Download Canine Chromosomes

Canine Chromosomes
PRE-LAB
Discuss laws of dominance and recessive, heterozygous and homozygous, genotype and phenotype
through PowerPoint lesson, Genetics Overview and/or Streaming Video. (Streaming Video may be used
as post lab.)
LAB
Imagine this microscopic drama. A sperm cell from a male dog fuses with an egg cell from a female dog.
Each dog's gamete carries 39 chromosomes. The zygote that results from the fusion of the gametes
contains 78 chromosomes-one set of 39 chromosomes from each parent. One pair of the zygote's
chromosomes is shown below.
mother dog
father dog
chromosome from mother dog
L
?
?
?
?
C
P
PUPPY’S CHROMOSOMES
P
C
tL
t
l
T
C
p
C
T
p
l
?
?
?
?
chromosome from father dog
Each chromosome of the homologous pair contains alleles for the same traits. But one chromosome may
have a dominant allele and the other a recessive allele. Use the drawings and the table to answer the
questions.
Trait
Dominant Gene
Recessive Gene
Hair length
Short (L)
Long (l)
Hair texture
Wiry (T)
Silky (t)
Hair curliness
Curly (C)
Straight (c)
Coat pattern
Spotted (P)
Solid (p)
KEY
1. Will the new puppy have a spotted coat? Yes Explain. He inherited a gene for spotted coat
from the mother.
2. Does the mother dog have a spotted coat? Yes Explain. She has at least one dominant allele.
3. Does the father dog have a spotted coat? Unknown Explain. Cannot be determined because we
only know half of the father’s genotype.
4. What will be the texture of the puppy's coat? Wiry
5. Will the texture of the puppy's coat resemble that of either of its parents? The father. Explain. The
father has at least one dominant allele for wiry textured hair, therefore the father has
wiry hair; the mother’s texture is unknown.
6. Will the puppy have curly hair or straight hair? Curly hair
7. Does the mother dog have curly hair? Yes; she has at least one dominant allele for curly
hair. Does the father dog have curly hair? Yes; he has at least one dominant allele for curly
hair.
Should this Dog be Called Spot - Teacher (Revised June 8, 2004)
(printed 6/28/2017) p. 1
8. Define the term heterozygous. Individuals who are heterozygous for a trait possess one
dominant allele and one recessive allele for a trait. (Example: Cc or Pp or Bb)
For which traits is the puppy heterozygous? Hair length (Ll), Hair texture (Tt), Coat Pattern
(Pp)
9. Define the term homozygous. Individuals who are homozygous for a trait possess two
identical alleles for a trait. (Example: cc or PP or bb or TT)
For which traits is the puppy homozygous? Hair curliness (CC)
10. Explain why you cannot completely describe the puppy's parents even though you can accurately
describe the puppy. You only know half of the genotype for each parent. In order to
describe the traits accurately for each parent, you would need to know what genes are on
the homologous chromosome for each of the parents.
Should this Dog be Called Spot - Teacher (Revised June 8, 2004)
(printed 6/28/2017) p. 2