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?).

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 / Puppy’s Genotype / Puppy’s Phenotype
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.
  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 t=short

  1. TT ______
  2. Tt ______
  3. tt ______

Which guinea pigs are black? B= black b= white

  1. BB ______
  2. bb ______
  3. Bb ______

What is the phenotype of the morning glories? B=blue b= white

  1. BB ______
  2. bb ______
  3. Bb ______

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.

  1. Ll ______
  2. LL ______
  3. ll ______

Cross the following: heterozygous green x homozygous yellowG = greeng = yellow Draw a Punnett square.

Gg / gg
Gg / gg
  1. phenotypic ratio: (Green : yellow) _2:2______
  2. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) _0:2:2______

Draw a Punnett square: Suppose a normal skin color man (AA) and an albino woman (aa) were expecting a child.

  1. What would the chance be of their having normal children? ______
  1. phenotypic ratio: (Normal : albino) ______
  2. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) ______

Cross two people heterozygous for albinism. Draw a Punnett square.

  1. phenotypic ratio: (Normal : albino) ______
  2. Genotypic ratio: (Homo Dom : Hetero : Homo Rec) ______

Cross a homozygous red rose and a white rose. Red is dominant. R = red r = white Draw a Punnett square

  1. Phenotypic ratio ______
  1. 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.

  1. Malaria Resistant: ______
  2. Normal ______
  3. Sickle Cell______
  1. 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)

  1. What is the genotype of the pink flower? ______

Now cross two of the F1 pink offspring. (makes the F2 generation)

  1. Phenotypic ratio ______

(How many Red : How many Pink: How many White)

  1. Genotypic ratio ______

(How many RR : How many WR : How many WW)

Key: E = free earlobes, e = attachedT = 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.

  1. What is the Cross? __EeTt_x eeTT_____ (this is like FOIL in algerbra)

EeTT / EeTt / eeTT / eeTt

How many will have:

  1. Free earlobes & a tongue roller ______

How many have at least one E and one T?

  1. Free earlobes and can’t roll tongue ______

How many have at least one E and two t’s?

  1. Attached earlobes & a tongue roller ______

How many have two e’s and at least one T?

  1. Attached earlobes & can’t roll tongue ______

How many have two e’s and two t’s?

  • When filling these out keep your dominant letters 1st and keep your E’s together and your T’s together
  • Once you count a box to fill in the questions you cannot count it again, so cross it off

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:

  1. Write a Key: ______
  2. What is the Cross? ______

How many possible offspring will have:

  1. Pink flowers and round seeds? ______
  2. Pink flowers and wrinkled seeds? ______
  3. White flowers and round seeds? ______
  4. White flowers and wrinkled seeds? ______