Inheritance

• Inheritance


  The transmission of genetic information from generation to generation
• Chromosomes


  • Located in the nucleus of cells
  • Thread-like structures of DNA, carrying genetic information in the form of genes
• Gene


  A short length of DNA found on a chromosome that codes for a specific protein
• Genes control our characteristics as they code for proteins that play important roles in what our cells do
• Alleles


  Different versions of a particular gene
• Alleles give all organisms their characteristics
• Sex chromosomes


  • Females have XX
  • Males have XY
• Determining the sex of a child

  1. Father produces sperm cells

  2. Half of sperm carry X chromosome

  3. Half of sperm carry Y chromosome

  4. If X chromosome fertilises egg, female

  5. If Y chromosome fertilises egg, male
• DNA base sequence


  Determines the amino acid sequence in protein
• Protein synthesis


  1. Transcription (rewriting DNA base code into RNA)

  2. Translation (using RNA base sequence to build amino acids into protein sequence)
• DNA unwinds


  1. DNA unwinds

  2. Gene is copied into mRNA

  3. mRNA moves out of nucleus into cytoplasm

  4. mRNA passes through ribosome

  5. Ribosome assembles amino acids into protein molecule
• Nucleus


  Where DNA is located
• Gene


  Sequence of DNA that codes for a protein
• mRNA


  Messenger RNA, carries the code from the nucleus to the ribosome
• Nuclear pore


  Allows mRNA to move out of the nucleus
• Cytoplasm


  Where ribosomes are located
• Ribosome


  Assembles amino acids into a protein molecule based on the mRNA code
• Amino acids


  Building blocks of proteins
• Protein molecule


  Final product assembled by the ribosome
• DNA cannot travel out of the nucleus to the ribosomes as it is far too big to pass through a nuclear pore
• The base code of each gene is transcribed onto an mRNA molecule
• The ribosome 'reads' the code on the mRNA in groups of three
• Each triplet of bases codes for a specific amino acid
• Once the amino acid chain has been assembled, it is released from the ribosome so it can fold and form the final structure of the protein
• Peptide bond


  Bonds that link amino acids together to form a protein
• Codon


  Triplet of bases on mRNA that codes for a specific amino acid
• tRNA


  Carries specific amino acids to the ribosome based on the codon
• DNA controls cell function by controlling the production of proteins
• Proteins may be enzymes, antibodies, or receptors for neurotransmitters
• Although all body cells in an organism contain the same genes, many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
• Gene expression


  Whether a gene is transcribed and translated in a particular cell
• Most genes are not expressed in a particular cell as that would be a waste of energy and other resources
• Only the genes whose proteins are vital to that cell's function are expressed
• Haploid cells


  Cells with one set of chromosomes
• Diploid cells


  Cells with two sets of chromosomes
• All humans have 23 different chromosomes in each cell
• In most body cells, not including the gametes (sex cells), we have 2 copies of each chromosome, leading to a total of 46 chromosomes
• Nuclei with two sets of chromosomes are known as diploid nuclei
• Diploid


  Cells with two copies of each chromosome
• Mitosis


  1. Chromosomes double

  2. Chromosomes line up in the centre of the cell

  3. Cell divides into two genetically identical daughter cells