1 / 24

Section 10.1

Section 10.1. pg. 253. Mendel’s Laws of Heredity. WHY MENDEL SUCCEEDED. Gregor Mendel (1822-1884) Austrian Monk known as the “father of modern genetics” Found that inheritance follows certain laws later known as Mendel’s Laws of Inheritance

ishana
Download Presentation

Section 10.1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Section 10.1 pg. 253 Mendel’s Laws of Heredity

  2. WHY MENDEL SUCCEEDED Gregor Mendel (1822-1884) Austrian Monk known as the “father of modern genetics” Found that inheritance follows certain laws later known as Mendel’s Laws of Inheritance Heredity is the passing on of characteristics from parent to offspring Inherited characteristics are called traits(factors) The branch of biology that studies heredity is called genetics – which was founded upon the rediscovery of his work.

  3. WHY MENDEL SUCCEEDED Mendel’s pea plant collection contained around 28,000 plants Pea plants reproduce sexually by producing male and female sex cells (gametes) Male gamete forms in pollen Female gamete formed in ovary Fertilization occurs when the male gamete unites with the female gamete Pollination is the transfer of pollen to ovary in a plant – normal reproduction. Remove male parts Snipping the stamen could prevent self-pollination

  4. Flower parts A similar figure is in the book on pg. 642

  5. WHY MENDEL SUCCEEDED Figure 10.1 Cross-pollination is transferring pollen of one plant to the ovary of another plant Mendel did this to get certain plants to breed with others to be sure of the parents Mendel was very careful with all of his work

  6. Figure 10.2 P1 MENDEL’S MONOHYBRID CROSSES Short pea plant Tall pea plant F1 Mendel was able to create tall plants and short plants (purebreds) He referred to the offspring of a purebred tall and a purebred short as a hybrid Crossing a 6’ tall plant with a 2’ tall (short) plant resulted in all 6’ tall plants Crossing the hybrid offspring resulted in 75% tall and 25% short P1 refers to the “Parental generation” F1 (“Filial”) refers to the offspring All tall pea plants F2 3 tall: 1 short

  7. MENDEL’S MONOHYBRID CROSSES So what does MONOHYBRID refer to? Referring to figure 10.3: When Mendel crossed a purebred tall with a purebred short he got all tall plants When he crossed a purebred purple flower with a purebred white flower he got all purple flowers He referred to the trait that was observed in these cases as ___________. The trait that seemed to “disappear” he called _____________. Mendel concluded that these plants have “factors” that control each of the traits (color, shape, height) We call these factors genes (parts of DNA) Alternative forms of genes (tall vs. short or yellow vs. green) are known as alleles.

  8. Plant height Figure 10.3 Seed shape Seed color Flower color Flower position Pod color Pod shape Dominant trait axial (side) round yellow purple green inflated tall Recessive trait terminal (tips) wrinkled green white yellow short constricted

  9. P1 MENDEL’S MONOHYBRID CROSSES Tall plant Short plant These two alleles for each trait can be expressed as a single letter For plant height we can use the letters “T” & “t” Dominant allele is ___. Recessive is ___. Mendel’s purebred tall plants were “TT” His purebred recessive plants were “tt” Fill in the blanks in the figure to the right which t goes where? F1 All tall plants T T T T T t t t

  10. MENDEL’S MONOHYBRID CROSSES Mendel concluded that the allele (gene form) of tall plants was dominant to the allele for short plants Confirming that the plants had two alleles for each trait (TT = Tall, Tt = Tall, or tt = short) Knowing that traits are inherited from parents, he also concluded that these alleles are inherited However a plant can only get one allele from each parent The gametes (sex cells) contained either one or the other form of the gene (T or t) The Law of _________________ states that every individual has two alleles of each gene and when gametes are produced, each gamete receives one of these alleles. T T

  11. PHENOTYPES AND GENOTYPES It’s vocab time… Phenotype refers to the organism’s physical characteristic (what you can see) Ex: Tall Genotype refers to the organism’s genetic makeup (what you can’t see) Ex: TT or Tt Homozygous/purebred represents two alleles that are the same (TT or tt) Heterozygous/hybrid organisms have different alleles (Tt) How are we going to distinguish Homo and Hetero? Law of Dominance states that hybrid organisms (Tt) will express the dominant allele (ex: tall).

  12. Monohybrid Cross (one trait) PUNNETT SQUARES Heterozygous tall parent T t T t T t 1905 - Reginald Punnett devised an easy way to find expected genotype proportions of offspring from known parent genotypes based off Mendel’s laws T T T t TT Tt t t Tt tt T t G= 50% Tt : 25% TT : 25% tt Heterozygous tall parent P= 3 Tall : 1 short

  13. PUNNETT SQUARES Round Yellow Round green Monohybrid crosses are easy to separate alleles according to Mendel’s Law of Segregation If we have heterozygous parents (Tt X Tt) we can just separate the T from the t For Dihybrid crosses, the gamete separation is a little tricky If we have two parents that are heterozygous for seed shape (Rr) and seed color (Yy) their genotype is RrYy To separate alleles into gametes we use the FOIL method from algebra RrYy makes four different gametes Using the FOIL method we get… wrinkled Yellow wrinkled green RY Ry rY ry

  14. RRYY MENDEL’S DIHYBRID CROSSES rryy Mendel also crossed plants with two different traits Round=R, wrinkled=r & Yellow=Y, green=y What is the genotype of a purebred (homozygous) plant with Round Yellow seeds? What is the genotype of a purebred (homozygous) plant with wrinkled green seeds? Purebred (homozygous) RoundYellow seeds X Purebred (homozygous) wrinkledgreen seeds Result of F1…All plants had Round Yellow seeds However crossing the Dihybrid F1 gives a ratio of 9:3:3:1 Which leads us to Mendel’s second law… The Law of __________________ states that genes for different traits are inherited independently of each other.

  15. Round Yellow (RRYY) X wrinkled green (rryy) P1 wrinkled green Round Yellow F1 All Round Yellow F2 1 9 3 3 wrinkled green Round Yellow Round green wrinkled Yellow R_Y_ rrY_ R_yy rryy

  16. Gametes from RrYy parent Starting here what are the gametes? ry RY Ry rY RY RRYY RRYy RrYY RrYy Ry Gametes from RrYy parent RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy

  17. 50% PROBABILITY 75% r R RR Rr R Knowing the parents genotype we can predict the probable offspring genotype and phenotype What is the probability of having Rr offspring? What is the probability of having Round offspring? Rr rr r

  18. PROBABILITY Given the parents genotype and number of offspring, you should be able to predict the number of each genotype and phenotype. PROBABILITY PROBLEM R=Round seeds & r=wrinkled seeds 1. P1 genotype: RR X rr 2. All of the F1 offspring will be ______. 3. Assume 140 F2 offspring are created from F1. 4. ________ will have their parents (F1) genotype. 5. ________ will have Round seeds. 6. ________ will have wrinkled seeds. 7. ________ will have the same genotype as the P1.

  19. R R Rr Rr PROBABILITY PROBLEM (#2) r 2. All of the F1 offspring will be ______. P1=RR X rr (always put first parent on top of square) Rr Rr r Rr (Round) 2. All of the F1 offspring will be ___________.

  20. R r # of F2 Offspring = _____ Expected % of genotype (Rr) that is same as parents= ______ 50% (2/4) of 140 = _____ 140 X .5 = 70 140 RR Rr PROBABILITY PROBLEM (#4) R 50% 70 Rr rr 4. ________ will have their parents (F1) genotype. F1= All Rr r 70 4. ________ will have their parents (F1) genotype.

  21. R r # of F2 Offspring = _____ Expected % of Round phenotype = ______ 75% (3/4) of 140 = _____ 140 X .75 = 105 140 PROBABILITY PROBLEM (#5) 75% RR R Rr 105 5. ________ will have Round seeds. rr r Rr 105 5. ________ will have Round seeds.

  22. R r # of F2 Offspring = _____ Expected % of wrinkled phenotype = ______ 25% (1/4) of 140 = _____ 140 X .25 = 35 140 PROBABILITY PROBLEM (#6) 25% RR R Rr 35 6. ________ will have wrinkled seeds. rr r Rr 35 6. ________ will have wrinkled seeds.

  23. R r # of F2 Offspring = _____ Expected % of RR or rr genotype = ______ 50% (2/4) of 140 = _____ 140 PROBABILITY PROBLEM (#7) 50% RR R Rr 70 7. ________ will have the same genotype as the P1 (RR or rr). rr r Rr 70 7. ________ will have the same genotype as the P1.

  24. Actual Results of Mendel’s Work

More Related