Biology: Protein synthesis & haploid and diploid cells

• Chromosome


  Made up of DNA which contains genetic information in the form of genes
• Gene


  A length of DNA that codes for a protein
• Allele


  An alternative form of a gene
• For example, a gene could be your hair and the allele will be the different hair colours you might express
• Sex determination in relation to XX and XY chromosomes


  • Sex in humans is determined by the presence or absence of the Y chromosome
  • Females contribute an X chromosome (XX)
  • Males contribute either an X or Y chromosome (XY)
  • If sperm carrying an X chromosome fertilises an egg, the embryo will develop into a female
  • If sperm carrying a Y chromosome fertilises the egg, the embryo will develop into a male
• DNA base sequence to amino acid sequence

  1. Transcription (rewriting the base code of DNA into bases of RNA)

  2. Translation (using RNA base sequence to build amino acids into sequence in a protein)
• The sequence of bases in a gene determines the sequence of amino acids that make a specific protein
• Different sequences of amino acids give different functions and shape of protein molecules
• Protein synthesis


  1. DNA code is transcribed onto mRNA

  2. mRNA moves out of nucleus and attaches to ribosome

  3. Ribosome reads mRNA code and assembles amino acid chain

  4. Amino acid chain is released from ribosome to fold into final protein structure
• Gene expression


  Whether or not a gene is transcribed and translated in a particular cell
• DNA controls cell function by controlling the production of proteins such as enzymes, antibodies or receptors
• Although all body cells contain the same genes, many genes aren't expressed as the cell only makes the specific proteins it needs
• Haploid


  Nuclei with one unpaired set of chromosomes
• Diploid


  Nuclei with 2 sets of chromosomes
• Humans have 23 different chromosomes in each cell, with 2 copies in most body cells (46 total)
• Gametes have only one copy of each chromosome (23 chromosomes)