Genetic Disorders• Illness that is caused by
changes to a persons genetic material– To a single gene that
affects protein production (cystic fibrosis)
– Increase or decrease in number of chromosomes (down syndrome)
– Multiple changes to one or more genes caused from environmental factors (cancer)
Mutation• A random change in the
DNA• Uncontrolled cell division
happens in one of two ways:– A checkpoint gene which
prevents the cell from dividing is damaged or switched off
– A gene which says ‘ok now divide’ is switched on (expressed) permanently
Cancer: A SERIES of Gene changes• Uncontrolled growth and division of cells • Failure in the cell cycle
Causes in DNA Damage• Carcinogens– Environmental factors that
increase the risk of cancer• Include– Tobacco smoke – Lung cancer– Radiation (x-rays, uv rays),
tanning beds– Organic solvents – Hodgkins
disease– Viruses – HPV virus – Cervical
cancer– Hepatitis B – Liver cancer
Nondisjunction• Increase or decrease in number of chromosomes
during meiosis– Both autosomal and sex chromosomes
• Gametes are affected• Happens during anaphase I & II
Aneuploidy• Presence of an abnormal number of chromosomes in a cell • 45 or 47• Common cause of genetic disorders• General Types 1. Monosomy – lack of one chromosome of the normal
complement (Turner Syndrome)2. Disomy – presence of two copies of a chromosome (normal
for humans unless uniparental disomy – non contribution of chromosome from other parent)
3. Trisomy – presence of three copies, instead of normal two (Down, Patau, Edwards syndrome)
4. Tetrasomy/Pentasomy – presence of four or five copies of a chromosome (sex chromosomes in humans – XXXX, XXYY, XXXXX, XXXXY, XYYYY)
Genetic Mutations• Positive and negative – Natural selection/
evolution – Cancer –death
• Small-Scale – Single base pair
• Large-Scale – Multiple base
pairs/whole genes
Large-scale mutations • Multiple nucleotides,
entire genes, whole regions of chromosomes
Large-scale mutations • Amplification – gene
duplication– Entire genes are copied to
multiple regions of chromosomes
Large-scale mutations • Large-scale deletions – Entire coding regions of DNA are removed • Muscular Dystrophy
Large-scale mutations • Chromosomal translocation– Entire genes or groups of genes are moved from one
chromosome to another – Enhance, disrupt expression of gene
Large-scale mutations • Inversion– Portion of a DNA molecule reverses its direction in the
genome– No direct result but reversal could occur in the middle of
a coding sequence compromising the gene
Causes of genetic mutations• Spontaneous mutations– Inaccurate DNA replication
• Induced mutations – Caused by environmental agent – mutagen – Directly alter DNA – entering cell nucleus – Chemicals, radiation
Chemical Mutagens • Modify individual
nucleotides– Nucleotides
resemble other base pairs
– Confuses replication machinery – inaccurate copying • Nitrous acid
• Mimicking DNA nucleotides – Ethidium bromide –
insert itself into DNA
Radiation - Low energy • UV B rays • Non-homologous end joining– Bonds form between adjacent nucleotides along DNA
strand – Form kinks in backbone – Skin cancer
Radiation – high energy • Ionizing radiation – x-ray, gamma rays • Strip molecules of electrons • Break bonds within DNA– Delete portions of chromosomes
• Development of tumors
Large-scale mutations • Trinucleotide repeat expansion– Increases number of repeats in genetic code – CAG CAG CAG CAG CAG CAG CAG CAG • Huntingtons disease
Biotechnology• Artificial Insemination– Sperm is collected and
concentrated before being placed in woman’s uterus
• In Vitro Fertilization– Eggs from mom are
retrieved and combined with sperm in petri dish
– After fertilization, zygote is placed in woman’s uterus
Genetic Testing• Determining if your baby carries a gene that is
associated with an increased risk of developing a disease
Aminocentesis• Benefits – Diagnosis of
chromosome abnormalities
– Diagnosis of other defects
• Risks– Discomfort for
expectant mother– Slight risk of infection– Miscarriage
Chorionic Villus Sampling
• Benefits– Diagnosis of
chromosome abnormalities
– Diagnosis of certain genetic defects
• Risks– Miscarriage– Infection– Newborn having limb
defects
Stem Cell – an undifferentiated cell that can
divide to form specialized cells
Embryonic Stem Cells – differentiate into any kind of
cell
Muscle Cell
Skin Cell
Nerve Cell
Heart Cell
Tissue Stem Cells (Adult Stem Cells) – exist within specialized tissue,
differentiate into certain types of cell s
Bone Marrow
Stem Cells
Cord Blood Banking• Blood (stem cells) found
in umbilical cord after birth
• Similar to tissue stem cells
• Develop into various blood cells
• These stem cells could be banked (stored)
• Used to treat variety of diseases
Gene Therapy• Experimental
treatment to cure genetic disorders
• Insert healthy genes into cells of tissues that are affected by a disorder
http://www.youtube.com/watch?v=8JTw2RpDo9o&feature=relatedhttp://www.youtube.com/watch?v=VOXJaIvRltMhttp://www.youtube.com/watch?v=czzCmgr0IgQ&feature=relatedhttp://www.youtube.com/watch?v=VOXJaIvRltMhttp://www.youtube.com/watch?v=qiQfGBOoMPM&feature=fvsthttp://www.youtube.com/watch?v=w9wIxe4WGFg&feature=relatedhttp://www.youtube.com/watch?v=L-Rj_rvBLZ0&feature=relatedhttp://www.youtube.com/watch?v=-FaGf0h20Vw