Cell Division Flashcards
Cell continuity
All cells develop from pre existing cells
Chromosomes
Are cooked threads of dna and protein that become visible in the nucleus at cell division
Chromatin contracts to form a number of chromosomes
Gene
Is a short section of dna which contains the instructions for the formation of a protein
Produced in enzymes
Haploid cell
Has one of each chromosome
Eg egg and sperm
Diploid cell
Two of each chromosome
2n
All cells in human except argh and soerm
Homologous pair
Consists of two chromosomes of similar size with the same sequence of genes
Each pair of chromosomes has similar genes
The cell cycle
Describes the life cycle of the cell
Not dividing = interphase
Is dividing = mitosis
Interphase
90% of the cells cycle
-organelles replicated - mito chloro ribosomes
-biomolecules produces - protein fat carb
Chromosomes are elongated =chromatin
Mitosis
A form of nuclear division in which one nucleas divides to form two identical daughter nuclei
Takes place in non reproductive cells knows ass somatic cells
Stage 1
Prophase
-nuclear membrane breaks down
-chromosomes shorten and becomes double stranded
-spindle fibers from in the cytoplasm
Stage 2
Metaphase
-chromosomes line up along the equator of the cell
-spindle fibers attach to chromosomes
Stage 3
Anaphase
-spindle fibers contract causing the centrometres to split
-one chromo from each double stranded chromo is pulled to opposite be poles of the cell
Stage 4
Telophase
-chromo lengthen to from chromatin
-spindle fibers break down
-nuclear membrane forms around each chromatin
-nucleas has divided into two identical nuclei
Cell division
Now it is complete the original cell immediately divides to form two new cells
Animal cells
A cleavage furrow forms
Deepens until it eventually divides the cytoplasm and the cell splits in two
Plant cells
Cell plate forms
Cell wall prevents a cleavage furrow from forming
Cell plate enlarges
Two cell walls form within the cell plate one for each cell
The region between the two adjacent cell walls is called the middle lamella
Functions of mitosis
Unicellular organisms
-asexual reproduction eg ameoba
Multicellular organisms
-growth produces new cells and repair of cells
Meiosis
Form of nuclear division in which the four daughter nuclei contain half the number of chromosomes of the parent nucleas
Takes place in a diploid cell
Eg production of gametes egg and sperm
Functions of mieosis
Allows for sexual reproduction
Gives rise to variation
Differences between mitosis and meiosis
Mitosis daughter cells have the same number of chromomes as the parent cells Two new cells form
Meiosis daughter cell have half the number of chromosomes than the parent cells Meiosis daughter. Four new cells form
Cancer
A group of disorders due to an uncontrolled rate of mitosis
Types of rumours
Benign - non life threatening - warts
Malignant - life threatening cancers
