B5

• Phenotype

  • observable characteristics
• 1. Genome- entire genetic material
  2. Genetic material is stored in nucleus and arranged into chromosomes
  3. Each chromosome have one very long molecule of DNA
  4. A gene is a short length of a chromosome
  5. Genes determine production of protein
• Genes

  • Allele
  • Variants
• genotype

  • ask of the genes and alleles that an organism has
  • affects phenotype- characteristics displayed
• Characteristics

  • influenced by genes and environmental factors
• Continuous variation

  • individuals In a population vary within range
  • No distinct categories
• Discontinuous variation

  • two or more distinct categories
• Mutation

  • change to the genome- random change in organisms DNA it inherited
  • Sequence of DNA bases in the gene changed- genetic variant
  • leads to changed in the protein that it codes for
  • Most genetic variations have little/no effect on the protein the gene codes for
  • Some can alter proteins function
  • most mutations have no effect on phenotype
  • Influence organisms phenotype
• Cystic fibrosis- gene mutation

  • cystic fibrosis- caused by deletion of three bases, huge effect on phenotype
  • protein controls movement of salts and water into and out of cells
  • Protein produced by mutated gene doesn't function properly
  • excess mucus production in the lungs and digestive system
  • difficult to breathe and digest food
• Non-coding DNA

  • sequences of bases that don't code for proteins
• Mutations and Coding and Non coding DNA

  • occur in both
  • Mutation in coding DNA effects the protein produced and the way it is structured and functions
  • non-coding DNA- affect how genes are expressed, stop transpiration of mRNA so protein is not produced at all
• Sexual production

  • Genetic information from two organisms and combined to produce offspring which are genetically different
  • Gametes- egg and sperm
  • Gametes only contain half the chromosomes- haploids
  • Fertilised egg is a diploid
  • Fertilised egg undergoes cell division and develops into an embryo
  • Embryo inherits from both parents
• Haploid

  • contain only half of the chromosomes
• Diploid

  • contains full number of chromosomes
• Meiosis - Division 1


  only happens in reproductive organs

  Divison 1

  1. Duplicates its DNA one arm of each X-shaped chromosome is an exact copy of the other arm
  2. Chromosomes line up in pairs in the centre
  3. Pairs pulled apart so each new cell contains one copy of each chromosome
  4. Each new cell has a mixture of mothers and fathers chromosomes= genetic variation
• Meiosis Division 2

  1. Chromosomes line up again in the centre
  2. Arms of chromosomes are pulled apart
  3. Four haploid gametes- single set of chromosomes
  4. Gametes are genetically different
• Asexual reproduction

  • Only one parent
  • genetically identical offspring
  • Happens by mitosis
  • Clone
  • Bacteria, some animals and planets
• Advantages of asexual reproduction

  • produce offspring quickly
  • only one parent is needed
  • Produce in any conditions
• Disadvantages of asexual reproduction

  • no genetic variation
  • environmental changed and unfavourable decisions- whole population can die
• Advantages of sexual reproduction

  • genetic variation
  • individuals don't have the same characteristics so changing conditions won't kill them all off
  • Over time it leads to evolution as species become better adapted
• Disadvantages of sexual production

  • takes more time and energy- produces fewer offspring
  • need to attract mate
  • Town parents needed - be problem if individuals are isolated
• Alleles 


  Dominant allele- version of characteristics that appears

  Recessive allele

  If both alleles are recessive= recessive
• Homozygous

  • two alleles the same
• Heterozygous

  • two different alleles
• Chromosomes control male or female

  • 23 pairs pf chromosomes
  • Male- XY Y- male characteristics
  • Female- XX lack of Y causes female characteristics
• Gregor mendel

  • characteristics in plants passed onto next generation
  • Tall pea plant with dwarf plant
• Classification

  Artificial-

  > Observable features

  > Still used but not best way to clarify

  Natural-

  > evolutionary relationships

  > uses information about common ancestors

  > Divided into 5 kingdoms

  > Kingdom is divided into smaller groups - phylum, class, order, family, genus, species

  > hierarchy ends with species

  Species- contain one type of organism able to reproduce
• How did technology help improve classification

  DNA sequencing- molecular phylogenetic

  > compares the sequence of DINA bases for different species, the more similar the more closely related
• Natural selection

  1. Variants arrive if DNA randomly mutates
  2. Individuals compete to survive
  3. Some genetic variants have better suit characteristics to a particular environment
  4. Providing an advantageous phenotype allowing them to breed and pass on their genes
  5. greater of next generation inherits advantageous variants
• Evolution 


  Change in inherited characteristics of a population over time, through the process of natural selection

  1. speed depends on efficiency to reproduce
  2. quicker reproduction- quicker adaption to environment due to inherited genes being passed down quicker
  3. phenotype changes to the point it creates a new species
  4. side happens when physical barrier separates species
• Evidence for evolution- fossils

  • found in rocks
  • the deeper the rock, the older the fossil
  • Identifies what it looked like and how long ago
  • arranging fossils in chronological order, gradual changed in organism is observed
• Evidence for evolution- Antibiotic- Resistant

  • Bacteria develop random mutations
  • introduces new variants
  • Changes in bacteria's phenotype
  • Emergence of antibiotic resistant bacteria provides evidence for evolution
• Darwins theory of evolution

  • 5 year voyage
  • variations in members of the same species
  • characteristics passed on
• The origin of species
• Seedbanks


  > protects biodiversity

  1. Store lots of seeds from lots of different species
  2. conserve biodiversity
  3. Extinct plants seeds can be used to grow new plants
  4. seedbanks conserve genetic variation