Download Genetic Practice Problems

Name: _____________________________
Date: ___________
Per. __________
Should This Dog be Called Spot?
Imagine this microscopic drama. A sperm cell from a male dog fuses with an egg cell from a female dog. Each dog’s
gamete is produced from a process of _______________ and carries 39 chromosomes. Gametes are ______________
(haploid or diploid?) or __________ (n or 2n?). The zygote that results from the fusion of the gametes contains
___________ chromosomes- one set of 39 chromosomes from each parent. A zygote is ______________ (haploid or
diploid?) or __________ (n or 2n?). One pair of the zygote’s chromosomes is shown below. This pair of chromosomes,
containing alleles for the same genes, is known as a _______________ pair. This combination of alleles for each trait,
known as the ______________ (genotype or phenotype?) determines the physical characteristics of the puppy, known as
its _________________ (genotype or phenotype?).
Chromosome from Female
(mom)
Chromosome from Male
(dad)
The following is a key for the alleles on the chromosomes shown above:
Trait
Dominant Allele
Recessive Allele
Hair length
Long (L)
Short (l)
Hair texture
Wiry (W)
Silky (w)
Hair curliness
Curly (C)
Straight (c)
Coat pattern
Spotted (S)
Solid (s)


Using the key, complete the table below.
Answer the “Questions to Ponder”. The answers do not have to be in complete sentences!
Trait
Allele from Mom
Allele from Dad
Hair length
Hair texture
Hair curliness
Coat pattern
Questions to Ponder and Discuss….
1. Does the female dog (puppy’s mom) have long hair? Explain.
Puppy’s Genotype
Puppy’s Phenotype
2. Does the male dog have long hair? Can you tell? Explain.
3. Does the female dog have curly or straight hair? Explain.(*hint: look at her one chromosome given, can you tell?)
4. Does the male dog have curly or straight hair? Explain. (*hint: look at her one chromosome given, can you tell?)
5. For which traits is the puppy heterozygous?
6. For which traits is the puppy homozygous?
7. Explain why you cannot completely describe the puppy’s parents even though you can accurately describe the
puppy.
8. Does this puppy have any characteristics that will definitely be seen in the puppy’s puppies? Explain.
9. in these dogs, n= ___________? 2n= ___________?
Genetic Practice Problems:
Write examples of the following: using long hair (L) and short hair (l) : Long hair is dominant
1. Two dominant alleles ________
2. Two recessive alleles ________
3. Homozygous alleles ________ & _________
4. Heterozygous alleles _______
Give the phenotype for the following plants T=tall
5. TT _________________
6. Tt __________________
7. tt ___________________
t=short
Which guinea pigs are black? B= black b= white
8. BB __________________
9. bb ___________________
10. Bb ___________________
What is the phenotype of the morning glories? B=blue
11. BB __________________
12. bb ___________________
13. Bb __________________
b= white
Given the 3 genotypes: ll, LL & Ll with L= long hair in dogs & l = short hair. In the space below tell which genotype is
homozygous recessive, which is heterozygous and which is homozygous dominant.
14. Ll _____________________________________
15. LL _____________________________________
16. ll ______________________________________
Cross the following: heterozygous green x homozygous yellow G = green g = yellow Draw a Punnett square.
17. phenotypic ratio: (Green : yellow) _________
18. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) _________
Draw a Punnett square: Suppose a normal skin color man (AA) and an albino woman (aa) were expecting a child.
19. What would the chance be of their having normal children? __________________
20. phenotypic ratio: (Normal : albino) _________
21. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) _________
Cross two people heterozygous for albinism. Draw a Punnett square.
22. phenotypic ratio: (Normal : albino) _________
23. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) _________
Cross a homozygous red rose and a white rose. Red is dominant. R = red
24. Phenotypic ratio ____________
r = white Draw a Punnett square
25. Genotypic ratio ______________
In humans, there is a disorder known as sickle cell anemia which is caused by a point mutation. This disorder changes the
shape of the red blood cells to where they cannot carry oxygen. Persons of African descent are affected with this disorder.
Normal red blood cells = HH
Resistance to a disease called malaria = Hh
Sickle cell anemia = hh
Cross two people who are resistant to malaria. Give the probability for the offspring that are normal, resistant to malaria, and
those that have sickle cell anemia. Give the proportions as ¼ or ½ ect…
Draw a Punnett square.
26. Malaria Resistant: ____________
27. Normal
_____________
28. Sickle Cell
______________
29. Mr. & Mrs. Miller have 2 sons. What is the probability that their next child will be a boy? _________ (XX=female,
XY= male)
Certain organisms have traits that show incomplete dominance. In this case there is a blending of traits with neither trait
being dominant or recessive. One example is the sweet pea plant flower, when red (RR) flowers are crossed with white
(WW) flowers you get pink (WR) flowers.
Draw a Punnett square showing a cross between a red x white flower. (F1 generation)
30. What is the genotype of the pink flower? ____________
Now cross two of the F1 pink offspring. (makes the F2 generation)
31. Phenotypic ratio ____________
32. Genotypic ratio ______________
Key: E = free earlobes,
e = attached
T = tongue roller,
t = non tongue roller
Cross a heterozygous free mom who is heterozygous for tongue rolling with a dad who has attached earlobes and
homozygous tongue roller.
33. Write a Key: ________________________________________________________________________________
34. What is the Cross? _________________________________
How many will have:
35. Free earlobes & a tongue roller ___________
36. Free earlobes and can’t roll tongue ________
37. Attached earlobes & a tongue roller ________
38. Attached earlobes & can’t roll tongue ______
In peas the allele for pink flower (P) is dominant over the allele for white flower (p). The allele for round seeds (R) is
dominant over the allele for wrinkled (r) seeds. Cross a plant homozygous dominant for flower color and heterozygous for
seed shape with one heterozygous for flower color and homozygous recessive for seed shape. After you have made the
cross, answer the following questions:
39. Write a Key: ______________________________________________________________________________
40. What is the Cross? ______________________________________
How many possible offspring will have:
41. Pink flowers and round seeds? ___________
42. Pink flowers and wrinkled seeds? __________
43. White flowers and round seeds? ___________
44. White flowers and wrinkled seeds? _________