cytokinesis occur in plant cells ?
Cytokinesis is initiated with formation of cell plate in the middle of the cell.
How do we investigate mitosis ?
-Treat tips of roots in HCl and break them open carefully and spread a few on microscope slide.
-Add a few drops of stain.
-Squash under coverslip and view under microscope.
What are gametes ?
Reproductive cells such as sperm and egg cells.
When 2 gametes form, what does it produce ?
It produces a zygote.
Are normal body cells diploid or haploid ?
Diploid meaning they have 46 chromosomes, that are the same size and genes, but may be alleles.
What are homologous chromosomes ?
Pair of matching chromosomes.
Are gametes haploid or diploid ?
Haploid meaning they have 23 chromosomes, only one copy of each chromosome.
What is meiosis ?
Cell division that produces gametes. Cells formed are genetically different because each cell ends up with a combination of chromosomes.
Interphase in meiosis
This is where meiosis begins as it is where the cells DNA unravels and replicates two produce double-armed chromosomes (sister-chromatids).