Topic 7 - Genetics, Populations, Evolution and Ecosystems

• What is the definition of genotype?

  All alleles an organism carries
• What is the definition of phenotype?

  Observable characteristics influenced by genotype
• Why do most organisms carry two alleles for each gene?

  Because they are diploid organisms
• What is a dominant allele?

  Only one allele needed for expression
• What does it mean if an organism is homozygous dominant?

  It has two dominant alleles for a trait
• What is a recessive allele?

  Expressed only if no dominant allele present
• What is codominance?

  Both alleles are expressed equally
• What does pure breeding mean?

  Homozygous pair of alleles
• What is an allele?

  Alternative form of a gene
• What is a locus?

  Specific position of a gene on a chromosome
• What is monohybrid inheritance?

  Inheritance controlled by a single gene
• What is the expected ratio in a monohybrid cross?

  3:1 ratio of phenotypes
• What is dihybrid inheritance?

  Inheritance of two characteristics from different genes
• What are the three alleles associated with the immunoglobulin gene?

  IA, IB, Io
• What does allele IA produce?

  Antigen A
• What does allele IB produce?

  Antigen B
• What does allele Io produce?

  Neither antigen A nor B
• What is sex linkage?

  Expression of allele depends on gender
• What chromosomes determine sex in humans?

  X and Y chromosomes
• How many alleles do females carry for sex-linked traits?

  Two alleles on X chromosomes
• How many alleles do males carry for sex-linked traits?

  One allele on X chromosome
• How is haemophilia inherited in males?

  Inherited from mother via X chromosome

  
• What is autosomal linkage?

  Two or more genes on the same chromosome
• What happens when genes are on different chromosomes?

  Four possible combinations of alleles
• What is epistasis?

  Interaction of different gene loci affecting expression
• What is recessive epistasis?

  Recessive allele prevents expression of another allele
• What is the phenotypic ratio for recessive epistasis?

  9:3:4 ratio
• What is dominant epistasis?

  Dominant allele masks alleles at another locus
• What is the phenotypic ratio for dominant epistasis?

  12:3:1 ratio
• What is the chi-squared test used for?

  To compare observed and expected results

  
• What is a null hypothesis?

  No statistical significance in results
• What criteria must be met for the chi-squared test?

  Sample size over 20, discrete categories
• What is the formula for the chi-squared test?

  Compare observed to expected results

  
• What is a population?

  Group of organisms of the same species
• What is a gene pool?

  Total number of alleles in a population
• What does allelic frequency express?

  Proportion of a certain allele in a gene pool
• What is the Hardy-Weinberg Equation used for?

  Estimate frequency of alleles in a population
• What are the assumptions of the Hardy-Weinberg principle?

  No mutations, migration, large population, random mating
• What is the Hardy-Weinberg formula for allele frequencies?

  $p +$$q =$$1.0$
• What is the Hardy-Weinberg formula for genotype frequencies?

  $p^2 +$$2pq +$$q^2 =$$1$