Inheritance mindmap

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  • Created by: ava.scott
  • Created on: 09-04-15 19:07
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  • Inheritance
    • terms
      • Genetics
        • the study of the mechanisms by which organisms inherit characteristics from their parents,
      • Genotype
        • the genetic makeup of an individual. includes all the allele combinations.
      • Allele
        • diifferent versions of the same gene.
      • Phenotype
        • the physical characteristics of a organism.
    • Genes
      • They can separate and combine
      • they can mutate
      • they code for a specific polypeptide
    • Monohybrid inheritance
      • Involves
        • the inheritance of a single characteristic by a single gene
      • Punnet square
        • make sure you label x and y labels with gametes from each parents
      • Mendels first law
        • characteristics come in pairs called factors (alleles) but only one allele can be present in a gamete.
    • Dihybrid inheritance
      • Involves
        • the inheritance of two separate characteristics by two genes.
      • To find a ratio, you divide the amount of each phenotype by the smallest one.
      • mendels second law
        • either one of a allelic pair can combine freely with one of another pair.
    • CHI2
      • expected ratio of a dihybrid is always 9:3:3:1
      • we use this statistic test to see if any variations in data ae down to chance or not.
      • Must be below 5% to be insignificant.
      • EQUATION
        • (O-E)^2/E
    • CO-DOMINANCE
      • When a individual is heterozygous dominant.
      • both alleles are expressed equally in the phenotype.
      • Parents would have to be homozygous dominant.
    • Sex determination and linkage
      • X and Y chromosomes. XX= girl XY= boy.
      • Alleles of the X chromosome ae described as sex linked.
        • because the Y chromosome carries few alleles
        • Haemophilia
          • A recessive allele on the X chromosome, which stops people from clotting.
          • Mainly boys as they only need to inherit one copy of the recessive allele.
    • Linkage
      • When two different genes are on the same chromosome and they are generally inherited together.
      • Separated by crossing over.
        • which only occurs in 10% meiotic divisions.
      • Doesnt follow typical mendelian pattern.
    • MUTATIONS
      • diiferent types
        • gene
          • Changes in the base pair within the gene producing a  different allele.
            • modifies the polypeptide by the primary sequence.
          • sickle cell anaemia
            • One mutation results in a different amini acid (glutamic acid instead of valine in the 6th position of the Beta globulin chain) in haemoglobin.
            • This reuslts in it beocming a sickle cell shape, and less able to carry oxygen, resulting in anaemia and possible death.
        • chromosome
          • changes in structure or whole number of chromosomes.
          • usually occur in meosis during metaphase 1.
          • change structure
            • crossing over matches up genes in the wrong way
          • numbers
            • non-disjunction
              • chromsomes dont separate properly, so daughter cells receive unequal numbers.
              • e.g. downs syndrome
          • sets
            • increasing number of complete sets/ polyploidy
            • often found in plants and associated with beneficial characteristics.
            • usually results in infertility.
      • mutation rate
        • spontaneous events so small rate
        • organisms with shorter life cycles have a higher rate of mutation.
        • increased by mutagens
          • ionising radiation e.g. UV, gamma
          • polycyclic hydrocarbons in cigarette smoke
      • occur mainly in somatic cells.
      • only those which occur in germinal cells can be inherited.
      • Carcinogens
        • mutagens that increase chance of cancer;
        • usually effects proto-oncogenes or tumour-suppressor genes
      • Importance
        • somatic mutations can lead to cancer
        • mutations cause sudden and distinct differences basis of discontinuous variation.
        • most mutations are recessive so must await many generations before meeting another of its kind.

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