Cell Division Flashcards
What is mitosis?
Produce genetically identical daughter cells
During it, mitosis replicates and produce identical copy of DNA
Source of variation is mutation
Important for growth, repair and asexual reproduction
What is haploid and diploid?
Haploid is single set of chromosomes i.e. one from each homologous set
Diploid is total set of chromosomes i.e. homologous pairs
What is stages of mitosis?
Interphase, prophase, metaphase, anaphase, and telophase
What is interphase and describe it?
Non-dividing cell and includes G1,S and G2
Cell is carrying normal cellular function
Towards the end it prepares for cell division:
-DNA content is doubled
-Other cell organelles replicate
-RNA and protein syntheis
-ATP increase as cell division requires it
Describe prophase?
Chromatin organised into chromosomes
DNA replication makes genetically identical sister chromatids
Each chromosome then shortens and thickens (condensation) via spiralisation
Condensation prevents tangling during movements
The centrioles move to opposite poles of cell and nucleoli&nuclear envelope breaks
Describe metaphase?
The centrioles form spindle
Spindle consist of microtubules (protein), centriole not present in plant cell
Each chromosome moves to equator of spindle and attaches to centromere, each sister chromatids oriented towards opposite poles
There is no association between members of each homologous pair
Desribe anaphase?
Sister chromatids are pulled to opposite poles of the cell by contraction of the microtubules
Numerous mitochondria supply the energy for this movement
Describe telophase?
The chromatids are at opposite poles of the cell and
Nucleoli and nuclear membranes reform around each group of chromosomes
The sister chromatids represent the chromosomes of each new cell
Two distinct cells are formed as cytoplasmic cleavage occurs and a cell membrane forms
What is cytokinesis?
Last stage before cell enters G1 interphase
Organelles move towards the poles of the cell
The cell membrane constricts at the equator of the cell
In plant cells a cell plate forms where new cell wall material is organised to form a new primary cell wall that eventually fuses with the old cell walls separating the two cells
Why is importance of meiosis?
Ensures haploid gametes are produced
So when 2 gametes fuse to form zygote produce diploid
To ensure each generation possesses a constant number of chromosomes
Introduce genetic variation in gametes
What is meiosis?
Produce 4 genetically different daughter
Describe meiosis?
Diploid parent cell duplicates DNA forming 2 pairs of chromatids
Meiosis I : homologous pairs are separated randomly, independent segregation and crossing over occurs also
Meiosis II : chromatis divide, forming haploid cells
Explain and describe independent segregation?
Happens in meiosis 1
Homologous pair are separated
Separation of the 2 members of pair is independent from another one, so whether maternal or paternal is random combination
To calculate number of varied combination 2^n is used, n is num of homologous pair
Describe and explain crossing over?
Happens in prophase of meiosis 1
2 members of homologous pair lie side by side called bivalent
Chromatids of homologous pair intertwine
Sometimes the chromatids break and equivalent portions are exchanged
This causes exchange of alleles of same genes so new combination of alleles known as recombinants
Relatively rare
What is general properties of gametes?
Most spicies have different male and female gametes
Female gametes are usually larger with more cytoplasm and food reserved than male gamates
Male gametes are usually produced in considerably larger number than female gametes
Male gamates are mobile, swimming to the female gamates using tail
Human sperm contain a large number of mitochondria to provide the energy required for swimmimg
