Mendelian
Genetics
PowerPoint Questions
Gregor Mendel
1. Who is responsible for our laws of inheritance?
Gregor Mendel
2. What organism did Mendel study?
Pea Plant
3. When was Mendel's work recognized?
His work wasn’t recognized until the turn of the 20th century.
4. When did Mendel perform his experiments & how many plants did he
grow?
Between 1856 and 1863, Mendel cultivated around 28,000 pea plants.
5. What did Mendel notice about offspring traits?
The offsprings retained the traits of the parents.
6. How is Mendel referred to today?
He is referred to as the “Father of Genetics”.
7. In what country did Mendel do his research on peas?
Czech Republic
8. Mendel stated that physical traits were inherited as
_______________.
particles
9. Today we know that particles are actually what?
Chromosomes and DNA
Terminology
10. Define these three terms:
a. trait – any characteristic that can be passed from parent to
offspring.
b. heredity – the passing of traits from parent to offspring.
c. genetics – the study of genetics
11. Name & describe two types of genetic crosses.
1. monohybrid cross-cross involving a single trait.
2. dihybrid cross-cross involving two traits.
12. What is used to solve genetic crosses?
Punnet square
13. Sketch a Punnett square & show how they are used to solve a
genetics problems.
14. Use a Punnett square to solve a cross between two parents that
both have the genotype Yy.
The genotype ratio would be 1:2:1 and the phenotype ratio would be 3:1.
*See slide #10 of the PowerPoint Presentation.
15. What are alleles & what are the two forms?
Alleles are two forms of a gene (dominant and recessive)
16. Explain the difference between dominant & recessive alleles.
The dominant gene is the stronger of the two genes expressed in the
hybrid (represented by a capital letter).
The recessive gene is the weaker of the two genes expressed in the
hybrid and shows up less often in a cross. (represented by a lowercase
letter).
17. Using a letter of the alphabet, show how each allele would be
represented.
Dominant: R
Recessive: r
18. What is a genotype and write 3 possible genotypes?
A genotype is a gene combination for a trait (ex: RR, Rr, rr)
19. What is a phenotype and write possible phenotypes for your
genotypes in question 18?
A phenotype is the physical feature resulting from the genotype. (ex:
red, white)
20. Using these alleles, R = red flower and r = yellow flowers, write all
possible genotypes & phenotypes.
Genotypes: RR, Rr, and rr
Phenotypes: red, white
21. What are homozygous genotypes?
A gene combination involving 2 dominant or 2 recessive genes.
22. Write a homozygous dominant genotype.
RR
23. Write a homozygous recessive genotype.
rr
24. What is meant by a heterozygous genotype?
A gene combination of one dominant and one recessive allele
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 are the two things that determine an organism’s
characteristics.
Pea Experiments
28. Give 4 reasons that Mendel used garden peas, Pisum sativum, for his
experiments.
1. They can be grown in a small area.
2. They produce lots of offspring.
3. They produce pure plants when allowed to self-pollenate.
4. They can be artificially cross-pollenated.
29. Name the male and female parts of a flowering plant and explain
how pollination occurs.
Male: stamen and it contains sperm. Female: pistil and it contains the
ovaries.
Pollen carries sperm to the ovaries for fertilization.
30. What is the difference between self and cross pollination?
Self-pollination can occur in the same flower.
Cross-pollination can occur between different flowers.
31. Explain how Mendel cross pollinated his pea plants.
He hand pollinated the pea plants with a paintbrush. He would snip the
stamens to prevent self-pollination.
Then, covered each flower with a cloth rag
32. How did Mendel get pure plants?
He allowed 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 ratio was 3:1. His observed ratio was 2:96:1. The
discrepancy was to statistical error.
35. What does P1 mean?
Parental generation.
36. What is the F1 generation?
The first generation.
37. What is the F2 generation?
The second generation.
38. What results from this cross --- TT x tt?
All alike. (Tt)
39. What results do you get from crossing two hybrids (Tt x Tt)?
1:2:1 ratio. (RR,Rr,rr)
40. Show all your work for solving a P1 monohybrid cross for seed shape.
Trait: Seed Shape
Alleles: R- Round r- wrinkled
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 __P1___ generation.
42. Show all your work for solving a F1 monohybrid cross for seed shape.
Trait: Seed Shape
Alleles: R- Round r- wrinkled
F1 cross: ____Rr______ x _____Rr_____
RR
Rr
Rr
rr
Genotype ____RR, Rr, and rr________
Phenotype ____Round and 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: Seed Shape
Alleles: R- Round r- wrinkled
F2 cross: _____RR___ x ___Rr_____ F2 cross: ___Rr__ x __rr__
Genotype ____RR,Rr____ Genotype _____Rr, rr_______
Phenotype ___Round____ Phenotype __Round and wrinkled
G. Ratio ______1:1_____ G. Ratio _____1:1________
P. Ratio _____all alike __ P. Ratio _____ 1:1_______
Mendel's Laws
Complete the following question:
44. _________ are responsible for inherited traits.
Genes
45. Phenotype is based on _______________.
Genotype
46. Each trait requires _____ genes, one from each ____________.
Two, 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.
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.
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.
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: 4 gametes
b. AaBbCCDd: 8 gametes
c. MmNnOoPPQQRrssTtQq: 64 gametes
51. What are the possible allele combinations in the egg and sperm from
the following cross --- RrYy x RrYy.
52. Show how to work an F1 dihybrid cross for seed shape & seed color.
Traits: Seed shape and 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
GR Genotypes PR Phenotypes
9:3:3:1 Phenotypic ratio
53. Complete this cross or crosses for eye color & curliness of the hair
--- bbC__ x bbcc.
* Refer to slide #54 on the powerpoint.
54. Draw a table summarizing Mendel's 3 laws.
* Refer to slide #55 on the powerpoint.
Incomplete and Co-Dominance
55. Incomplete dominance occurs in __________ and produces a
phenotype _______________ the phenotype of the two parents.
56. Show your work solving a cross for flower color in snapdragons when
there is incomplete dominance.
Trait: Flower color
Alleles: R-red r-white
Cross: RR x rr
Rr
Rr
Rr
Rr
Genotype _____Rr_______
Phenotype ____pink_______
G. Ratio _____all Rr_______
P. Ratio ___all pink________
57. What is codominance & give an example?
Two alleles are expressed (multiple alleles) in heterozygous individuals.
Example: blood type
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.
1/2 = IAIB
1/2 = IBi
60. Solve this codominance problem for blood type: ii x IAIB.
1/2 = IAi
1/2 = IBi
Sex-Linked Traits
61. What are sex linked traits?
Genes that are located on the sex chromosomes.
62. Name the sex chromosomes.
X and Y.
63. Write the genotype for male and for female.
XX: female
Xy: male
64. Most sex-linked traits are carried on what chromosome?
Most are carried on the X chromosome.
65. Give an example of a sex-linked trait in fruit flies.
Eye color in fruit flies.
66. Show the results of crossing a red-eyed male (XRY) with a whiteeyed female (XrXr) fruit fly.
RR = red eye
Rr = red eye
rr = white eye
XY = male
XX = female
Cross: ____ XRY ______ x ____ XrXr ______
XR Xr
XR Xr
Xr Y
Xr Y
Genotype _____ XR Xr , Xr Y _______
Phenotype __Red and White_________
G. Ratio ______1:1_______
P. Ratio _______1:1________
67. What is meant by a female carrier?
In sex-linked traits (like hemophilia), women are carriers, men have the
phenotype more often.
68. Name a disease that can be carried in this manner.
Hemophilia.