topic 6- inheritance, variation and evolution

• DNA


  The chemical that all of the genetic material in a cell is made up from
• DNA


  • It contains coded information-basically all the instructions to put an organism together and make it work
  • It determines what inherited characteristics you have
• Chromosomes


  Really long molecules of DNA found in the nucleus of animal and plant cells
• Gene


  A small section of DNA found on a chromosome that codes for a particular sequence of amino acids which are put together to make a specific protein
• Genome

  The entire set of genetic material in an organism
• Genome


  • Understanding the human genome is an important tool for science and medicine to identify genes linked to different types of inherited diseases
  • Knowing which genes are linked to inherited diseases could help us understand them better and develop effective treatments
• Nucleotides

  The repeating units that DNA strands are made up of, consisting of a sugar, phosphate group and one base
• Protein synthesis

  1. DNA code transcribed into mRNA

  2. mRNA carries code to ribosomes

  3. Ribosomes assemble amino acids into proteins
• Proteins


  • They have many different functions such as enzymes, hormones, and structural proteins
• Mutation


  A random change in an organism's DNA
• Types of mutation

  • Insertions
  • Deletions
  • Substitutions
• Sexual reproduction

  Genetic information from two organisms is combined to produce genetically different offspring
• Asexual reproduction


  There is only one parent, so the offspring are genetically identical to that parent
• Meiosis


  Cell division that produces gametes with half the normal number of chromosomes
• Variation in offspring from sexual reproduction

  Increases the chance of a species surviving changes in the environment
• Selective breeding


  Allows us to produce organisms with desirable characteristics
• Examples of organisms that can reproduce both sexually and asexually

  • Malaria parasite
  • Many fungus species
  • Many plant species
• X and Y chromosomes

  The 23rd pair of chromosomes that determine biological sex
• At various points along the runner, a strawberry plant forms that is identical to the original plant
• New bulbs can form from the main bulb and grow off. Each new bulb can grow into a new identical plant
• Both sexual and asexual reproduction have their own different advantages
• There are 23 pairs of chromosomes in every human body cell
• Of the 23 pairs of chromosomes, 22 are autosomes and the 23rd pair are the sex chromosomes labelled XY or XX
• 1. chromosome


  Allows female characteristics to develop
• 1. chromosome


  Causes male characteristics
• Meiosis (sperm formation)


  X and Y chromosomes are divided apart in the first division
• There's a 50% chance each sperm cell gets an X-chromosome and a 50% chance it gets a Y-chromosome
• Eggs all have the X-chromosome
• Genetic diagrams


  • Models used to show all the possible genetic outcomes when crossing different genes or chromosomes
  • Put the possible gametes from one parent down the side, and those from the other parent along the top
  • Fill in the middle squares with the combinations of the gametes
• Genetic diagrams show a 50:50 probability of getting a boy or girl
• Some characteristics are controlled by single genes, but most are controlled by several genes interacting
• Alleles


  Different versions of a gene
• Homozygous


  Having two alleles for a particular gene that are the same
• Heterozygous


  Having two alleles for a particular gene that are different
• Dominant allele


  The allele for a characteristic that is shown, represented by a capital letter
• Recessive allele


  The allele that is not shown when the organism is heterozygous, represented by a lowercase letter
• Genotype


  The combination of alleles an organism has
• Phenotype


  The characteristics an organism displays
• A homozygous dominant organism (BB) crossed with a homozygous recessive organism (bb) will produce all normal offspring (Bb)
• A heterozygous organism (Hh) crossed with a homozygous recessive organism (hh) will produce a 1:1 ratio of long hair to short hair offspring