Finding Genotypes for Dog Genetics Problem

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In summary, the question asks for the most probable genotypes of the parents based on the phenotypes of their offspring in different crosses. The dominant traits are dark coat color and short hair, while the recessive traits are albino coat color and long hair. By examining the data of the offspring's phenotypes, it is possible to determine the genotypes of the parents. For example, in the cross of dark short x dark long, there are no albino offspring, indicating that both parents must have at least one dominant allele for coat color. This narrows down the possible genotypes to DDSS or DDSs for the dark short parent, and DdSs or DdSS for the dark long
  • #1
cmantzioros
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The question:

In dogs, dark coat colour is dominant over albino, and short hair is dominant over long hair. If these effects are caused by two independently segregating gene pairs, write the most probable genotypes for the parents of each of the following crosses: (Use the symbols D and d for dark and albino coat colour alleles, and S and s for the short- and long-hair alleles, respectively.)

Parental Phenotypes Phenotypes of the Offspring
Dark, Short Dark, Long Albino, Short Albino, Long
a) dark short x dark short 89 31 29 11
b) dark short x dark long 18 19 0 0
c) albino short x albino short 0 0 28 9
d) dark long x dark long 0 32 0 10
e) dark short x dark short 46 16 0 0
f) dark short x dark long 29 31 9 11Attempt at solution:

I'm trying to write out the genotypes but there are so many possibilities. I know I can narrow it down using the data provided but I don't know what to look for. For example for letters (a) and (e):

dark short: DDSS DDSs DdSS DdSs
dark short x dark short (crossing possibilities):
DDSS x DDSS DDSs x DDSs DdSS x DdSS DdSs x DdSs
DDSS x DDSs DDSs x DdSS DdSS x DdSs
DDSS x DdSS DDSs x DdSs
DDSS x DdSs

Is this correct? If so, how would I go about deciding which ones would best fit the outcomes given?

I know how to find the genotypes given the crossing but I don't think I need to find the genotypes of all possible crosses to find the answer. Any suggestions?

*Sorry about the table... it looks fine when I write it here but in the post it's all scrunched up together. Don't know what to do about it.
 
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  • #2
cmantzioros said:
The question:

In dogs, dark coat colour is dominant over albino, and short hair is dominant over long hair. If these effects are caused by two independently segregating gene pairs, write the most probable genotypes for the parents of each of the following crosses: (Use the symbols D and d for dark and albino coat colour alleles, and S and s for the short- and long-hair alleles, respectively.)

Parental Phenotypes Phenotypes of the Offspring

Dark, Short Dark, Long Albino, Short Albino, Long
a) dark short x dark short 89 31 29 11
b) dark short x dark long 18 19 0 0
c) albino short x albino short 0 0 28 9
d) dark long x dark long 0 32 0 10
e) dark short x dark short 46 16 0 0
f) dark short x dark long 29 31 9 11
Okay, the numbers of each phenotype in the offspring is the key to answering this question. If you recall something about the probability of each outcome with different genotypes crossed, you can start working backward to determine the genotypes of the parents.

The easiest ones to start with are the ones with some zeros. These help tell you something about alleles absent in one or both parents. For example, in (b), there are no albino offspring. What does this tell you about the genotypes of the phenotypically dark-haired parents?

(In the meantime, I'm going to see if I can find someone to help us both learn how to format tables here! At least I can read it correctly when quoting.)
 
  • #3
Okay, I goofed around the formatting, so now it'll be easier to refer to the table when working on this. I hope there's an easier way than I used, but it at least works for now. :smile:

Parental Phenotype.......Phenotypes of the Offspring
.........Dark, Short...Dark, Long ... Albino, Short... Albino, Long
a) dark short x dark short... 89 .....31...... 29...... 11
b) dark short x dark long... 18..... 19......0.....0
c) albino short x albino short ... 0...... 0......28...... 9
d) dark long x dark long ... 0..... 32......0......10
e) dark short x dark short ... 46..... 16......0.....0
f) dark short x dark long ... 29..... 31..... 9...... 11
 
  • #4
Looking for something like this, perhaps?

Code:
     Parental Phenotype                 Phenotypes of the Offspring

                              Dark,Short  Dark,Long  Albino,Short  Albino,Long

a) dark short x dark short        89           31          29           11
b) dark short x dark long         18           19          0            0
c) albino short x albino short    0            0           28           9
d) dark long x dark long          0            32          0            10
e) dark short x dark short        46           16          0            0
f) dark short x dark long         29           31          9            11

Too late, eh?
 
  • #5
Gokul43201 said:
Looking for something like this, perhaps?

Code:
     Parental Phenotype                 Phenotypes of the Offspring

                              Dark,Short  Dark,Long  Albino,Short  Albino,Long

a) dark short x dark short        89           31          29           11
b) dark short x dark long         18           19          0            0
c) albino short x albino short    0            0           28           9
d) dark long x dark long          0            32          0            10
e) dark short x dark short        46           16          0            0
f) dark short x dark long         29           31          9            11

Too late, eh?

Dang! Too easy. :biggrin: Now, after I put in all those dots, where did the OP disappear to?
 

Related to Finding Genotypes for Dog Genetics Problem

1. What is a genotype?

A genotype refers to the genetic makeup of an individual, including all of their inherited genes. It is represented by a combination of letters or symbols that represent the specific alleles (versions) of each gene.

2. How do you determine a dog's genotype?

A dog's genotype can be determined through DNA testing, specifically through a process called genotyping. This involves analyzing the DNA sequence of the dog to identify the specific alleles present for each gene.

3. What is the importance of knowing a dog's genotype?

Knowing a dog's genotype can provide valuable information about their genetic predisposition to certain diseases or traits. It can also aid in selective breeding to produce desired traits in future generations.

4. Can a dog's genotype change over their lifetime?

No, a dog's genotype is determined at the time of conception and remains the same throughout their lifetime. However, environmental factors can influence the expression of certain genes, leading to different observable traits.

5. How can genotypes be used to predict the traits of offspring?

By knowing the genotypes of the parents, it is possible to predict the probability of certain traits appearing in their offspring. This can be done using Punnett squares and understanding the inheritance patterns of different genes.

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