Download 11.1 Mating insects

Lab 11 – Mendelian Genetics
Objectives



Determine the difference between dominant and recessive traits
Predict possible genotypes of offspring from different parental trait combinations
Calculate probability of blood types in offspring
Introduction
Throughout history, people have wondered how offspring inherit their characteristics.
Many people believed that inheritance was based on blood. They thought that the blood of
parents blended and eventually poured into their children. This idea still remains in the
language, as, for example, in the phrase “blood relatives.”
Because people did not understand the biological basis of heredity, they developed
fanciful ideas about the origin of organisms. One author suggested that a giraffe was the result
of a cross between a camel and a leopard. The camel contributed the long neck and the leopard
contributed the spots!
Only during the last century has biology been able to explain the mechanisms of
inheritance. Today scientists know that characteristics are not the result of blood but of the DNA
in cells.
In the mid-1800s, an Austrian monk named Gregor Mendel carried out an amazing
scientific investigation while working in a monastery school near what is now Bruno in the
Czech Republic. Mendel observed that the offspring of certain plants had physical
characteristics similar to the physical characteristics of the plants' parents or ancestors. Mendel
wondered why related organisms, both plant and animal, tended to resemble one another and
how these similarities might be explained. He reasoned that close observation of inheritance
might provide him with the answer for which he searched. He therefore set out to examine and
quantify the physical traits in pea plants (because of their speedy reproductive cycles) in an
attempt to predict the traits that would occur in future generations.
Mendel studied seven different traits, including plant height, flower color and position,
seed color and shape, and pod color and shape. After many arduous years and over 30,000
plants, Mendel concluded that certain particles or "factors" were being transmitted from parent to
offspring and so on, thus providing a connection from one generation to the next. Mendel
suggested that these factors were directly
responsible for physical traits. His interpretation
of the experimental data further suggested that
each individual had not one, but two factors for
each trait, and that these factors interacted to
produce the final physical characteristics of the
individual. Both the location and the identity of
Mendel's factors remained unknown for years.
Mendel suspected that heredity depends on
contributions from both parents, and that specific
characteristics from each parent are passed on
rather than being blended together in the
offspring.
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Lab 11 – Mendelian Genetics
The drawing illustrates his experiment with peas in which he demonstrated his concept. A parent
homozygous for the allele for spherical seeds is crossed with a parent homozygous for the allele
for wrinkled seeds. Each parent makes gametes of only one kind, either S or s, and these
combine at fertilization to form plants that all have the genotype Ss and the spherical seed
phenotype. When the F1 plants self-pollinate, they produce two kinds of gametes, S and s.
These combine randomly in four different ways to form F2 plants. Three of the four possible
combinations produce genotypes that determine the spherical seed phenotype, and the fourth
produces the genotype for the wrinkled seed phenotype, so that the observed phenotypic ratio is
3:1. The illustration, called a Punnett Square, is a handy device for keeping track of the ways
gametes can combine at fertilization.
11.1 Mating insects
1.
2.
3.
4.
You will be given several bags with chromosomes (genes) belonging to the female insect
and several bags with chromosomes (genes) belonging to the male insect.
Look at the genotypes written on the bags. Using these genotypes listed for the parents,
complete Table 1 of expected genotypic and phenotypic ratios in the offspring.
Reach in the bag and randomly draw 1 chromosome (i.e., one allele) from each parent’s
gene bag and line up homologous chromosomes.
From the chromosomes drawn, fill in Table 2, indicating the genotype and the phenotype
of the offspring result.
5.
Make a detailed drawing of your insect offspring, showing all observable characteristics
seen in Table 2.
6.
Ask another group for a “suitable” mate for your offspring insect. Fill in Table 3 with
information from the mating of your insect with another group’s insect.
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Lab 11 – Mendelian Genetics
11.2 Blood Group
1.
2.
3.
4.
Important reminders:
A. Wear gloves throughout this exercise.
B. Dispose of all items that touch the chemicals in the BIOHAZARD bag.
Consider this scenario. Two babies, born at approximately the same time, may have been
mixed up in the nursery. The parents of the children have decided to provide blood
samples to help determine if the babies have been mixed up. Mr. and Mrs. Smith and Mr.
and Mrs. Jones are furious with the hospital staff.
Obtain a compartmented test tray, toothpicks, Mr. Smith’s blood, Mrs. Smith’s blood,
Mr. Jones’ blood, Mrs. Jones’ blood, Child 1’s blood, Child’s 2’s blood, Anti-A serum,
and Anti-B serum.
Place the appropriate number of drops in the compartments according to the table below.
Mr. Smith
Anti- 3 drops antiA
A
serum
3 drops Mr.
Smith’s
blood
Anti- 3 drops antiB
B
serum
3 drops Mr.
Smith’s
blood
5.
6.
Mrs. Smith
3 drops antiA
Mr. Jones
3 drops antiA
Mrs. Jones
3 drops antiA
Child 1
3 drops antiA
Child 2
3 drops antiA
3 drops Mrs.
Smith’s
blood
3 drops antiB
3 drops Mr. 3 drops Mrs. 3 drops
Jones’ blood Jones’ blood child 1’s
blood
3 drops anti- 3 drops anti- 3 drops antiB
B
B
3 drops
child 2’s
blood
3 drops antiB
3 drops Mrs. 3 drops Mr. 3 drops Mrs. 3 drops
Smith’s
Jones’ blood Jones’ blood child 1’s
blood
blood
3 drops
child 2’s
blood
Stir each mixture with a different clean toothpick for 30 seconds. Use only one toothpick
per compartment to avoid cross contamination.
Examine each compartment for agglutination (or clumping).
Mr. Smith
Mrs. Smith
Mr. Jones
Mrs. Jones
Child 1
Child 2
Anti-A
serum
Anti-B
serum
QUESTION: Using the above table, indicate if clumping occurred or not. Check with
instructor. Sometimes, clumping may not be obvious.
7.
Answer the questions on the QUESTIONS page.
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Lab 11 – Mendelian Genetics
11.1 QUESTIONS
The table below shows the allele and phenotype designations for insect traits.
Dominant Allele Phenotype
Resistant to DDT (D)
Small Head (H)
Long Thorax (T)
Short Abdomen (A)
Short Legs (S)
Dark Body (B)
Antennae Absent (P)
Long Wings (W)
Recessive Allele Phenotype
Not resistant to DDT (d)
Large Head (h)
Short Thorax (t)
Long Abdomen (a)
Long Legs (s)
Light Body (b)
Antennae Present (p)
Short Wings (w)
Male (XY)
Female (XX)
1.
Complete Table 1 below.
Table 1. Expected offspring genotypic and phenotypic ratios based on parental genotypes. All
ratios MUST be the simplest ratio possible. Unreduced ratios will be wrong.
Trait
Male parent
Genotype
Female
parent
Genotype
Expected
genotypic ratio
in offspring
Resistant to DDT
__DD:__Dd:__dd
Expected
phenotypic
ratio
in offspring
__yes:__no
Head size
__HH:__Hh:__hh
__small:__large
Thorax length
__TT:__Tt:__tt
__long:__short
Abdomen length
__AA:__Aa:__aa
__short:__long
Leg length
__SS:__Ss:__ss
__short:__long
Body color
__BB:__Bb:__bb
__dark:__light
Antennae presence
__PP:__Pp:__pp
__absent:__there
Wing length
__WW:__Ww:__ww
__long:__short
Sex of individual
__XX:__XY
__male:__female
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Lab 11 – Mendelian Genetics
2.
Complete Table 2 below.
Table 2. Data from your parental insects mating.
Trait
Parent (M)
Allele
Parent (F)
Allele
Offspring Insect’s
Genotype and Phenotype
DDT
Head Size
Thorax Size
Abdomen
Leg Length
Body Color
Antennae
Wing Size
Sex
3.
Make a detailed drawing of your insect based on the phenotypes in Table 2. Make sure to
label all characteristics.
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Lab 11 – Mendelian Genetics
4.
Complete Table 3 below.
Table 3. Mating of your insect (from Table 2) with another group’s insect.
Trait
Parent 1 (yours)
Genotype: from
Table 2
Parent 2 (other)
Genotype
Genotypic Ratio in
offspring
DDT
__DD
__Dd
__dd
Head Size
__HH
__Hh
__hh
Thorax Size
__TT
__Tt
__tt
Abdomen Size
__AA
__Aa
__aa
Leg Length
__SS
__Ss
__ss
Body Color
__BB
__Bb
__bb
Antennae
__PP
__Pp
__pp
Wing Size
__WW
__Ww
__ww
Sex
___ Males
5.
___ Females
If the insects that you just mated had 120 offspring, how many would we expect to have
no antennae?
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Lab 11 – Mendelian Genetics
11.2 QUESTIONS
6.
Complete Table 4 using the information in the paragraph below.
If a person’s blood sample clumped in the presence of anti-A and anti-B serum, his blood
type is AB, and his genotype is IAIB. If a person’s blood sample clumped in the presence
of anti-A serum and not in anti-B serum, his blood type is A, and his genotype could be
IAIA or IAi. If a person’s blood sample clumped in the presence of anti-B serum and not
in anti-A serum, his blood type is B, and his genotype could be IBIB or IBi. If no
clumping occurred in either serum, the blood type is O, and the genotype is ii.
Table 4. Possible genotypes of individuals based on clumping patterns. Use the blood type
genotype designations seen in the above paragraph.
Blood type
Possible genotypes
Mr. Smith
Mrs. Smith
Mr. Jones
Mrs. Jones
Child 1
Child 2
7.
Even though A and B blood types correspond to two different genotypes, an individual
can only have one specific genotype. Using the information in the table above, decide
what the specific genotypes are for each person based on who could be the parents of
child 1 and child 2.
Specific genotype
Mr. Smith
Mrs. Smith
Mr. Jones
Mrs. Jones
Child 1
Child 2
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Lab 11 – Mendelian Genetics
8.
Now that you know the specific genotypes of Mr. and Mrs. Smith, determine the
probability that any child of theirs would have the following blood types.
Blood type A: __________ %
Blood type B: __________ %
Blood type AB: _________ %
Blood type O: __________ %
9.
Now that you know the specific genotypes of Mr. and Mrs. Jones, determine the
probability that any child of theirs would have the following blood types.
Blood type A: __________ %
Blood type B: __________ %
Blood type AB: _________ %
Blood type O: __________ %
10.
A man and a woman with genotypes IAIB and IBi may have children. Determine the
probability that any child of theirs would have the following blood types.
Blood type A: __________ %
Blood type B: __________ %
Blood type AB: _________ %
Blood type O: __________ %
TURN IN QUESTIONS PAGES 4-8.
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