Inheritance

• variation


  the differences in the characteristics of individuals from the same species
• species


  group of organisms that share many similarities
• genetic variation


  differences in genes inherited from parents (e.g. face shape, eye colour, dimples, blood group)
• environmental variation


  features that we gain in the surroundings where we develop
• continuous variation


  a variable that can take a large range of values (e.g. height: 1.65m, 1.66m, 1.67m, 1.68m)
• discontinuous variation


  a variable that has a fixed number of options (e.g. eye colour: blue, brown, green)
• Some variation is due to a combination of both genes and environment (e.g. height, mass, hair colour, skin colour).
• A continuous variation is represented with a histogram. It doesn't have any gaps between the bars.
• A discontinuous variation is represented with a bar chart. It has gaps between the bars.
• Where are the chromosomes found?


  nucleus
• What are the chromosomes made out of?


  They are made out of deoxyribonucleic acid (DNA) and protein
• DNA


  chemical molecule carrying the different codes to make different amino acids, which carry genetic information
• nucleus


  holds the genetic material which controls the activities of the cell
• cell


  small units that make up all living things
• gene


  unit of inheritance that carry the codes that determine our physical characteristics
• chromosome


  very small 'x' shaped structures carrying genes
• Alleles are alternative forms or versions of a specific gene. The combination of the two genes or alleles you inherit will determine the feature you will show.
• Chromosomes come in pairs and your genes/alleles come in pairs.
• homozygous


  two alleles of the specific gene are the same (e.g two recessive [ee] or two dominant alleles [EE])
• heterozygous


  two alleles of the specific genes are different from each other (e.g one recessive and one dominant allele [Ee or eE])
• genotype


  allele combination for a specific characteristic represented by letters (e.g BB or Bb or bb)
• Punnett squares can be used to predict what traits offspring may have based on their parents’ genotypes.
• phenotype


  physical characteristics that can be observed (e.g red hair, green eyes)
• One or two dominant alleles present will show the dominant characteristics.
• Two recessive alleles are needed for the recessive characteristics to show.
• There are 46 chromosomes in the human body cell.
• There are 23 chromosomes in an egg.
• Alleles is the word used for different versions of the same gene.
• Organisms evolve by a process known as natural selection. A change in species that happens slowly, over a very long time.
• The process of natural selection:

  1. There is variation in characteristics within a species due to differences in genes.
  2. Organisms better adapted to the environment will survive and breed.
  3. The useful characteristics are passed on to the offspring through the genes.
  4. After many generations, more individuals will show the useful characteristics.
• How is genetic information passed on from parent to offspring?


  Genes in the egg and sperm cells (gametes = sex cells) are passed from parent to offspring.