Wednesday, January 7, 2009

(Form 5) Variations and Inheritance - Terms / Definitions

Dear students of 5J and 5C,

Here's the list of terms explained during our lessons this week:
  • Gene: a unit of inheritance
  • Alleles: an alternate form of gene
  • Dominant: an allele that masks the expression of another allele
  • Recessive: an allele whose expression is masked by the activity of another allele
  • Codominant: alleles that are both expressed in the heterozygote
  • Autosome: a non-sex chromosome
  • Genotype: genetic constitution of an individual
  • Phenotype: observable expression of a genotype
  • Heritability: the proportion of a trait attributable to heredity
  • Heterozygous: possessing two different alleles for a particular gene
  • Homozygous: possessing two identical alleles for a particular gene
  • Independant assortment: random organization of chromosome homologs during metaphase I of meiosis I
  • Segregation: allele separation during meiosis
  • Law of segregation: Mendel's principle stating that one of each gene pair is placed in a separate gamete
  • Mutant: a phenotype or allele that is not most common for a certain gene in a population or has been altered from the normal condition
  • Pedigrees: a chart showing relationships of relatives and which ones have a particular trait
  • Polygenic: a trait caused by more than one gene
  • Punnett square: a device used to diagram the various possible genetic results of combining gametes
  • Wild-type: the most common phenotype or allele for a certain gene in a population
  • Pure breed: the plant carries two genes that are the same for a particular trait and these genes are passed on from the plant to the progeny through self-fertilization only
For those who are using the old Success (green book), you can start reading from the start of the chapter until dihybrid inheritance.

For those who have the new Success, you can refer to Pg. 518 for the list of terms.

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