I need a really in-depth tutorial on constructing punnett squares.?

Question

I'm in an online biology course (instructor doesn't help) and I really don't understand this concept. I've already found all the online tutorials and they don't seem to help much either. Any suggestions?

Answer 1

In a simple monohybrid cross, follow these steps. Let's say that T is tall and t is short.

1. Parents in this example problem are Tt and tt.
2. Show the gametes from each parent. The gametes are formed by separating the two alleles (genes) for this trait from each other and putting them into different gametes.
Parent Tt makes gametes T and t.
Parent tt makes gametes t and t.
3. Put the gametes from the first parent on the left side of the Punnett square - write them on the outside, not in the boxes. Put the gametes from the second parent across the top of the Punnett square - write them above the square, not in the boxes.
4. Fill in the four boxes of the Punnett square by writing the gamete from the far left and the gamete from the top. For the first box, this will be Tt. The second box on the top row has a T to the far left and a t above; write Tt in this box. The first box on the bottom row has a t to the left and a t above the column; write tt in this box. The second box on the bottom row has a t to the far left and a t above the column; write tt in this box.
5. The expected phenotype ratio tells how you would expect the offspring to turn out. This is kind of like telling the score of the results in the Punnett square. In the example we've been doing, there are two Tt which are tall and there are two tt which is short. This is a score or a ratio of 2 tall:2short. Reduce the twos just like you would reduce a fraction -- divide them both by 2. So the expected phenotype ratio is 1 tall: 1 short.

Answer 2

so you make a square and cut it in half in both directions so you have 4 squares within the big one then say you are using BB and Bb . on the outside of the top 2 boxes you would place a B and B. then on the left hand side on the outside of the box you would place B and on the next on ewould go the b. Then you match them so you would get in the top left box BB, top right box BB. Bottom left box you get BB and bottom right box would be Bb. Hope this helps

Answer 3

http://www.usoe.k12.ut.us/curr/science/sciber00/7th/genetics/sciber/punnett.htm

these are easier than you think...tackle em!