inheritance

• what is a chromosome

  long coiled molecule of dna that carries genetic material in the form of genes
• define gene

  section of dna that codes for a specific sequence of amino acids, which then forms a protein
• what are alleles

  different versions of the same gene
• define genotype


  the alleles they have
• define phenotype


  observable charecteristics of an organism
• define homozygeous


  two identical alleles e.g. MM, mm
• define heterozygous


  two different alleles of a gene e.g. Mm
• what is the dominant allele


  the allele that is always expressed, represented with capital letter e.g. M
• what is the recessive allele


  allele that is only expressed in the absence of the dominant allele, represented with lower case e.g. m
• what is monohybrid inheritancee


  inheritance of a single gene
• what is the problem with single gene crosses


  most charecteristics are controlled by multiple alleles, rather than just one
• what is a sex-linked charecteristic


  charecteristic that is coded for by an allele found on a sex chromosome (usually the X chromosome)
• why are majority of genes found on the X chromosome, not the Y chromosome

  the X chromosome is bigger and carry more genes
• why are men more likely to show the phenotype for a recessive sex-linked trait than women

  many genes are found of the x chromosome. women have two alleles for sex-linked gene where as men often only have one allele. so only one recessive allele is required to produce recessive phenotype in males
• name the different blood groups

  • A
  • B
  • O
  • AB
• what are codominant alleles 


  alleles that contribute to an organisms phenotype
• describe codominance in blood groups


  IA and IB are codominant. blood group IA and IB gives group AB