HEREDITY
& THE ENVIRONMENT
Edited 1.21.07
Don't forget to
click on all indicated links such as this one.
Introduction to Heredity
and the Environment
1. E _ V _ _ _ N _ _ _ T A _ factors
often interacts with G _ _ _ _ (Fig. 1)
Figure 1
in the development and expression of I _ H
E _ _
T _ _ traits.
2. Some common environmental
factors which can influence how genes express themselves are:
a. Amount of S _ _ L I _ _ T
(Hint the local star!) (Fig. 2)
b. T _ _ _ E R _ _ U _ E
(Fig. 3)
c. Amount of P _ E _ I _ _ T _
_ I _ N
(Fig. 4)
d. V _ _ A M _ _ S and M
_ _ E R _ L _ in your diet (Fig. 5)
e. Acidity or Alkalinity measured in
units of _ _
(Fig. 6)
Figure
2
Figure 3
Figure 4
Figure 5
Figure 6
3. We don’t actually inherit many P _ Y _ I _ _ L
characteristics. We inherit only the genetic
possibilities for them. The environment affects
if certain genes show up (are E _ P R E _ _ _ D)
and the degree to which they are expressed..
Click here for the answers to this Intro. section.
a.
Example -- The Affect of the Environment on Heredity
In rabbits, fur color varies in several
types of H _ _ _ S such as the _ N O _ _ H _ E H _ _ _
of North America. In this species,
(1) in the W _ _ _ _ _ , when the body temperature drops, this
species is pure _ H _ _ _ (Fig. 7)
Figure 7
Figure 8
Figure 9
(2) In warmer T _ _ _ E
R _ _ U _ _ S ,
the species is pure _ R _ _ _ (Fig. 8)
The North American hare in Figure 9 shows both
some snow and
some grass in its
surroundings.
Is this hare in its Summer or Winter coloration? _______________
(3) Even more striking is the study of the H _ _ A L _ Y A _ H _ _ _ from the mountains
of Asia.
Like its American cousin, they change color, but this time from White to Black
depending on the temperature
in different parts of their body.. Surprisingly, it is the Black
fur which grows in
on the coldest parts
of their body.
If a portion of the white back is
shaved & an ice pack is placed there, new _ _ _ _ _
fur grows at that location.
What would happen if you alternately shaved small squares
of fur and strapped
mini-ice packs to the back of the hare? You might get something
that
looked like
this. Obviously, this link is messed up. (SDK 5:50 PM 2.5.08)
I regret that my image searches on both Yahoo and Google did not turn up any
photos
of this Asian
species in its winter coloration. Such is life. Here are a few other
Himalayan
Hare photos/sketches (10A,
10B, 10C, 10D) for
your inspection.
10 A
10 B
10 C (1)
10 C (2)
(4) In several species
of hares, the environmental variable that
controls the fur color gene is
T _ _ _ _ R _ _ _ _ _
From the January
2007 TLE Regents Exam (Qu. #6) , we have the following (question).
Which statement best explains the change
shown
in the diagram on the left?
(1) Gene expression in an organism
can be modified
by interactions
with the environment.
(2) Certain rabbits produce mutations that affect
genes in
specific areas of the body.
(3) Sorting and recombination of genes can be
influenced by
very cold temperatures.
(4) Molecular arrangement in existing proteins
can
be altered by environmental factors.
Click
here for the answers to this hairy section.
b. Scientific Method in Heredity vs. the
Environment
Any properly controlled experiments allows
________ Independent Variable(s)
But we have a definite problem.
Only you have your specific set of G _ _ _ S and only you
have your specific _ N _ I _ _ N
_ _ _ T A _ history. That sounds like ________
Independent Variables, but it does not have to be that way if we decide to study humans
that
are the same ( _ D _ _ _ I C _ _
_ _ I N S) , since these siblings have the same
H _ _ E _ _ _ Y.
Researchers have
used twin studies in their long search for an answer to how much of each of
us is determined by our G _ _ E
_ _ _ S and how much of us is determined by our
_ _ V _ _ O _ M E _ T.
This search is
also known as the case for N _ T U R E versus N _ _ T U
R E,
with the
first blanked word representing our
_ _ R _ D _ _ Y (Fig. 11) and the second blanked word
representing our _ N _ _
_ O N
_ _ _ _ A L variables (Fig. 12).
Fig. 11
Fig. 12
The pendulum of time
swings back and forth like that on a grandfather clock. In some eras,
researchers felt strongly that
H _ _ E _ _ _ Y was the dominant factor in determining your
behaviors. In others, researchers
leaned more strongly to our social _ N _ _ _ O _ M _ _ _
as the dominant factor in determining our
behaviors. Nobody can put an actual percentage
on these two determiners of our behaviors.
For a more detailed
historical account of this long running debate, click on the following link:
nature vs. nurture For an even more technical argument (Bio H students
and selected Bio R
students), click on this topic in ...
Wikipedia
(two links were saved
to SDell/school/Web Activities/genetics)
Click here for
the answers to this section!!
c. Effect of L I G H T
on human pigmentation
We have special
cells in our skin that contain the colored molecules known as melanin.
The production of this melanin P
I _ _
E _ T is dependent on both your H _ _ E D _ _ _ and
on your environmental exposure to
_ I _ _ T . Melanin pigment independently occurs in
human skin, hair and eyes.
Those people
who's ancestors came from lands near the
equator were in great danger from
the sun. Too much sun exposure
not only caused painful burns, but also led to an increase
in genetic M _ _ A T _ _
_ S, some of which were cancers. Those with lighter skins
(less M _ _ A _ _ N) and
therefore less protection from the sun tended to get worse burns
and more cancers. The lighter
pigmented people on
average died younger than others and left
F _ _ _ R offspring.
Those with
darker skins (more M E _ _ _ I _) and therefore more protection from the
_ _ _
tended to have fewer burns and fewer
cancers. They tended to live longer, well into their
R _ _ _ O D _ _ T _ _ E
years, and left M _ _ _ offspring. The offspring of these
darker
peoples tended to have _ A _ _
_ R skins, hair and eye pigments. (See Figure 13).
Which photo is from Australia, which
is from Africa and which is from India?
13
13
13
Those people who's
ancestors came from lands distant from the
equator had the
opposite events. It was
those with the L _ _ _ _ _ R pigmented skin, hair and eyes who
had, for a number of different
reasons, greater survival advantage. They tended to live longer
and produce more children like
themselves. (See Figure 14) Which photo is from Sweden,
which photo is from Iceland, and
which photo is from Norway? Since the cultural differences
from these three Nordic peoples is
similar, this one is very difficult.
14
14
14
This line
of reasoning about differing pigmentation in people from different parts of
Earth is part
of the Theory of Evolution of Charles D _ _ _ _ _. We will
leave this famous man and his
theories to a later unit of this course.
Click here for
the answers to this section!!
A
Local Example of Human Pigmentation
Some times, a
person has inconsistent melanin production is their skin cells, their hair or
even their eye pigments. They
will appear different from most of the population, but only
some of the time. Don't forget
that genetics is only one of the two variables that determines
pigmentation. The other
variable is E _ _ _ R _ _ M _ _ _ A _ exposure to the
sun.
Many years ago,
a then current biology student "Bob", volunteered that he had such uneven
pigmentation in his arms and hands as did
others in his family. It certainly sounds like this was
a(n) _ _ R E _ I _ A _ Y trait.
"Bob" came back to class several times over several years
to have his arms photographed for class
discussion. Here are the results of those photos.
Here's "Bob" the
former Shen. football star
showing off his pectoral muscle development. .
14 A (Look at the date on the board)
In this first photo (14A), taken
during his senior year, his hands look normal. This
is because in W _ _ _ _ _, he was exposed to much less
L _ _ _ _ to trigger
his skin cells to produce the P _ _ _ E _ T
melanin.
14 B
14 C
In the photo
on the left (14 B) taken during the end of his sophomore year and
the photo on the right (14 C) taken during the start of his
junior year, "Bob's"
hands appear to be blotchy in pigmentation. This is
because in both late
S _ _ I _ _ & late S _ _ _ E _, his arms & hands have been exposed to much
L _ _ _ _
and only those regions with the G _ _ _ for M _ _ A
_ _ N production make
enough of this chemical to tan his arms and hands.
Click here for
the answers to this section!!
d. Plant
pigmentation experiment
(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
seedlings appeared ________ (color) (Fig. 15) several days later. They did not
make any
C _ _ _ _ O P _ Y _ L. due to the absence of _ _ _ _ _
(See Experiment #1
above).
(3) In Experiment #2
below,
the all (100%) white seedlings were
then transferred to adequate
L _ _ _ _
(an environmental variable)
normal vs. albino seedling
normal vs. albino seedling
16 A
16 B
Note, I had
to replace 16B on 2.4.08 & again on 2.5.08; somebody
must have it
in for these seedling photos.
(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 (Fig. 16 A, 16B), 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 rational number (an integer followed by a decimal). Please calculate the ratios for
these two experiments
from d (4) above and round to two decimal places. .
(a) For 157:43 -- Green/White
ratio = _____ : __
(b) For 146:54 -- Green/White
ratio = _____ : __
(6) Biologist also know that data is most reliable when we have a
_________
(small/large) sample size. The way to achieve this more reliable data is
to ________
(add/multiply) the data from the twin identical 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 = _____ : __
(7) The more reliable Green:White ratios in d
(6) above approximates the more common
__:__ integer ratio that soon will become very
familiar to you (I hope!)
(8) The gene
for chlorophyll production (Sumbol C) (green) is a _ _ M _ N _ N _
|
The gene for no chlorophyll (Symbol c)
(white) is a _ _ C _ S _ _ V _
Any plant with the gene symbols __ __ or __ __ has the potential to turn
green.
Let's see the different possible outcomes in matings between plants all of
which have
different gene combinations for chlorophyll production. The type of
graphical
representations below were first developed by Reginald Punnett. In honor
of
this breakthrough, we call these charts Punnett Squares. And this is a
very good
thing. Otherwise, these charts might be known as Reggie Boxes.
Refer to a reference sample on how to complete
a Punnett Square on your screen!!
C C
c Cc Cc
c Cc Cc
Now, you complete the rest of these Punnett Squares! Thank you very
mucho!
(a) If one parent is CC & the other is Cc,
C C
then the Punnett Square for this cross
C
is shown on the right.
c
Complete the four boxes
What percent of these offspring are green? ___ %
(b) If one parent is Cc & the other is Cc,
C c
then the Punnett Square for this cross
C
is shown on the right.
c
Complete the four boxes
What percent of these offspring are green? ___ %
This is a __ : __ ratio.
(c) If one parent is Cc & the other is cc, C c
then the Punnett Square for this cross c
is shown on the right.
c
Complete the four boxes
What percent of these offspring are green? ___ %
This is a __ : __ ratio.
(9)
Using only the symbols C &/or c, and your answers to 8(a), (b),
or (c) above,
determine the
genotypes of the PARENTS of
the plants in (d.(6) & d (7)) on the
prior page.
These parental genotypes are __ __ & __ __
Click here for
the answers to this section!!
e.
SUMMARY TIME:
(10) The reason that ALL the plants were
initially white was the lack of _ _ G _ _
necessary for the production of
_ H _ _ R _ P _ _ _ _
(11) Once sufficient light
was given to these young plants,
about __/__ (a fraction) of the
seedlings, having one or more genes to make chlorophyll (genotypes __ __ or __
__)
made this pigment and
the seedling after a few days then turned _ _ E _ _.
Click here for the answers to the Summary
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