Genetics

• genotype 


  the genetic constitution of an organism
• phenotype


  the expression of genes and its interaction with the environment
• homozygous

  a pair of homologous chromosomes carrying the same alleles for a single gene
• heterozygous

  a pair of homologous chromosomes carrying two different alleles for a single gene
• recessive allele

  an allele that is only expressed if no dominant alleles are present
• dominant allele


  an allele that will always be expressed in the phenotype
• codominant 


  both alleles are equally dominant and expressed in the phenotype
• multiple alleles

  more than two alleles for a single gene
• sex-linkage


  a gene whose locus is on the X chromosome
• autosomal linkage

  genes that are located on the same chromosome
• epistasis

  when one gene modifies or masks the expression of a different gene at a different locus
• monohybrid 


  genetic inheritance cross of a characteristic determined by one gene
• dihybrid

  genetic inheritance cross of a characteristic determined by two genes
• when is chi squared test used ?

  to investigate a difference between frequencies
• give an example of a null hypothesis

  There is no significant difference between the results in condition one and condition two.

  Any difference found is due to chance.
• if the chi squared value is less than the critical value when p = 0.05

  there is a more than 5% probability that the results are due to chance.

  The null hypothesis is accepted.
• hardy weinberg principle

  a mathmatical equation used to predict the allele frequencies within a population
• gene pool

  all the alleles of all the genes within a population at one time
• population

  all the individuals of one species in one area at one time
• allele frequency

  the proportion of an allele within a gene pool