biology

• somatic -> mitosis -> diploid
• germline -> mitosis -> diploid

  germline -> meiosis -> haploid
• germline = sex cells and stem cells dividing to form gametes
• somatic cells = everything EXCEPT sex cells
• diploid sets have 23 pairs of homologous chromosomes
• haploid cells have 23 chromosomes
• fertilisation is the fusion of the nuclei of two gametes to form a diploid zygote
• cellular differentiation is when a cell develops more specialised functions by expressing genes producing proteins characterised by that cell type
• stem cell uses:

  • repair diseased or damaged organs (corneal repair)
  • grow skin grafts for burn victims
  • repair spinal cords (reverse paralysis)
• embryonic cells self renew, under right conditions in lab, provides culture cells for model cells to research how diseases develop and for drug testing
• use of embryonic cells controversial = destruction of human life, ethical issues
• cancer cells divide excessively, fail to respond to normal regulatory signals = produce mass of abnormal cells (tumour)
• cancer cells fail to attach to each other, spread around body = secondary tumour
• the cytoplasm is the site of fermentation
• tissue cells in bone marrow can differentiate into blood cells (red blood cells, platelets, different types of phagocytes and lymphocytes)
• Describe what is meant by differentiation?

  when different genes are turned on and off/expressed to allow the cell to function in a certain way
• DNA is a double-helix consisting of repeating units of DNA nucleotides
• The 2 DNA strands in the double helix are anti-parallel.
• There is a Deoxyribose sugar at the 3’ end and a Phosphate group at the 5’ end.
• The DNA nucleotides in a strand of DNA are joined together by strong chemical bonds between the phosphate group of one nucleotide and the deoxyribose sugar of another nucleotide. This creates a sugar-phosphate backbone.
• There is complementary base pairing between the 2 strands in the double helix.
• There are 2 weak Hydrogen bonds between Adenine and Thymine
• There are 3 weak hydrogen bonds between Cytosine and Guanine.
• DNA is the molecule that holds the instructions for growth and development in every living thing. Its structure is described as a double-stranded helix held together by complementary base pairs.
• Each PCR cycle DOUBLES the amount of DNA present
• Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.
• TRANSLATION:

  tRNA is involved in the translation of mRNA into a Polypeptide at a Ribosome.
• Translation begins at a START CODON and ends at a STOP CODON.
• TRANSLATION:

  Anticodons bond to Codons by complimentary base pairing, translating the genetic code into a sequence of Amino Acids.
• TRANSLATION:

  Peptide Bonds join the amino acids together.
• TRANSLATION:

  Each tRNA then leaves the Ribosome as the Polypeptide is formed.
• Proteins have a large variety of shapes which determines their functions.
• Cellular Differentiation is the process by which a cell expresses certain genes to produce PROTEINS characteristic for that type of cell. This allows a cell to carry out specialised functions.
• Therapeutic uses of stem cells involve the repair of damaged or diseased organs or tissues
• Research uses of stem cells involves them being used as model cells to study how diseases develop or being used for drug testing.
• Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work
• Use of EMBRYONIC stem cells can offer effective treatments for disease and injury, however, it involves destruction of embryos and therefore the destruction of a potential life.
• Other sequences that do not code for protein can either:

  • regulate transcription
  • transcribed but never translated. E.g tRNA and rRNA are non-translated forms of RNA.
• the Genome contains DNA sequences that regulate transcription AND sequences that are transcribed to RNA but never translated (tRNA and rRNA) AND sequences from which primary transcripts are produced ( GENES).
• Mutations are changes in the DNA that can result in no protein or an altered protein being synthesised.