The Human Genome Chapter 12-1 & 12-2 THINK ABOUT IT What does a can of Diet Coke and this song have to do with human.
Download ReportTranscript The Human Genome Chapter 12-1 & 12-2 THINK ABOUT IT What does a can of Diet Coke and this song have to do with human.
The Human Genome Chapter 12-1 & 12-2 THINK ABOUT IT What does a can of Diet Coke and this song have to do with human genetics? (Answers to come in this slide show!) HUMAN GENETICS Dominant and Recessive Homozygous/Heterozygous work for human genes too! REMEMBER YOUR MOLECULES! Proteins are made by joining ________ amino acid ___________ subunits together REMEMBER YOUR MOLECULES Genetic code is carried __________ sequence of in the ________ A, T, G, C’s on a DNA molecule _____ The sequence of A’s, T’s, G’s & C’s ORDER of amino acids in tells the _______ ________ the ________ protein Changes in the gene code _______________ change the protein that is made A change in the genetic code = MUTATION ________________ KINDS OF MUTATIONS SOMATIC CELLS BODY ________ CELLS = ___________ Somatic cell mutations can: ______________________ Cause cancer Make cell not able to function ______________________ _____________ Kill cell WON’T BE passed on to offspring BUT _________ Kinds of Mutations GAMETES ___________ (sperm & eggs) GERM = _________cells CAN BE passed Germ cell mutations ________ on to offspring http://anthro.palomar.edu/biobasis/images/meiosis.gif Mistakes in Meiosis • Chromosomes fail to separate properly during meiosis, i.e., nondisjunction • ANEUPLOIDY -- an abnormal number of chromosomes • Examples: – Down’s Syndrome (Trisomy-21) – Klinefelter’s Syndrome – Turner’s Syndrome MUTATIONS can be: ____________Most mutations have little NEUTRAL function or no effect on gene ____________. REDUNDANCY in _____________ code can absorb many mutations without changing the amino acid sequence. UUC and UUU both code for same amino acid MUTATIONS can be: ____________ HARMFUL - Mutations that produce defective proteins are usually harmful. ______________ Harmful mutations are associated with many genetic disorders and can cause ________________ ____________ cancer MUTATIONS can be: ____________ - Some mutations LETHAL change proteins that are so vital to life that they cause death, usually before birth. 50% of pregnancies that abort spontaneously have genetic abnormalities MUTATIONS can be: BENEFICIAL ____________Mutations are also a genetic variation source of ______________ in the population Mutations can help an organism survive and reproduce _________________ Provide a way for species to change over time REMEMBER! _______________ MUTATIONS are changes in the genetic material. Mutations can happen: mistakes in copying DNA • when cells make_________ • when cells are exposed to environmental carcinogens like ___________ radiation __________X-rays, tanning booths chemicals - cigarette smoke, pollutants __________ viruses __________ - HPV Images from: http://www.bbc.co.uk/scotland/education/bitesize/higher/img/biology/genetics_adaptation/mutations/02gene_mutation.gif KINDS OF MUTATIONS Mutations that produce changes in a single gene = GENE MUTATIONS _________________ Mutations that produce changes in whole chromosomes = CHROMOSOMAL MUTATIONS _____________________ MANY HUMAN GENES HAVE BECOME KNOWN THROUGH THE STUDY OF GENETIC DISORDERS DISORDERS result from Many genetic ___________ changes in the DNA code so NON-FUNCTIONING _________________ proteins are produced. http://patentdocs.typepad.com/photos/uncategorized/2007/05/28/dna1.gif A mutation that causes a protein to be NON-FUNCTIONAL would appear RECESSIVE _______________ to the normal working allele. AUTOSOMAL RECESSIVE Examples of __________________________ GENETIC DISORDERS: PHENYLKETONURIA (PKU) ____________________ TAY-SACHS DISEASE ____________________ CYSTIC FIBROSIS ____________________ Phenylketonuria (PKU) CAUSE: ENZYME Mutation in gene for an ___________ that __________ called breaks down an ___________ amino acid phenylalanine X X MENTAL RETARDATION Build up causes ________________________ http://biology.clc.uc.edu/courses/bio104/protein.htm Phenylketonuria (PKU) ALL babies are ________ tested ____ for PKU before they leave the hospital. http://labspace.open.ac.uk/file.php/2588/SK195_6_002i.jpg Treatment: LOW in phenylalanine to Need a diet _____________________ extend life and ______________ mental PREVENT retardation amino acid If phenylalanine is an _____________, what type of foods should PKU patients avoid? PROTEINS ! __________________ THINK ABOUT IT What does a can of Diet Coke have to do with human genetics? LOOK AT THE WARNING LABEL ! NUTRASWEET is made with phenylalanine ______________ Common Pedigree Symbols Male Marriage Female Sex Unknown Consanguineous Marriage Affected Female No Known Pregnancy Female Carrier of Sex-linked Recessive Female Carrier (Heterozygous) Dead Unmarried Divorce and Remarried Common Pedigree Symbols Pregnancy in Progress 3 Three Males 5 Five Individuals (both sexes) Dizygotic (nonidentical, fraternal) twins Monozygotic (identical) twins Spontaneous Abortion Proband, propositus, or index case Adopted Child Happy new wife! Famous Kid Bad Divorce Triplets! TAY-SACHS DISEASE AUTOSOMAL RECESSIVE ___________________ CAUSE: Mutation in gene for an ___________ ENZYME that breaks down a kind of _________in the LIPID developing _________ BRAIN Build up of lipids in brain cells leads to: mental retardation, blindness, and DEATH in early childhood Found more frequently in people with Jewish _____________ Mediterranean ______________, Middle Eastern _______ ancestry Image from: http://www.djsfoundation.org/images/Steeler%20pics%20Dylan.jpg Autosomal Recessive • Disease manifests itself if offspring inherits one recessive gene from each parent. • If parents are carriers, 25% of offspring will have disease. Tay-Sachs Disease • 1 in 600 Jews of European descent born with it • Lipids deposited in nervous system, causing brain to be damaged -- blindness, loss of movement, mental deterioration. • No break down of cellular wastes in lysosome due to absence of hexosaminidase A – mutation causes nerve death • Symptoms appear around 6 months of age and victims die due to paralysis and/or convulsions before the age of five. Tay-Sachs Disease Tt Tt or TT Tt tt Tt or TT TT or Tt What are the genotypes of all TT or Tt individuals in this family? Tt Tt tt heterozygous person A __________ who carries a recessive allele for a _________ genetic disorder, but doesn’t show ______________ the disorder themselves is called a CARRIER _____________ http://www.biochem.arizona.edu/classes/bioc460/spring/rlm/RLM36.1.html Polygenic Inheritance • Most human characteristics are polygenic, meaning they are influenced by several genes, e.g. skin color influenced by 3-6 genes; also, eye color, height, hair color • Complex characters are those that are influenced strongly by both the environment and genes, e.g., diabetes, heart disease, stroke, skin color, height More patterns of inheritance….. • Multiple alleles - genes with three or more alleles, e.g., ABO blood groups • Incomplete dominance – condition that results in a display of a trait that is intermediate between the two parents • X-linked traits – determined by x-linked genes, e.g., color blindness • Sex-influenced traits – usually autosomal, e.g. baldness is influenced by testosterone • Single-allele traits – more than 200 human traits are governed by single dominant alleles, e.g., Huntington’s disease Single Gene Inheritance Pedigree Analysis • Autosomal dominant traits – Huntington’s Disease on chromosome #4 – Marfan Syndrome on chromosome #15 – Breast Cancer on chromosomes #17 • Autosomal recessive traits – Tay-Sachs Disease on chromosome #15 – Cystic Fibrosis on chromosome #7 – Sickle Cell Anemia on chromosome #11 • X-Linked Disease (Sex-Linked) – Hemophilia --Duchenne’s muscular dystrophy – Color Blindness Multiple Alleles • Blood type, using I gene. • Human blood types include: Phenotype Genotype –A –B – AB –O IAIA or IAi IBIB or IBi IAIB (Universal Recipient) ii (Universal Donor) If a child has type O blood and its mother has type A, could a type B man be the father? Why couldn’t a blood test be used to prove he is the father? CYSTIC FIBROSIS CAUSE: Loss of 3 DNA bases in a gene for the _____________ that transports _________ so protein Cl- ions salt balance is upset thick mucous Causes a build up of _________________ in lungs and digestive organs Image from: BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006 Cystic Fibrosis • Found in Caucasians. – Most common lethal genetic disorder among white Americans. – Autosomal recessive on chromosome 7 • Thick mucus produced in lungs, intestines, and pancreas. • 1/20 of Caucasian population are carriers. – One in 2,000 children born to white Americans inherits the disorder. – CF kills ~500 children and young adults each year. A mutation that codes for a new protein whose action masks the normal allele appears as a ______________ DOMINANT mutation. AUTOSOMAL DOMINANT Examples of _________________________ GENETIC DISORDERS: Huntington’s disease ____________________ Achondroplasia ____________________ HUNTINGTON’S DISEASE AUTOSOMAL DOMINANT ______________________ CAUSE: CAG repeats at end of gene Extra 40-100 ______________ on chromosome 4 more repeats . . . the more __________ severe The _____________ the symptoms. http://www.healthsystem.virginia.edu/internet/huntdisease/images/cag.gif HUNTINGTON’S DISEASE Huntington’s brain loss Causes progressive _____ muscle control of ________________ and mental ___________function 1 in 10,000 people in U.S. have Huntington’s disease Normal brain http://www.scielo.br/img/revistas/bjmbr/v39n8/html/6233i01.htm A person with Huntington’s disease 50% chance of has a _____ passing the disorder on to their offspring. Problem: Symptoms of disorder usually don’t show until ____________ MIDDLE AGE . . . so you don’t know you have it until ________ AFTER you have had children. Huntington’s Disease • Begins to show up by age 45-55, within 1020 years, death is eminent. • Progressive degeneration of nervous system; irregular body movements and slurred speech. • If one parent has HD, offspring have 50% chance of inheriting disease. • Autosomal dominant on chromosome 4; 1 in 10,000 births Huntington’s Disease Hh hh What are the genotypes of the parents? THINK ABOUT IT Click to hear Woody’s song What does the song have to do with human genetics? “This Land is My Land” was written by a musician named Woody Guthrie before he began to show the symptoms of Huntington’s disease. Woody Guthrie had a son named Arlo that was a popular musician during the 70’s Click to hear one of Arlo’s songs Before 1993 there was no test for Huntington’s. If one of your parents showed symptoms, you had to wait to see if it had been passed on to you. http://www.jimdirden.com/woodyfest2004/artists/index_3.htm Arlo Guthrie is still performing today. He never developed symptoms for Huntington’s disease. If there is no cure, would YOU want to be tested and find out if you have the gene? http://webs.wichita.edu/depttools/depttoolsmemberfiles/accomp/question_mark%20(WinCE).jpg ACHONDROPLASIA (One kind of Dwarfism) AUTOSOMAL DOMINANT CAUSE: ___________________________ gene 1 in 20,000 births 200,000 “little people” worldwide One of oldest known disorders – seen in Egyptian art ACHONDROPLASIA (One kind of Dwarfism) Normal size head and torso; short arms and legs Problem with way cartilage changes to bone as bones grow DISORDERS CAUSED AUTOSOMAL CODOMINANT ALLELES BY ____________________ SICKLE CELL DISEASE ____________________ CAUSE: T changed to A in gene for HEMOGLOBIN __________________ (protein in red blood cells that carries oxygen in blood) SICKLE CELL DISEASE SYMPTOMS: RED BLOOD CELLS become sickle _____________ TWO shaped in persons with ______ ALLELES sickle cell ________ SICKLE CELL DISEASE Circulatory problems Cells stick in capillaries Loss of blood cells (anemia) Organ damage (brain, heart, spleen) Can lead to DEATH SICKLE CELL DISEASE AFRICAN AMERICANS More common in _________________ 1 in 500 = have sickle cell disease 1 in 10 = carriers for allele MEDITERRANEAN Also affects persons of _______________ and _________________ MIDDLE EASTERN descent Why do so many African Americans carry the sickle cell allele? SICKLE CELL DISEASE Many can trace their ancestry to west MALARIA central Africa where ___________, a serious parasitic disease that infects red blood cells is common. Watch a video about sickle cell and malaria Images from: http://en.wikipedia.org/wiki/Malaria A person who is __________________ for HOMOZYGOUS the ____________allele (ss) will have sickle cell _______________ sickle disease HOMOZYGOUS A person who is _________________ for normal hemoglobin alleles will have normal blood cells, but can become infected with malaria __________ (SS) HETEROZYGOUS person (Ss) A _________________ (with one normal/one sickle cell allele) is generally healthy and has the benefit of resistant to malaria being _________ KARYOTYPE is a picture of A __________ an organism’s chromosomes Chromosomes that determine the sex of an organism = _________________ Sex chromosomes http://www.angelbabygifts.com/ All other chromosomes = _________________ autosomes Humans have two sex chromosomes X y and _____ 44 autosomes SEX DETERMINATION XX = female Xy = male Who decides? Mom can give X Dad can give X or y X X X XX XX y Xy Xy Dad determines sex of the baby. SO ____ If dad gives X with mom’s X = girl If dad give y with mom’s X = boy SEX CHROMOSOMES CAN CARRY OTHER GENES TOO = ___________________ SEX LINKED TRAITS These traits show up in different _______________ in males and females percentages because they move with the sex chromosomes Y-LINKED GENES: carried on Y Genes ______________ chromosome EXAMPLE: Hairy pinna ONLY show up _______ in males Y linked _________genes _____ X-LINKED GENES: ____________ are carried on the X chromosome X-linked recessive disorders MORE frequently show up _____________ in MALES ______ than females because males only have ONE X chromosome. ______ Males ONLY HAVE ONE X DEFECTIVE They either have the disorder NORMAL Or They are normal FEMALES HAVE TWO X CHROMOSOMES DEFECTIVE NORMAL DEFECTIVE Females have one normal gene that works. need 2 Females __________ defective recessive alleles to show the disorder The X chromosome in males . . . flies WITHOUT a copilot! . . . there’s NO BACK UP X to help them! X-LINKED RECESSIVE Examples of ________________________ DISORDERS: HEMOPHILIA ____________________ COLORBLINDNESS ____________________ DUCHENNE MUSCULAR DYSTROPHY ____________________ HEMOPHILIA CAUSE: Mutation in genes for __________________ Blood clotting proteins on X chromosome carried ______ Blood clotting proteins are missing so person with this disorder can’t stop bleeding when bleed to death from minor injured; can ________________ cuts or suffer internal bleeding from bruises or bumps. • Hemophilia -“Bleeder’s Disease” Deficient blood coagulation due to absence of coagulation factor 8 that helps cause blood to clot. • 50% of daughters will also be carriers. • 1 in 7,000 born with it • X-linked recessive on chromosome X XHXh XHY HEMOPHILIA Treatment: injections of normal clotting Need ____________ proteins to stop bleeding More common in ______ males because it is _____________ TWO recessive X-linked, but females with ______ hemophilia alleles will also show the trait. 1 in 10,000 males has hemophilia COLORBLINDNESS CAUSE: Mutation in one of three genes for _______________ carried on X chromosome Color vision Persons with this disorder have trouble distinguishing colors. Red-green _________________ colorblindness is most common Seen in 1 in 10 males 1 in 100 females http://gizmodo.com/gadgets/peripherals/samsung-develops-lcd-for-colorblind-036306.php Red-Green Color Blindness Duchenne Muscular Dystrophy CAUSE: deletion in gene that codes for a muscle protein _______________ Results in progressive weakening ____________________ and loss of skeletal muscle ___________________ http://www.cadenhead.org/workbench/gems/jerry-lewis-telethon.jpg http://www.tokyo-med.ac.jp/genet/chm/dei.gif Duchenne Muscular Dystrophy (DMD) SYMPTOMS: 1 in 3000 male births Appears before age 5 Progressive muscle weakening Most in wheelchair by age 13 Eventually lethal What’s the pattern: Y-linked traits show up _______ ONLY in _______ males ________ X-linked recessive traits: __________________ ______________________ more common in males than females. ________________ ONLY FEMALES can be ________. carriers AUTOSOMAL RECESSIVE traits: _______________________ FEMALES can be ________ carriers BOTH MALES ______ & _________ CHROMOSOMAL Abnormalities ________________ • 1 infant in 200 newborns has a chromosomal abnormality • 28% of first trimester miscarriages have a chromosomal abnormality • Abnormalities in larger chromosomes don’t usually survive CHROMOSOMAL MUTATIONS ____________________________: structure or Change in the ______________ number ____________ of chromosomes Homologous chromosomes fail to separate during MEIOSIS ________________ NONDISJUNCTION = _________________________ One cell gets 2 copies of the chromosome the other cell gets none. Nondisjunction Nondisjunction Since it happens to a sperm or egg, the new baby can end up 3 copies with _____________ of a chromosome TRISOMY = __________________ OR one copy of a only ___________ chromosome = ___________________ MONOSOMY Human Abnormalities caused by Non-Disjunction __________________ Down syndrome Klinefelter syndrome __________________ Turner syndrome __________________ TRISOMY 21 Down syndrome (= ____________) Down syndrome (Trisomy 21) • 1 in 800 births • Similar facial features • Slanted eyes • Protruding tongue Down syndrome (Trisomy 21) Simian line on palm Down syndrome (Trisomy 21) • Most common chromosomal abnormality • 50% have heart defects that need surgery to repair • Mild to severe mental retardation • Increases susceptibility to many diseases • Risk of having a child with Down syndrome increases with age of mom Down syndrome (Trisomy 21) • Risk of having a child with Down syndrome related to age of mom • More common in women UNDER 16 or OVER 35 Cells that make eggs start meiosis in embryo Stop in PROPHASE I (synapsis) One egg restarts & finishs division each month So an egg released at age 40 has been in synapsis for 40 years . . . chromosomes more likely to “stick” Turner syndrome XO Turner syndrome ____ • • • • • • • • • 1 in 5000 births Females have only one X chromosome Small size Slightly decreased intelligence 35% have heart abnormalities Hearing loss common Broad chest Reproductive organs don’t develop at puberty Can’t have children http://medgen.genetics.utah.edu/photographs/diseases/high/611.gif Klinefelter syndrome XXy Klinefelter syndrome • 1 in 1000 births • Males have extra X chromosomes (Can be XXy, XXXy, or XXXXy) • Average to slight decrease in intelligence • Small testes/can’t have children • Usually not discovered until puberty when don’t mature like peers If having extra chromosomes causes genetic problems, how come having two X chromosomes in females and one X in males is not a problem? X-chromosome Inactivation ONE X chromosome In female cells ______ SWITCHED OFF is randomly ________________ It condenses and forms a dense region in the nucleus called a BARR BODY _____________ http://fig.cox.miami.edu/~cmallery/150/gene/barr.htm CAT COLOR http://www.islandstrolling.com/mainland/peloponnes/photo/mystra_cat_white_orange_black.jpg In cats, a gene that controls the SPOT COLOR _____________ is carried on the X chromosome ____________________ In some female cells the X with the allele for orange spots is switched off and in some cells the X with the allele for black spots is switched off, so cat has different colored spots. See a video CAT COLOR http://ascensionparish.net/forum/messages/14/2493.jpg Male cats have only _________ one X chromosome, so they can only have ____________ one color of spots! THINK ABOUT IT? How many colors of spots could a male cat with Klinefelter syndrome have? Detecting Genetic Disease • Genetic Screening – examination of a person’s genetic makeup involving karyotypes, blood tests for certain proteins, or direct tests of DNA – 200 genetic disorders can be detected in the fetus – Amniocentesis – removal of amniotic fluid from the sac that surrounds the fetus between the 14th and 16th week of pregnancy – Chorionic villi sampling – sample of cells derived between the 8th and 10th week from the zygote - cells grow between the mother’s uterus and the placenta; cells chromosomes, and proteins analyzed Detecting Genetic Disease – Chorionic villi sampling – CVS can help identify chromosomal problems such as Down syndrome or other genetic diseases such as cystic fibrosis, TaySachs disease and sickle cell anemia. CVS is considered to be 98% accurate in the diagnosis of chromosomal defects, such as Down syndrome.