Inheritance

• Vertebrate


  Animal with a backbone
• Invertebrate

  Animal without a backbone
• 5 groups of vertebrates


  • Mammals
  • Reptiles
  • Fish
  • Amphibians
  • Birds
• Variation


  Differences in characteristics between organisms (living things)
• Environmental variation


  Variation depends on changes in the surroundings and/or lifestyle (e.g. skin tone, language, scars)
• Inherited variation


  • Blood group, eye colour
• Characteristics affected by both inherited and environmental factors


  • Body mass, height
• DNA


  Genetic information that contains all the information needed to make an organism. It is found in the nucleus of cells.
• Nucleus


  Controls the cell. Contains DNA.
• Chromosome


  A long coiled strand of DNA that contains many genes
• There are 46 chromosomes in human body cells
• There are 23 chromosomes in human sex cells (sperm and ovum/egg)
• Gene


  Section of a chromosome that contains the information for a particular characteristic e.g. eye colour
• Allele


  Different versions of the same gene
• Dominant allele


  Allele that has an effect on an organism's features even if another allele is present. Represented with a capital letter e.g. A
• Recessive allele


  An allele that only has an effect on the organism if the dominant allele is not present. Represented by a lower case letter e.g. a
• Genotype


  The alleles an organism has (its genetic makeup) e.g. Aa
• Phenotype


  What an organism looks like (because of its genes). Its observable characteristics.
• Fertilisation


  When a male gamete (sperm cell in animals and pollen in plants) joins with a female gamete (egg cell in animals and ovule in plants)
• Gamete


  A sex cell - sperm and egg in animals and pollen and ovule in plants
• Offspring have characteristics of both parents because they inherit half their DNA from each parent
• Sex chromosomes in males and females


  • Males - XY
  • Females - XX
• Identical twins


  A fertilised egg cell splits in two and the two cells split apart to form two identical babies - they will have identical DNA
• Non-identical (fraternal) twins


  Two egg cells are fertilised by two sperm cells - their DNA will be different
• Punnett square showing inheritance of sex chromosomes


  50% chance of male, 50% chance of female
• Genetic disorder


  An inherited issue caused by an abnormality or mutation in the DNA. E.g. sickle cell disease, cystic fibrosis.
• IVF (In Vitro Fertilisation)


  A medical procedure where an egg is fertilised by a sperm outside of the body
• Embryo


  The ball of cells formed when a fertilised egg cell divides
• Fetus


  The embryo is called a fetus when it begins to look more like a baby. This is after about 8 weeks of development.
• The embryo is implanted in the uterus during IVF
• Genetically modified organisms (GMOs)


  When an organism's genes have been changed to alter its characteristics
• Reasons crops may be genetically modified


  • To be resistant to attack by insects, herbicides or frost
  • To increase yield (amount that can be grown)
• Some people have concerns about GM foods, such as possible effects on wild flowers, insects or human health