Help needed to draw a mating diagram where L is the dominant gene for the digestion of lactose and shows the crosses between two heterozygotes and wiht the the phenotypic and genotypic ratio of the offspring in the F1 generation.
I also need to know the phenotypic prportions of the offspring of another cross between a person with lactose intolerance and one who is heterozyous.
any help would be very much appreciated.
http://en.wikipedia.org/wiki/Punnett_square
thank you, this helps a lot.
To draw a mating diagram, also known as a Punnett square, you need to understand the principles of Mendelian genetics and how alleles are inherited.
In this case, you mentioned that "L" is the dominant gene for digestion of lactose. So, individuals can either be homozygous dominant (LL), heterozygous (Ll), or homozygous recessive (ll) for the lactose digestion gene.
For the first cross between two heterozygotes (Ll x Ll), you would create a 4x4 grid Punnett square. Label the rows and columns with the possible gametes from each parent (L and l for both parents). Then fill in the boxes with the possible combinations of the alleles.
Here is an example of the Punnett square:
L l
------------------
L | LL Ll
l | Ll ll
In this Punnett square, you can see that there are four possible genotypes of offspring: LL, Ll, Ll, and ll. To calculate the phenotypic ratio, you need to determine which genotypes correspond to the phenotype of lactose digestion.
Because L is the dominant allele, individuals with either LL or Ll genotype will have the ability to digest lactose, resulting in a phenotype of lactose digestion. Only individuals with the ll genotype will be lactose intolerant.
So, the phenotypic ratio of the offspring in the F1 generation would be 3:1, with three individuals able to digest lactose (LL or Ll) and one individual being lactose intolerant (ll).
For the second cross between a person with lactose intolerance (ll) and one who is heterozygous (Ll), you can use a similar approach to create a Punnett square. However, this time, one of the parents will always contribute the l allele.
Here is an example of the Punnett square:
L l
------------------
l | Ll ll
In this case, there are only two possible genotypes: Ll and ll. Since individuals with the ll genotype are lactose intolerant, the phenotypic ratio would be 1:1, with one individual being lactose intolerant and one individual being able to digest lactose.
Remember that Punnett squares are a visual representation of the possible combinations of alleles and can help determine the genotypic and phenotypic ratios of offspring in specific crosses.