Genetics

• What is sexual reproduction?

  A type of reproduction that involves the gametes from each parents to fuse to form a zygote
• What are gametes?


  Sex cells (haploid)
• What is meiosis?


  Cell division involved in the formation of gametes

  chromosome number is halved

  involves two divisions
• What must occur prior to meiosis?


  Interphase
• First stage of meiosis

  • Chromosome pairs line up along the cell equator
  • pair of chromosomes are separated and move to the opposite poles of the cell
  • Chromosome number is halved
• Second stage of meiosis

  • Chromosomes line up along the cell equator
  • Chromatids are separated and moved to the opposite poles of cell
  • Four unique haploid gametes are produced
• Why is meiosis important for sexual reproduction?


  Increases genetic variation

  Ensures that the resultant zygote is diploid
• What is DNA?


  A double stranded polymer of nucleotide, wound to form double helix
• Monomers of DNA


  Nucleotide
• What are DNA nucleotides made up of?


  Common sugar

  Phosphate group

  one of the four bases, A,T,C or G
• Full name of the four bases found in nucleotides

  Adenine

  Thymine

  Cytosine

  Guanine
• How do nucleotides interact to form a molecule of DNA


  Sugar and phosphate molecules join to form a sugar phosphate back bone in each DNA strand

  Base connected to each sugar

  Complementary base pairs (A+T and G+C) joined by weak hydrogen bonds
• Define genome


  Entire genetic material of an organism
• Chromosome


  A long, coiled molecule of DNA that carries genetic information in the form of genes
• Define gene


  A section of DNA that codes specific sequence of amino acids which undergo polymerisation to form a protein
• The method used to extract DNA from a fruit

  1. place fruit in beaker, crush it
  2. add detergent and salt,mix it
  3. filter mixture, collect liquids in a test tube
  4. Pour chilled ethanol into the test tube
  5. DNA precipitates forming a fibrous white solid
  6. Use a glass rod to collect DNA sample
• Why is detergent added to crushed fruit?


  Disrupts cell membrane, releasing DNA into the solution
• Why is salt added to the crushed fruit?


  Salt encourages the precipitation of DNA
• Why is chilled ethanol added rather than water?


  DNA is insoluble in ethanol
• What are alleles?


  Different versions of same gene
• Genotype


  An organisms genetic composition
• Phenotype


  An organisms observable characteristics due to the interactions of the genotype and environment
• Define homozyguous


  Having two identical alleles of a gene e.g. FF
• Define heterozygous


  Having two different alleles of a gene e.g. Ff
• Dominant allele


  An allele that is always expressed

  represented as a capital letter
• Recessive allele


  An allele that is only expressed in the absence of a dominant allele
• What is a monohybrid inheritance?

  Inheritance of a single gene
• problem with single gene crosses


  Most characteristics are controlled by most alleles rather than one
• What are sex chromosomes?


  A pair of chromosomes that determine gender

  Males have X and Y chromosome

  Females have two X chromosomes
• Two causes of variation within species

  Genetics

  Environment
• What is genetic variation?


  Variation in the genotypes of organisms of the same species due to the presence of different alleles
• What creates genetic variation in a species?

  Spontaneous mutations

  sexual reproduction
• What is mutation?


  a change to the base sequence in DNA which results in genetic variants
• Three types of gene mutation


  Insertion

  Deletion

  Substitution