Genetic Disorders Diseases Genetic Disordersdiseases l l Many

Genetic Disorders & Diseases

Genetic Disorders/diseases l l Many disorders/diseases caused by mutations. A mutation is any type of change in genetic material. Usually recessive, 1/50 dominant Mutations are caused by Mutagenic Agents: – Radiation l X-rays, U-V rays, radioactive substances – Chemicals l Benzene, asbestos, PCBs

Mutations l l Pass only if the mutation is in your sex cells!! Mutations in body cells can be passed on to other cells of your body only!! – l cell may die or other cells may give the cell what it lacks. Cancer (not inherited)

Types of Mutations l l A new trait that suddenly appears = mutation 2 major groups– Gene mutations. l – One gene affected Chromosomal mutationsl l entire chromosomes are missing or extra copies are found in all cells of the organism. Segments of chromosomes are deleted or duplicated or inverted. Can you think of examples?

You were wondering… l l Different types of Down Syndrome Hereditary cancers (10%)

Overview Mutations Gene Mutations “Reading frame” shift Substitution Chromosomal Mutations Entire chromosomes added/deleted Pieces of chromosomes added/deleted

Gene Mutations l l Mutated allele Gene cannot properly produce whatever protein it normally codes for These are usually recessive Why do you think so?

Gene Mutations l l A new allele for an existing trait 2 types l l “reading frame” shift substitution

“reading frame” shift THE BIG DOG CAN SIT l. Add a letter to the front, space every three letters it becomes…. TTH EBI GDO GCA NSI T l Your turn…remove HEB IGD OGC ANS IT

Substitution THE BIG DOG CAN SIT SHE DIG DOT FAN HIT

Gene Mutations l Recessive examples – – – Sickle cell Phenylketonuria Tay-Sachs Cystic Fibrosis Huntington’s Disease

Sickle Cell l l Change one base in gene hurts production a polypeptide chain in hemoglobin 300 amino acids in this chain. glutamic acid is replaced by Valine Sickle cells don’t carry oxygen well. Catch in capillaries

Phenylketonuria - PKU l l enzyme necessary to break down the amino acid phenylalanine. Lack causes the amino acid to convert to harmful chemicals that affect the brain leading to mental retardation. Most screened at birth for PKU Avoid foods

Tay-Sachs Disease l l Lack enzyme to break down lipids in the brain. Lipids build up in the brain cells and destroy them. appears before the age of one and death usually occurs before the age of three. https: //www. youtube. com/watch? v=Rz. Epk. BUITA

Cystic Fibrosis l l recessive disorder Stops production of a protein involved in salt uptake of cells in the lung, pancreas or other organs – Affects about 1 in 2500 births in the US – https: //www. youtube. com/watch? v=__QT 583 xp. U 8 (5: 30)

Huntington’s Disease l l l dominant disease, you need to inherit only 1 copy of the disease to have it. Abnormal protein is produced that kills brain tissue occurs around middle age – mood swings, paralysis, loss of memory, uncontrolled movements and eventually death – 1 in 20, 000 in western hemisphere, 1 in 1 million in Asia – https: //www. youtube. com/watch? v=Tkf. Vnzav. REw (3: 17 – 4: 44)

Chromosomal Mutations 2 kinds 1. Whole chromosomes are missing or extra 2. Pieces of chromosomes are duplicated, missing, or misplaced

Chromosomal Mutations Whole chromosomes are missing OR there are extra chromosomes. l This is caused by nondisjunction which happens during meiosis when chromosomes did not segregate or separate and distribute to the gametes properly.

Chromosomal Mutations l Examples: – – Trisomy 13 2 N+1= 47 chromosomes Trisomy 21 2 N+1= 47 chromosomes Turner’s Syndrome 2 N-1+ 45 chromosomes Kleinfelter’s Syndrome 2 N+1=47 chromosomes

Trisomy 13 l Chromosomal condition that is associated with severe mental retardation and certain physical abnormalities. small eyes that may exhibit a split in the iris – an opening in the roof of the mouth (a cleft palate) and/or a cleft lip, – weak muscle tone – skeletal abnormalities, Affected individuals rarely live past infancy because of the lifethreatening medical problems associated with this condition – Trisomy 13 affects approximately 1 in 10, 000 newborns. The risk of having a child with trisomy 13 increases as a woman gets older.

Trisomy 21 – Down’s Syndrome l Extra copy of chromosome 21 The incidence of Down syndrome is estimated at 1 per 800 to 1, 000 births, although these statistics are heavily influenced by the age of the mother.

Turner’s Syndrome l l One sex chromosome X Females with underdeveloped sex characteristics One in 2500 births

Kleinfelter’s Syndrome l l 2 XX’s 1 Y Males with underdeveloped sex organs

Polyploidy l l l Nondisjunction of an entire set of chromosomes The resulting 2 N gamete fuses with a 1 N gamete producing a 3 N zygote. If 2 -2 N gametes fuse the result would be a 4 N zygote. This condition is rare in animals. In animals it tends to be lethal. Common in plants, polyploidy results in larger more vigorous strain that are often sterile, but that produce large, luscious fruits.

2. Sections of Chromosomes are missing or misplaced con’t…

Human Genetic Disease l Difficulty in studying human genetic diseases: – – – Time between generations is too long. Number of offspring is too few. No controlled experiments are possible.

Genetic Counseling l l l Trace appearance of traits over several generations. Pedigree give parents an accurate idea of the risks Pedigree charts show the presence or absence of a particular trait in each member of each generation.

Pedigree Showing Colorblindness

Genetics Testing l l Amniocentesis- amniotic fluid which contains cells of the fetus. Culture them and do a karyotype or test for the presence or absence of certain enzymes or hormones. Karyotype- a photograph of a fetal cell undergoing mitosis is taken and then enlarged. Compare with a normal karyotype. Sex of the child as well as chromosomal abnormalities can be seen.

Genetic Applications to Animal and Plant Breeding l Selective Breeding- done for 1000’s of years. – – Artificial selection- individuals w desirable traits Inbreeding- offspring with desirable traits bred Hybridization- crossing for 2 desirable traits Vegetative propagation- asexual reproduction to perpetuate a trait

Current Genetic Applications and Research l l Cloning- genetically identical offspring from a single cell of an organism. Vegetative propagation and regeneration are naturally occurring cloning. Bacterial transformation- two strains of bacteria are mixed and the DNA of one strain enters the cells of the other strain. The receiving strain may be able to produce new proteins in this way.

Current Genetic Applications and Research l Genetic engineering- Genes are transferred from one organism to another producing what is called recombinant DNA. The recipient organism then has the ability to produce the protein coded for by the transferred gene. “Gene Splicing” has been used to produce strains of bacteria that are able to produce useful proteins like insulin or human growth hormone.

Genetic Engineering Using Bacteria

Applications of Biotechnology l l Sequencing genes can help make treatments Genetically engineering bacteria – produce a certain hormone or enzyme, which certain humans cannot, is more economical and safer than extracting these chemicals from related animals. Movie explaining DNA gel electrophoresis for Dry Lab