inheritance

• gene:

  section of DNA that codes for a protein
• allele:

  alternative forms of genes
• genotype

  genetic constitution of an organism

  (different alleles of an organism)
• phenotype

  the expression of the genetic constitution and its interaction with the environment 

  (expressed/observed characterisitcs)
• dominant allele:

  allele that is always expressed
• recessive allele:

  allele that is expressed if no dominant allele is present
• homozygous

  pair of homologous chromosomes carrying the same allele
• heterozygous

  pair of homologous chromosomes carrying 2 different allele
• monohybrid inheritance

  inheritance cross of characteristics determined by one gene
• dihybrid inheritance

  inheritance cross of characteristics determined by 2 genes
• codominance

  both alleles expressed in the phenotype 
• causes of genetic variation

  mutation

  random fertilisation

  independent segregation/ crossing over
• suggest two reasons why observed ratios are often not the same as expected ratios.

  small sample size

  random fertilisation

  selection advantage
• statistical test used to compare observed ration with expected  ratio

  chi squared test
• chi squared value greater than critical value

  there is significant difference between expected and observed result

  • reject null hypothesis
  • not due to chance
  • p<0.05
• chi squared value is smaller than critical value

  there isn't a significant difference between 2 variables

  • accept null hypothesis/ fail to reject
  • due to chance
  • p>0.05
• species

  group of organisms that can reproduce and produce fertile offspring
• gene pool

  complete range of alleles present in a population