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Unit 6: Genetics & Heredity Ch 8: Heredity & Ch 11: Human Genetics • What is genetics? – __________________ = the passing of traits from parents to offspring – Why is your combination of genes unique? Gregor Mendel – the Father of Genetics 1822-1884 Mendel’s Experiments • Studied garden peas – _____ different traits with clearly different forms – Tried to determine how these traits were transmitted from parent to offspring Mendel’s Experiments • Male & female parts in same flower –Normally • Self pollinate –Produce pure offspring » ______ parents produce______ offspring » ______ parents produce _________ offspring Mendel’s Experiments • Cross pollination of pure purple parent & pure white parent (parent generation) • Purple offspring (________ ____________ generation) • Hybrids (genes for both purple & white in all offspring) Mendel’s Experiments • Offspring allowed to self pollinate • New offspring (F2, second filial, generation) weren’t all purple Parent – _______ – _______ First filial Crossed 2 F1 plants to get F2 Second Filial Mendel’s Principle of Dominance • Mendel noted that for each trait one form dominates the other – In other words, the __________ trait prevents the expression of the _______________ trait. • Ex. In peas, purple x white gives all purple offspring – ____________________ – ____________________ Punnett Squares • Helps to predict the results of crosses – all possible resulting offspring • & the probability of each offspring’s genes • Ea. parent can contribute 1 of 2 genes for a trait (______)- found on homologous chromosomes – Represent with letters • ________________ = dominant gene • ________________ = recessive gene • ________________ – alleles same – ex. AA or aa • ________________ – alleles different – ex. Aa Genotype vs. Phenotype • ____________________ = actual genetic make-up of individual – represented by letters • __________ = outward (physical) expression of the genotype – (due to) the protein that is produced • Ex. Let P = purple & p = white – Genotypes PP & Pp both have the same phenotype (purple) • PP = ________________ dominant • Pp = ________________________ – Genotype pp has (white) phenotype: • pp = ________________ recessive Mendel’s Principle of Segregation • During gamete formation, the pair of genes responsible for each trait separates so that each gamete receives only 1 gene for each trait. – happens during meiosis I when homologous chromosomes line up (randomly) @ equator (metaphase 1) & separate (anaphase 1) Draw diagrams Mendel’s Principle of Segregation Mendel’s Principle of Segregation • tested segregation using heterozygous purple flower & homozygous white flower – Predicted _______ purple & ____ white offspring b/c: • P gene would combine w/ p gene _______ the time – producing __________ _____________ flowers • p gene would combine w/ p gene _______ the time – producing ___________ _____________ flowers Draw Punnett Square Mendel’s Principle of Independent Assortment • Genes for different traits segregate independently during gamete formation when they are located on different chromosomes… – What if they are on the same chromosome? Genes on same chromosome meiosis Genes on same chromosome Probability • The chance an event will occur • What is the chance of getting heads? Tails? – If you flip two coins, of getting 2 heads? 2 tails? – What is the chance of a couple having a boy? A girl? Of having four boys? Five girls? Draw Punnett Square Ratios • _________________________= probable ratio of genotypes in offspring of a cross – Ex. If cross PP & pp • 1PP : 2Pp : 1 pp • _________________________= probable ratio of phenotypes resulting from the genotypic ratio • Ex. If cross PP & pp • 3 purple : 1 white • ________________________________ = ratio expected based on probability (Punnett Square) • ___________________ = what actually occurs – Why would these be different? Phenotype genotype Pp Pp Phenotype genotype Pp Pp Monohybrid Cross • a cross where __________________________ ________________________ (gene) is studied – ex. only height, flower color, eye color, etc... Draw Punnett Square T t Dihybrid Cross • involves study of inheritance patterns for organisms differing in _______ (ea. w/ 2 forms). – Mendel determine if different traits of pea plants, such as flower color & seed shape, were inherited independently. Dihybrid Cross Animation Dihybrid Cross 2 traits with 2 forms Test Cross • Used to determine __________________ of dominant phenotype – Cross ______________ phenotype w/ ________ phenotype Show as P_ • If any offspring show recessive trait, unknown parent ____________ • If all show dominant trait, then parent ________ ____________________ Draw Punnett Squares Dominant/Recessive is Not Always the Mode of Inheritance • Traits are not always as clearly defined as the 7 pea plant traits Mendel studied – Incomplete dominance – Codominance – Multiple alleles – Sex-linked inheritance – Polygenic inheritance • Continuous variation Incomplete Dominance • No allele is ________ __________________ – results in _ phenotypes – ________________, ___________ (mixed), __________________. • Genotypic & phenotypic ratios same – ___________________ – ___________________ – Ex. Pink four o’clock flowers Draw Punnett Square Codominance • heterozygote displays the protein products of both alleles __________ – Ex. Roan cow has a mixture of both red & white hairs. Multiple Alleles • More than _______________ different forms of an allele exist, but individual still has just 2. • Ex. alleles that code for human blood types – A = _____ – B = _____ – O = _____ – exhibit both codominance & multiple alleles • (______= ______ ) > ______ •How many possible genotypes are there? •How many phenotypes? •Can you spot the blood type that is a product of codominance? Copy Chart antigen antigen antigens No antigens Multiple Alleles • Agouti rabbits – 4 alleles: C, cch, ch, c – w/ dominance relationship to one another: _________________________________ • agouti rabbit (wild type) – Phenotype: brown, Genotype: CC, Ccch, Cch, or Cc • “Chinchilla” (mutant) – Phenotype: silvery gray, Genotype: cchcch, cchch, or cchc • “Himalayan” (mutant): – Phenotype: white w/ black points, Genotype: cchcch chch or chc • “Albino” (mutant) – Phenotype: white, Genotype: cchcch cc Sex Determination • In humans chromosomes: – Pairs 1 – 22 = ____________________ – 23rd pair determine gender = __________________ • __________ = female • __________= male Draw Punnett Square What is the probability of having a son? A daughter? Sex-linked Inheritance • X & Y chromosomes not fully homologous – X is bigger & carries more genes • Males will have _____________________ for traits carried only on X – called _______________________________ • Ex.: – In Drosophila (fruit flies) eye color – In humans _______________________________ ___________________________________________ – X-linked traits more common in males • Why??? Sex-linked Inheritance • Predictions made using Punnett square – Include sex of each parent – Consider the sex chromosomes & genes they carry together as a unit… • ex. XG (= dominant gene), Xg (= recessive gene), Y (= no gene) XG female Xg XG Male Y Complete Punnett Square Sex-linked Inheritance • Ex. In Drosophila (fruit flies) eye color – What are the sex, genotype, & phenotype of each F2 offspring? • Are there any female carriers for the white eye gene? P generation genotypes were XRXR & XwY red-eyed Heterozygous redeyed carrier for white eye allele Sex-linked Inheritance •Hemophilia is X-linked recessive – If mother is carrier & father has hemophilia: • genotypic ratio? • phenotypic ratio? Draw Punnett Square – If mother is carrier & father is normal: • Make a Punnett square – genotypic ratio? – phenotypic ratio? Sex-linked Inheritance • pedigree chart showing inheritance of hemophilia – Does hemophilia affect one gender more often? • Why? Sex-linked Inheritance • Colorblindness is X-linked recessive – In this Punnett square, what are the genotypes & phenotypes of the parents? Ishihara test for redgreen color blindness Polygenic Inheritance • ______________ ______________ affect a single trait – shows range of phenotypes from one extreme to another (_______ ______________) • Ex. in humans: hair color, height, skin color Expression of Genes • Genes can _______________________ to control various other patterns of inheritance – Most characteristics that make up individual’s phenotype not inherited in Mendelian patterns • Ex. Modifier genes affect eye color – influence amount, intensity, & distribution of melanin (color pigment) in eye cells Expression of Genes • ____________________________ in which organism develops is another factor that affects expression – Probably due to how enzymes (proteins) operate at different temperature • Higher temps may “deactivate” enzyme & prevent a reaction form occurring (therefore, changing phenotype) • Examples: – temp & size of fruit fly wings: Warmer temps = larger wings & colder temps = smaller wings – __________: Low altitudes = taller & high altitudes = shorter – ____: Poor soil or drought may produce shorter (or no) ears – _______ seedlings: Green (dominant) & albino (recessive)… • however green color is also affected by environment – No sunlight green color cannot be expressed due to lack of chlorophyll production – Put in light green will appear b/c chlorophyll being produced Human Genetic Disorders Pedigree Charts • A ____________________________ ______________________________ of family over several generations –Scientist or a genetic counselor would find out about your family history & make this chart to analyze. • used to find out probability of a child having a disorder in a particular family –To begin to interpret a pedigree, determine if the disease or condition is autosomal or Xlinked and dominant or recessive. Pedigree Chart Square = ___________________________ Circle = ____________________________ Shaded = __________________________ Marriage = _________________________ Offspring = _________________________ Human Genetic Disorders • Due to DNA mutation (usually recessive) or chromosome abnormalities (# or structure) – Causes production of abnormal proteins • Examples: – ______________________________ (***most genetic disorders) » Cystic Fibrosis » Sickle-cell Anemia » Tay-Sachs Disease – _________________________________________________________ » Huntington’s Disease – _____________________________________________________ » Hemophilia » Color Blindness – _________________________________________________________ » Down Syndrome (trisomy 21) » Klinefelter’s Syndrome Autosomal Recessive • Must be _____________ b/c allele needed to produce trait is _______ – Cystic Fibrosis – Sickle-cell Anemia (A normal, S sickle-cell trait) – Tay-Sachs Disease Complete Punnett Squares A Male S A female S Autosomal Dominant • Can be homozygous or heterozygous b/c allele needed to produce trait is dominant – Huntington’s Disease Draw Punnett Square Sex-linked Disorders •Hemophilia •Color blindness Complete Punnett Squares Chromosomal Abnormalities • Affects ________ ____________ of chromosomes – #: • Down Syndrome (____________ … _______ copies of chromosome # __) – Cause _______ ______________ (failure of paired chromosomes to ______________ during meiosis 1 or meiosis 2) Detecting Abnormalities • Klinefelter’s Syndrome – Sex chromosome disorder » Males have ________ __________________ _______ chromosome *XXY (or 47, XXY b/c 47 total chromosomes) » Cause __________ __________________ (failure of paired chromosomes to __________________ during meiosis 1 or meiosis 2) Chromosomal Abnormalities • Affects # or structure of chromosomes – Structure: • Added, deleted, inverted, or translocated pieces Detecting Abnormalities • ______________ – “picture of human chromosomes” • From blood sample – Can detect _____ ______________ ______________ ______________ ______________ (additions, deletions, inversions, translocations) Detecting Abnormalities • _________________ – sample of fluid surrounding fetus (karyotype then made) • Can detect _________ __________________ – 14th + week of preg. • _________________ _____ sample of cells from chorion (part of structure by which fetus linked to mother) – 9th + week of preg. Review & Animations • Vocab interactive – http://nortonbooks.com/college/biology/animations/ch10a02.htm • Crosses – http://www.sonefe.org/online-biyoloji-dersleri/grade-12/monohybridcross/ • Drag & drop genetics – http://www.zerobio.com/drag_gr11/mono.htm • Various – http://www.abpischools.org.uk/page/modules/genome/dna4.cfm?coSiteN avigation_allTopic=1 • Pedigrees – http://www.learnerstv.com/animation/animation.php?ani=13&cat=biology • Genetic disorders – http://www.humanillnesses.com/original/Gas-Hep/Genetic-Diseases.html