science bio Y10

• DNA


  Found in the nucleus of cells and contains coded genetic information which determines the characteristics of all organisms
• Gene


  A section of DNA, on chromosomes, that contains information about the characteristics of an organism, it is the unit of inheritance
• Chromosome


  A Long strand of DNA tightly coiled many times around protein, it contains many genes and is located in the nucleus of cells
• Mitosis


  A type of cell division producing daughter cells with the same number and type of chromosomes as the parent cells
• Meiosis


  A type of cell division producing daughter cells with half the number of chromosomes as the parent cells
• Mutation


  A change in genetic information
• Replication


  The process of creating an identical copy of DNA
• Punnett square


  A diagram used to predict an outcome of a particular cross or breeding experiment
• Pedigrees


  A method of describing how characteristics are inherited over several generations, using a set of standard symbols
• Inherited


  A distinguishing characteristic or quality
• Offspring


  An organism resulting from reproduction
• Phenotype


  Describes the characteristics which can be observed due to the expression of dominant or recessive genotype
• Genotype


  Describes genetic makeup of an organism (BB, Bb, bb)
• Allele


  Different forms of the same gene
• Homozygous


  When a particular gene has identical allele on both homologous chromosomes (BB, bb)
• Heterozygous


  When a particular gene has different alleles on both homologous chromosomes (Bb)
• Dominant allele


  A variation of a gene that will always express a certain phenotype, even in the presence of other alleles
• Recessive allele


  A variation of a gene that will only be expressed if both recessive alleles are present
• James Watson and Francis Crick: 'Credited with the discovery of the double helix structure of DNA'
• DNA


  • Made up of smaller molecules called nucleotides, these being: Phosphate group, Deoxyribose sugar and Nitrogen bases (one out of four)
  • Double-stranded molecule twisted into a helix shape, with each strand being made up of a sugar-phosphate backbone and attached paired bases
  • The four nitrogen bases are: Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)
• Chromosomes


  A long strand of DNA coiled tightly many times around protein
• Genes


  Sections of DNA
• Parts of the male reproductive system


  • Testes
  • Scrotum
  • Epididymis
  • Sperm duct (vas deferens)
  • Seminal vesicles
  • Urethra
  • Penis
  • Prostate Gland
  • Bladder
• Parts of the female reproductive system


  • Uterus
  • Ovaries
  • Fallopian tube
  • Urethra
  • Vagine

  
• Mitosis


  1. Chromosomes condense and become visible

  2. Chromosomes double but are attached at centromere, nuclear membrane begins to disintegrate

  3. Doubled chromosomes line up along 'equator', centromeres attached to spindle fibres

  4. Doubled chromosomes separate, move to opposite ends of cell

  5. Membranes form to produce 2 daughter cells, identical to parent cell
• Meiosis


  1. 2 pairs of chromosomes visible

  2. Chromosomes double but are attached at centromere, nuclear membrane begins to disintegrate

  3. Homologous chromosomes line up along 'equator', centromeres attached to spindle fibres

  4. Homologous chromosomes separate, one of each pair moves to opposite end

  5. Membranes form to produce 2 cells with same number of chromatids as parent

  6. Chromosomes in both cells line up along 'equator'

  7. Chromosomes separate, move to opposite ends

  8. Membranes form to produce 4 daughter cells
• Pedigree symbols


  • Female without the trait
  • Female with the trait
  • Male without the trait
  • Male with the trait
  • Showing children of the couples
  • Showing marriages
• DNA replication


  1. DNA unwinds from double helix to ladder shape

  2. Enzyme helicase breaks hydrogen bonds between base pairs, splitting DNA into 2 strands

  3. Free floating nucleotides bind with complementary base pairings

  4. Enzyme polymerase binds newly synthesised DNA

  5. DNA replication complete, DNA winds back up into double helix
• Mutations are caused by alterations to single base units or rearrangement of large sections of genes
• Types of single gene mutations


  • Substitution - changes 1 nucleotide into another
  • Insertion - adds 1 nucleotide
  • Deletion - deletes 1 nucleotide
• Types of chromosome structure mutations


  • Duplications - a section of genes is copied and inserted
  • Inversion - a section of genes is inverted
• Stages of mitosis


  1. Prophase: Chromosomes condense (become visible), Nuclear membrane dissolves

  2. Metaphase: Chromosomes align along 'equator' of cell, Chromosomes double

  3. Anaphase: Chromosomes are pulled apart to opposite ends of the cell as the spindle fibers elongate

  4. Telophase: Spindle fibers break down, 2 new nuclei are formed (one for each set of chromosomes), Nuclear membrane and nucleoli reappear