Unit 1.6 - The cell cycle and cell division Flashcards
Simple GCSE recap on Mitosis
- parent cell passes on same amount of chromosomes to daughter cells (diploid)
- has only 2 daughter cells
- 1 cell division
- daughter cells are genetically identical
- functions: growth, repair, replacing cells (to repair tissue)
Simple GCSE recap on Meiosis
- parent cell chromosomes half in daughter cells (haploid)
- has four daughter cells
- 2 cell divisions
- daughter cells are genetically varied
- functions: create gametes, variation in reproduction
What does IPMAT stand for?
Interphase
Prophase
Metaphase
Anaphase
Telophase
What does interphase do/significance.
-synthesis of ATP in mitochondria
-synthesis of new organelles,
-replication of DNA/chromosome
-growth
-protein synthesis
What is the process of Prophase?
- chromosomes condense to become shorter and thicker
- chromosomes become more visible as two sister chromatids attached by a centromere - centrioles move to opposite poles - nuclear envelope disintegrates - nucleolus disappears
What is the process of Metaphase?
- spindle forms
- chromosomes align at the equator of the cell attached to spindle microtubules (protein) via centromere
What is the process of Anaphase?
- spindle fibres shorten
- centromeres divide and sister chromatids are pulled towards opposite poles
What is the process of Telophase?
- chromatids reach poles and become indistinct by uncoiling
- nuclear envelope reforms
- nucleolus reforms
- spindle disintegrates
What is the equation used to calculate the mitotic index?
no. of actively dividing cells in F.O.V divided by the total no. of cell in the F.O.V
What is cytokinesis?
the division of the cytoplasm to form two daughter cells following mitosis
What is the significance of mitosis in animals?
skin and blood cells are constantly being replaced
What is the significance of mitosis in plants?
root and shoot tip meristems are constantly undergoing mitosis
Why is mitosis important in asexual reproduction?
genetically identical offspring can be produced resulting in a rapid increase in numbers during favourable conditions.
What are tumours?What are they formed from? What do tumours prevent? When are cancers thought to be initiated?
-irregular mass of cells
-tumours form from uncontrollable mitosis/cell division
-tumours prevent normal function of body organs
- thought to be initiated when mutations occur in the genes that control cell division
Why doesn’t meiosis form tumours?
bc its a controlled process which leads to the formation of gametes with a reduced chromosome no.
How do you calculate the length of a stage in the cell cycle? Give an example
- Calculate the proportion of cells in that stage by counting using microscope
- Apply proportion to the length of cell cycle
e.g - 20 cells seen with 16 in interphase so 16/20 is 80%
- in a 24 hour cycle so 24 x 80% = 19.2 hours = length of interphase
Define the term gene
a base sequence of DNA that codes for the amino acid sequence of a polypeptide
Define homologous chromosomes
same shape and size and carry the same genes
What is an allele?
a different form of the same gene
What is the significance of meiosis?
- generates variation through crossing over (prophase 1) and independent assortment (metaphase 1+2)
- keeps chromosome no. constant by producing haploid gametes that recombine during fertilisation, restoring the diploid no. in the zygote
What happens during prophase 1 and what is the chromosome no. per cell?
- chromosomes condense to become shorter and thicker
- centrioles move to opposite poles
- chromosomes come together in homologous pairs (bivalent)
- crossing over occurs where part of 1 chromatid is exchanged w/another
- nucleolus and nuclear membrane disintegrates
- 2n
What happens during metaphase 1 and what is the chromosome no. per cell?
- spindle forms
- bivalents align at the equator of cell attached to spindle fibres via centromere
-> this alignment is random and called independent assortment - 2n
What happens during anaphase 1 and what is the chromosome no. per cell?
- spindle fibres shorten
- bivalents separate and chromosomes are pulled towards opposite poles
- 2n
What happens during telophase 1 and what is the chromosome no. per cell?
- chromosomes reach poles
- nuclear envelope reforms
- nucleolus reforms
- spindle disintegrates
- 2n
