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Transcript
Introduction to Genetics Chapter 6 THE WORK OF GREGOR MENDEL Transmission of characteristics from parents to offspring _______________________is heredity called ___________________. The _________ that studies _____ science how passed on those characteristics are _________ from one generation to the next is genetics called___________________. Father of Genetics The __________________ is Gregor Mendel _________________, a monk whose ____study _____ of genetic traits was the beginning of our_______________ understanding how genes work about _____________________. Mendel’s Experiments Gregor Mendel - Untamed Science http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif Mendel designed experiments ____________ using Pea plants __________ in the monastery garden MALE _______ part of flower makes Pollen ___________ (sperm) __FEMALE ________ part of flower makes __egg _____ cells http://www.cedarville.edu/academics/education/resource/schools/chca/2scideb/debwebpv.htm In pea plants, the pollen normally joins with an egg from the same _______ plant Self pollinating (=_______________ ) so seeds ONE parent have “_________________” http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif MENDEL’S PEA EXPERIMENTS Mendel started his experiments with peas that were true breeding _________________ = if allowed to self pollinate _________________ they would produce offspring identical ____________________ to themselves. http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif MENDEL’S PEA EXPERIMENTS removed pollen Mendel ____________________ added pollen making parts and ____________ another from _______ plant. This allowed him to cross-breed _____________ plants different with ______________ characteristics and study ________ the results specific characteristic A _____________________ is trait called a ____________ studied 7 traits Mendel ______________ in peas. Pearson Education Inc,; Publishing as Pearson Prentice Hall MENDEL’S EXPERIMENTS P1 ____ generation parental (_________) F1 ____ generation filial (______= offspring) F2 ___ generation Principles of Dominance Section 11-1 P Generation Tall Short F1 Generation Tall Tall F2 Generation Tall Tall Tall Short Principles of Dominance Section 11-1 P Generation Tall Short F1 Generation Tall Tall F2 Generation Tall Tall Tall Short crossed PURE When Mendel ______________ PLANTS contrasting with 2 ______________ traits: (EX: Tall crossed with short) He always found same pattern: ONE trait ____________ showed 1. ONLY ______ F in the ____ generation BUT . . . 1 Missing trait ____________ returned 2. ___________ 2 in the __F__ generation in a 3:1 _________ ratio PATTERNS ARE THE KEY Image modified from: http://www.laskerfoundation.org/rprimers/gnn/timeline/1866.html http://www.accessexcellence.org/AB/GG/mendel.html Mendel decided that there must be a pair of FACTORS __________________ that control ________each trait and that one factor __________ must be able to _______ the other. HIDE We now know that Mendel’s factors are genes ________________ carried on homologous the pair of________________ chromosomes _________________ http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif DIFFERENT ________ gene CHOICES _______ for a trait are called ALLELES ___________. http://sps.k12.ar.us/massengale/genetics%20tutorial.htm DOMINANT __________________ = An HIDES allele that ________ the presence of another allele RECESSIVE __________________ = An allele is hidden by that __________________ the presence of another allele F1 offspring __________ received ____ an allele TALL for tallness from their _______ parent and an allele for shortness SHORT from their ________ parent. LOOK TALL The F1 plants ALL ___________ but are ___________ an carrying shortness allele for _____________ Images from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006 EXPLAINING the F1 CROSS SEGREGATION LAW OF ___________________ alleles are separated when the F1 plants made gametes ______________ When these gametes recombined to make the F2 generation, the recessive _____________ trait reappears _______________ in ¼ of the offspring Law of Segregation • Organisms inherit two copies of each gene, one from each parent • Organisms donate only one copy of each gene in their gametes. • Thus, the two copies of each gene segregate, or separate, during gamete formation Mendel’s Experiments Mendel’s Experiments/History Ticket Out the Door 1. 2. 3. 4. 5. 6. 7. 8. 9. What is heredity? What is genetics? Who is the Father of Genetics? What type of plant is this person most famous for studying? What is a trait? What are alleles? What is dominant? What is recessive? What is the law of segregation? Introduction to Genetics Chapter 6 PUNNETT SQUARES AND PROBABILITY PROBABILITY ____________________ likelihood is the __________ that a particular event will occur _________________ It can be written as a: 1/4 Fraction ____ 25% Percent ____ 3:1 Ratio ____ http://www.arborsci.com/CoolStuff/CoinFlip.jpg COIN FLIP There are 2 possible outcomes: HEADS TAILS The chance the coin will land on either one is: 1/2 50% 1:1 ____ ____ ____ Alleles segregate randomly just like a coin flip. . . So you can use probability to predict outcomes of genetic crosses. PROBABILITIES DON’T affect PAST outcomes ______ _____ FUTURE _________ones If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too. Probability best _____________ works ______ in predicting large ___________ a ________ number of events. The more flips. . . The closer results will be to the expected 50:50 average. DOMINANT/RECESSIVE Dominant _____________ allele is represented by a capital ____________ letter. (usually the first letter of the trait) Recessive ____________ allele is represented by the SAME _________________ letter. lower-case T EX: Tall = ______ t NOT S for short Short =______ HOMOZYGOUS/HETEROZYGOUS When both alleles in the pair are SAME the _______, the organism is HOMOZYGOUS PURE _______________ or __________ TT EX: ____ or tt ___ Homozygous dominant Ex: TT - _____________________ Homozygous recessive Ex: tt - ______________________ When both alleles in the pair are DIFFERENT _____________, the organism is HETEROZYGOUS or _____________ HYBRID _________________ Tt Ex: ____ PHENOTYPE/GENOTYPE genetic makeup The ________________ of an GENOTYPE organism is its _____________ Example: TT or tt appearance The ____________of an organism is PHENOTYPE its _____________. It is what you see in a photograph. Example: round or smooth MAKING A CROSS for only a ONE GENE __________ trait = MONOHYBRID CROSS ____________________ A Punnett square for a MONOHYBRID CROSS looks like this: PUNNETT SQUARES are used to show possible offspring from a cross between 2 parents Parent alleles _______________ go at top and on left side Boxes show T possible offspring ____________ combinations ___________________ t T T Steps for Making Punnett Squares Figure out 1. ___________________ what _________________ are. parent alleles Choose 2. ___________________ correct size ________ Punnett square ____________. Put in 3. ___________________ possible parent gametes _____________________________. 4. ___________________ boxes with Fill in offspring combinations ___________________. probabilities 5. Determine ________________ of genotypes ____________________ & ___________________________. phenotypes IN PEA PLANTS Tall is dominant over short T TALL = ____ t SHORT = ____ LET’S MAKE A CROSS! PURE TALL X PURE SHORT PURE TALL parent What are the parent alleles? TT T _________ HOMOZYGOUS DOMINANT T What gametes can it make? PURE SHORT parent What are the parent alleles? HOMOZYGOUS RECESSIVE tt t _________ t What gametes can it make? T T t Tt Tt t Tt Tt ALL _____ of the offspring 100 % ____ 4 ___/4 will be Tt TALL GENOTYPE _____ PHENOTYPE _______ HYBRID TALL parent What are the parent alleles? Tt T HETEROZYGOUS _________ t What gametes can it make? T t T TT Tt t Tt tt GENOTYPES TT ¼ = _____ Tt ½ = _____ tt ¼ = _____ 75 TALL 3/4 PHENOTYPES ____ or ____% _________ SHORT 25 ____ _________ 1/4 or ____% PRACTICE MAKING GAMETES for a MONOHYBRID CROSS T Tall = ____ t Short = ____ R Round seeds = ___ r Wrinkled seeds = ___ What are the possible gametes? What gametes can it produce? TT T Homozygous Tall parent = T What are the possible gametes? What gametes can it produce? Rr R Heterozygous Round parent = r What are the possible gametes? Hybrid Tall parent = What gametes can it produce? Tt T t Punnett Square Animation Punnett Square Animation Ticket out the Door Make Punnett Squares for the following (List the genotypes and phenotypes for each Punnett, that means letter combinations and physical appearance): 1. A green pea plant (Gg) is crossed with a yellow pea plant (gg). 2. A tall plant (TT) is crossed with a tall plant (Tt). 3. A tall plant (Tt) is crossed with a short plant (tt). 4. A red flower (Rr) is crossed with a white flower (rr).
