Inheritance

• dominant


  An allele that is always expressed, even if only one copy is present
• cystic fibrosis

  A disorder of cell membranes that is caused by a recessive allele
• asexual reproduction


  The production of offspring from a single parent by mitosis. The offspring are clones of the parent
• gamete


  Sperm cell and egg cell in animals; pollen and egg cell in plants
• genome


  The entire genetic material of an organism
• meiosis

  The two-stage process of cell division that reduces the chromosome number of the daughter cells. It makes gametes for sexual reproduction
• Females carry two X chromosomes
• phenotype


  The characteristic expressed because of the combination of alleles
• recessive


  An allele that is only expressed if two copies of it are present
• heterozygous


  A genotype that has two different alleles, one dominant and one recessive
• The recessive phenotype has a ratio of 1:3 because only one combination will show the phenotype while the other three will not
• There are four possible combinations of gametes that offspring can inherit
• Meiosis produces four daughter cells, which are not genetically identical. The cell divides twice and the chromosome number is reduced by half (23 chromosomes in humans). It produces gametes for sexual reproduction
• chromosome


  Structures that contain the DNA of an organism and are found in the nucleus
• homozygous


  A genotype that has two of the same alleles. Either two dominant alleles or two recessive alleles
• genotype


  The combination of alleles
• mutation


  A change in DNA
• fertilisation


  The fusion of male and female gametes
• DNA


  A polymer that is made up of two strands that form a double helix
• Mitosis produces two daughter cells, which are genetically identical. The cell divides once and the chromosome number of the daughter cells is the same as the parent cells (46 chromosomes in humans). It is used for growth and repair, and asexual reproduction
• allele


  An alternative form of a gene
• gene


  A small section of DNA that codes for a specific protein
• One of these four combinations has the genotype aa – that’s ¼, 25% or 0.25
• polydactyly


  Having extra fingers or toes. It is caused by a dominant allele
• sexual reproduction


  The production of offspring by combining genetic information from the gametes of two parents. Leads to variation in the offspring
• Males carry one X and one Y chromosome
• Chromosome


  A thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes
• DNA

  Deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes
• Variation may be due to differences in genes that have been inherited (genetic causes), the conditions in which they have developed (environmental causes), or a combination of genes and the environment
• Alleles

  • XX
  • XY
  • X
  • Y
  • A
  • a
  • AA
  • Aa
  • aa
• Linnaeus classified living things into kingdom, phylum, class, order, family, genus, and species. Organisms are named by the binomial system of genus and species
• Fossils help us understand how much or little organisms have changed as life developed on earth
• Keywords related to Inheritance, Variation, and Evolution

  • embryo screening
  • evolution
  • evolutionary tree
  • extinction
  • fossils
  • genetic engineering
  • natural selection
  • selective breeding
  • speciation
  • variation
• Nucleus


  The central and most important part of an object, movement, or group, forming the basis for its activity and growth
• Gene


  A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring
• Inheritance

  1. Step 3: Put the alleles from the first parent into the two boxes underneath them

  2. Step 4: Put the alleles from the second parent into the two boxes to the right of them
• To reduce the rate at which antibiotic-resistant strains appear: Antibiotics should only be used when they are really needed, patients should complete their courses of antibiotics, even if they start to feel better, and the agricultural use of antibiotics should be restricted
• All species of living things have evolved from simple life forms by natural selection
• Genetic Engineering

  1. The plasmid is isolated from the cell

  2. The DNA is isolated from the nucleus

  3. Bacteria multiplies many times

  4. The plasmid (vector) is used to insert the gene into the required cell

  5. The plasmid is cut by enzymes. The gene is inserted into the plasmid

  6. The gene that is needed is cut from the DNA by enzymes
• Variation in bacterial population

  • One bacterium develops a mutation by chance that means it is resistant to an antibiotic
  • The antibiotic kills some of the bacteria, the resistant bacterium survives and reproduces
  • The antibiotic kills the rest of the non-resistant bacteria so the person may start to feel a little better. The resistant bacterium has survived the antibiotic and continues to multiply