7.1

• Dominant


  An allele that is always expressed in the phenotype of an organism.
• Recessive


  The trait will only be expressed in the organism if there are two copies of the allele.
• Co-dominant 


  Both alleles for the same characteristic are simultaneously expressed.
• Gene


  A section of DNA that codes for a polypeptide.
• Allele


  A variation of a gene.
• Genotype 


  An organisms underlying genetic makeup.
• Phenotype


  The observable traits expressed by an organism.
• Homozygote


  An organism with two copies of the same allele.
• Heterozygote 


  An organism with different alleles.
• Monohybrid cross


  Two parents differ in one characteristic.
• Dihybrid cross


  Two parents differ in two characteristic.
• Linkage 


  When genes that are close to each other on a chromosome are likely to be inherited together.
• Autosomes


  All chromosomes except the sex chromosomes.
• Epistasis


  Where two non-linked genes interact, one masking the other.
• Diploid


  Organism carries two alleles per gene.
• Monohybrid inheritance


  Where one phenotypic characteristic is controlled by a single gene.
• Punnet square


  A diagram used to predict the possible genotypes and phenotypes of offspring in a genetic cross.
• Sex-linkage 


  Where an allele is located on one of the sex chromosomes, meaning it’s expression depends on the sex of the individual.
• Autosomal linkage


  Where two or more genes are located on the same non-sex chromosome.
• Recessive epistasis 


  Where two homozygous recessive alleles mask expression of another allele.
• Dominant epistasis


  Where one dominant allele masks expression of multiple alleles.
• Chi-squared test

  A statistical test to find out whether the difference between observed and expected data is due to a chance or a real effect.
• Epistatic allele


  The alleles that mask effects.
• Hypostatic alleles


  The allele whose effect is being masked.