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3.2- sexual reproduction and cell specialization
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Biology Mindmap am 3.2- sexual reproduction and cell specialization, erstellt von victoria.graham96 am 28/05/2013.
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Zusammenfassung der Ressource
3.2- sexual reproduction and cell specialization
Why sexual reproduction?
Is the production of a new individual
Joining of two gametes
Haploid cells
Form zygote
Male
Many, mini, motile
In animals
Testes
Produce spermatozoa (sperm)
In plants
Anthers
Produce pollen
Female
Few, fat, fixed
In plants
Ovaries
Produce ovules
In animals
Ovaries
Produce ova (eggs)
Not genetically the same
Contain genetic info from both parents
Increases genetic variety
Increase chance of surviving
Using totipotent cells
Plant cells
Easy to clone
Remain totipotent throughout life
Single cells can be grown in a rich nutritive medium
Animal cells
Embryo splitting
Every cell in early embryo is totipotent
Take embryos from the best stock
Separate embryo into individual cells
Put in rabbits for shipment
Embryos placed in seragate mothers
What causes cell differentiation
Cells switch genes on nd off
Restoring totipotency
Cloning animals is difficult because cells no longer totipotent
Many dificulties with this technique
Difficult to culture
Embryo development and cell differentiation
Totipotent
Can form any cell type
After fertilisation
Cleavage
Repeated mitosis
Form blastocyst
Mass of small undifereciated cells
Pluripotent
Can form all cells appart from tissue (placenta)
Meiosis
A reduction division
Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Metaphase 2
Anaphase 2
Telophase 2
Nuclear envelopes reform
Chromosomes return to interphase state
4 daughter cells half the chromosomes
centromeres divide
Chromatids move to opps ends
New spindles formed
Chromosomes line on equator
Nuclear membrane reforms
Brief interphase NO replication
Centromeres DON'T divide
One chromosome from each moves to side of cell
Spindle fibers form
Pairs of chromasomes line on equator
Crossing over occurs
Multienzymes 'cut and stick' bits together
Chiasmata- Points where chromatids break
Coil and condensed form
2 chromatids
Half chromosomes number
4 daughter cells
Fertilisation
Humans
Digestive enzymes pour out acrosome
Digest zona pellucida
Sperm touches oocyte
Membranes fuse
Nucleus released
Decondenses and releases chromosomes
Oocyte releases cortical granules
Combine wid zona pellucida
Form tough fertilization membrane
Plants
Pollen tube nucleus grows a tube
This enters the ovule then degenerates
1 male gamete fuses wid polar bodies
The other fues with female gamete
Produces diploid zygote
Produce triploid endosperm nucleus
Gametogenesis
Humans
Oogenesis
Primordial germ cell
Mitosis twice
4 oogonia
Grow into primary oocyte
Meiosis 1
1 secondary oocyte
Meiosis 2
1 Ovum
Cytoplasm with food reserves
Cell surface membrane
Jelly like layer-zona pellucida
1 polar body (dies)
1 polar body(may not divide)
2 polar bodies (die)
Spermatogenesis
Primordial germ cell
Mitosis twice
4 spermotogonia
Grow into primary spermotocyte
Meiosis 1
2 secondary spermatocytes each
Meiosis 2
4 spermatids
4 spermatozoa (sperm)
Acrosome- storage site for digestive enzyme
Nucleus-contains chromosomes
Mitochondria-provide energy for tail
Microtubules-produce whip like movement
Plants
Megagametogenesis
Megaspore mother cell
Meiosis twice
4 haploid cells
3 degenerate
Growth
Megaspore
3 mitosis
Mature embryo sac
3 antipodal cells
2 polar nuclei
2 synergids
Female gamete
Microgametogenesis
Microspore moX, ther cell
Meiosis twice
4 haploid cells
Mitosis
Pollen grain (microspore)
Pollination
Pollen grain on a stigma
Mitosis of generative nucleus
Pollen tube nucleus
Generative nucleus
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