Chapter 10: Mendel and Meiosis (Part 1)

1. In the mid- nineteenth century, Gregor Mendel, an Austrian monk, carried out important studies of heredity.

2. Heredity is the passing on of characteristics from parents to offspring.

3. Characteristics that are inherited are called traits.

4. List five human traits 1. Shape of face (probably polygenic) Oval dominant, square recessive 2. Cleft in chinNo cleft dominant, cleft recessive 3. Hair curl (probably polygenic) Assume incomplete dominance Curly: homozygous Wavy: heterozygous Straight: homozygous 4. HairlineWidow peak dominant, straight hairline recessive 5. Eyebrow sizeBroad dominant, slender recessive 6. Eyebrow shapeSeparated dominant, joined recessive 7. Eyelash lengthLong dominant, short recessive 8. DimplesDimples dominant, no dimples recessive 9. EarlobesFree lobe dominant, attached recessive 10. Eye shape Almond dominant, round recessive 11. Freckles Freckles dominant, no freckles recessive 12. Tongue rolling Roller dominant, nonroller recessive 13. Tongue folding Inability dominant, ability recessive 14. Finger mid-digital hair Hair dominant, no hair recessive 15. Hitch-hiker's thumbStraight thumb dominant, hitch-hiker thumb recessive 16. Bent little fingerBent dominant, straight recessive 17. Interlaced fingersLeft thumb over right dominant, right over left recessive 18. Hair on back of handHair dominant, no hair recessive 19. Tendons of Palmar MuscleTwo tendons dominant, three tendons recessive

5. Genetics is the branch of biology that studies heredity.

6. Mendel chose to use the pea plant in his experiments

7. Male and female sex cells are called gametes.

8. In a process called fertilization, the male gamete unites with the female gamete

9. The resulting fertilized cell is called a zygote.

10. The transfer of pollen grains from a male reproductive organ to a female reproductive organ in a plant is called pollination.

11. A hybrid is the offspring of parents that have different forms of a trait, such as tall and short height.

12. In Mendel’s experiments, the original parents, the true- breeding plants were known as the P 1 generation. 13. The P stands for parent.

14. The offspring of the parent plants are known as the F 1 generation. 15. The F stands for filial- - son or daughter.

16. List the seven traits that Mendel studied in pea plants.

17. Mendel found that one trait of a pair seemed to disappear in the F 1 generation, only to reappear unchanged in one-fourth of the F 2 plants.

18. Mendel concluded that each organism has two factors that control each of its traits.

19. We now know that these factors are genes and that they are located on chromosomes.

20. Genes exist in alternate forms. We call these different gene forms alleles.

21. An organism’s two alleles are located on different copies of a chromosome-- one inherited from the female parent and one from the male parent.

22. In a situation in which only one trait is observed, Mendel called the observed trait dominant and the trait that disappeared recessive.

23. When recording the results of crosses, it is customary to use the same letter for different alleles of the same gene.

24. An uppercase letter is used for the dominant allele and a lowercase letter for the recessive allele.

25. The law of segregation states that every individual has two alleles of each gene and when gametes are produced, each gamete receives one of these alleles.

26. During fertilization, these gametes randomly pair to produce four combinations of alleles.

27. The way an organism looks and behaves is called its phenotype.

28. The allele combination an organism contains is known as its genotype.

29. An organism’s genotype can’t always be known by its phenotype.

30. An organism is homozygous for a trait if its two alleles for the trait are the same.

31. If an organism has two dominant alleles for a trait, they are homozygous dominant for that trait.

32. If an organism has two recessive alleles for a trait, they are homozygous recessive for that trait.

33. An organism is heterozygous for a trait if its two alleles for the trait differ from each other.

34. Mendel’s second law states that genes for different traits are inherited independently of each other.

35. This conclusion is known as the law of independent assortment.

36. A shorthand way of finding the expected proportions of possible genotypes in the offspring of a cross is called a Punnett square.

37. Punnett squares are good for showing all the possible combinations of gametes and the likelihood that each will occur.

38. In reality, genetics is like flipping a coin – it follows the rules of probability.

39. The results predicted by probability are more likely to be seen when there is a large number of offspring.