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TOPIC: Genetics AIM: What is the gene chromosome theory? How do genetic disorders occur? TOPIC: Genetics AIM: How do genetic disorders occur? DO NOW: Write the complimentary DNA strand that would be attached to the one below: CTAACCGAG Chromosomes & Genes… • The human DNA code is made up of about three thousand million A,T, C, and Gs on each side of the DNA strand. • If one were to recite the ATCG sequence in one's DNA which is 3 billion long and would utter at a rate of 100 ATCG sequences per minute without taking a break for sleeping, eating or drinking, one would speak for 57 long years. Genetics: chromosomes & inheritance Untitled Page Sex •2 chromosomes of 46 in each cell •X & Y • Eggs = X • Sperm = X or Y •XX = female •XY = male Female chromosomes Male chromosomes inherited • Genetic disorders diseases • Caused by genetic mistake • Caused by mutations mutation • Change in gene or chromosome new trait • Can only be passed on to offspring if in sex cells Deletion Duplication Insertion Translocation Examples: 1. Addition: GTACA GTGCA 2. Insertion: ATG GTC AAT GGT C 3. Deletion: ATG GTC TCA AGG TCT CA • Nondisjunction = • Chromosomes don’t separate properly during meiosis • RESULT: some cells have too many, some cells have too little Harmful • May cause Mutations various diseases & disorders Helpful •Cause mutations desirable traits •Examples: • Potatoes = • Resistant to disease • Look and taste better • Bacteria = • Become more resistant to antibiotics that kill them •Seedless oranges Bardet-Biedl Syndrome is a rare genetic disorder that affects many parts of the body. Only about 1 in 100,000 children have the disease, but those who do have it have multiple disorders in development throughout their bodies. A kitten named Cy was born with a defect called holoprosencephaly. Animals born with holoprosencephaly are born with one eye and an unformed brain. Little Cy, adorable despite his deformity, sadly lived less than twenty-four hours after his birth. A piglet owned by Llu Shuping, a pig farmer in Northwest China, has one head, two mouths, two noses, and three eyes. In China the little misfit is a television celebrity. A two-headed turtle calls an Aquarium in Pennsylvania home. A genetic mutation has left this small kitten born in Perth, WI with two complete faces. Despite its deformities it is an affectionate kitten that constantly purrs with happiness. The two-headed calf born in Iowa, US in April 1998 had four eyes and three ears and was appropriately named Reflections. One-eyed frog Two-headed python Three-legged duck Five-legged lamb Frog With Mutation Venus Fly Trap with 2 traps Six-legged fawn Left: A normal fruit fly Right: A fruit fly with its legs growing out of its head. This is a mutation caused by radiation. Genetic Disorders 1. Sickle • Blood disorder cell • Caused by anemia mutation • Red blood cells change shape • Cannot obtain enough oxygen • Clump together and clog up blood vessels 2. Down • Caused by Syndrome NONDISJUNCTION • Extra copy of chromosome 21 • Trisomy 21 Down syndrome (DS) causes delays in the way a child develops, and often leads to mental retardation, which means they may have trouble learning. It affects 1 in every 800 babies born. You have probably seen people who have DS. They have certain physical features, such as a flatter face & upward slanting eyes. It's important to note, though, that not all people with DS look alike or have all these features. They may have medical problems such as heart defects. Kids with DS can go to regular schools, make friends, enjoy life, and get jobs when they're older. DS affects kids' abilities in different ways. Kids with DS can and do learn, and are capable of developing skills throughout their lives. They simply reach goals at a different pace. Kids with DS have a wide range of abilities, and there's no way to tell at birth what they will be capable of as they grow up. How can genetic disorders be detected? • 1. AMNIOCENTESIS = • Long needle removes amniotic fluid • Fetal cells are tested • 2. KARYOTYPE = • Picture of all chromosomes in a cell Female = XX Male = XY Down Syndrome Review: 1. What two sex chromosomes do all males have? 2. Explain what a mutation is. 3. In order for a mutation to be passed on to offspring, where must it occur? 4. What causes Down Syndrome to occur? 5. What is a karyotype? Klinefelter Syndrome occurs in 1 in 500 to 1 in 1000 births. Men and boys with Klinefelter Syndrome have a Y chromosome and 2 X chromosomes. They develop as males with subtle characteristics that become apparent during puberty. They are often tall and usually do not develop secondary sex characteristics such as facial hair, or underarm and pubic hair. Trisomy 13 is a very severe genetic disorder with early death. The babies frequently have cleft lip and palate, and congenital heart malformations. Trisomy 18 (Edwards syndrome) is a serious syndrome where the babies generally die in the first life year. The babies have malformations of many organs. Turner syndrome (TS) affects about 1 in every 2,500 girls. They are born with only 1 X chromosome. Girls with TS are usually short in height (about 4’7”). When diagnosed while still growing, they can be treated with hormones to help them grow taller. TS prevents the ovaries from developing properly, which affects a girl's sexual development. Most won’t go through all changes associated with puberty unless they get treatment, and will be unable to become pregnant on their own. Other features may include a "webbed" neck, a low hairline at the back of the neck, drooping of the eyelids, differently shaped ears that are set lower on the sides of the head than usual, and abnormal bone development (especially the bones of the hands and elbows). Cri du Chat Syndrome ("Cry of the cat" in French) is a genetic disorder (1 in 50,000 live births) caused by the a missing part of the 5th chromosome. It was first identified in 1963 and named after the sound that many of the babies and children make when crying. The cry is caused by abnormal larynx development, which becomes normal within a few weeks of birth. Infants typically have low birth weight, slow growth, a small head, and poor muscle tone. They may have congenital heart defects. Individuals with cri du chat syndrome have language difficulties, delayed motor skill development, and mental retardation. Behavioral problems may also develop as the child matures. Cri-du-chat Syndrome Tay-Sachs Disease • Caused by mutation • Gene is recessive (both parents must carry gene) • Abnormal gene stops the body from making an enzyme that breaks down fat • Fat gathers in the brain brain damage and death Tay-Sachs disease (TSD) is an inherited, incurable disease of the central nervous system. Symptoms first appear at about 6 months, when an apparently healthy baby stops smiling, crawling or turning over, loses their ability to grasp or reach out, and gradually becomes blind and paralyzed. There is no cure and death usually occurs before the age of five. Cystic Fibrosis • Caused by mutation (recessive) • Body makes abnormally thick mucus in the lungs & intestines • Can lead to infection by bacteria, lung damage Cystic fibrosis affects more than 30,000 children and young adults in the United States. It can be mild or severe, depending on the person. To make normal mucus, the body needs a special protein. This protein is defective in cystic fibrosis, producing the thick, sticky mucus that causes problems for people with CF. Doctors may suspect that a baby has CF if he or she coughs a lot and gets a lot of lung infections. The baby also might have unusual large, bulky bowel movements or may not gain weight as expected. PKU • Phenylketonuria • Caused by a mutation (recessive) • Missing important enzyme • Can’t break down certain chemicals in food • Leads to build up brain damage High amounts of phe in the body can lead to mental retardation, seizures or convulsions, eczema, and an unusual odor in the urine. PKU is treated with a special diet that limits the amount of phe eaten. Foods high in protein (milk, eggs, meats, fish, cheese), aspartame, & wheat products containing gluten (high in protein), can’t be eaten if a person has PKU. This way, blood phe levels can be reduced. Since phe is an essential AA, it shouldn’t be totally omitted from the diet. A person with PKU has to drink a special formula every day which has the necessary ingredients for the body's growth and development but contains very little or no phenylalanine. It contains the right amounts of essential amino acids other than phe.