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

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