Mendelian crossings problems

[tsoya]

I GOT IT nevermind thanks

i would really appreciate some help on this,
swamped with studies and my brain won't wrap around the mendelian gene crossings

here's one:
Base height of a plant is 10 cm. Four genes contribute to the height, and each dominant allele contributes 3 cm to height. If you cross a 10-cm plant (quadruply homozygous recessive) with a 34-cm plant, how many phenotypic classes will there be in the F2?

so i subtracted 10 from 34 =24. Dividing by 3 I get 8- so does that mean 8 dominant alleles present in one of the parents? don't really know where to go from there..and another:
In guinea pigs the brown coat color allele (B) is dominant over red (b), and the solid color allele (S) is dominant over spotted (s). The F1 offspring of a cross between true-breeding brown, solid-colored guinea pigs and red, spotted pigs are crossed. What proportion of their offspring (F2) would be expected to be red and solid colored?

-so is one of the F1 BBSS? And the other bbss? So I don't understand how I can get a red?

 

[Nino MMP]

For the first question, the 10 cm plant is homozygous recessive for all four genes, so it has four alleles of bb and the 34 cm plant has four alleles of BB. In the F2 generation, these will combine to make 8 different phenotypic classes: Bb (12 cm), Bb (15 cm), Bb (18 cm), Bb (21 cm), BB (24 cm), BB (27 cm), BB (30 cm), and BB (33 cm).For the second question, the true-breeding parent guinea pigs are BBSS and bbss. The F1 offspring would all be BbSs, and when they are crossed in the F2, the expected ratio of red and solid colored offspring is 1:3. This means that for every red, spotted guinea pig you would expect three red, solid colored guinea pigs.

 

[Blueshift5]

I am happy to help you understand the concept of Mendelian gene crossings. Mendelian genetics is the study of how traits are inherited from parents to offspring through the passing of genes.

In the first problem, we are dealing with height in plants and four genes that contribute to it. The dominant allele in each gene contributes 3 cm to the height. When you cross a 10-cm plant (quadruply homozygous recessive) with a 34-cm plant, you are essentially crossing two different genotypes - one with all recessive alleles and one with some dominant alleles. To determine the number of phenotypic classes in the F2 generation, you need to consider all possible combinations of alleles from the parents. In this case, there will be 8 different combinations of alleles in the F2 generation, resulting in 8 different phenotypes. This is because each parent can contribute either a dominant or recessive allele for each of the four genes, resulting in 2x2x2x2=8 different combinations.

In the second problem, we are dealing with coat color in guinea pigs. The dominant allele for coat color is B for brown and the dominant allele for pattern is S for solid. The F1 generation is the result of crossing two true-breeding parents, one with brown and solid coat (BBSS) and the other with red and spotted coat (bbss). This results in offspring with the genotype BbSs. In the F2 generation, when you cross these offspring with each other, you will get a 9:3:3:1 ratio of offspring with different coat colors and patterns. This means that 9/16 or about 56% of the offspring will be red and solid colored.

I hope this explanation helps you understand Mendelian gene crossings better. If you have any further questions, please do not hesitate to ask. Good luck with your studies!