In: Biology
5. Now cross two of the heterozygous F1 offspring from question #2.
Parent #1 |
|||
Parent #2 |
Y |
y |
|
Y |
YY |
Yy |
|
y |
Yy |
yy |
What is the genotypic ratio of the offspring in Question 5?
25%(YY):50%Yy:25%(yy)
What is the phenotypic ratio of the offspring in Question 5?
3(Yellow):1(Green)
6. Consider the resulting ratio of crossing the two heterozygous
pea plants in question #5. We will use this ratio in a short
activity exploring probability. Keep in mind that crossing two
individuals that are heterozygous for a certain trait is similar to
flipping two coins. Each coin has two sides (we might think of each
side as an “allele”) and the chances of flipping heads/heads,
heads/tails or tails/tails should be similar to the ratio we see
when crossing two heterozygotes.
For this simple activity, you will need two coins (pennies,
nickels, dimes, quarters, or a mix of any of those). Alternatively,
you may google a coin-flipper simulator that will allow you to flip
two coins at once. You will also need a piece of scratch paper and
a pen or pencil.
Directions: Flip the two coins simultaneously at
least 50 times. For each flip of the pair of coins, you will record
the results on a piece of scratch paper. You might set up a table
like the one below to record your results. Once you have flipped
the coins at least 50 times, enter the number of heads/heads,
heads/tails and tails/tails in Table 1 below.
Now determine the ratio for your results. You will do this by
dividing the number for each result by the total number of flips,
and then multiply by 100.
(Example: If the number of heads/heads is 9 then 9/50 = .18,
.18x100 = 18%), Repeat this mathematical procedure for heads/tails
and tails/tails)
Table 1 |
|
Heads/heads (hh) |
|
Head/tails (ht) |
|
Tails/tails (tt) |
|
Ratio (hh:ht:tt) |
Compare the resulting ratio from the question #5 cross of two
heterozygous parents to the ratio from the coin flipping exercise.
Are there similarities? If so, what are they?
What might be done to make the ratio from the coin flipping
exercise become more similar to the ratio from question #5?
(Hint: Consider that more data equals better
accuracy.)
Result obtained on flipping coins 50 times -
Number of Flip | Result obtained |
1 | HH |
2 | HT |
3 | HT |
4 | HH |
5 | HT |
6 | HT |
7 | HH |
8 | HT |
9 | HT |
10 | TT |
11 | HH |
12 | TT |
13 | HT |
14 | HT |
15 | HH |
16 | HT |
17 | TT |
18 | HH |
19 | TT |
20 | HT |
21 | HT |
22 | TT |
23 | TT |
24 | HT |
25 | HT |
26 | TT |
27 | HT |
28 | HH |
29 | HT |
30 | HT |
31 | TT |
32 | HT |
33 | TT |
34 | HT |
35 | HH |
36 | HT |
37 | TT |
38 | HT |
39 | HH |
40 | TT |
41 | HT |
42 | HT |
43 | TT |
44 | HH |
45 | TT |
46 | HH |
47 | TT |
48 | HH |
49 | TT |
Number of observations -
HH -
HT -
TT-
Probability of obtaining HH
%
Probability of obtaining HT
%
Probability of obtaining TT
%
Yes the only similarity observed is higher percentage of selection of heterozygous (Yy) or hybrid pair (HT)
With larger number of sampling it is possible to obatin the same frequency of distribution as that of F1 cross of hybrid plants. Large sample size helps in removing inconsistencies and errors.