Cell division & stem cells

• nucleus

  contains genetic material in the form of long molecules of DNA
• stage 1 of cell cycle

  cells grow bigger & increase cell mass, DNA is replicated to form two copies of each chromosome, increase in number of organelles
• stage 2 of cell cycle

  mitosis
• stage 3 of cell cycle

  cytoplasm & cell membranes divide to form two identical daughter cells
• mitosis use

  growth & repair, replacement
• stem cells

  undifferentiated cells which have the ability to differentiate
• 3 types of stem cells

  embryonic, foetal, adult
• health problems that can be cured with stem cells

  Parkinson’s, paralysis, diabetes, blindness
• location of adult stem cells

  gut, bone marrow, heart
• stem cells in plants

  meristems
• potential disadvantages of stem cells

  Ethical issues & viral infection
• mitosis

  Asexual cell division where 2 identical daughter cells are formed from 1 parent cell. The chromosome number stays the same
• cell cycle

  the three stage processes of cell division that a body cell go through in order to divide by mitosis
• meiosis

  two stage process of cell division which halves the chromosome number of the daughter cells & makes the gametes for sexual reproduction
• gene


  a short section of DNA located on a chromosome carrying genetic information for a characteristic
• allele

  a different form of gene
• homozygous

  an individual with two identical alleles for a characteristic
• heterozygous

  an individual with different alleles for a characteristic
• genotype

  describes the genetic makeup of an individual regarding particular characteristics
• phenotype

  describes the physical appearance of an individual regarding a particular chacteristic
• dominant

  the characteristic that will show up in the offspring even if only one of the alleles is inherited
• recessive

  the characteristic that will show up in the offspring only if both of the alleles are inherited
• trait

  also referred to as a characteristic
• diploid

  a cell with a full set of chromosomes
• haploid

  a cell with half the number of chromosomes
• gametes

  the sex cells which have half the chromosome number
• examples of gametes

  egg, sperm, pollen
• zygote

  a fertilised egg that has started to divide into a ball of unspecialised cells
• homologous pair

  a pair of chromosomes, one from the mother and one from the father
• asexual reproduction

  reproduction involving one parent, no fusion of gametes
• sexual reproduction

  reproduction involving 2 parents and fertilisation of an egg
• sex chromosomes

  the pair of chromosomes that determine the sex of the offspring
• female sex chromosomes

  XX
• male sex chromosomes

  XY
• genetic disorder

  a disease which is inherited
• carrier

  an individual who is heterozygous for a faulty allele that causes a genetic disease in the homozygous form
• Gregor Mendel

  a monk who did many experiments using pea plants
• why were Gregor Mendel’s ideas not recognised initially

  he was not a scientist, DNA & genes weren’t known about
• DNA

  chemical which makes up genetic material