genetics population and ecosystem

• What is a genotype?

  All alleles an organism carries
• What is a phenotype?

  Observable characteristics of an organism due to genotype/ allele and environmental factors
• 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 is a recessive allele?

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

  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?

  • Controlled by a single gene
  • Example: cystic fibrosis
  • Affected individuals have a doubly recessive phenotype
• What is the outcome of crossing a pure breeding green podded pea plant with a yellow podded pea plant?

  All offspring have green pea pods
• What ratio is observed in a second cross of monohybrid inheritance?

  A 3:1 ratio is observed
• What is dihybrid inheritance?

  • Involves two characteristics
  • Determined by two different genes
  • Present on two different chromosomes
• What are the three alleles associated with the immunoglobulin gene in humans?

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

  Antigen A
• What does allele IB produce?

  Antigen B
• What does allele Io produce?

  Produces neither antigen A nor B
• What is sex linkage?

  Expression of an allele depends on gender
• What chromosomes do males have?

  One X and one Y chromosome
• What chromosomes do females have?

  Two X chromosomes
• Why do males carry only one allele for sex-linked traits?

  They have only one X chromosome
• How is haemophilia inherited in males?

  Inherited from the mother
• What is autosomal linkage?

  • Two or more genes on the same autosomal chromosome
  • Fewer combinations of alleles if linked
  • More combinations if on different chromosomes
• What is epistasis?

  • Interaction of different loci on a gene
  • One gene locus affects another
  • Can mask or suppress expression of another gene
• What is recessive epistasis?

  Recessive allele prevents expression of another allele
• What ratio does recessive epistasis give?

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

  Dominant allele masks alleles at another locus
• What ratio does dominant epistasis give?

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

  • Establish differences between observed and expected results
  • Tests the null hypothesis
  • Determines if differences are due to chance
• What is a null hypothesis?

  No statistical significance in results
• What is the minimum sample size for the chi-squared test?

  Over 20
• What type of data can be used in the chi-squared test?

  Data in discrete categories
• What is the formula for the chi-squared test?

  Value compared to critical value
• What is the critical value in chi-squared tests?

  p=0.05
• What happens if the chi-squared value is greater than the critical value?

  Null hypothesis is accepted
• What happens if the chi-squared value is less than the critical value?

  Null hypothesis is rejected
• What is a population in biology?

  • Group of organisms of the same species
  • Occupying a particular space at a particular time
  • Can potentially interbreed
• What is a gene pool?

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

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

  • Estimate frequency of alleles in a population
  • Determine changes in allele frequency over time
  • Assumes no mutations, migration, selection, and random mating