1 / 22

Mitosis

Mitosis. Aims:. Be able to name and explain the events occurring during each stage of mitosis. Recall that during mitosis, the parent cell divides to produce two genetically identical daughter cells. Recognise that mitosis increases the cell number in this way in growth and tissue repair.

livingston-aron
Download Presentation

Mitosis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mitosis

  2. Aims: • Be able to name and explain the events occurring during each stage of mitosis. • Recall that during mitosis, the parent cell divides to produce two genetically identical daughter cells. • Recognise that mitosis increases the cell number in this way in growth and tissue repair. • Be able to recognise the stages of mitosis from drawings and photographs

  3. Chromosomes • Each chromosome is a single very long strand of DNA. • The DNA is supported and neatly packaged by a histone protein bound to it. • At different times, these proteins cause the DNA to be spread out or tightly condensed into the X-shaped chromosomes we can see in the microscope. • Each chromosome has a central constricted region called a CENTROMERE that serves as an attachment point for the machinery of mitosis.

  4. More Chromosomes Chromosomes exist in 2 different states Before replication, chromosomes have one chromatid. After replication, chromosomes have 2 sister chromatids, held together at the centromere. Somatic cells have 46 chromosomes and are said to be diploid (2n). Sex cells have 23 chromosomes and are said to be haploid (n).

  5. Somatic Cells • Form the majority of cells in the body. • They are characterised as having: • 46 chromosomes • 23 homologous pairs (50% from each parent) • They are said to be diploid cells.

  6. Diploid Cells • This is a cell containing two sets of chromosomes, one set inherited from each parent. • Each chromosome has a partner with exactly the same: • Length • Genes • Diploid cells are formed in a process known as Mitosis. • In humans the diploid number is 46, which is abbreviated to 2n. 2n = 46

  7. Sex Cells (Gametes) • These cells are distinct from somatic cells. • They are characterised as having: • 23 chromosomes • 0 homologous pairs • They are said to be haploid cells.

  8. Haploid Cells • A cell containing only one set of chromosomes. • Each chromosome is unique with respect to its: • Length • The genes it contains • Haploid cells are formed in a process known as meiosis. • In humans the haploid number is 23, which is abbreviated to n. n = 23

  9. What do you remember about mitosis?

  10. Mitosis • The process whereby a mother cell divides to give rise to TWO daughter cells that are GENETICALLY IDENTICAL to the original mother cell. • In mitosis, the 2 chromatids of each chromosome separate, with each chromatid going into a daughter cell. • Remember that diploid cells have two copies of each chromosome, one from each parent. These pairs of chromosomes are NOT attached together. • Diploid (2n)  2 X Diploid (2n)

  11. Functions of Mitosis • Growth • Repair • Cloning/Asexual Reproduction

  12. Interphase The ‘living’ phase of the cell Cell obtains its nutrients, grows, and replicates it’s DNA Prepares the cell for mitosis or meiosis The cell spends the majority of time in this phase

  13. Prophase The chromosomes condense becoming more tightly coiled. They appear to shorten and thicken. Pairs of sister chromatids become visible. The nuclear envelope disappears. The Microtubule Organising Centre (MTOC) and their centrioles move to opposite poles. The spindle starts to form, growing out of the MTOC towards the chromosomes. Some microtubules make contact with the centromere , others with the other pole of the cell

  14. Metaphase Replicated chromosomes line up at the equator of the cell (middle) and divide. The spindle fibre is fully formed One sister chromatid from each pair is attached by microtubules to one pole; the other is attached to the other, by the centromere

  15. Anaphase The centromeres divide. At this point, each individual chromosome goes from: 1 chromosome with 2 chromatids to: 2 chromosomes with 1 chromatid each. The spindle fibers contract The sister chromatids are pulled to opposite poles. EACH POLE RECEIVES ALL OF THE GENETIC INFORMATION REQUIRED

  16. Telophase The two sets of chromosomes reach the poles of the cell The spindle disintegrates The nuclear envelope re-forms around the two sets of chromosomes. The cytoplasm is divided into 2 separate cells, the process of cytokinesis.

  17. Cytokinesis

  18. To Do • You have been given pictures of the different stages of mitosis. • You should: • Order the pictures and diagrams • Name the stage • Explain what is happening in terms of chromosome behaviour

  19. Exam Practice Q1 Jan 03 Q1 Jan 04 Q2 Jan 05 Q7b Jan 06 Q1 Jun 03 Q2 Jun 04 Q2 Jun 05

More Related