biology sac help please

[sally baker]

help with biology sac. im writing a sac up and  our study was an   experiment cross of two inherited maize grains on a cob of maize from a F2 generation descended from a parental cross of pure breed male and female. However on the corn their were 4 combinations yellow wrinkle . yellow smooth and black wrinkled and black smooth. In the experiment their were more black smooth then their were black wrinkled and their were more yellow smooth then black wrinkled. which one would be dominant

[jane1234]

Which was greater out of black smooth and yellow smooth? Which one was greater would be the two dominant traits.

We know for sure that smooth is dominant over wrinked (more black smooth than black wrinkled) and I'm assuming that yellow is dominant (as yellow smooth > black wrinkled). However, if you had a small sample size then your results won't be very accurate. If black is dominant then yellow smooth should be approximately the same as black wrinkled, but if you have a small sample then yellow smooth could end up being slightly greater.

But based on what you've said I'd go with yellow smooth as the dominant pair of characteristics (with yellow being dominant over black, and smooth being dominant over wrinkled).

[sally baker]

okay yes my data is kind of accurate because its a tally of the whole class's result. yes in black smooth is more dominat then black wrinkled and yellow smooth is more domiant  then yellow wrinkled. When im doing the punnet squared how could i represent  gametes should i represent them in terms of colours yellow smooth i would put A and Black smooth i would put B and yellow wrinkled recessive which would just be a and black wrinkled would just be "b " . sorry thanks

[jane1234]

No, these traits are represented with 4 letters. Using A = colour (with A being dominant and a being recessive) and B = shape (with B being dominant and b being recessive):

AA = yellow Aa = yellow and aa = black
BB = smooth Bb = smooth and bb = wrinkled.

Put any combination together, for example AABb = yellow smooth, and you can figure out the phenotype.

In a punnet square for a dihybrid cross it is usually 4 X 4, if both parents are heterozygous for the traits. I don't know what you started with, but I'll assume both parents are AaBb.

So across one row would be AB Ab aB ab (all the possible gamete combinations). The same would be down the column. Then you should just fill in the 16 squares with the full combination in that square (ie AaBb would be yellow smooth). You should have 9 squares that show the yellow smooth phenotype, 3 squares with black smooth, 3 squares with yellow wrinkled and 1 square (ab X ab) for black wrinkled.

[sally baker]

oh thanks it says both parents are pure breeds for both dominant and the other was pure breeding for both recessive characters . it says write down genotype

[jane1234]

Are you sure? If one parent is pure (homozygous) for dominant in both traits, and the other recessive then all offspring would have genotype AaBb.

[sally baker]

both parents are pure breed , one parental plant was pure breeding for both dominant and the other was pure breeding for both recessive.  i dont get it because i got the ratio  1:2:2:4:1:2:1:2:1 for doing a dihbryid cross  so one was. AABB   and the other is aabb .... Omg stupid corn i dont get the point of counting all the corn if the work sheet says that their pure breeds.