inheritance, variation and evolution

    Cards (112)

    • Meiosis
      The formation of four non-identical cells from one cell
    • Mitosis
      The formation of two identical cells from one cell
    • Sexual reproduction
      Joining of male and female gametes, each containing genetic information from the mother or father
    • Gametes
      • Sperm and egg cells in animals
      • Pollen and egg cells in flowering plants
    • Gametes are formed by meiosis, as they are non identical
    • A normal cell has 46 chromosomes, in 23 pairs, one from each parent
    • Each gamete has 23 chromosomes and they fuse in fertilisation
    • The genetic information from each parent is mixed, producing variation in the offspring
    • Asexual reproduction
      One parent with no gametes joining, using mitosis to form two identical cells
    • Asexual reproduction leads to clones, which are genetically identical to each other and the parent
    • Organisms that reproduce asexually
      • Bacteria
      • Some plants
      • Some animals
    • Meiosis
      Cell makes copies of chromosomes, divides into two cells with half the chromosomes, then divides again to form four genetically different gametes
    • Gametes with 23 chromosomes join at fertilisation to produce a cell with 46 chromosomes
    • The cell divides by mitosis to produce many copies, forming an embryo which then undergoes differentiation
    • Advantages of sexual reproduction
      • Produces variation in offspring
      • Allows selective breeding
    • Advantages of asexual reproduction
      • Only one parent needed
      • Uses less energy and is faster
    • Organisms using both sexual and asexual reproduction
      • Malarial parasites
      • Some fungi
      • Some plants
    • DNA
      The genetic material in the nucleus of a cell, a polymer made up of two strands in a double helix structure
    • Gene
      A small section of DNA on a chromosome that codes for a specific protein
    • Genome
      All the genes coding for all of the proteins within an organism
    • The whole human genome has now been studied, improving understanding of genes linked to disease and human migration
    • Nucleotide
      A small part of DNA, made up of a sugar, phosphate and one of four organic bases
    • A and T bases, and C and G bases, form complementary base pairs in the DNA double helix
    • Protein synthesis
      DNA in nucleus transcribed to mRNA, mRNA transported to ribosomes, amino acids brought to ribosomes and joined to form protein
    • Mutation
      A change in the sequence of bases in DNA, can be an insertion, deletion or substitution
    • Most mutations do not alter the protein or only do so slightly, but some can have a serious effect on the protein structure and function
    • Gamete
      An organism's reproductive cell, with half the normal number of chromosomes
    • Chromosome
      A structure in the nucleus made up of a long strand of DNA
    • Gene
      A short section of DNA that codes for a protein, contributing to a characteristic
    • Allele
      The different forms of a gene, humans have two alleles for each gene
    • Dominant allele

      Only one is needed to be expressed and observed
    • Recessive allele
      Two copies are needed to be expressed and observed
    • Homozygous
      Both inherited alleles are the same
    • Heterozygous
      One inherited allele is dominant, the other is recessive
    • Genotype
      The combination of alleles an individual has
    • Phenotype
      The physical characteristics that are observed in the individual
    • Homozygous
      When both inherited alleles are the same (i.e. two dominant alleles or two recessive alleles)
    • Heterozygous
      When one of the inherited alleles is dominant and the other is recessive
    • Genotype
      The combination of alleles an individual has, e.g. Aa
    • Phenotype
      The physical characteristics that are observed in the individual, e.g. eye colour
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