Presentation on theme: "What is a Gene? Gene = a segment of DNA that codes for a protein that controls a trait. Humans have approximately 30,000 genes We have 2 copies of."— Presentation transcript:
What is a Gene? Gene = a segment of DNA that codes for a protein that controls a trait. Humans have approximately 30,000 genes We have 2 copies of each gene (one on each chromosome we inherited from our parents). Each gene has different forms... Allele –one of the many forms of a gene.
Examples of Genes and Alleles in Pea Plants Gene – Seed Shape Alleles: _____________ _____________ _____________ Gene – seed color Alleles: _____________ _____________ _____________ Gene – flower color Alleles: _____________ _____________ _____________
Chromosomes occur in pairs because offspring inherit one from each parent *We have 46 Chromosomes (23 pairs of chromosomes) Chromosomes are made of genes Circle one gene. What are the 2 alleles for that gene? *Each chromosome is made up of DNA that contains hundreds to thousands of GENES. *HIERARCHY: CHROMOSOMES CONTAIN DNA MADE OF GENES CODE FOR A PROTEIN MAKE TRAITS
Dominant vs. Recessive NOT ALL ALLELES ARE EXPRESSED! Some alleles are dominant, while others are recessive
DescriptionMore InfoExamples Dominant Alleles This trait always shows up in an organism if it is present *These usually code for a protein so they are the “normal” form of a gene. -Widows Peak -free earlobes REPRESENTED WITH CAPITAL LETTER Recessive Alleles This trait only shows up if there is no dominant allele present *These usually code for a different protein, or deactivate the “normal” protein. -No widow’s peak -attached earlobes REPRESENTED WITH LOWERCASE LETTER
WHAT HAPPENS IF WE CHANGE OUR DNA?
Don’t let this happen to you!!
MUTATIONS Changes in DNA that affect genetic information
Gene Mutations Point Mutations – changes in one or a few nucleotides Substitution THE FAT CAT ATE THE RAT THE FAT HAT ATE THE RAT Insertion THE FAT CAT ATE THE RAT THE FAT CAT XLW ATE THE RAT Deletion THE FAT CAT ATE THE RAT THE FAT ATE THE RAT
Gene Mutations Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function. Insertion THE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA T Deletion THE FAT CAT ATE THE RAT TEF ATC ATA TET GER AT H H
Chromosome Mutations Changes in number and structure of entire chromosomes What do scientists use to identify these type of mutations? Original Chromosome ABC * DEF DeletionAC * DEF DuplicationABBC * DEF InversionAED * CBF TranslocationABC * JKL GHI * DEF
Your body cells have 23 pairs of chromosomes. –Homologous pairs of chromosomes have the same structure. –For each homologous pair, one chromosome comes from each parent. Chromosome pairs 1-22 are autosomes. Sex chromosomes, X and Y, determine gender in mammals. Your cells have autosomes and sex chromosomes.
By investigating body tissue, scientists can detect problems. Genetic problems can be identified by defective proteins/enzymes or a negative affect on the bodies metabolism. Genes can be studied directly
Electrophoresis (DNA fingerprinting)
Karyotypes a set of photographs of chromosomes grouped in order in pairs from one cell. What are some observations we could make from this karyotype?
Male vs. Female Males have XY sex chromosomes. Females have XX sex chromosomes The Y chromosome carries very few genes essential for life. The X chromosome is a much longer DNA molecule and contains many, many genes that are needed for cells to function.
Karyotype Notation A short-hand way to write a person’s karyotype. Total # of chromosomes, sex chromosomes, extra or missing chromosomes Normal Female 46XX Normal Male 46XY
Significance of Mutations 1. Most are neutral Eye colorEye color Birth marksBirth marks 2. Some are harmful Sickle Cell AnemiaSickle Cell Anemia Down SyndromeDown Syndrome 3. Some are beneficial Sickle Cell Anemia to MalariaSickle Cell Anemia to Malaria Immunity to HIVImmunity to HIV
What Causes Mutations? There are two ways in which DNA can become mutated: 1. Mutations can be inherited. Parent to child 2. Mutations can be acquired. Environmental damage Mistakes when DNA is copied Non-disjunction-failure of chromosomes to separate properly during Meiosis.
What are we making during Meiosis? In your own words what is a non-disjunction?
Genetic Disorders an illness caused by one or more abnormalities in the genome, especially a condition that is present from birth. Conditions may or may not be inherited. Mutations occur all the time in every cell in the body. Each cell, however, has the remarkable ability to recognize mistakes and fix them before it passes them along to its descendants. But a cell's DNA repair mechanisms can fail, or be overwhelmed, or become less efficient with age.
Turners Syndrome Affects1 in 2,500 newborns 45 chromosomes; have only 1 X chromosome #23 Monosomy girls fail to go thru puberty Caused by a nondisjunction, if a pair of sex chromosomes fails to separate during the formation of an egg or sperm
Turners Syndrome 96-98% do not survive to birth stocky appearance short webbed neck Other medical symptoms include: lymphedema (swelling of hands and feet) heart and/or kidney defects high blood pressure infertility (inability to have children)
Cri-Du-Chat Syndrome Estimated 1 in 20,000-50,000 newborns Found in ALL ethnic backgrounds Not inherited Can be XY or XX #5 Deletion These children have a deleted portion of chromosome number 5.
Cri-Du-Chat Syndrome Cry that is high-pitched and sounds like a cat Downward slant to the eyes Low birth weight and slow growth Low-set or abnormally shaped ears Mental handicap (intellectual disability) Partial webbing or fusing of fingers or toes Slow or incomplete development of motor skills Small head (microcephaly) Small jaw (micrognathia) Wide-set eyes
WAGR Syndrome 1 in 500,000 children under age 15 7 in 1000 cases have Wilms Tumor 46 chromosomes XY or XX #11 Deletion of upper arm The condition results from a deletion on chromosome 11 resulting in the loss of several genes
Aniridia-Wilms Tumor Syndrome Predisposed to Wilms kidney tumor Mentally handicapped Severe childhood obesity Growth retardation Blindness Tumors on kidneys Short lifespan Missing the iris of the eye
Thirteen Q Deletion Syndrome 600 cases worldwide 1 st diagnosed 20 years ago 46 chromosomes Affects XY or XX #13 Deletion of lower arm
Thirteen Q Deletion Syndrome Mentally retarded Deformed face No thumbs Heart disease Short lifespan
Prader-Willi Syndrome 1 in 15,000 live births 46 chromosomes XY=97% XX=3% #15 Deletion of lower arm Prader-Willi syndrome is caused by a gene missing on part of chromosome 15. Normally, your parents each pass down a copy of this chromosome. Most patients with Prader-Willi syndrome are missing the genetic material on part of the father's chromosome.
Prader-Willi Syndrome Low muscle tone Short stature Incomplete sexual development Cognitive disabilities Problem behaviors Chronic feeling of hunger Obesity Shorter lifespan
Eighteen Q Deletion Syndrome 1 in 40,000 newborns Estimated 100 babies per year 46 chromosomes XY or XX #18 Deletion of lower arm
Eighteen Q Deletion Syndrome Symptoms correlate with the size of the deletion Mentally handicapped Heart disease Abnormal hands and feet Large eyes Large ears Normal lifespan
Cat-Eye Syndrome 1 in 1,000,000 births 46 chromosomes Affects XY or XX #22 Deletion of bottom arm
Cat-Eye Syndrome Cat-Eye Syndrome Normal to severe malformations Fused fingers and toes Mentally handicapped Small jaw Heart problems Normal lifespan
Four-Ring Syndrome 1 in 10,000,000 births 46 chromosomes XY or XX #4 Inversion
Four-Ring Syndrome Cleft palate Club feet Testes don’t descend Short lifespan
Down Syndrome 1 in 31,000 births 46 chromosomes XY=97% XX=3% #14/21 Translocation 1 in 850 newborns Estimated 250,000 people are affected in the US 47 chromosomes XY or XX #21 Trisomy Nondisjunction Trisomy 21 Down Syndrome
Short, broad hands Stubby fingers Rough skin Impotency in males Mentally handicapped Cognitive delays Small round face Protruding tongue Short lifespan Increased risk of developing Alzheimer disease
Patau’s Trisomy Syndrome 1 in 14,000 births 47 chromosomes XY or XX #13 Trisomy Nondisjunction
Patau’s Trisomy Syndrome Small head Small or missing eyes Heart defects Extra fingers Mentally handicapped Cleft palate Most die a few weeks after birth
Edward’s Trisomy Syndrome Small head Mentally handicapped Internal organ abnormalities 90% die before 5 months of age
Jacob’s Syndrome 1 in 1,800 births 47 chromosomes XYY only #23 Trisomy Nondisjunction
Jacob’s Syndrome Normal physically Normal mentally Increase in testosterone More aggressive Normal lifespan ?
Klinefelter Syndrome 1 in 1,100 births 47 chromosomes XXY only #23 Trisomy Nondisjunction
Klinefelter Syndrome Klinefelter Syndrome Scarce beard Longer fingers and arms Sterile Delicate skin Low mental ability Normal lifespan
Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only #23 Trisomy Nondisjunction
Triple X Syndrome Normally physically Normal mentally Fertile Short lifespan
Cystic Fibrosis (CF) Clogs the lungs and leads to life- threatening lung infections. Obstructs the pancreas and stops natural enzymes from helping the body break down food and absorb vital nutrients Fluid in lungs, potential respiratory failure Common among Caucasians 1 in 20 are carriers Therefore is it dominant or recessive?
Cystic Fibrosis (CF) Monogenic Cause: deletion of only 3 bases on chromosome 7 Estimated in 30,000 children and adults in the U.S. 70,000 people worldwide
Muscular Dystrophy X-linked or autosomal genetic disorder. Muscular dystrophy is a disease in which the muscles of the body get weaker because of a lack of a certain protein Can be passed on by one or both parents, depending on the form of MD Symptoms: Muscle weakness that slowly gets worse Delayed development of muscle motor skills Difficulty using one or more muscle groups Eyelid drooping (ptosis) Loss of strength in a muscle or group of muscles as an adult Loss in muscle size Problems walking (delayed walking)
Huntington’s Disease Huntington's disease (HD) is an inherited, degenerative brain disorder which results in an eventual loss of both mental and physical control. The disease is also known as Huntington's chorea. Chorea means "dance-like movements" and refers to the uncontrolled motions often associated with the disease.
Hemophilia, the royal disease Hemophilia is the oldest known hereditary bleeding disorder. Caused by a recessive gene on the X chromosome. There are about 20,000 hemophilia patients in the United States. One can bleed to death with small cuts. The severity of hemophilia is related to the amount of the clotting factor in the blood. About 70% of hemophilia patients have less than one percent of the normal amount and, thus, have severe hemophilia.
ALS (Amyotrophic Lateral Sclerosis, or Lou Gehrig’s disease)
the disease strikes people between the ages of 40 and 70, and as many as 30,000 Americans have the disease at any given time This monogenic mutation is believed to make a defective protein that is toxic to motor nerve cells. A common first symptom is a painless weakness in a hand, foot, arm or leg, other early symptoms include speech swallowing or walking difficulty
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Chromosome Mutations Cri-du-chat Deletion of material on 5 th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps
Sex Chromosome Abnormalities Klinefelter’s Syndrome XXY, XXYY, XXXY Male Sterility Small testicles Breast enlargement
Sex Chromosome Abnormalities XYY Syndrome Normal male traits Often tall and thin Associated with antisocial and behavioral problems
Sex Chromosome Mutations Turner’s Syndrome X Female sex organs don't mature at adolescence sterility short stature
Sex Chromosome Mutations XXX Trisomy X Female Little or no visible differences tall stature learning disabilities limited fertility
What’s an Autosome? AAAAutosome: refers to chromosomes 1-22 EEEEx: Autosomal disorders: gene for the disease is found on chromosomes 1-22 AAAAutosomal Recessive Inheritance MMMMust inherit two copies of the disorder to be affected HHHHealthy is dominant (HH or Hh) DDDDisease is recessive (hh) EEEEx: Cystic fibrosis, PKU, Albinism, Sickle cell anemia AAAAutosomal Dominance Inheritance OOOOnly need to inherit one copy of the disorder to be affected DDDDisease is dominant (HH or Hh) HHHHealthy is recessive (hh) EEEEx: Familial hypercholesterolemia (also called FH), Huntington’s disease, Neurofibromatosis
Autosomal Dominance Inheritance DDDDisease is dominant (FF or Ff) HHHHomozygous dominant: early death and don’t survive to reproduce HHHHeterozygous live into adulthood HHHHealthy is recessive (ff) eeeex: Paul has familial hypercholesterolemia and Stacy is healthy. The two have 3 children. After testing, the middle child is the only healthy child. Key F = FH disease f = healthy disease healthy
Autosomal Dominance Inheritance Huntington’s disease is a dominant disorder found on chromosome 4. Betty and Marcus met at a support clinic they have been attending to help them cope with the knowledge of their illness with Huntington’s disease. They would like to know the risk of having a healthy child, now that Betty is pregnant. Key H = Huntington’s disease h = healthy diseasedisease diseasehealthy