MITOSIS & MEIOSIS

1. MITOSIS & MEIOSIS

2. TERMS TO KNOW • Chromosome – contain genetic code/DNA. • Gene – found in chromosomes. They determine an individual’s characteristics such as eye colour & nose shape. • Diploid – a cell with the full number of chromosomes. • Haploid – cell with half the number of chromosomes.

3. MITOSIS • See Atwaroo-Ali for info on chromosome number, cell cycle & importance of chromosome number. • One way in which cells divide – Mitosis • Is the process in which one eukaryotic cell divides into two cells identical to the parent cell • Mitosis occurs during growth & asexual reproduction • Two daughter cells are produced – identical to parent (i.e. same # & type of chromosomes) • Occurs in all body cells divide except sex cells

4. MITOSIS • In order for identical daughter cells to be formed the dividing cell must do 2 things: • Must copy each chromosome before it divides. Hence, each daughter cell will have a copy of each chromosome • Cell must divide to ensure that each daughter cell receives one copy of every chromosome otherwise it won’t contain all the genes.

5. IMPORTANCE OF MITOSIS • Growth • Repair • In asexual reproduction – necessary for maintenance of species number & identical combination of genes in daughter cells.

6. ASEXUAL REPRODUCTION & MITOSIS • Examples (see Atwaroo-Ali pg 226): • Binary fission • Vegetative propagation • Cuttings • Grafting • Tissue culture

7. CLONING: • the processes used to create an exact genetic replica of another cell, tissue or organism. The copied material, which has the same genetic makeup as the original, is referred to as a clone

8. Fusion cell cloning • Fusion cell cloning involves replacing the nucleus of an unfertilised egg with the nucleus from a different cell. The replacement nucleus can come from an embryo, but if it comes from an adult cell, it is called adult cell cloning. • Dolly the sheep was the first mammal to be cloned using adult cell cloning. She was born in the UK in 1996 and died in 2003. Here's how she was produced: • An egg cell was removed from the ovary of an adult female sheep, and its nucleus removed. • The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell. • The fused cell then began to develop normally, using genetic information from the donated DNA. • Before the dividing cells became specialised, the embryo was implanted into the uterus of a foster mother sheep. The result was Dolly, genetically identical to the donor sheep.

10. Learn advantages and disadvantages of cloning • Do you condone cloning? • Do you think that humans should be cloned? Explain your answer • What are some concerns with cloning humans?

11. GROWTH AND MITOSIS • Growth – increase in # of cells. Done via mitosis. • Irreversible increase in mass • Development – increase in complexity, as cells differentiate into tissues & carry out specific functions.

12. GROWTH IN ANIMALS • Growth in animals occurs via the production of many cells. • Continuous process until organism reaches a certain size as an adult. • In some organisms, this increase is not easily seen e.g. grasshopper w.r.t. its length. However, the increase in mass in a grasshopper is constant.

13. This difference is due to exoskeleton of grasshopper. When this skeleton gets too small – shedded. • New one is initially soft allowing grasshopper to inflate body to stretch it. • Skeleton hardens at inflated size, leaving room for the insect to grow. • Process is called ecdysis or moulting.

14. Human growth shows gradual increase until adulthood. • However, different parts of body grows at different rates at different times. • Boys & girls grow at same rate until teens. • Girls have an adolescent growth spurt before boys & reach adult body size at an earlier age. • Boys are bigger than girls when adults. • These growths caused by secretion of sex hormones which stimulates pituitary gland to secrete growth hormone. Growth stops @ adulthood.

15. GROWTH IN PLANTS • Growth also involves an increase in cells • Only cells in certain places (meristems) divide via mitosis • Meristems occur at the ends of shoots & roots. • Thus most plants grow in a branching shape • See Chinnery and Atwaroo Ali for more info

16. In flowering plants, there is an initial growth period after fertilisation • This results in formation of an embryo within a seed – germination • Germination needs the following conditions: • Oxygen - why? • Water – why? • Suitable temperature – why?

17. A seed contains an embryo plant • Embryo – radicle (root) & plumule (shoot) • Food (starch, lipids & protein) is stored for the embryo in cotyledons. Cotyledon also contains enzymes. • Cotyledons surrounded by testa – prevents damage to embryo & bacteria & fungi from entering seed. • Testa has a tiny hole (micropyle). This hole is near to hilum (scar) where seed is joined onto the pod (See Chinnery). • Learn & draw seed structure

18. Uptake of water through micropyle initiates germination as metabolic reactions begin • Seed swells, testa bursts, plumule & radicle able to penetrate testa • At germination, enzymes digest food into soluble substances: • Starch – to? • Proteins – to? • Lipids – to? • What enzymes do the above? • Plumule grows above ground allowing what?

19. TYPES OF GERMINATION • Hypogeal

20. Epigeal

21. Primary growth • This occurs when there is growth behind the ends of the root & shoot and ends of any side branches (all regions called apical meristems). • Mitosis within cells occurs • New cells elongate to cause growth

22. Secondary growth • Shoots & roots - thicker & longer as they grow • Rings of cells develop in roots & shoots

23. Plants and animals grow and differentiate their tissues in different ways. The main differences are outlined in the table on the next slide.

25. REFERENCES • http://www.nlm.nih.gov/medlineplus/cloning.html • http://bruceleeeowe.wordpress.com/2009/11/07/human-cloning-surrogate-mother-and-why-is-it-wrong/ • http://news.bbc.co.uk/2/hi/science/nature/371378.stm • http://science-education.nih.gov/home2.nsf/Educational+ResourcesTopicsGenetics/BC5086E34E4DBA0085256CCD006F01CB?OpenDocument&Highlight=0,cloned+and+sheep • http://videos.howstuffworks.com/hsw/5995-the-importance-of-meiosis-video.htm • http://www.vcstulsa.org/Portals/25/Editors/Teachers/mitosis2.ppt#256,2,The Importance of Mitosis • http://www.biology-questions-and-answers.com/cell-division.html • http://www.sci.sdsu.edu/classes/bio100/Lectures/Lect05/lect05.html • http://www.rapidlearningcenter.com/biology/genetics/04-Mitosis-and-Meiosis.html

26. http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/genes/reproductionandcloningrev4.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/genes/reproductionandcloningrev4.shtml • http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway/living/cloningrev4.shtml • http://www.bbc.co.uk/schools/gcsebitesize/science/21c/genetics/cloningstemcellsrev2.shtml • http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway/living/growinguprev1.shtml • ***http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/evolution/reproductionrev1.shtml • Hypogeal Germination http://encyclopedia.farlex.com/_/viewer.aspx?path=hut&name=c01094.gif • Epigeal Germination http://www.uq.edu.au/_School_Science_Lessons/9.112.GIF • Epigeal http://store.tkc.go.th/multimedia/webproducer/p01/html/cell2/bodyhtm/image/pic42.gif • http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml • Secondary growth http://www.biologie.uni-hamburg.de/b-online/library/plant_biology/surecell.html • http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Tilia1_to_3.gif • **http://fig.cox.miami.edu/Faculty/Dana/16002_12.html • Primary growth http://www.uic.edu/classes/bios/bios100/lectf03am/lect18.htm