A female guinea pig is heterozygous for both fur color and coat texture Is cross

Question

A female guinea pig is heterozygous for both fur color and coat texture Is crossed with a male that has light fur color and is heterozygous for coat texture. What possible offspring can they produce? Dark fur color is dominant (D) and light fur (d) Is recessive. Rough coat texture (R) is dominant, while smooth coat (r) is recessive. 6 dark, rough: 6 light, rough: 2 dark, smooth: 2light, smooth 9 dark, rough: 3 dark, smooth: 3light, rough: 1 light, smooth 6 dark, rough: 2 light, rough: 6 dark, smooth: 2light, smooth 9 light, smooth: 3 light, rough: 3 dark, rough; 1 dark, smooth 100 % dark, rough In a genetics laboratory, two heterozygous tall plants are crossed. If tall is dominant over short, are the expected phenotypic results? 100% tall 75% short: 25% tall 50% tall: 50% short 25% short: 75% tall None of the above

Explanation / Answer

Answer 2:
Here’s how it’s solved!
We know that dark fur color is dominant (D) and light fur (d) is recessive. Rough coat
texture (R) is dominant, while smooth coat (r) is recessive.
Step 1: The guinea pig that is heterozygous for both color and texture this means it has
one allele for each trait. Therefore its genotype would be “DdRr”. The other guinea pig
has light fur, since that is a recessive trait the genotype for that trait must be “dd”. It is
also heterozygous for fur texture, which means a genotype of “Rr”. All together its
overall genotype must be “ddRr”.
Step 2 and 3: The Punnett square will be larger now because there are more possible
sperm and egg combinations. During the formation of sperm a “D” could go with a “R”
producing a sperm “DR”, or a “D” could go with a “r” forming a sperm with “Dr”. Filling-in
the Punnett square it should look like the one we started below . Finish off filling in the
blank squares in the Punnett square.
Step 4: After filling-in the Punnett square you should obtain the following genotypic ratio:
*remember the numbers should add up to the number of squares filled in:
4 DdRr : 2 DdRR : 4 ddRr : 2 ddRR : 2 Ddrr : 2 ddrr
Step 5: There will be only four different phenotypes because the 4 DdRr and the 2
DdRR will have dark fur with rough coat, and the 4 with ddRr and the 2 ddRR will have
light fur with rough coat, while the 2 Ddrr will have dark fur with smooth coat and the 2
ddrr will have light fur with smooth coat. Therefore the phenotypic ratio would be:
6 dark, rough : 6 light rough : 2 dark smooth : 2 light smooth.

Answer 3: correct answer is A)

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