Mendel’s Genetics: Understanding Monohybrid Cross Experiment

1. Mendel’s Genetics Monohybrid Cross

2. Gregor Mendel • As discussed last class, he was an Austrian monk • He worked at St. Thomas Monastery • He studied both mathematics and botany

3. Why did he actually Succeed? • He chose the appropriate organism to study • He designed and performed his experiments correctly • Analysis of the data was done properly

4. The Patient • The common ______ also known as Pisumsativium • It was chosen for 4 reasons • It was _________ available • Easy to _____and mature • The sex organs are entirely ________ in the flower • Different varieties had different ________

6. Purebred • What is a purebred organism? • __________________________________________________________ • Why was this important to Mendel and his pea plants? • This is because he used purebred plants to conduct all of his experiments

7. How did he make sure? • How did Mendel make sure that his organisms (pea plant) were pure bred? • He bred them as everyone else bred plants, and he looked at _____ ______ at a time • He selected from the ________, only the plants that had the trait that he was looking for • He then bred them together (________) and then he continued this for several generations until no more of the other trait showed up

8. What happened Next? • He repeated this for all the other traits until he had pure bred plants with each trait.

9. The first of the Crosses • So what did he end up doing next? • He started to _______________ • He designated the parents as the ____ generations and crossed a true-breeding _____pea plant, with a true-breeding ______ pea plant • The offspring were of course the F1 generation and he also denoted them as __________

10. That F1 Generation • What do you think he saw? • What was the phenotype of the plants? • ____________________________ • What is this type of crossing called?

11. Creatively • Creatively the name given to this type of cross is _____________ • It is a _______ cross between two purebred plants giving us a hybrid species

12. What did his experiment look like?

13. That’s the Phenotype • We have now seen the phenotype • All of the F1 generations plants were _____ • What do you think the genotype must be of the offspring? • First we have to learn some more terms

14. Terms • ___________________ (TT) – Two alleles for a trait that are the same as a result of pure breeding • ___________________ – Having two alleles for a trait that are different • ___________________ - Two alleles for a trait that are the same as a result of pure breeding

15. The First Cross PF1 Tall Short

16. Lets back track • Yesterday we looked at the different combinations of alleles that an individual can have • We also talked about dominance and recessiveness • What did we say the dominant allele was? • What about the recessive allele

17. What were the parents? • The parent that was tall had a double _______ allele • The parent that was short had a double _______ allele • Both of these parents were homozygous

18. When he Crossed • When the parents were crossed, the F1 generation was completely ____________ • They all expressed the dominant trait, but why? • __________________________________________________________

19. So the First cross is done, what about the second?

20. Second Cross Genotype

21. Mendelian Ratio • As Mendel completed the experiment, he found that ____of the offspring of the F1 cross were the ________ (tall) and ____ were the _______ (short) • The Ratio of _____ is known as the _________________

22. Based on observations, Why did this happen? • Each parent in his F1 Generation starts with two hereditary “factors.” One factor is _______ and the other ________ • The factors separate out in the and only one of the two factors contribute to the phenotype of the offspring

23. Why did this happen? • The offspring inherit ____ factor from ____ and ____ from ____. If the dominant factor is present, it will be _______, even if the recessive one is present • The recessive factors will be expressed ___ if the recessive factors are present

24. The first Law of heredity • His results gave rise to his first law The law of Segregation

25. The law of segregation • His law of segregation states: __________ _________________________________ • These factors segregate in the gametes (after meiosis) • Mendel did not know that his factors were actually genes, we know this today

26. What do we call this?

27. Punnett Square

28. What do they do for us? • Well, they are used by geneticists so that they can _________ the expected ratio (__________) and to suggest possible combinations of _______ in the offspring • They also tell us something about the __________ (the appearance of a trait in an organism)

29. So we saw TT x tt • And for that cross we ended up having a ratio of? • All were Heterozygous (100% - 0%) • What about when we cross the F1 x F1 generations?

30. F1 X F1 • What’s the ratio when we are talking about phenotype? • 3:1 as well, three of the offspring will present the dominant gene while the fourth will present the recessive gene • What about the genotype ratio? • _______________________________________________________________________________________

31. Example

32. Class Work • Read Pages 202 -212 • Complete Questions 205 #1, 5, 6 • Page 207 #1, 3, 6, 9, 10, 11, 12