Mendelian GeneticsPowerPoint Questions All Materials © cmassengale

Gregor Mendel

1. Who is responsible for our laws of inheritance? Gregor Mendel

2. What organism did Mendel study? pea plants

3. When was Mendel's work recognized? 20th century

4. When did Mendel perform his experiments & how many plants did he grow?

Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants

5. What did Mendel notice about offspring traits? retained traits of the parents

6. How is Mendel referred to today? “Father of Genetics"

7. In what country did Mendel do his research on peas? Czech Republic and austria

8. Mendel stated that physical traits were inherited as __“particles”__.

9. Today we know that particles are actually what? “particles” are actually Chromosomes & DNA

Terminology

10. Define these three terms:   a. Trait - any characteristic that can be passed from parent to offspring

b. Heredity - passing of traits from parent to offspring

c. Genetics - study of heredity

11. Name & describe two types of genetic crosses.

 Monohybrid cross - cross involving a single traite.g. flower color

Dihybrid cross - cross involving two traits e.g. flower color & plant height

12. What is used to solve genetic crosses? Punnet squares help solve genetics problems

13. Sketch a Punnet square & show how they are used to solve a genetics problems.

 

14. Use a Punnet square to solve a cross between two parents that both have the genotype Yy.

 

15. What are alleles & what are the two forms? 

alleles are two forms of a gene (dominant & recessive)

16. Explain the difference between dominant & recessive alleles.

Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R)

Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r)

17. Using a letter of the alphabet, show how each allele would be represented.

 A- dominant a- recessive

18. What is a genotype and write 3 possible genotypes?

 Genotype - gene combination for a trait (e.g. RR, Rr, rr)

19. What is a phenotype and write possible phenotypes for your genotypes in question 18?

 Phenotype - the physical feature resulting from a genotype (e.g. red, white)

20. Using these alleles, R = red flower and r = yellow flowers; write all possible genotypes & phenotypes.

Genotype of alleles: R = red flower r = yellow flower

All genes occur in pairs, so 2 alleles affect a characteristic

 Genotypes RR Rr rr

Phenotypes RED RED YELLOW

STOPPING POINT 11/24/09

21. What are homozygous genotypes?

 gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure 

22. Write a homozygous dominant genotype. RR

23. Write a homozygous recessive genotype. rr

24. What is meant by a heterozygous genotype?

 gene combination of one dominant & one recessive allele (e.g. Rr)

25. Write a heterozygous genotype. Rr

26. Heterozygous genotypes are also called _ hybrid____.

27. What two things actually determine an organism's characteristics? Genes and Environment

Pea Experiments

28. Give 4 reasons that Mendel used garden peas, Pisum sativum, for his experiments.

1) Can be grown in a small area

2) Produce lots of offspring

3) Produce pure plants when allowed to self-pollinate several generations

4) Can be artificially cross-pollinated  

29. Name the male and female parts of a flowering plant and explain how pollination occurs.

 Pollen contains sperm and is produced by the stamen

Ovary contains eggs and is found inside the flower

30. What is the difference between self and cross pollination?

 Pollen carries sperm to the eggs for fertilization

Self-fertilization can occur in the same flower

Cross-fertilization can occur between flowers

31. Explain how Mendel cross pollinated his pea plants.

 Mendel hand-pollinated flowers using a paintbrush,

He could snip the stamens to prevent self-pollination, then covered each flower with a cloth bag

He traced traits through the several generations

32. How did Mendel get pure plants?

produced pure strains by allowing the plants to self-pollinate for several generations

33. Name 8 pea plant traits and give the dominant & recessive form of each.

 Seed shape --- Round (R) or Wrinkled (r)

Seed Color ---- Yellow (Y) or  Green (y)

Pod Shape --- Smooth (S) or wrinkled (s)

Pod Color ---  Green (G) or Yellow (g)

Seed Coat Color ---Gray (G) or White (g)

Flower position---Axial (A) or Terminal (a)

Plant Height --- Tall (T) or Short (t)

Flower color --- Purple (P) or white (p)

34. How did Mendel's experimental results compare to the theoretical genotypic ratios? Explain.

 The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round :1 wrinkled

Mendel’s observed ratio was 2.96:1

The discrepancy is due to statistical error

The larger the sample the more nearly the results approximate to the theoretical ratio

35. What does P1 mean? Parental P1 Generation = the parental generation in a breeding experiment.

36. What is the F1 generation? F1 generation = the first-generation offspring in a breeding experiment. (1st filial generation)

From breeding individuals from the P1 generation

37. What is the F2 generation? F2 generation = the second-generation offspring in a breeding

experiment. (2nd filial generation)

From breeding individuals from the F1 generation

38. What results from this cross --- TT x tt? All hybrids (Tt)

39. What results do you get from crossing two hybrids (Tt x Tt)?

you would get the following genotypes TT, Tt, tt

Assuming T represents tall and t represents short; you would get 3 tall and 1 short

40. Show all your work for solving a P1 monohybrid cross for seed shape.Trait: Seed Shape

Alleles: R – Round r – Wrinkled

Cross: Round seeds x Wrinkled seeds

P1 cross:  __RR___ x _ rr __

Rr Rr

Rr Rr

Genotype __ Rr ____Phenotype __Round _G. Ratio _ All alike _P. Ratio _ All alike _

41. The offspring of the above cross are called the _F1____ generation.

42. Show all your work for solving a F1 monohybrid cross for seed shape.Trait: Seed Shape

Alleles: R – Round r – Wrinkled

Cross: Round seeds x Round seeds

F1 cross:  _ Rr _ x _ Rr _

RR Rr

Rr rr

Genotype: RR, Rr, rr

Phenotype: Round & wrinkled

G. Ratio: 1:2:1

P. Ratio: 3:1

43. Show all your work for solving both F2 monohybrid crosses for seed shape.

Trait: cross 1: Round, Round cross 2: wrinkled roundAlleles: cross 1 RR, Rr cross 2: rr, Rr

F2 cross:  __ RR ______ x ___ Rr _____  F2 cross:  __ rr ______ x ___ Rr _____

 

Genotype: RR, Rr Genotype: Rr, rr

Phenotype: Round & Wrinkled Phenotype: Round

GenotypicRatio: 1:1 G. Ratio: 1:1

PhenotypicRatio: All alike P. Ratio: 1:1

Mendel's Laws

Complete the following question:

44. __genes_______ are responsible for inherited traits.

45. Phenotype is based on __genotype_____________.

46. Each trait requires _2__ genes, one from each _parent__.

47. State the Law of Dominance and give an example.

 In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.

All the offspring will be heterozygous and express only the dominant trait.

RR x rr yields all Rr (round seeds)

R

R

rR

RR

RrRR

Rr r

r

rR

Rr

rrRr

rr

3 genotypes yields 3 phenotypes

48. State the Law of Segregation and tell when alleles are "recombined".

During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.

Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

49. State the Law of Independent assortment & tell what type of crosses show this.

 Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

This law can be illustrated using dihybrid crosses.

50. Using the formula 2n where n = the number of heterozygotes, tell how many gametes will be produced by each of the following allele combinations:a. RrYy = 22 = 4b. AaBbCCDd = 23 = 8c. MmNnOoPPQQRrssTtQq = 26 = 64

51. What are the possible allele combinations in the egg and sperm from the following cross --- RrYy x RrYy.

 RY Ry rY ry from egg RY Ry rY ry from sperm

52. Show how to work an F1 dihybrid cross for seed shape & seed color.

Traits: Seed shape & Seed color

Alleles: R round r wrinkled Y yellow y green

F1 cross   _RrYy _______ x _RrYy _________

 

RRYY RRYy RrYY RrYy

RRYy RRyy RrYy Rryy

RrYY RrYy rrYY rrYy

RrYy Rryy rrYy rryy

Genotypes   PhenotypesRound/Yellow: 9

Round/green: 3

wrinkled/Yellow: 3

wrinkled/green: 1

53. Complete this cross or crosses for eye color & curliness of the hair --- bbC__ x bbcc.

 Could be C or c

 

 

54. Draw a table summarizing Mendel's 3 laws.

 

Incomplete and Co-Dominance

 55. Incomplete dominance occurs in __ F1 hybrids _____ and produces a phenotype __between _the phenotype of the two parents.

56. Show your work solving a cross for flower color in snapdragons when there is incomplete dominance.

Trait: red white

Alleles: (RR) x (rr)

RR = red flower

rr = white flower

Cross:  RR x rr

LAWLAWPARENT PARENT CROSSCROSS

OFFSPRINGOFFSPRING

DOMINANCEDOMINANCE TT x ttTT x tt

tall x shorttall x short

100% Tt 100% Tt

talltall

SEGREGATIONSEGREGATIONTt x TtTt x Tt

tall x talltall x tall

75% tall 75% tall

25% short25% short

INDEPENDENT INDEPENDENT ASSORTMENTASSORTMENT

RrGg x RrGgRrGg x RrGg

round & round & green x green x

round & round & greengreen

9/16 round seeds & green 9/16 round seeds & green pods pods

3/16 round seeds & yellow 3/16 round seeds & yellow pods pods

3/16 wrinkled seeds & 3/16 wrinkled seeds & green pods green pods

1/16 wrinkled seeds & 1/16 wrinkled seeds & yellow podsyellow pods

Rr Rr

Rr Rr

All Rr = pink

57. What is codominance & give an example?

 Two alleles are expressed (multiple alleles) in heterozygous individuals.

58. Write the genotypes for each of these blood types:

type A = IAIA or IAi

type B IBIB or IBi

type AB IAIB

type O ii

59. Solve this codominance problem: IBIB x IAi.

 homozygous male Type B (IBIB) x heterozygous female Type A (IAi)

Ia iIb IaIb IbiIb IaIb Ibi

60. Solve this codominance problem for blood type: ii x IAIB.

  

IA IB

i IAi IBi

i IAi IBi

 

Sex-Linked Traits

61. What are sex linked traits?

 Traits (genes) located on the sex chromosomes

62. Name the sex chromosomes.

Sex chromosomes are X and Y

63. Write the genotype for male and for female.

XX genotype for females

XY genotype for males

64. Most sex-linked traits are carried on what chromosome?

X chromosome

65. Give an example of a sex-linked trait in fruit flies.

Eye color

66. Show the results of crossing a red-eyed male (XRY)  with a white-eyed female (XrXr) fruit fly.RR = red eyed

Rr = red eyed

rr = white eyed

XY = male

XX = female

Cross:    __ Xr Xr_______ x __ XRy________

50% red eyed female

XR Xr

Xr Y

XR Xr

Xr Y

XR

Xr Xr

Y

50% white eyed male

67. What is meant by a female carrier?

  A trait that is carried by females, men will have the phenotype more often

68. Name a disease that can be carried in this manner.

  Hemophilia