biology worksheet...b) explain monohybrid cross. c) state mendel’s first law (law of segregation)....
TRANSCRIPT
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CHAPTER 4: GENETIC INHERITANCE
SUBTOPIC: 4.1 Mendelian genetics: Monohybrid and Dihybrid
LEARNING OUTCOMES:
a) State the terminologies used in genetic inheritance: allele, gene, locus, genotype,
phenotype, homozygous, heterozygous, dominant, recessive, self-cross and test cross.
b) Explain monohybrid cross.
c) State Mendel’s first law (Law of Segregation).
d) Show genetic diagram on the monohybrid cross and include the genotypic ratio
(1:2:1) and phenotypic ratio (3:1) of F2 generation.
e) Show genetic diagram on the monohybrid test cross and include the genotypic ratio
(1:1) and phenotypic ratio (1:1) of F2 generation
f) Explain dihybrid cross.
g) State Mendel’s second law (Law of Independent Assortment).
h) Show genetic diagram on the dihybrid cross and include only phenotypic ratio
(9:3:3:1) of F2 generation using Punnett square.
i) Show genetic diagram on the dihybrid test cross and include the genotypic ratio
(1:1:1:1) and phenotypic ratio (1:1:1:1) of F2 generation using Punnet square.
1. Match the vocabulary word with the proper definition.
Vocabulary
Definition
1 Allele involves the breeding of an individual with a
phenotypically recessive individual,
2 Gene masks the recessive allele; an organism with a
dominant allele will exhibit that form of the trait;
represented by a capital letter
3 Locus the genetic constitution of a individual; genetic
makeup
4 Genotype sequence of DNA that codes for a protein and
determines a trait
5 phenotype term used to refer to an organism that has two
different alleles for the same trait
6 homozygous any location on a chromosome, or any region of
genomic DNA
7 heterozygous term used to refer to an organism that has two
identical alleles for a particular trait
8 Dominant A cross between male and female from the same
plants/generation
9 recessive describes the total physical appearance of an
organism; physical characteristics
10 Self pollination
one of a number of different forms of a gene
BIOLOGY WORKSHEET
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11 test cross masked by the dominant allele; organisms will only
exhibit this form of the trait if the dominant allele is
not present; represented by a lower case letter
2. Multiple Choice: Circle the letter of the correct choice.
Mendel’s First Set of Experiments
At first, Mendel experimented with just one characteristic at a time. He began with flower colour. As
shown in the figure below, Mendel cross-pollinated purple- and white-flowered parent plants. The parent
plants in the experiments are referred to as the P (for parent) generation.
This diagram shows Mendel’s first experiment with pea plants. The F1 generation results from cross-
pollination of two parent (P) plants. The F2 generation results from self-pollination of F1 plants.
F1 and F2 Generations
The offspring of the P generation are called the F1 (for filial, or “offspring”) generation. As you can see
from the figure above, all of the plants in the F1 generation had purple flowers. None of them had white
flowers. Mendel wondered what had happened to the white-flower characteristic. He assumed some type
of inherited factor produces white flowers and some other inherited factor produces purple flowers. Did
the white-flower factor just disappear in the F1 generation? If so, then the offspring of the F1 generation
— called the F2 generation — should all have purple flowers like their parents.
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To test this prediction, Mendel allowed the F1 generation plants to self-pollinate. He was surprised by the
results. Some of the F2 generation plants had white flowers. He studied hundreds of F2 generation plants,
and for every three purple-flowered plants, there was an average of one white-flowered plant.
Law of Segregation
Mendel did the same experiment for all seven characteristics. In each case, one value of the characteristic
disappeared in the F1 plants and then showed up again in the F2 plants. And in each case, 75 percent of F2
plants had one value of the characteristic and 25 percent had the other value. Based on these observations,
Mendel formulated his first law of inheritance. This law is called the law of segregation. It states that
there are two factors controlling a given characteristic, one of which dominates the other, and these
factors separate and go to different gametes when a parent reproduces.
1.Why did Mendel choose to work with the garden pea plant?
a. Because the pea plant is easy to work with.
b. Because pea plants are fast growing.
c. Because the pea plant has a number of characteristics, each with only two forms.
d. all of the above
2.In Mendel's first experiment
a. the F1 displayed all purple-flowered plants.
b. the F1 displayed all white-flowered plants.
c. the F2 displayed all purple-flowered plants.
d. the F2 displayed half purple-flowered and half white-flowered plants.
3.The law of independent assortment states that
a. two factors of the same characteristic separate into different gametes.
b. there are dominant and recessive factors.
c. factors controlling different characteristics are inherited independently of each other.
d. there are two factors that control inheritance.
4.Looking at your cat will give information concerning
a. the cat's genotype.
b. the cat's phenotype.
c. the cat's recessive alleles.
d. the cat's heterozygous alleles.
5.Which sentence is correct?
a. Different alleles of the same gene are located at the same locus on different homologous
chromosomes.
b. Different alleles of the same gene are located at different loci on different homologous
chromosomes.
c. Different genes of the same alleles are located at the same locus on different homologous
chromosomes.
d. Different alleles of the same gene are located at different loci on the same chromosome.
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6.An Aa individual
a. has a homozygous genotype.
b. has a heterozygous phenotype.
c. has a heterozygous genotype.
d. has a homozygous phenotype.
7.In Mendel's initial experiments, an example of the F2 generation would be
a. 75 round seed plants to 25 wrinkled seed plants
b. 75 green seed plants to 25 yellow seed plants
c. 75 white-flowered plants to 25 purple-flowered plants
d. all of the above
8.Which of the following is part of the law of segregation?
(1) there are two factors controlling a given characteristic,
(2) one factor is dominant over the other factor,
(3) the two factors separate into different gametes.
a. 1 and 2
b. 1 and 3
c. 2 and 3
d. 1, 2, and 3
3. Set up the Punnett squares for each of the crosses listed below. Round seeds are dominant to
wrinkled seeds.
(a) RR x rr
What percentage of the offspring will be round?
(b) Rr x rr
What percent of the offspring will be round?
(c) RR x Rr
What percent of the offspring will be round?
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(d) Rr x Rr
What percent of the offspring will be round?
(e) From (a), (b), (c), and (d), which one produces genotypic ratio (1:2:1) and phenotypic
ratio (3:1)?
4. In Mendel’s experiment, true-breeding pea plants with spherical seeds were crossed with true-
breeding plants with dented seeds. Mendel collected the seeds from this cross, grew F1 generation
plants, let them pollinate to form a second generation, and analysed the seeds of the resulting F2
generation.
a) State the Law of Segregation.
___________________________________________________________________________
___________________________________________________________________________
b) Suggest symbols for the seed shape and show a genetic diagram to explain the genotypic and
phenotypic ratio you would expect if the F1 generation sere self-pollinate.
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5. A male and female bird has 4 un-hatched eggs. The female on the left is heterozygous; the male
on the right is homozygous recessive. Use G or g for your genotypes.
(a) Write the genotype of the female (left): _________________________________
(b) Write the genotype of the male (right): __________________________________
(c) Which colour is dominant, grey or black? How do you know?
___________________________________________________________________
___________________________________________________________________
(d) Write the phenotype of the female and the phenotype of the male below:
___________________________________________________________________
___________________________________________________________________
(e) Complete the Punnett square below for this couple:
(f) What is the predicted genotypic ratio of the offspring?
___________________________________________________________________
(g) What will be the colour of the baby birds?
___________________________________________________________________
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6. Dihybrid crosses examine two unlinked (on different chromosomes) gene loci. The following
problem uses many of the skills you learned in the section on monohybrid crosses.
In peas, a single gene codes for stem length and another single gene codes for seed shape. Each
gene has two alleles, one dominant and one recessive. For stem length, tall plants are dominant
over short plants. For seed shape, smooth peas are dominant over wrinkled peas.
A. Choose letters to represent each gene and its alleles.
Seed shape: Smooth:_____ wrinkled:_____
Stem length: Tall:______ short:______
B. In Table 4.1 is a list of all the possible phenotypes for this pair of traits. Determine the
genotypes for these plants, in some cases there will be multiple possible genotypes. When we
worked with one gene locus, each individual genotype was represented by 2 letters since
individual organisms are diploid. Now we are working with two gene loci, so each individual
genotype will be represented by 4 letters, 2 letters for each gene locus. The first genotype is
given.
C. For each of the individuals in part B, list all the unique gametes that can be produced.
Remember, each gamete will have 1 allele from each gene locus. When we worked with a single
gene, each gamete genotype was represented by 1 letter. Now we are working with 2 gene loci, so
each gamete genotype will be represented by 2 letters, one from each gene locus. Fill in the rest
of the Table with all the possible gamete genotypes for each parent genotype listed. The first
gamete genotype is given.
TABLE 4.1 Table of Genotypes for Two Loci
Phenotype Possible genotype Possible gametes
SMOOTH, TALL SSTT ST
wrinkle, TALL
SMOOTH, short
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wrinkle, short
(a) Determine the F1 genotypes and phenotypes resulting from a cross of a homozygous smooth and
homozygous tall plant with a wrinkled, short plant.
(b) What are the F2 genotypes and phenotypes (crossing two F1)
7. In pea plants, green pod colour is dominant over yellow pod colour. Tall plant height is dominant
over short plant height.
(a) A tall green pea plant (TTGG) is crossed with a short white pea plant (ttgg).
TT or Tt = tall tt = short GG or Gg = green gg = white
Parental Generation genotypes: ___________ x ___________
Possible gametes: ___________________________________
Phenotypic Ratio: ___ tall/green : ___ tall/yellow : ___ short/green : ___short/ yellow
Genotypic Ratio: _______________________________________________________
(b) A tall green pea plant (TtGg) is crossed with a Short white pea plant (ttgg).
Parental Generation genotypes: ___________ x ___________
Possible gametes: ___________________________________
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Phenotypic Ratio: ___ tall/green : ___ tall/yellow : ___ short/green : ___short/ yellow
Genotypic Ratio: _______________________________________________________
(c) Two heterozygous tall, green pea plants are crossed.
Parental Generation genotypes: ___________ x ___________
Possible gametes: ___________________________________
Phenotypic Ratio: ___ tall/green : ___ tall/yellow : ___ short/green : ___short/ yellow
Genotypic Ratio: _______________________________________________________
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8. Set up a Punnett square using the following information:
Dominant allele for black fur in guinea pigs = B
Recessive allele for white fur in guinea pigs = b
Dominant allele for rough fur in guinea pigs = R
Recessive allele for smooth fur in guinea pigs = r
Cross a heterozygous parent (BbRr) with a heterozygous parent (BbRr).
a. What is the probability of producing guinea pigs with black, rough fur? Possible genotype(s)?
____________________________________________________________________________
b. What is the probability of producing guinea pigs with black, smooth fur?
Possible genotype(s)?
____________________________________________________________________________
c. What is the probability of producing guinea pigs with white, rough fur?
Possible genotype(s)?
____________________________________________________________________________
d. What is the probability of producing guinea pigs with white, smooth fur? Possible genotype(s)?
____________________________________________________________________________
9. State Mendel’s Second Law. Under what conditions are these laws applicable?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
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10. In rats, short fur is controlled by dominant allele (A) while long fur is controlled by
recessive allele (a). Black fur is controlled by allele (B) and brown fur by allele (b). The
two genes concerned are located on different chromosomes. A cross is made between a
female rat and a male rat. What are the expected parental genotypes if the phenotypic
ratio in F2 generation is 9 short,black : 3 short,brown : 3 long, black : 1 long, brown.
Show a genetic diagram to proof your answer.
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SUBTOPIC: 4.2 Deviations from the Mendelian inheritance
LEARNING OUTCOMES:
a) Define and give example of the following
-codominant (MN blood group)
-incomplete dominant (Antirrhinum sp.)
-multiple allele (human ABO blood group)
-polygene (human skin color)
-linked gene (wing size and body color of Drosophila sp.)
-sex-linked gene (haemophilia)
Complete table below:
Description Types of inheritance that
deviate from Mendelian
Examples
Both alleles of a pair are fully
expressed in a heterozygote
Codominant alleles
Incomplete dominant
alleles
Colour of snapdragon flower
Antirrhinum majus
More than two alleles control
for particular trait of a
character
Multiple alleles
Linked genes
Genes that are carried by
either sex chromosomes (X
and Y)
Sex-linked genes
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Polygenes
Skin colour
Codominant alleles
1. The alleles governing the MN blood group system in man are codominant and
may be represented by the symbols LM and LN.
Genotype Blood group (phenotype)
LMLM M
LMLN MN
LNLN N
Use the genetic diagram to show the expected phenotypic ratio for the crosses
between two heterozygous individuals.
2. Human blood types are determined by genes that follow the CODOMINANT pattern of
inheritance. There are two dominant alleles (IA and IB) and one recessive allele (i).
Blood Type
(Phenotype)
Genotype Can donate blood to: Can receive blood from:
O
ii
A,B,AB and O
(universal donor)
O
AB
IAIB
AB
A,B,AB and O
(universal receiver)
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A
IAIA or IAi
AB, A
O,A
B
IBIB or IAi
AB,B
O,B
(a) Write the genotype for each person based on the description:
a. Homozygous for the “B” allele : _______________________________________
b. Heterozygous for the “A” allele : _______________________________________
c. Type O : __________________________________________________________
d. Type “A” and had a type “O” parent : ___________________________________
e. Type “AB” : _______________________________________________________
f. Blood can be donated to anybody : _____________________________________
g. Can only get blood from a type “O” donor : ______________________________
(b) Pretend that Brad Pitt is homozygous for the type B allele, and Angelina Jolie is type
“O.” What are all the possible blood types of their baby?
(c) Draw a Punnett square showing all the possible blood types for the offspring produced by
a type “O” mother and an a Type “AB” father.
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Incomplete dominant alleles
1. Snapdragon are incomplete dominant for colour, they have phenotypes red, pink and
white. The red and white flowers are homozygous, and the pink flowers are
heterozygous. Give the genotypes for each of the phenotypes, using the letters “R” and
“W” for alleles:
a. Red snapdragon : ___________________________________________________
b. Pink snapdragon : ___________________________________________________
c. White snapdragon :__________________________________________________
2. Show genetic crosses between the following snapdragon parents, using the punnett
squares provided, and record the genotypic and phenotypic ratios below:
a. Pink x Pink
% Red snapdragon : _____________________________
% Pink snapdragon : _____________________________
% White snapdragon : ___________________________
Genotypic ratio : ________________________________
Phenotypic ratio: _______________________________
b. Red x White
% Red snapdragon : _____________________________
% Pink snapdragon : _____________________________
% White snapdragon :___________________________
Genotypic ratio : ________________________________
Phenotypic ratio: _______________________________
gametes
gametes
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c. Pink x White
% Red snapdragon : _____________________________
% Pink snapdragon : _____________________________
% White snapdragon : ___________________________
Genotypic ratio : ________________________________
Phenotypic ratio: _______________________________
3. The shapes and colours in carrots are determined by two pairs of different alleles. Both
pairs of alleles did not show dominancy. Each genotype produces different phenotypes.
Colours of carrots are red (CRCR), purple (CRCW) or white (CWCW). The shapes are long
(SLSL), oval (SLSN) or round (SNSN).
(a) What type of inheritance is shown by the shape and colours of carrot? [1 mark]
__________________________________________________________________
(b) The long, red carrot is crossed with the round, white carrot. With a genetic
diagram, show the parent genotypes, gametes and F1 generation. [3 marks]
gametes
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(c) If the F1 generation is self-crossed, what are the frequencies for the following
phenotypes? [4 marks]
Phenotypes Frequency
Red, oval
Purple, long
White, long
White, round
(d) If the purple, oval carrot has the highest demand in the market, give TWO
possible crosses that can be done to meet the demand. [2 marks]
__________________________________________________________________
__________________________________________________________________
4. With the aid of genetic diagram, explain incomplete dominance and its inheritance in
snapdragon (Antirrhinum sp.) [12 marks]
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Multiple alleles
1. Human blood types are determined by genes with multiple alleles. Each person can have
two of the four possible alleles. These alleles will specify if there is a type of molecule on
the surface of blood cells (A, B, AB) or none (O).
Blood type
(Phenotype)
Genotype Can donate blood to Can receive blood from
O ii A, B, AB and O
(Universal donor)
O
AB IAIB AB A, B, AB and O
(Universal receiver)
A IAIA
IAi
AB, A O, A
B IBIB
IBi
AB, B O, B
(a) Draw a Punnett square showing all the possible blood types for the offspring produced by
a type “O” mother and an a type “AB” father. Draw genetic diagram and record the
genotypic and phenotypic ratios
P phenotype :
P genotype :
Gamete :
F1 generation :
Genotypic ratio :
Phenotypic ratio :
gametes
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(b). Two parents think their baby switched at the hospital. It’s 1968, so DNA fingerprinting
technology does not exist yet. The mother has blood type “O”, the father has blood type
“AB” and the baby has blood type “B”.
a. Mother’s genotype :_______________________________________________
b. Father’s genotype :_______________________________________________
c. Baby’s genotype :_______________________________________________
d. Punnett square showing all possible genotypes for children produced by this
couple:
e. Draw genetic diagram for the above cross.
P phenotype :
P genotype :
Gamete :
F1 generation :
Genotypic ratio :
Phenotypic ratio :
f. Was the baby switched?
__________________________________________________________________
gametes
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2. The ABO blood group system in human is an example of interactions of alleles that
are illustrated by multiple alleles.
(a) What is meant by multiple alleles? [2 marks]
____________________________________________________________________
____________________________________________________________________
(b) State the alleles that control the ABO blood group system in humans. [1 mark]
____________________________________________________________________
(c) State the likely allele combinations in ABO blood group system. [3 marks]
____________________________________________________________________
____________________________________________________________________
(d) The table below shows three husband and wife couples with their respective blood
groups and their percentage of the number of children produced in accordance with
blood groups. State the parents’ genotype for each of the crossed couples in the table
below. [3 marks]
Couple Parents’
blood
Percentage of number of
children in accordance with
blood group
Parents’ genotype
A
B AB O
First O X A 50 - - 50
Second B X A 25 25 25 25
Third A X AB 50 25 25 -
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Linked genes
1. In pea, the gene for green seed (G), and smooth seed (S), are dominant over the
genes for yellow seed and wrinkled seed. Pure breeding strains of the dominant and
recessive varieties were crossed. A test cross of the F1 generation produced the following
results:
Green seed, smooth seed 180
Yellow seed, wrinkled seed 193
Green seed, wrinkled seed 7
Yellow seed, smooth seed 6
(a) (i) Does the above cross follow the Mendelian ratio? [1 mark]
__________________________________________________________________
(ii) Explain how the situation in (a)(i) occurs. [2 marks]
__________________________________________________________________
__________________________________________________________________
(b) Draw the genetic diagram for the test cross of F1 generation. [4 marks]
(c) Calculate the distance between the two genes. Show your calculation. [3 marks]
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3. Black coloured body and vestigial wings in Drosphila sp. are controlled by two recessive
alleles b and vg. Dominant alleles, b+ and vg+ produce wild type (grey coloured body
and normal wings). A homozygous wild type is crossed to a homozygous black coloured
body and vestigial wings. The F1 progenies produced are all of wild type and are crossed
with homozygous recessive. The F2 generations are as follows:
442 wild type : 458 black, vestigial : 46 black, normal : 54 grey,vestigial
(a) Using genetic diagram, explain the results shown above. [6 marks]
(b) Calculate the distance between the genes controlling the body colour and the type of
wing. [2 marks]
(c) If the genes are not linked, what is the expected number of individuals of each
phenotype in the F2 generation? [2 marks]
_____________________________________________________________________
_____________________________________________________________________
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Sex-linked genes
1. In fruit flies, eye color is a sex linked trait. Red is dominant to white.
(a) What are the sexes and eye colors of flies with the following genotypes:
X R X r _______________ X R Y _______________
X R X R _______________ X r Y _______________
(b) What are the genotypes of these flies:
white eyed, male ______________ red eyed female (heterozygous) _______________
white eyed, female ______________ red eyed, male _______________
(c) Show the cross of a white eyed female X r X r with a red-eyed male X R
Y .
(d) Show a cross between a pure red eyed female and a white eyed male.
i) What are the genotypes of the parents:
__________________________________________________________________
ii) How many are:
white eyed, male _______________
white eyed, female _______________
red eyed, male _______________
red eyed, female _______________
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(e) Show the cross of a red eyed female (heterozygous) and a red eyed male.
i) What are the genotypes of the parents?
__________________________________________________________________
ii) How many are:
white eyed, male_______________
white eyed, female _______________
iii) What if in the above cross, 100 males were produced and 200 females. How
many total red-eyed flies would there be?
red eyed, male _______________
red eyed, female _______________
2. In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the
disease. Males will either have the disease or not (but they won’t ever be carriers)
= female, normal
= female, carrier
= female, hemophiliac
= male, normal
= male, hemophiliac
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(a) Show the cross of a man who has hemophilia with a woman who is a carrier. What is the
probability that their children will have the disease?
(b) A woman who is a carrier marries a normal man. Show the cross. What is the
probability that their children will have hemophilia? What sex will a child in the
family with Hemophilia be?
(c) A woman who has hemophilia marries a normal man. How many of their children will have
hemophilia, and what is their sex?
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TEST TOUR SELF
Multiple Choice Questions
1. Mendel crossed pure breeding plants having smooth seeds with pure breeding plants
having wrinkled seeds. The F1 plants had smooth seeds. Then the F1 plants were allowed
to self-fertilize. Mendel collected 600 F2 plants. How many of these would be expected
to have smooth seeds and how many wrinkled seeds?
A. 400 smooth seeds and 200 wrinkled seeds
B. 300 smooth seeds and 300 wrinkled seeds
C. 450 smooth seeds and 150 wrinkled seeds
D. 150 smooth seeds and 450 wrinkled seeds
2. A genetic cross between an individual showing a dominant phenotype (unknown
genotype) and a homozygous recessive individual is known as a_________________
A. back cross
B. reciprocal cross
C. self-cross
D. test cross
3. Which of the following is (are) TRUE for allele
A. They can be identical or different for any given gene in a somatic cell
B. They can be dominant or recessive
C. They can represent alternative forms of a gene
D. All of the above
4. A genetic cross of two plants results in offspring with 9:3:3:1 ratio for a particular trait.
This condition shows ______________
A. the genes controlling the traits were located on same chromosome
B. multiple allele
C. that both parents were heterozygous
D. monohybrid cross
5. How many unique gametes could be produced through independent assortment by an
individual with the genotype RrSsTTUu?
A. 4
B. 8
C. 16
D. 32
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6. A pointed contour off the hairline on the forehead or known as widow’s peak is dominant
to straight hairline in human. A woman with widow’s peak married a man with straight
hairline. They had a daughter with widow’s peak which later also married to a man with
straight hairline. What is the percentage of their first child having widow’s peak?
A. 100%
B. 70%
C. 50%
D. 25%
7. A cross between two true-breeding pea plants were done in which one parent has purple,
axial flowers and other has white, terminal flowers. All the F1 progenies have purple,
axial flowers. The F1 progenies were self-crossed and produced 1500 F2 offsprings.
Approximately how many of them would you expect to have white flowers with axial
position?
A. 90
B. 280
C. 560
D. 850
8. The term ‘true-breeding’ refers to
A. Organism that are homozygous for all traits
B. Organisms that come from genetically pure lines
C. Organisms that will produce offspring with the same characteristics as the parents
D. Organisms that have a high rate of reproduction
9. A plant with purple flowers is allowed to self-pollinate. Generations after generations, it
produces purple flowers. This is an example of
A. Hybridization
B. Incomplete dominance
C. True-breeding
D. Polygenes
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10. In humans, brown eyes are dominant to blue eyes. A marriage between two brown.eyed
individuals produces a child with blue-eyes. This indicates that
A. The possibility that their second child will have brown eyes is ¼
B. The possibility that their second child will have blue eyes is ½
C. Both parents are homozygous for brown eyes
D. Both parents are heterozygous for eye colour
11. In the F2 generation of a dihybrid cross between yellow, round seed pea plants and green,
wrinkled seed pea plants, 35 out of 496 pea seeds were green and wrinkled. Other seeds
were yellow and round , green and round, yellow and wrinkled. These results show that
A. The alleles for green and wrinkled are linked
B. Crossing over has occurred
C. Green and wrinkled are both recessive characteristics
D. The allele for green is recessive but not the allele for wrinkled
12. Two plants are crossed, resulting in offspring with a 3:1 phenotypic ratio for a particular
trait. This suggest
A. That the parents were true-breeding for contrasting traits
B. Incomplete dominance
C. That are blending of traits has occurred
D. That the parents were both heterozygous
13. Two characters that appear in a 9:3:3:1 ratio in the F2 generation should have which of
the following properties?
A. Each of the characters is controlled by a single gene
B. The genes controlling the characters obey the Law Of Independent Assortment
C. Each of the genes controlling the characters has two alleles
D. A, B and C are correct
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14. Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long
tails (t). What fraction of the progeny of the cross BbTt x BBtt will have black fur and
long tails?
A. 1/16
B. 1/2
C. 3/16
D. 3/8
15. A sexually reproducing animal has two unlinked genes, one for head shape (H) and one
for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a
gamete from this organism?
A. HT
B. Hh
C. HhTt
D. tt
16. Which of the following is FALSE, regarding the Law of Segregation?
A. It states that each of two alleles for a given trait segregate into different gametes.
B. It can be explained by the segregation of homologous chromosomes during meiosis
C. It is a method that can be used to determine the number of chromosomes in a plant.
D. It can be used to predict the likelihood of transmission of certain genetic diseases
within families.
17. A couple has three children, all of whom have brown eyes and blond hair. Both parents
are homozygous for brown eyes (BB), but one is a blond (rr) and the other is a redhead
(Rr). What is the probability that their next child will be a brown-eyed redhead?
A. 1/16
B. 1/4
C. 1/8
D. 1/2
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18. An advantage that made Mendel’s experiment successful is
A. He used true breeding members of plants for mating
B. His plants had many phenotypes for a trait
C. His plants required many years to develop
D. He used mathematical laws to interpret his results
19. Two organisms with genotype TtGg mate. The chance of producing an offspring that has
the dominant phenotype for height and recessive phenotype for colour is
A. 9/16
B. 7/16
C. 6/16
D. 3/16
20. Two different phenotypes result among the offspring from a genetic cross. The genotypes
of the parents should be
A. TT and TT
B. TT and Tt
C. Tt and tt
D. tt and tt