4. To identify the genotype of yellow-seeded pea plants as either homozygous dominant (YY) or heterozygous (Yy), you could do a test cross with plants of genotype ________. (explain your answer)

Do we do a punnet square?

Yes you would use a Punnet Square

I think I would Yy, if it heterozygous, you will get 1/4 yy,

Yes, to identify the genotype of yellow-seeded pea plants as either homozygous dominant (YY) or heterozygous (Yy), you can perform a test cross with plants of genotype yy.

A test cross involves crossing an individual with a known genotype (in this case, yy) with an individual of unknown genotype (yellow-seeded plant). By analyzing the traits of the offspring resulting from this cross, you can determine the genotype of the unknown individual.

To set up a Punnett square, you would write the genotype of the unknown yellow-seeded plant as Y_ (where _ represents the unknown allele). Then, you would cross it with a plant homozygous recessive for that trait (yy). The resulting Punnett square would show the possible genotypes and phenotypes of their offspring, allowing you to determine the genotype of the yellow-seeded plant by observing the ratio of dominant to recessive phenotypes.

To identify the genotype of yellow-seeded pea plants as either homozygous dominant (YY) or heterozygous (Yy), you can perform a test cross. A test cross involves crossing an individual with the dominant phenotype but unknown genotype with an individual that is homozygous recessive (yy).

The reason for using a homozygous recessive individual is that if the dominant individual is homozygous dominant (YY), all the offspring from the cross will have the dominant phenotype (yellow seeds) and be heterozygous (Yy). On the other hand, if the dominant individual is heterozygous (Yy), the offspring will be a mix of the dominant phenotype (yellow seeds) with a 1:1 ratio of heterozygous (Yy) and homozygous recessive (yy) genotypes.

By observing the phenotypes of the offspring, you can determine whether the dominant individual is homozygous dominant (YY) or heterozygous (Yy). If all the offspring have a dominant phenotype (yellow seeds), it indicates homozygous dominant (YY) genotype. If you observe a ratio of 1:1 between individuals with the dominant phenotype and individuals with the recessive phenotype (green seeds), it indicates a heterozygous (Yy) genotype in the dominant individual.

Regarding the use of a Punnett square, it is not necessary in this case. A Punnett square is a visual representation of potential offspring genotypes resulting from a cross between two parents with known genotypes. In a test cross, one of the parents has a known genotype (homozygous recessive), and the unknown genotype is being tested. By observing the phenotypes of the offspring, you can determine the genotype of the dominant individual without constructing a Punnett square.