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Biology, Chapter 10.1 Mendel 10.1 Mendel's Laws of Heredity Why Mendel Succeeded Intro Mendel chose his subject carefully 1. What characteristics of Pisum made it a good subject for Mendel's studies? Reproduce _________________ Haploid male and female gametes fuse during ___________________________ Meiosis in anthers gives pollen, in ovules gives eggs Easy to __________________________ for mating Closed flowers most often self-pollinate Can open the flowers, _________________________, and use separate pollen Easy to grow; give many offspring per plant; many known traits Mendel was a careful researcher 2. How did Mendel's application of the scientific method lead to success? Performed ________________________________: studied one trait at a time, at first _______________________ his experiments Mathematically and statistically analyzed his data ___________________ his results Mendel's Monohybrid Crosses Intro 3. Contrast true breeding and hybrid peas. ___________________________ are genetically pure Ex.: true breeding tall always gave tall Ex.: pure bred dogs ____________ are the offspring of parents with contrasting traits Ex.: the offspring of one ______ parent and one ___________ parent Monohybrid means have one contrasting characteristic in the parents The first generation 4. Exemplify Mendel's _____________________ crosses. Parents: true breeding tall X true breeding short F1 generation = first generation of offspring F = "filial" In the example, pure tall X pure short ________________________ The second generation Next cross: _______________ X ________________ from the F1 F2 generation: _______________________________________ The rule of unit factors 5. Differentiate genes and alleles and give examples. Genes govern traits like plant height and flower color ___________ are forms of genes Height gene; 2 alleles; tall and short Flower ________ gene; 2 ________________; purple and white The rule of dominance 6. Define dominant and recessive in terms of the behavior of alleles in crosses. Dominant traits ________________________ recessive traits Ex.: dominant tall covered up recessive short in the F1 Symbols Dominant alleles are given a ____________ letter; T for tall Recessive alleles are given the corresponding small letter; t for short They are two forms of the same gene The law of segregation 7. Summarize the law of segregation. Each offspring gets _______ of each allele from ______________________ The ______________________ of alleles determines the trait When the offspring reproduce one of its two alleles is given ________________ Phenotypes and Genotypes 8. Contrast genotype and phenotype. ______________ = the combination of alleles in an individual _______________ = the appearance of the trait 9. Contrast homozygous and heterozygous. ________zygous = two alleles that are the ________; ex.: TT or tt _________zygous = two alleles that are ________________; ex.: Tt Mendel's Dihybrid Crosses Intro 10. Exemplify Mendel's dihybrid crosses. Parental: pure ______________________ X pure _____________________ The first generation F1: __________________________________________________ The second generation Next cross: round, yellow hybrid X round, yellow hybrid from the F1 F2 generation: ____ round, yellow ____ round, green ____ wrinkled, yellow ____ wrinkled, green The law of independent assortment 11. Summarize the law of independent assortment. Genes for different traits are ________________________________ For the above example: seed shape allele is independently from seed color allele Mainly because the genes are on ___________________________________ Punnett Squares Intro Monohybrid crosses 12. For practice, draw and analyze Punnett squares for monohybrid crosses of: Two heterozygous axial plants Two heterozygous plants with yellow seeds Two heterozygous six-fingered people Two heterozygous people with free-hanging earlobes Dihybrid crosses 13. For practice, draw and analyze Punnett squares for monohybrid crosses of: Two heterozygous axial plants also heterozygous for yellow seeds Two heterozygous six-fingered people also heterozygous for free-hanging earlobes Probability 14. How did Mendel apply the laws of probability to predict the outcomes of individual and large groups of crosses? For monohybrid example 1/2 chance of getting dominant gene from the father 1/2 chance of getting dominant gene from the mother 1/2 X 1/2 chance of both happening to give homozygous dominant For dihybrid example 1/4 chance an offspring will be homozygous recessive for one trait 1/4 chance an offspring will be homozygous recessive for the other trait 1/4 X 1/4 = 1/16 chance of the offspring being homozygous recessive for both traits 10.2 [continued from the previous test] Meiosis Provides for Genetic Variation Intro Genetic recombination 15. Describe two sources of genetic recombination in meiosis. _________________ switches alleles on homologous chromosomes Parental chromosomes randomly align and separate in ____________________ Meiosis explains Mendel's results 16. Correlate the behavior of chromosomes with the behavior of Mendel's factors. __________________ are in pairs, _______________ are in pairs Chromosomes separate in anaphase I, factors separate in anaphase I We inherit ________ of chromosomes, __________ of factors from each parent Different pairs of homologues separate independently, same for factors Nondisjunction Intro 17. Define nondisjunction and some of its possible consequences. = failure of chromosomes to _________________ properly in meiosis Consequences One extra chromosome [2n +1] = trisomy; ______________________ One less [2n -1] = _____________; Turner syndrome Extra whole sets [3n] = __________________ Polyploidy 18. Differentiate the effects of polyploidy in animals and plants. In animals, almost always ______________ In plants, polyploids are often ________________________________ Gene Linkage Maps 19. How does the behavior of genes on the same chromosome violate the law of independent assortment. Genes on the same chromosome are a ________________________ Part of the same DNA strand, tend to __________________________________ 20. How is crossing over used to create chromosome maps. __________________ separates genes on the same chromosome The _________________ of separation is a measure of _____________ The closer two genes are the lower the frequency of crossing over And, vise versa Example: A-B, 5; C-B, 40; A-D, 25; C-D, 10 Draw map starting with longest interval C-B, 40 Work from longest two shortest Try out hypothetical arrangements Chapter 12, Patterns of Heredity and Human Genetics 12.1 Mendelian Inheritance of Human Traits Making a Pedigree Pedigrees illustrate inheritance 1. List the rules for organizing a pedigree. ____________ = females, ____________ = males Each row is a generation Biological parents are connected by horizontal lines Biological children are connected by a bracket under their parents ______________ individuals are shaded; ____________ half-shaded Death is indicated by a slash Analyzing a pedigree 2. List guidelines for recognizing simple patterns of heredity in a pedigree. Rare recessives _________________________________ People marrying into the family are assumed to not carry Marriage ________________________ is a tipoff Dominants ______________________ ____________________ affects males usually exclusively Simple Recessive Heredity Intro 3. How significant are human recessive disorders? Most genetic disorders are ______________________ Cystic fibrosis 4. Describe the prevalence, symptoms, and treatment of cystic fibrosis. 1 in 28 whites are ______________________; 1 in 2500 white babies has it Defect in a plasma membrane protein ________________________ Physical therapy, special diet, lung transplant Tay-Sachs disease 5. Describe the prevalence, symptoms, and treatment of __________________ disease. Most common in Jewish people from Eastern Europe Lack a protein that ______________ brain lipids early neural degeneration Experimental therapies only: enzyme replacement, gene therapy Phenylketonuria 6. Describe the prevalence, symptoms, and treatment of __________________________. 1 in 15,000 births; postnatal hospital testing in the US Lack the enzyme to degrade phenylalanine; _____________________ _______ low in phenylalanine completely ______________________________ Simple Dominant Heredity Intro Simple dominant traits 7. List common non-pathological human dominant traits. Cleft chin, widow's peak, freely hanging earlobes, hitchhiker's thumb, mid-digital hair Huntington's disease 8. Describe the prevalence, symptoms, and treatment of _____________________________. 10 in 100,000 births in Western Europe; 0.1 in 100,000 in Africa ___________________________; slow neural degeneration Testing but little treatment 12.2 When Heredity Follows Different Rules Complex Patterns of Intelligence Incomplete dominance: Appearance of a third phenotype 9. Contrast the appearance of incomplete dominance with simple dominance and recessiveness. Simple dominance and recessiveness: heterozygote looks like dominant homozygote Incomplete dominance: heterozygote has an ___________________________________ 10. Describe an example of incomplete dominance. Snapdragon flower color: red = RR, white = R'R', pink = RR' _____________________ all pink ____________________ 1/4 red + 1/2 pink + 1/4 white Codominance: Expression of both alleles 11. Contrast the appearance of codominance with simple dominance and recessiveness. Simple dominance and recessiveness: heterozygote looks like dominant homozygote ____________________: heterozygote has both homozygote phentotypes side-by-side 12. Describe an example of codominance. Chicken feathers [one gene]: white = WW, black = BB, checkered = WB _________________________ all ____________________ Checkered x checkered 1/4 black + 1/2 checkered + 1/4 white Multiple phenotypes from multiple alleles 13. Define and exemplify multiple alleles. ___________________ for a gene Examples Pigeon color BA is red, B is blue, b is chocolate BA is dominant to B is dominant to b _______ blood type: IA and IB are codominant, i is recessive to both Sex determination 14. How is sex determined in humans? 22 pairs of chromosomes look the same in both sexes = autosomes One pair looks different = sex chromosomes ____ = female ____ = male Sex-linked inheritance 15. How was sex-linkage discovered? T.H. Morgan found _______________________________; it was male He crossed it with a normal, re-eyed female All of the offspring had normal eyes = the F1 He mated the F1 together in the F2 _____________________________________________________ Conclusion: eye color gene is on the ___________________________ 16. Predict the outcomes of crosses involving sex-linked traits. Ex.: white-eyed male x heterozygous red-eyed female XrY x XRXr [no R gene on the Y chromosome] Male gametes: 1/2 Xr + 1/2 Y Female gametes: 1/2 XR + 1/2 Xr Ex.: red-eyed male x heterozygous red-eyed female Polygenic inheritance 17. Define polygenic inheritance and give examples of such traits. = governed by _____________________; give a range of phenotypes Traits: ________________, weight, ___________________ Environmental Influences Influence of external environment 18. Give examples of external influences on phenotype. Temperature affects _________________________________ Shapes of leaves are affected by the amount of sunlight Influence of internal environment 19. Give examples of internal influences on phenotype. Female sheep have slender curved horns; males are heavy coiled _______________________________ is dominant in men, recessive in women 12.3 Complex Inheritance of Human Traits Codominance in Humans Sickle-cell anemia 20. How is sickle-cell expressed as a codominant trait? How is it recessive? ________ normal and sickle hemoglobins are made in the heterozygote The anemia is _____________________ Disease is caused by receiving sickle allele from both parents _________________________________ with "sickle-cell trait" 21. Draw and analyze the Punnett square for the marriage of two people with sickle-cell trait. Multiple Alleles Govern Blood Type 22. List the phenotypes and genotypes for ABO blood type in humans. ___________ blood: IAIA or IAi ___________ blood: IBIB or IBi ___________ blood: IAIB ___________ blood: ii The importance of blood typing 23. How is blood typing important in our society? Medically: wrong blood is __________________ after transfusion Evidence: can easily ________________ someone as a source or parent 24. Determine possible parentage give ABO blood types for prospective parents and children. Can a type O child come from an A father and a B mother? Can an A child have a type B father? Can an AB mother and a type O father have a type A child? Sex-linked Traits in Humans Red-green color blindness 25. Predict the offspring of a red-green colorblind father and a mother heterozygous for redgreen color blindness. Red-green color blindness is ____________________ Father is XcY; gametes are 1/2 Xc and 1/2 Y Mother is XCXc; gametes are 1/2 XC and 1/2 Xc Hemophilia: An X-linked disorder 26. Describe hemophilia and its treatment. ____________________________; missing a blood clotting factor Purified ________________________ now completely control the condition 27. Predict the offspring of a normal father and a hemophiliac mother. Father is XHY; gametes are 1/2 XH and 1/2 Y Mother is XhXh; gametes are all Xh Polygenic Inheritance in Humans ________________: A _____________________ trait Changes in Chromosome Numbers Abnormal numbers of autosomes 28. Describe a ___________________. Photographs of chromosomes lined up in pairs Used to detect chromosomal abnormalities Down syndrome: Trisomy 21 29. Describe Down syndrome. _________________; 1 in 700 births Some retardation Diagnosed in _______________________ and ultrasound Abnormal numbers of sex chromosomes 30. Describe common abnormal numbers of sex chromosomes. XO 45 total chromosomes; _____________________________ ____________________________ with varying degrees of retardation XXY 47 total; _______________________ syndrome Sterile ______________________ males XYY 47 total; 1 in 1000 boys Boys with increased risk of ___________________________ and delayed speech and language skills