d. Plant pigmentation experiment -- ANSWERS
(1) 2 sets of 200 seeds (set (a) & set (b)) each were first germinated in the dark (no light)
An albino seedling (doomed I must say!)
15
EXPERIMENT #1 GREEN COLOR WHITE COLOR
(a) 0 200
(b) 0
200
(2) All
appeared _WHITE_ (color) several days later. They did not make any
C H L O R O P H Y L L. due to the absence of L I G H T (See Experiment #1
above).
(3) In Experiment #2,
the all (100 %) white seedlings were
then transferred to adequate L I G H T
(an environmental variable)
normal vs. albino seedling
normal vs. albino seedling
16 A
16 B
(4) The actual results of Experiment #2 (sets (a) & (b)) below were as follows:
EXPERIMENT #2 GREEN COLOR WHITE COLOR
(a) 157 43
(b) 146 54
(5)
Some seedlings, like the pairs above, were then green & some were white.
Biologists use math as a tool. It is
not the absolute number of green vs. white
that is important. It is the
green to white ratio that is very
important. To calculate
a ratio,
divide the number of green seedlings by the number of white
seedlings.
The mathematical interpretation of these ratio results is always in the format
x:1, in which
x is a mixed number (an integer followed by a decimal). Please calculate the ratios for
these two experiments
from d (4) above:
(a) For 157:43 -- Green/White ratio = 3.65 : 1
(b) For 146:54 -- Green/White ratio = 2.70 : 1
(6) Biologist also know that data is most reliable when we have a
_LARGE_ sample size.
The way to achieve this more reliable data is
to ADD the data from the twin experiments
in d (4) above.
After we do this computation, we now have 200 + 200 seedlings = 400 seedlings;
of
which 157 + 146 (303) were green and 43 + 54 (97) were white.
Please now calculate this new and more reliable Green to White ratio.
for 303:97, the Green/White ratio = 3.12 : 1
(7) The more reliable Green:White ratios in d
(6) above approximates the more common
3 : 1 integer
ratio that soon will become very
familiar to you (I hope!)
(8) The gene
for chlorophyll production (C) (green) is a D O M I N A N T |
The gene for no chlorophyll (c)
(white) is a
R E C E S S I V E
Now, you complete the rest of these Punnett Squares! Thank you very
mucho!
To save time, I've eliminated the boxes in the following Punnett Squares.
Please have it in your
to forgive me for this!
weird photo gone here!
(a) If one parent is CC & the other is Cc,
C C
then the Punnett Square for this cross
C CC CC
is shown on the right.
c Cc Cc
Complete the four boxes
What percent of these offspring are green? _100_ %
(b) If one parent is Cc & the other is Cc,
C c
then the Punnett Square for this cross
C CC Cc
is shown on the right.
c Cc cc
Complete the four boxes
What percent of these offspring are green? _75_ % (all but the lower right!)
(c) If one parent is Cc & the other is cc, C c
then the Punnett Square for this cross c
Cc cc
is shown on the right.
c Cc cc
Complete the four boxes
What percent of these offspring are green? _50_ %
(9)
Using only the symbols C &/or c, and your answers to (a), (b),
or (c) above,
determine the
genotypes of the PARENTS of
the plants in (d. (4)): The seedling
offspring were in an approximate 3:1 (green:white) ratio.
These parental genotypes are C c & C c