Variation and inheritence

• Meiosis


  The process by which gametes (sex cells) are made, involving the division of a diploid cell to produce four haploid cells
• Meiosis


  1. Chromosomes are copied

  2. Similar chromosomes pair up

  3. Genes are swapped between them

  4. Cell divides to make two diploid cells

  5. Cells divide again to make four haploid cells
• Variation in offspring


  Occurs through the process of meiosis and fusion of gametes
• Asexual reproduction


  Daughter cells are genetically identical to the parent, a clone is made
• Advantages of sexual reproduction

  • Variation occurs which can result in organisms becoming better suited to their environment
  • More likely to survive
• Advantages of asexual reproduction

  • Only one parent is needed
• Genome


  The term given to all the genetic material in an organism
• DNA


  A two-stranded polymer in a double helix shape that stores the genetic code
• Gene


  A section of DNA that codes for a specific protein
• The Human Genome Project completed its initial goal in 2003 when scientists mapped out what every gene is responsible for coding
• Genotype


  The code stored in your DNA specifically
• Phenotype


  How the genotype is expressed in your characteristics and physiology
• Nucleotides


  The monomers between the two strands of DNA, made from a sugar and phosphate group
• There are four types of nucleotides: A, T, C, and G
• A and T always match to each other in the DNA sequence, as do C and G
• Protein synthesis


  1. Three nucleotides (a codon) code for an amino acid

  2. mRNA copies the DNA sequence

  3. mRNA is taken to a ribosome

  4. Amino acids are connected in the order needed to make a protein

  5. Protein is folded into its final shape
• Mutation


  A change in a gene that can result in a protein being synthesized that doesn't do the job it's supposed to
• Epigenetics


  DNA that doesn't directly code for proteins but influences how other genes are expressed
• Alleles


  Different types of the same gene
• Dominant allele


  An allele that results in a characteristic being expressed even if there is another (recessive) allele present
• Recessive allele


  An allele that is only expressed when there is no dominant allele present
• Homozygous


  Having only one type of allele
• Heterozygous


  Having two different types of alleles
• Punnett square


  Used to predict the probability of a certain phenotype
• Sex chromosomes


  XX = female, XY = male
• The expression of sex genes affects every cell in the body
• Charles Darwin's theory of evolution

  • Random variation in offspring will result in some being better suited to their environment
  • Those better suited are more likely to survive and reproduce
• Lamarck's theory of evolution

  Adaptation of variation is guided by DNA in response to a changing environment
• Bacterial resistance to antibiotics is evidence of evolution
• Species


  Organisms that can produce fertile offspring are considered the same species
• Selective breeding


  • Breeding dogs to produce desired characteristics like Labradors, Collies, and Pugs
• Genetic engineering


  1. A gene is cut from an organism using enzymes

  2. The gene is inserted into a vector like a bacteria plasmid or virus

  3. The vector inserts the gene into another organism, usually in the early stage of development
• Fossils


  The remains of organisms that died a very long time ago, where minerals have replaced the organic material
• Cloning


  Making exact copies of plants by taking cuttings or cloning from a tissue culture

  Cloning animals by taking the nucleus from a cell and inserting it into an egg cell
• Classification


  The system of categorizing organisms into Kingdom, Phylum, Class, Order, Family, Genus, and Species
• Domains


  The three domains of life: Archaea, Bacteria, and Eukarya
• Archaea are often found in extreme environments and are called extremophiles