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• What is a dominant allele?

  Allele which is always expressed in the phenotype even when theres only one copy of it
• What are recessive alleles?


  Alleges that only appear in the phenotype if 2 copies are present
• What are codominant alleles?


  Alleles that are both expressed in the phenotype because neither one is recessive
• If an organism carries two copies of the same allele it said to be ........

  Homozygous at the locus
• If an organism carries two different alleles it is said to be......

  Heterozygous at that locus
• What is mono hybrid inheritance?


  Inheritance of a characteristic controlled by a single gene
• What do monohybrid crosses show?


  The likelihood of the different alleles of that gene being inherited by the offspring of certain parents
• What type of offspring would a monohybrid cross with 2 homozygous parents produce?

  Will always produce all heterozygous offspring
• What is a phenotypic ratio?


  The ratio of different phenotypes in the offspring
• What is the usual phenotypic ratio you would get if you did a monohybrid cross with two heterozygous parents?

  3:1 ratio of dominant:recessive characteristics
• What ratio would you expect to see if you did a monohybrid cross with 2 heterozygous parents involving codominant alleles?

  1 : 2 : 1
• What is dihybrid inheritance?

  The inheritance of 2 characteristics which are controlled by different genes.
• What can dihybrid crosses show?

  The likelihood of offspring inheriting certain combinations of two characteristics from particular parents
• What phenotypic ratio would you expect to see if you did a dihybrid cross with 2 heterozygous Parents?

  9 : 3 : 3 : 1 dominant both : dominant first, recessive second : recessive first, dominant second : recessive both
• What does sex linked mean?

  The alleles that code for them are located on a sex chromosome
• Which sex chromosome carries most genes?

  X chromosome
• Which gender is more likely to to express the characteristic of sex linked genes? Why?

  Males- they have one X chromosome so they only have one copy of the allele, they expressive it even if it's recessive
• What are two x linked disorders ?

  Colour blindness and haemophilia
• Why can't males be carriers of X-linked disorders?

  Because they only have one copy of each chromosome so if they have the allele they have the disease whether is recessive or not
• What is an autosome?

  any chromosome that is not a sex chromosome
• What are genes on the same autosome said to be? Why?

  Linked - they'll stay together during the independent segregation of chromosomes in meiosis 1 and their alleles will be passed on to their offspring together
• What can cause autosomal genes not to stay together during independent segregation ?

  If crossing over splits them up first
• What is independent segregation?

  The random division of homologous chromosomes into separate daughter cells during meiosis
• If two genes are autosomally linked, what ratio would you expect to see and why?

  3 : 1 because the 2 autosomally linked alleles are inherited together
• What is epistasis?


  A phenomenon when the genotype of one gene can mask the effects of a separate gene
• What happens if the epistatic allele is recessive?

  Two copies of it will mask the expression of the other gene
• In recessive epistasis alleles , if you cross a homozygous recessive parent with a homozygous dominant parent what phenotypic ratio would you get in the F2 generation?

  9 : 3 : 4 dominant both : dominant epistasic, recessive other : recessive epistatic
• What happens when the epistatic allele is dominant?

  Having at least one copy will block the expression of the other
• What is the chi-squared test?


  Statistical test that's used to see if the results of an experiment support a theory
• what are the 5 steps in the chi- squared test?

  Theory

  Expected results

  Observed results

  Null hypothesis

  Chi-squared test
• What is the null hypothesis

  Is always " there is no significant difference between the observed and expected results"
• What is the formula for the chi squared value?

  The sum of = (O-E)2 / E. O = observed result E = expected result
• If the chi squared value is larger or equal to the critical value then .................. the null hypothesis

  Reject
• If the chi squared value is less that the critical value then .................. the null hypothesis

  Fail to reject the null hypothesis
• What is a species?

  A group of organisms that can interbreed and produce fertile offspring in nature
• What is a population?


  A group of individuals of the same species living in the same area at the same time.
• What is a gene pool?


  Is the complete range of alleles present in a population
• What is the hardy- Weinberg principle?

  Mathematical model that predicts the frequencies of alleles in a population won't change from one generation to the next
• What is the allele frequency and what's the equation?


  The total frequency of all possible alleles for a characteristic in a certain population. Is always 100% 1.0 .

  P+q = 1. P = the frequency of one allele q = the frequency of the other allele
• What is the genotype frequency and the equation?

  The total frequency of all possible genotypes for one characteristic in a certain population is 1.0 (100%)

  P2+2pq+q2 = 1 P2=frequency of homozygous dominant genotype 2pq= frequency of heterozygous genotype q2 = frequency of homozygous recessive genotype