Genetic crosses

  • Created by: vezting
  • Created on: 22-03-16 11:06
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  • genetic crosses
    • Genotype and phenotype
      • genotype is genetic make up of an organism
      • organism with two identical alleles for one gene is homozygous, and two different alleles is heterozygous
      • genes code for proteins that are part of structure or code for enzyme. there are no genes coding for genetic disease. its altered alleles that produce altered proteins.
      • phenotype is characteristics that are expressed
      • phenotype is determined by genotype and environment
    • dominant, recessive, codominant
      • allele is dominant if it is always expressed in phenotype
      • recessive is only expressed in phenotype when 2 identical copies of the allele are present
        • or in absence of a dominant allele
      • 2 alleles are codominant if they are both expressed in the phenotype of a hetrozygote
    • Linkage and sex linkage
      • linkage refers to two or more genes that are located on the same chromosome
      • the linked alleles of these genes are usually inherited together because they don't segregate independently at meisois
        • unless chiasmata have formed between them
      • at cross over the allels from one chromatid become linked to alleles on other chromatid, reducing number of phenotypes
      • characteristics are sex linked if the gene that codes for them is on one of the sex chromosomes.
        • Y chromosomes has fewer genes so most sex linked genes are likely to be found on X chromosome
      • in linkage alleles are shown together EG PLPL


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