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 each."— Presentation transcript:
1What is a Gene?Gene = a segment of DNA that codes for a protein that controls a trait.Humans have approximately 30,000 genesWe have 2 copies ofeach gene (one on each chromosomewe inherited from our parents).Each gene has different forms . . .Allele –one of the many forms of a gene.
2Examples of Genes and Alleles in Pea Plants Gene – Seed ShapeAlleles: __________________________Gene – seed colorGene – flower color
3Chromosomes occur in pairs because offspring inherit one from each parent *We have 46 Chromosomes(23 pairs of chromosomes)Chromosomes are made of genesCircle 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
4Dominant vs. RecessiveNOT ALL ALLELES ARE EXPRESSED! Some alleles are dominant, while others are recessive
5Description More Info Examples DominantAllelesThis 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 LETTERRecessiveThis 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
8Changes in DNA that affect genetic information MUTATIONSChanges in DNA that affect genetic information
9Gene Mutations Point Mutations – changes in one or a few nucleotides SubstitutionTHE FAT CAT ATE THE RATTHE FAT HAT ATE THE RATInsertionTHE FAT CAT XLW ATE THE RATDeletionTHE FAT ATE THE RAT
10Gene MutationsFrameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function.InsertionTHE FAT CAT ATE THE RATTHE FAT HCA TAT ETH ERA TDeletionTEF ATC ATA TET GER ATHH
11Chromosome MutationsChanges in number and structure of entire chromosomesWhat do scientists use to identify these type of mutations?Original Chromosome ABC * DEFDeletion AC * DEFDuplication ABBC * DEFInversion AED * CBFTranslocation ABC * JKLGHI * DEF
12Your cells have autosomes and sex chromosomes. 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.
13Molecular TechniquesBy 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
15How do they get the chromosomes? Chorionic villus samplingAmniocentesis
16Karyotypesa set of photographs of chromosomes grouped in order in pairs from one cell.What are some observations we could make from this karyotype?
17Male vs. Female Males have XY sex chromosomes. Females have XX sex chromosomesThe 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.
18Karyotype Notation A short-hand way to write a person’s karyotype. Total # of chromosomes, sex chromosomes, extra or missing chromosomesNormal Female46XXNormal Male46XY
20Significance of Mutations 1. Most are neutralEye colorBirth marks2. Some are harmfulSickle Cell AnemiaDown Syndrome3. Some are beneficialSickle Cell Anemia to MalariaImmunity to HIV
21What Causes Mutations?There are two ways in which DNA can become mutated:1. Mutations can be inherited.Parent to child2. Mutations can be acquired.Environmental damageMistakes when DNA is copiedNon-disjunction-failure of chromosomes to separate properly during Meiosis.
22What are we making during Meiosis? In your own words what is a non-disjunction?
23Genetic Disordersan 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.
24Turners Syndrome 45 chromosomes; have only 1 X chromosome #23 Monosomy Caused by a nondisjunction, if a pair of sex chromosomes fails to separate during the formation of an egg or spermAffects1 in 2,500 newborns45 chromosomes; have only 1 X chromosome#23 Monosomygirls fail to go thru puberty
25Turners Syndrome96-98% do not survive to birthstocky appearanceshort webbed neckOther medical symptoms include:lymphedema (swelling of hands and feet)heart and/or kidney defectshigh blood pressureinfertility (inability to have children)
26Cri-Du-Chat Syndrome Estimated 1 in 20,000-50,000 newborns These children have a deleted portion of chromosome number 5.Estimated 1 in 20,000-50,000 newbornsFound in ALL ethnic backgroundsNot inheritedCan be XY or XX#5 Deletion
27Cri-Du-Chat Syndrome Cry that is high-pitched and sounds like a cat Downward slant to the eyesLow birth weight and slow growthLow-set or abnormally shaped earsMental handicap (intellectual disability)Partial webbing or fusing of fingers or toesSlow or incomplete development of motor skillsSmall head (microcephaly)Small jaw (micrognathia)Wide-set eyes
28WAGR Syndrome 1 in 500,000 children under age 15 The condition results from a deletion on chromosome 11 resulting in the loss of several genes1 in 500,000 children under age 157 in 1000 cases have Wilms Tumor46 chromosomes XY or XX#11 Deletion of upper arm
29Aniridia-Wilms Tumor Syndrome Predisposed to Wilms kidney tumorMentally handicappedSevere childhood obesityGrowth retardationBlindnessTumors on kidneysShort lifespanMissing the iris of the eye
30Thirteen Q Deletion Syndrome 600 cases worldwide1st diagnosed 20 years ago46 chromosomesAffects XY or XX#13 Deletion of lower arm
32Prader-Willi Syndrome 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.1 in 15,000 live births 46 chromosomesXY=97% XX=3%#15 Deletion of lower arm
33Prader-Willi Syndrome Low muscle toneShort statureIncomplete sexual developmentCognitive disabilitiesProblem behaviorsChronic feeling of hungerObesityShorter lifespan
34Eighteen Q Deletion Syndrome 1 in 40,000 newbornsEstimated 100 babies per year46 chromosomes XY or XX#18 Deletion of lower arm
35Eighteen Q Deletion Syndrome Symptoms correlate with the size of the deletionMentally handicappedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan
36Cat-Eye Syndrome 1 in 1,000,000 births 46 chromosomes Affects XY or XX #22 Deletion of bottom arm
37Cat-Eye Syndrome Normal to severe malformations Fused fingers and toes Mentally handicappedSmall jawHeart problemsNormal lifespan
38Four-Ring Syndrome 1 in 10,000,000 births 46 chromosomes XY or XX #4 Inversion
39Four-Ring Syndrome Cleft palate Club feet Testes don’t descend Short lifespan
40Trisomy 21 Down Syndrome Down Syndrome 1 in 31,000 births 46 chromosomesXY=97% XX=3%#14/21 Translocation1 in 850 newbornsEstimated 250,000 people are affected in the US47 chromosomes XY or XX#21 Trisomy Nondisjunction
50Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only #23 Trisomy Nondisjunction
51Triple X Syndrome Normally physically Normal mentally Fertile Short lifespan
52Cystic 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 nutrientsFluid in lungs, potential respiratory failureCommon among Caucasians1 in 20 are carriersTherefore is it dominant or recessive?
53Cystic Fibrosis (CF) Monogenic Cause: deletion of only 3 bases on chromosome 7Estimated in 30,000 children and adults in the U.S.70,000 people worldwide
54Muscular 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 proteinCan be passed on by one or both parents, depending on the form of MDSymptoms:Muscle weakness that slowly gets worseDelayed development of muscle motor skillsDifficulty using one or more muscle groupsEyelid drooping (ptosis)Loss of strength in a muscle or group of muscles as an adultLoss in muscle sizeProblems walking (delayed walking)
55Huntington’s DiseaseHuntington'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.
56Hemophilia, 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.
57ALS (Amyotrophic Lateral Sclerosis, or Lou Gehrig’s disease)
58the disease strikes people between the ages of 40 and 70, and as many as 30,000 Americans have the disease at any given timeThis 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
64Sex Chromosome Mutations XXXTrisomy XFemaleLittle or no visible differencestall staturelearning disabilitieslimited fertility
65What’s an Autosome? Autosome: refers to chromosomes 1-22 Ex: Autosomal disorders: gene for the disease is found on chromosomes 1-22Autosomal Recessive InheritanceMust inherit two copies of the disorder to be affectedHealthy is dominant (HH or Hh)Disease is recessive (hh)Ex: Cystic fibrosis, PKU, Albinism, Sickle cell anemiaAutosomal Dominance InheritanceOnly need to inherit one copy of the disorder to be affectedDisease is dominant (HH or Hh)Healthy is recessive (hh)Ex: Familial hypercholesterolemia (also called FH), Huntington’s disease, Neurofibromatosis
66Autosomal Dominance Inheritance Disease is dominant (FF or Ff)Homozygous dominant: early death and don’t survive to reproduceHeterozygous live into adulthoodHealthy is recessive (ff)ex: Paul has familial hypercholesterolemia and Stacy is healthy. The two have 3 children. After testing, the middle child is the only healthy child.ffFfFfKeyF = FH diseasef = healthyFdiseasediseasefffffhealthyhealthy
67Autosomal 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.HhHHHhKeyH = Huntington’s diseaseh = healthyHdiseasediseaseHhhhhdiseasehealthy