Inheritance, variation and evolution

Cards (84)

  • Alleles
    A different version of the same gene
  • Mutation
    A change in the DNA sequence
  • Gamete
    Sex cell (sperm or egg)have 1/2 number of chromosomes as they need to make correct number when they fuse together
  • Chromatids
    One of the two strands that make up a single chromosome when it is preparing to divide
  • Phenotype
    The physical characteristics of an organism. Described by words (brown eyed)
  • Genotype
    The genetic content of an organism, describing the alleles an organism has. Represented by letters (Bb)
  • Homologous
    A pair of chromosomes that contain the same genes in the same locations, their alleles may differ
  • Haploid
    The number of chromosomes contained in a gamete is referred to as this
  • Diploid
    The number of chromosomes contained in all somatic (body) cells are referred to ad this
  • Heterozygous
    When 2 different alleles are present for a gene in the genotype (Bb)
  • Homozygous
    When the 2 alleles for a gene are the same in the genotype (BB)if both chromosomes in a pair contain the same allele of a gene, the individual is homozygous for that gene
  • Dominant allele (capital letter)

    Always expressed even if only 1 copy is present (brown eyes allele = B, Bb or BB)
  • Recessive allele (lowercase letter)

    2 copies needed for it to be expressed in the phenotype (blur eyes = bb, phenotype)
  • Clone
    An organism that is genetically identical to its parent
  • At fertilisation ..
    Gametes join to form a single body cell with new pairs of chromosomes. This cell repeatedly divides by meiosis to form many cells.
  • Genetic variation examples
    Eye colourHair colourBlood group
  • Environmental variation examples
    Height Weight Teeth condition
  • Polydactyl
    Genetic disorder - Having extra fingers or toes DOMINANT ALLELEcan be passed on by only one parent who has the disorder
  • Cystic fibrosis
    Genetic disorder - disorder of cell membranes, causes production of sticky mucus - can affect several organs; lungs, pancreasRECESSIVE ALLELEcan be passed on by parents who may be carriers, and not actually have the disorder themselves
  • Sickle cell anemia
    Genetic disorder - affects red blood cells, affects shape of RBC, which cannot carry O2 efficiently + may block small blood vessels->painRECESSIVE ALLELE
  • Downs syndrome
    Extra chromosome
  • Embryo screening
    -DNA isolated from embryo cells -gene probe that will bind onto the gene for a specific disorder is produced -probe usually has fluorescent chemical attached to it -probe added to mixture containing DNA sample from embryo-UV light used to detect probe attached to gene for the disorder
  • How DNA controls you?
    -genes made from DNA-code for proteins-proteins such as enzymes control reactions in body/characteristics
  • asexual reproduction:

    cloningone parentno variation - genetically identical
  • sexual reproduction:
    2 parentsvariety in offspring because inherit mix of genes from each parent
  • causes of variation?
    - mutation of genes/DNA- inheriting features- environmental effects
  • 4 methods of cloning:
    1- cuttings2- tissue culture3- embryo cloning4- adult cell cloning
  • cuttings:
    plantsDNA comes from adult plantcut piece of plant offsometimes use hormones and nutrient mixes
  • tissue culture:
    plantsDNA comes from adult plantuse a cell scraped from a planthormone solutions, nutrients required
  • embryo cloning:
    animalsDNA comes from embryopull apart embryo into separate cells before they become specialised - these grow into clonesneed surrogate mothers
  • adult cell cloning:
    animalsDNA comes from adult animalfuse nucleus from one animal with empty egg - clones nucleus donorneed surrogate mothers
  • genetic engineering?

    changing DNA of an organism
  • Cloning?
    making a genetically identical organism
  • For questions on genetic engineering remember...
    plasmids are only used to transfer DNA to microorganisms (bacteria)if youre trying to engineer an animal/plant, you insert DNA directly into them when theyre still an embryo
  • For ethics questions on gene technology, cover the following:
    -benefits-economics/costs-effects on environment-religious opposition-morality/ethics-health and safety
  • difference in the characteristics of individuals of the same kind may arise due to differences in:
    - genes they've inherited (genetic causes)- condition in which they have developed (environmental causes)- a combination of the above
  • Size order or gene, nucleus and chromosome?
    nucleus containschromosomes carry genes
  • genetic diagrams:
    biological models used to predict outcome of crossesGreger Mendel was the first to suggest separately inherited factors which we now call genes
  • chromosome made up of ...
    large molecules of DNA (deoxyribonucleic acid)
  • DNA contains?
    coded information that determines inherited characteristics