Reproduction in man & plants

• Chromosomes


  Thread-like structures of DNA, carrying genetic information in the form of genes
• Inheritance


  The transmission of genetic information from generation to generation
• Chromosomes


  • Located in the nucleus of cells
• Gene


  A short length of DNA found on a chromosome that codes for a specific protein
• Proteins coded by genes

  • Structural protein such as collagen
  • Enzyme
  • Hormone
• Genes


  Control our characteristics as they code for proteins that play important roles in what our cells do
• Alleles


  Different versions of a particular gene
• ABO gene for blood group type

  • IA
  • IB
  • IO
• Alleles give all organisms their characteristics
• The Zoom model is always useful when trying to visualise where you are in a cell, and what molecules are doing what
• Haploid cell


  Has one copy of each chromosome
• Diploid cell


  Has two copies of each chromosome
• Mitosis

  1. Chromosomes double beforehand

  2. Chromosomes line up along the centre of the cell

  3. Cell divides into two, each new cell has a copy of each chromosome
• Mitosis


  • Nuclear division giving rise to genetically identical cells
  • Used for growth, repair of damaged tissues, replacement of cells, and asexual reproduction
• Stem cells


  Unspecialised cells that divide by mitosis to produce new daughter cells that can become specialised
• Meiosis


  1. Chromosomes double themselves

  2. First division: chromosomes pair up, recombination occurs, cell fibres pull the pairs apart

  3. Second division: chromosomes line up, cell fibres pull them apart

  4. Four haploid daughter cells produced
• Meiosis


  • Produces gametes (sex cells)
  • Halves the chromosome number from diploid to haploid
  • Increases genetic variation of offspring
• Differences between Mitosis and Meiosis

  • Mitosis: Two diploid daughter cells produced
  • Meiosis: Four haploid daughter cells produced
  • Mitosis: Daughter cells genetically identical
  • Meiosis: Daughter cells genetically different
  • Mitosis: One cell division
  • Meiosis: Two cell divisions
• Cancer


  Caused by mutations in DNA leading to uncontrolled cell growth and division, resulting in tumour formation
• Types of tumour

  • Benign: Contained in one area, not cancerous
  • Malignant: Invade neighbouring tissues, spread to different parts of body, cancerous
• Asexual reproduction


  Does not involve sex cells or fertilisation, produces genetically identical offspring
• Asexual reproduction in bacteria

  • Binary fission
• Asexual reproduction in plants

  • Bulbs and tubers
  • Runners
• Advantages of asexual reproduction

  • Rapid population increase
  • Genetically identical offspring
  • More time and energy efficient
  • Faster than sexual reproduction
• Disadvantages of asexual reproduction

  • Limited genetic variation
  • Vulnerable to changes in conditions
  • Whole population affected by disease
• Gamete


  Sex cell (sperm, ovum, pollen nucleus, ovum)
• Zygote


  Fertilised egg cell, contains full diploid chromosome number
• Advantages of sexual reproduction

  • Increases genetic variation
  • Allows adaptation to new environments
  • Less likely for disease to affect whole population
• Disadvantages of sexual reproduction

  • Takes time and energy to find mates
  • Difficult for isolated members to reproduce
• Flowers


  • Reproductive organ of plants
  • Usually contain both male and female reproductive parts
• Male reproductive parts of flowers

  • Stamen: anther and filament
• Female reproductive parts of flowers

  • Carpel: stigma, style, ovary, ovules
• Pollen


  Contains male gamete nucleus
• Pollination


  Transfer of pollen from anther to stigma
• Pollination mechanisms

  • Insect-pollinated
  • Wind-pollinated
• Flower


  Reproductive organ of the plant
• Flower


  • Usually contain both male and female reproductive parts
• Male reproductive parts of a flower

  • Stamen
  • Anther
  • Filament
• Female reproductive parts of a flower

  • Carpel
  • Stigma
  • Style
  • Ovary
  • Ovules
• Pollen


  Contains a nucleus that is the male gamete