Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 9 Patterns of Inheritance

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Purebreds and Mutts–A Difference of Heredity Purebred dogs –Are very similar on a genetic level due to selective breeding

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mutts, or mixed breed dogs on the other hand –Show considerably more genetic variation

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MENDEL’S LAWS 9.1 The science of genetics has ancient roots The historical roots of genetics, the science of heredity –Date back to ancient attempts at selective breeding

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.2 Experimental genetics began in an abbey garden Modern genetics –Began with Gregor Mendel’s quantitative experiments with pea plants Petal Carpel Stamen Figure 9.2 BFigure 9.2 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mendel crossed pea plants that differed in certain characteristics –And traced traits from generation to generation Figure 9.2 C 1 Removed stamens from purple flower 2 Transferred pollen from stamens of white flower to carpel of purple flower 3 Pollinated carpel matured into pod 4 Planted seeds from pod Offspring (F 1 ) Parents (P) Purple Carpel White Stamens

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mendel hypothesized that there are alternative forms of genes –The units that determine heritable traits Flower color Flower position Seed color Seed shape Pod color Pod shape Stem length Purple White Axial Terminal RoundWrinkled InflatedConstricted Tall Dwarf Green Yellow GreenYellow Figure 9.2 D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.3 Mendel’s law of segregation describes the inheritance of a single characteristic From his experimental data –Mendel deduced that an organism has two genes (alleles) for each inherited characteristic Figure 9.3 A P generation (true-breeding parents) F 1 generation F 2 generation Purple flowersWhite flowers  All plants have purple flowers Fertilization among F 1 plants (F 1  F 1 ) of plants have purple flowers 3434 of plants have white flowers 1414

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings For each characteristic –An organism inherits two alleles, one from each parent

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings If the two alleles of an inherited pair differ –Then one determines the organism’s appearance and is called the dominant allele The other allele –Has no noticeable effect on the organism’s appearance and is called the recessive allele

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mendel’s law of segregation –Predicts that allele pairs separate from each other during the production of gametes Figure 9.3 B P plants Gametes Genetic makeup (alleles) Gametes F 1 plants (hybrids) F 2 plants PP pp All P All p All Pp Sperm 1212 P P P p p PP Pp pp Eggs Genotypic ratio 1 PP : 2 Pp: 1 pp Phenotypic ratio 3 purple : 1 white 1212 p

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.4 Homologous chromosomes bear the two alleles for each characteristic Alternative forms of a gene –Reside at the same locus on homologous chromosomes Figure 9.4 Genotype: PPaaBb Heterozygous P a b P a B Gene loci Recessive allele Dominant allele Homozygous for the dominant allele Homozygous for the recessive allele

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.5 The law of independent assortment is revealed by tracking two characteristics at once By looking at two characteristics at once –Mendel tried to determine how two characteristics were inherited

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mendel’s law of independent assortment –States that alleles of a pair segregate independently of other allele pairs during gamete formation Figure 9.5 A Hypothesis: Dependent assortment Hypothesis: Independent assortment RRYY rryy Gametes RRYY rryy RrYy RY ry RY Sperm RY ry RY ry Ry ry RY RRYY RrYY RRYy RrYy RrYY rrYY RrYy rrYy RRYy RrYy RRyy Rryy RrYy rrYy Rryy rryy RY ry RY Actual results contradict hypothesis Actual results support hypothesis Yellow round Green round Yellow wrinkled Green wrinkled Eggs P generation F 1 generation F 2 generation Eggs 

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings An example of independent assortment Black coat, normal vision B_N_ Black coat, blind (PRA) B_nn Chocolate coat, normal vision bbN_ Chocolate coat, blind (PRA) bbnn Blind 9 black coat, normal vision 3 black coat, blind (PRA) 3 chocolate coat, normal vision 1 chocolate coat, blind (PRA) BbNn  BbNn Phenotypes Genotypes Mating of heterozygotes (black, normal vision) Phenotypic ratio of offspring Figure 9.5 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.6 Geneticists use the testcross to determine unknown genotypes The offspring of a testcross, a mating between an individual of unknown genotype and a homozygous recessive individual –Can reveal the unknown’s genotype Testcross: Genotypes Gametes Offspring  B_ bb Two possibilities for the black dog: BB or Bb B B b b Bb b bb All black 1 black : 1 chocolate Figure 9.6

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.7 Mendel’s laws reflect the rules of probability Inheritance follows the rules of probability

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The rule of multiplication –Calculates the probability of two independent events The rule of addition –Calculates the probability of an event that can occur in alternate ways Figure 9.7 F 1 genotypes Bb female Formation of eggs F 2 genotypes Bb male Formation of sperm B b B B B B b b b B b b

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 9.8 Genetic traits in humans can be tracked through family pedigrees The inheritance of many human traits –Follows Mendel’s laws Dominant TraitsRecessive Traits FrecklesNo freckles Widow’s peakStraight hairline Free earlobeAttached earlobe Figure 9.8 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Family pedigrees –Can be used to determine individual genotypes Dd Joshua Lambert Dd Abigail Linnell D ? John Eddy D ? Hepzibah Daggett D ? Abigail Lambert dd Jonathan Lambert Dd Elizabeth Eddy Dd Dd dd Dd Dd Dd dd Female Male Deaf Hearing Figure 9.8 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 9.9 Many inherited disorders in humans are controlled by a single gene Some autosomal disorders in humans Table 9.9

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Parents Offspring Sperm Normal Dd Normal Dd  Eggs D d DD Normal Dd Normal (carrier) Dd Normal (carrier) dd Deaf Figure 9.9 A Recessive Disorders Most human genetic disorders are recessive

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 9.9 B Dominant Disorders Some human genetic disorders are dominant

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 9.10 New technologies can provide insight into one’s genetic legacy New technologies –Can provide insight for reproductive decisions

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Identifying Carriers For an increasing number of genetic disorders –Tests are available that can distinguish carriers of genetic disorders

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 9.10 A Amniocentesis Chorionic villus sampling (CVS) Ultrasound monitor Fetus Uterus Amniotic fluid Fetal cells Several weeks Biochemical tests Several hours Fetal cells Uterus Cervix Suction tube inserted through cervix to extract tissue from chorionic villi Needle inserted through abdomen to extract amniotic fluid Centrifugation Ultrasound monitor Fetus Placenta Chorionic villi Karyotyping Placenta Cervix Fetal Testing Amniocentesis and chorionic villus sampling (CVS) –Allow doctors to remove fetal cells that can be tested for genetic abnormalities

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 9.10 B Fetal Imaging Ultrasound imaging –Uses sound waves to produce a picture of the fetus

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Newborn Screening Some genetic disorders can be detected at birth –By simple tests that are now routinely performed in most hospitals in the United States

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ethical Considerations New technologies such as fetal imaging and testing –Raise new ethical questions

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings VARIATIONS ON MENDEL’S LAWS 9.11 The relationship of genotype to phenotype is rarely simple Mendel’s principles are valid for all sexually reproducing species –But genotype often does not dictate phenotype in the simple way his laws describe

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.12 Incomplete dominance results in intermediate phenotypes When an offspring’s phenotype is in between the phenotypes of its parents –It exhibits incomplete dominance Figure 9.12 A P generation F 1 generation F 2 generation Red RR Gametes  White rr Gametes Sperm Eggs Pink Rr R R R r r R r r Red RR Pink rR Pink Rr White rr Genotypes: HH Homozygous for ability to make LDL receptors Hh Heterozygous hh Homozygous for inability to make LDL receptors Phenotypes: LDL receptor Cell Normal Mild diseaseSevere disease Figure 9.12 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.13 Many genes have more than two alleles in the population In a population –Multiple alleles often exist for a characteristic

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The ABO blood type in humans –Involves three alleles of a single gene The alleles for A and B blood types are codominant –And both are expressed in the phenotype Figure 9.13 Blood Group (Phenotype) Genotypes Antibodies Present in Blood Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left O A B AB O A B AB ii I A or I A i I B or I B i IAIBIAIB Anti-A Anti-B Anti-A —

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.14 A single gene may affect many phenotypic characteristics In pleiotropy –A single gene may affect phenotype in many ways Individual homozygous for sickle-cell allele Abnormal hemoglobin crystallizes, causing red blood cells to become sickle-shaped Sickle-cell (abnormal) hemoglobin Sickle cells Breakdown of red blood cells Clumping of cells and clogging of small blood vessels Accumulation of sickled cells in spleen Physical weakness Anemia Heart failure Pain and fever Brain damage Damage to other organs Spleen damage Impaired mental function Paralysis Pneumonia and other infections Rheumatism Kidney failure 5,555  Figure 9.14

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.15 A single characteristic may be influenced by many genes Polygenic inheritance –Creates a continuum of phenotypes Figure 9.15 P generation F 1 generation F 2 generation Sperm Eggs aabbcc (very light) AABBCC (very dark) AaBbCc  Skin color Fraction of population 

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.16 The environmental affects many characteristics Many traits are affected, in varying degrees –By both genetic and environmental factors Figure 9.16

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 9.17 Genetic testing can detect disease-causing alleles Predictive genetic testing –May inform people of their risk for developing genetic diseases

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings THE CHROMOSOMAL BASIS OF INHERITANCE 9.18 Chromosome behavior accounts for Mendel’s laws Genes are located on chromosomes –Whose behavior during meiosis and fertilization accounts for inheritance patterns

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The chromosomal basis of Mendel’s laws All round yellow seeds (RrYy) Metaphase I of meiosis (alternative arrangements) Anaphase I of meiosis Metaphase II of meiosis Gametes F 1 generation F 2 generation Fertilization among the F 1 plants (See Figure 9.5A) 1414 RY 1414 ry R R R R R R R y Y Y Y Y Y y Y Y r r y R Y r y R r r r r rr y r Y R y r Y R y 1414 rY 1414 Ry 9 : 3 : 1 y y y y Y Figure 9.18

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.19 Genes on the same chromosome tend to be inherited together Certain genes are linked –They tend to be inherited together because they reside close together on the same chromosome Experiment Explanation: linked genes PpLI  PpLI Long pollen ObservedPrediction Phenotypesoffspring(9:3:3:1) Purple long Purple round Red long Red round Parental diploid cell PpLI Most gametes Most offspring Eggs 3 purple long : 1 red round Not accounted for: purple round and red long Meiosis Fertilization Sperm P I P L P I P L P I P L P I P L Purple flower Figure 9.19

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.20 Crossing over produces new combinations of alleles Crossing over can separate linked alleles –Producing gametes with recombinant chromosomes AB ab Tetrad Crossing over AB Ab ab aB Gametes Figure 9.20 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Thomas Hunt Morgan –Performed some of the early studies of crossing over using the fruit fly Drosophila melanogaster Figure 9.20 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Morgan’s experiments –Demonstrated the role of crossing over in inheritance Figure 9.20 C Experiment Gray body, long wings (wild type) GgLI Female  Black body, vestigial wings ggll Male Offspring Gray long Black vestigialGray vestigial Black long Parental phenotypes Recombinant phenotypes Recombination frequency = = 0.17 or 17% 391 recombinants 2,300 total offspring Explanation GgLI (female) ggll (male) GL g l g l g l GL g lGl g L g l EggsSperm GL g l g l g l g l g l L g l G Offspring

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.21 Geneticists use crossover data to map genes Morgan and his students –Used crossover data to map genes in Drosophila Figure 9.21 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Recombination frequencies –Can be used to map the relative positions of genes on chromosomes. Figure 9.21 B Mutant phenotypes Short aristae Black body (g) Cinnabar eyes (c) Vestigial wings (l) Brown eyes Long aristae (appendages on head) Gray body (G) Red eyes (C) Normal wings (L) Red eyes Wild-type phenotypes Chromosome g c l 9%9.5% 17% Recombination frequencies Figure 9.21 C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings SEX CHROMOSOMES AND SEX-LINKED GENES 9.22 Chromosomes determine sex in many species In mammals, a male has one X chromosome and one Y chromosome –And a female has two X chromosomes (male)(female) Parents’ diploid cells Sperm Egg Offspring (diploid) 44 + XY 44 + XX 22 + X 22 + Y 22 + X 44 + XX 44 + XY Figure 9.22 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The Y chromosome –Has genes for the development of testes The absence of a Y chromosome –Allows ovaries to develop

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Other systems of sex determination exist in other animals and plants 22 + XX 22 + X 76 + ZW 76 + ZZ Figure 9.22 D Figure 9.22 C Figure 9.22 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 9.23 Sex-linked genes exhibit a unique pattern of inheritance All genes on the sex chromosomes –Are said to be sex-linked In many organisms –The X chromosome carries many genes unrelated to sex

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In Drosophila –White eye color is a sex-linked trait Figure 9.23 A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The inheritance pattern of sex-linked genes –Is reflected in females and males FemaleMale Sperm XrXr Y XRXR X r Y  X R X R X r X R Y Eggs R = red-eye allele r = white-eye allele FemaleMale Sperm XRXR Y XRXR X R Y  X R X r X R X R Y Eggs XrXr X r X R X r Y Female Sperm XrXr Y XRXR X r Y  X R X r X R Y Eggs Male XrXr X r X r Y Figure 9.23 BFigure 9.23 CFigure 9.23 D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 9.24 Sex-linked disorders affect mostly males Most sex-linked human disorders –Are due to recessive alleles –Are mostly seen in males Queen victoria Albert Alice Louis Alexandra Czar Nicholas II of Russia Alexis Figure 9.24 AFigure 9.24 B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A male receiving a single X-linked allele from his mother –Will have the disorder A female –Has to receive the allele from both parents to be affected