7A genetics

• What is a genotype

  The genetic constitution of an organisms (the alleles it has for a gene)
• what is a phenotype

  The expression of the genes and its interaction with the environment
• what is homozygous

  A pair of homologous chromosomes carrying the same alleles for a single gene
• what is hetrozygous?

  A pair of homologous chromosomes carrying two different alleles for a single gene
• what is a recessive allele?

  An allele only expressed if no dominant allele is present
• what is a dominant allele?

  An allele that will always be expressed in the phenotype is present in the genotype
• what does codominant mean?

  Both alleles are equally dominant and expressed in the phenotype
• what are multiple alleles?

  More than two alleles for a single gene
• what is sex linkage?

  A gene whose locus is on the X chromosome
• what is autosomal linkage?

  Genes that are located on the same chromosome (not the sex-chromosomes)
• what is epistasis?

  When one gene modifies or masks the expression of a different gene at a different locus
• In a dihybrid cross of two heterozygous parents what will the ratio be?

  9.3.3.1

  unless there is autosomal linkage or crossing over
• how does crossing over affect gametes that we have predicted in a punnet square?

  results in new combinations of alleles in the gametes
• how does autosomal linkage affect the predicted gametes from a punnet square?

  alleles for each gene are linked on the same chromosome and must be inherited together

  this means that only possible gametes are the two split.
• if an organism has autosomal linkage then what could affect results to provide more possible gametes?

  crossing over during meiosis
• what is a gene pool?

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

  all the individual species within an area at one time
• what is allele frequency?

  the proportion of alleles within the gene pool