Cell Division

    Cards (33)

    • What is Mitosis?
      • mitosis is a type of cell division where cells produce identical copies of themselves
      • used for growth, repair and asexual reproduction
      • differs from meiosis which produces gametes
    • What are the stages of mitosis?
      • interphase
      • prophase
      • metaphase
      • anaphase
      • telophase
    • What 3 phases make up interphase?
      • G1 phase
      • S phase
      • G2 phase
    • What occurs in the G1 phase?
      • gap phase 1
      • cell grows bigger
      • organelles replicate
      • a high amount of protein synthesis is taking place in order to build new organelles
    • What occurs in the S phase?
      • synthesis phase
      • cell replicates its DNA
    • What occurs in the G2 phase?
      • gap phase 2
      • the cell keeps growing until all of the organelles have duplicated
    • What occurs after interphase?
      • each chromosome now consists of two sister chromatids, connected by a structure called the centromere
      • mitochondria produce more ATP which will provide the energy for cell division and the ribosomes will be synthesising a high level of protein to replicate organelles
    • What are the 2 checkpoints in the cell cycle?
      • one before S phase
      • one after S phase
      • during the checkpoints the cell is checking its DNA for errors
      • minimises the chances of duplicating any mutated DNA into the replicated cell
    • Stages of mitosis
      • prophase
      • metaphase
      • anaphase
      • telophase and cytokinesis
    • What occurs in prophase?
      • chromosomes condense
      • nuclear envelope disintegrates
      • centrioles move to opposite poles of the cell
      • form spindle fibres
    • What occurs in metaphase?
      • chromosomes line up along the middle of the cell
      • attach to the spindle fibre by their centromere
    • What occurs in anaphase?
      • centromere splits
      • chromatids are pulled to opposite poles of the cell
    • What occurs in telophase and cytokinesis?
      • two groups of chromosomes decondense
      • nuclear envelope reforms
      • forms two new nuclei
      • cytoplasm divides
      • plasma membrane pinches off to form two new genetically identical cells
    • Investigating mitosis in squashed root tips
      • Method:
      • cut a thin section of tissue from the tip of a growing root
      • pipette a set volume of 1M hydrochloric acid into a boiling tube and place in a 60C60^{\circ}C water bath
      • place the plant tissue in the boiling tube and leave for five minutes
      • rinse the root tip with cold water and dry using a paper towel
      • cut the root tip so that you have a thin layer of cells an spread out onto a microscope slide using a mounted needle
      • add a drop of toluidine blue O stain to the tissue and place a cover slip on top
      • push down on the cover slip to squash the cells and allow light to pass through (be careful not to push sideways otherwise the chromosomes will become damaged)
      • use a light microscope to visualise the cells and identify the stages of mitosis, any cells with visible chromosomes will be undergoing mitosis
    • What are gametes?
      • gametes are sex cells
      • they are haploid which means they contain half the number of chromosomes as the rest of the cells which make up our body
      • when 2 gametes fuse during reproduction the fertilised egg contains the full number of chromosomes
      • the nucleus of the sperm cell fuses with the nucleus of the egg cell
      • the fusion of nuclei is called fertilisation
    • What is meiosis?
      • produces gametes for sexual reproduction
      • daughter cells are genetically different from the parent cell
      • contain only half the number of chromosomes
      • when 2 haploid gametes fuse a diploid cell called a zygote is formed
    • What occurs during meiosis I
      • interphase
      • prophase I
      • metaphase I
      • anaphase I
      • telophase I
    • What occurs during interphase in meiosis?
      • DNA replicates
      • there are now two identical copies of each chromosome
    • What occurs during prophase I in meiosis?
      • chromatids condense
      • chromosomes form homologous pairs (known as bivalents)
      • crossing over occurs
      • the nuclear envelope disintegrates
      • spindle fibres form
    • What occurs during metaphase I in meiosis?
      • homologous chromosomes line up along the equator
      • chromosomes attach to the spindle fibre by their centromere
    • What occurs during anaphase I in meiosis?
      • homologous chromosomes are separated
    • What occurs during telophase I in meiosis?
      • chromosomes reach opposite poles
      • nuclear envelope reforms around the chromosomes
      • cytokinesis results in the formation of two daughter cells
    • What occurs during prophase II in meiosis?
      • chromosomes condense
      • nuclear envelope disintegrates
      • spindle fibres form
    • What occurs during metaphase II in meiosis?
      • chromosomes attach to the spindle fibre by their centromere
    • What occurs during anaphase II in meiosis?
      • sister chromatids are separated
    • What occurs during telophase II in meiosis?
      • chromatids reach opposite poles of the cell
      • nuclear envelope reforms
      • cytokinesis takes place
      • 4 genetically unique daughter cells are produced
    • How does genetic variation occur during meiosis?
      • occurs through crossing over and independetn assortment
      • crossing over
      • during prophase I
      • homologous chromosomes move towards each other and exchange genetic material
      • a chromatid from the maternal chromosome becomes twisted around th paternal chromosome
      • connect through the chiasmata
      • pieces of chromosome are exchanges and the chromatids separate with different combinations of alleles
      • independent assortment
      • depends on the order in which the chromosomes line up along the equator during metaphase
      • different combinations of chromosomes will end up in each gamete
      • the order the chromosomes line up in is entirely random
    • What are stem cells?
      • stem cells are unspecialised cells
      • process by which a stem cell is specialised is known as cell differentiation
      • unlimited capacity to divide to produce more stem cells by mitosis
    • Different levels of potency
      • totipotent:
      • ability to divide into any type of cell
      • including extraembryonic cells eg - the placenta
      • pluripotent:
      • ability to divide into any type of cell
      • not including extraembryonic cells
      • multipotent:
      • can only divide into a handful of different cells
      • unipotent
      • can only divide into one type of cell
    • Examples of stem cells
      • adult bone marrow
      • contains multipotent stem cells
      • differentiate to replace old blood cells
      • form all the different types of red and white blood cells
      • meristems
      • found at the tips of roots and shoots
      • greater potency than adult stem cells
      • divide to form almost any kind of cell
    • Stem cells in medicine
      • stem cell transplants
      • used to replace lost stems cells
      • used to treat leukaemia as it destroys stem cells in the bone marrow
      • research
      • developing ways to grow whole organs
      • organs can then be transplanted into patients to replace organs that have been damaged or are diseased
      • would allow us to give patients organs who would have previously had to wait years to receive organs
    • Levels of organisation - plant leaves
      • upper epidermis
      • covered in a waterproof waxy cuticle to reduce transpiration
      • palisade mesophyll
      • tightly packed cells filled with mitochondria
      • located towards the top of the leaf to absorb as much light as possible
      • where most photosynthesis takes place
      • spongy mesophyll
      • loosely arranged cells
      • air spaces allow circulation of gases for gas exchange
      • phloem
      • transport of sugars and amino acids (translocation)
      • xylem
      • transport of water and mineral ions (transpiration)
      • lower epidermis
      • contains stomata which open and close to allow gas exchange to take place
    • Levels of organisation - the lungs
      • endothelium
      • forms the capillary walls which supply alveoli with oxygen and nutrients
      • fibrous connective tissue
      • helps to push air out of the lungs during exhalation
      • squamous epithelial tissue
      • makes up the walls of the alveoli