Monohybrid and dihybrid crosses?complete a punnet square to illistrate your answer? please help me out here?

Question

Monohybrid and dihybrid crosses?complete a punnet square to illistrate your answer?

1) in pea plants, yellow peas r dominate over green peas.use a ppunnett square to podict the phenotypic and genotypicoutcome of a cross bettween a plant heterozygous for yellow peas and a plant homozgous for green peas. use Y for dominate and y for recessive.

q2)a tall pea plant crossed with a short pea plant produces offspring;of which about half are tall and half are short. what are the genotypes of the parents? show the possible gamete combinations using a punnett square.

please i really need help.

Answer 1

1) this is the best square I can draw on here

                      Y           y

            y         Yy        yy        2 homozygous green

            y          Yy       yy         2 heterqygous Yellow

2)  When it is half and half, the geontypes are the same as above

Answer 2

First:  heterozygous means the parent has one gene for the dominant (Y) and one gene for the recessive (y); this is the parent's genotype.  The parent will LOOK yellow (phenotype) because yellow is dominant.

           homozygous means BOTH genes from the parent are the SAME; in this case yy.  This is the parents genotype.  The parent will LOOK green (phenotype).

Set up your punnet square with one side Yy and the other side yy.  It doesn't matter which one you put at the top.

............y............y

   Y

  

    y    

Now, fill in the two letters for each of the 4 offspring.  Use one letter from the top and one letter from the left.  You will get:

Yy    Yy

yy    yy

These are the genotypes for the four offspring

For the phenotype, indicate what color you would SEE if you were looking at the offspring.  If there is at least one Y, the offspring will be the dominant color.  If both letters are small, the offspring will be the recessive color.

For your q2, look at what you have in question 1 and work backwards to what the parents would have been like.

Good luck; it's not that hard.