4. Basics of genetics.pdf

Basics of genetics Aarni Auerniitty  DNA  In eukaryotic cells most of the DNA is inside the nucleus  Some located in mitochondria and chloroplasts  Section of DNA = gene  DNA is coiled around histone-proteins packing it tightly  Tightly packed DNA forms chromosomes  Due...

Basics of genetics Aarni Auerniitty  DNA  In eukaryotic cells most of the DNA is inside the nucleus  Some located in mitochondria and chloroplasts  Section of DNA = gene  DNA is coiled around histone-proteins packing it tightly  Tightly packed DNA forms chromosomes  Due to efficient packing there is a couple meters of DNA inside every nucleus  Humans have 46 chromosomes (23 with two copies each) DNA  The main body of the strands is formed from phosphates and sugar  Base pairs connect to each other with strong hydrogen bonds  complementary base pairs  Adenine (A) – Thymine (T)  Cytosine (C) – Guanine (G)  The order of bases  content of genes  Most important features of DNA 1. It includes information 2. It can replicate 3. The information in DNA can change Mutation  Mutations can happen to single genes, chromosomes and the entire genome  In gene mutations new alleles (new variant of a gene) are formed as the order of bases changes  Mutations occur by random chance during cell division or they can be caused by external factors like radiation, heavy metals or other toxic compounds Genes and proteins  Humans have approx. 20 000 genes  For organism to function it requires at least 500 genes  Human gene length is usually around 27 000 bases  Proteins are built according to the instructions in the genes  Proteins are formed from chains of amino acids (20 different ones)  Protein synthesis occurs on ribosomes Protein synthesis 1. In the nucleus the double helix structure of DNA is opened 2. Messenger RNA (mRNA) is assembled using one strand of DNA as template (gene)  Thymine is replaced with uracil 3. mRNA moves to the cytoplasm through pores in the nuclear envelope 4. mRNA attaches to a ribosome (free or on ER) 5. Transfer RNA (tRNA) move amino acids to the ribosome according to the instructions of mRNA  chain of amino acids 6. When the amino acid chain is ready it is separated from the ribosome and finalized in Golgi apparatus Enzymes  Proteins that make metabolic reactions faster or enable them  Enzymes catalyse reactions  Enzymes break down or build molecules  Temperature, pH and substrate concentration affect enzyme function  Inhibitors prevent enzymes from functioning Cell division and mitosis  Mitosis = nuclear division of all cells except gametes  Chromosomes replicate and are divided evenly by centrioles to new cells  Information in the DNA stays identical to the parent cell  In cytokinesis the two new cells separate Experiment: DNA extraction 1. Swirl some water thoroughly in your  Equipment: mouth and spit it back in the plastic  Water cup  NaCl 10% 2. Measure about 10 ml of the saliva water  Cold ethanol 3. Scrape the inside of your cheek  Dish washing liquid with the toothpick and mix with the  Measuring glass saliva water  Test-tube 4. Pour the water in the test tube  Tooth pick 5. Add 15 drops of NaCL  Plastic cup 6. Add 15 drops of dish washing liquid  Glass rod 7. Mix carefully using a glass rod 8. Add carefully 4 ml of ethanol in the bottom of the test tube