3. PRINCIPLES OF INHERITANCE AND VARIATION
2020
SAY
1.
Select a female
heterogametic animal from the following: (1)
(a)
Human beings (b) Drosophila
(c)
Birds (d) Grasshopper
ü Answer:
(c) Birds
2.
Complete the
table using appropriate terms: (2)
|
Klinefelter’s syndrome |
(a) |
Sterile male |
|
(b) |
44A + XO |
(c) |
|
(d) |
Trisomy 21 |
Mental retardation |
ü Answer:
(a) 44A + XXY
(b) Turner’s syndrome
(c) Sterile female/
ovaries are rudimentary etc.
(d) Down’s syndrome
3. In a cross between
a true breeding red flowered and a true breeding white flowered plants, the F1
generation was pink coloured flowers. From this cross
(a)
Identify the
Inheritance.
(b)
Give an example
for this type of Inheritance.
(c)
Write the F2
phenotypic and genotypic ratio. (2)
ü Answer:
(a) Incomplete
dominance
(b) Flower colour in
Snap dragon
(c) Phenotypic ratio =
1:2:1
Genotypic ratio =
1:2:1.
2020
MARCH
1. From the
following, find out the symbol used in the human pedigree analysis representing
male. (1)
ü Answer:
(c) ¨
2. Observe the
figure given below showing Mendel's experiment using pea plants. (2)
a. Identify the
cross.
b. Which are the
laws proposed by Mendel based on these observations?
ü Answer:
(a) Monohybrid cross
(b) Law of Dominance, Law of Segregation.
3. Correct the
following statements, if there is any mistake: (2)
a. Haemophilia is an
autosome linked recessive disease.
b. Turner's
syndrome is due to the presence of an additional copy of X chromosome.
ü Answer:
(a) Haemophilia is a sex-linked recessive disease.
Or
Sickle cell anaemia is an autosome linked recessive
disease.
(b) Turner's syndrome is due to the absence of an X
chromosome
Or
Klinefelter’s syndrome
is due to the presence of an additional copy of an X chromosome.
2019
SAY June
1. Identify the
following symbols in pedigree Analysis. (1)
ü Answer:
(a) Mating (b)
Mating between relatives
2. Observe the
cross of a pure violet and white flower. (2)
a. By using the F1
progeny design a test cross.
b. Mention the significance
of test cross.
ü Answer:
(a)
(b) It is used to find out the unknown genotype of a
character.
3. Each symptom of
two chromosomal disorders are given below: (2)
· Gynaecomastia
· Rudimentary ovary and lack of secondary sexual characters
a. Identify the
disorders.
b. Give the reason
for these disorders.
ü Answer:
(a) Gynaecomastia: Klinefelter’s syndrome.
Rudimentary ovary and lack of secondary sexual
characters: Turner’s syndrome.
(b) Klinefelter’s syndrome: Presence of an
additional copy of X-chromosome in male.
Turner’s syndrome: Absence of one X chromosome in female
2019
MARCH
1. "The sex of
the baby is determined by the father and not by the mother." Do you agree
with this statement ? Substantiate your answer. (2)
ü Answer:
Yes. Because male can produce two types of gametes
(sperms) – one with X chromosome and other with Y chromosome. Y chromosome is
responsible for the male sex of the baby. Female can produce only gametes (Egg)
containing X chromosome. X chromosome is responsible for female sex of the
baby.
2. Find the odd
one out. Justify your answer. (2)
Down's syndrome, Turner's syndrome, Phenylketonuria, Klinefelter's
syndrome.
ü Answer:
Phenylketonuria. Because it is a Mendelian disorder.
Others are chromosomal disorders.
3. The amino acid
composition of the relevant portion of chain of two haemoglobin molecules (A
& B) are shown below. (3)
a.
Which one of
the polypeptide chain is abnormal?
b.
Name the
disorder caused by it.
c.
What is the
reason for this abnormality?
d.
What is the
effect of this abnormality in such individuals?
ü Answer:
(a) Chain B.
(b) Sickle cell anaemia.
(c) This is due to the single base substitution at
the sixth codon of the β-globin gene from GAG to GUG.
(d) The mutant Hb molecule undergoes polymerization
under low oxygen tension causing the change in shape of the RBC from biconcave
disc to elongated sickle like structure.
2018
SAY
1. Observe the
following cross between heterozygous dominant progeny and homozygous recessive
parent. Answer the following questions. (2)
a. Identify the
cross.
b. Mention the
significance of this cross.
ü Answer:
(a) Test cross.
(b) It is used to find out the unknown genotype of a
character.
2. Following diagram shows amino acid sequences of a part of b-chain of Haemoglobin of two individuals. Observe the amino acid sequence and answer the following questions: (2)
a. Which among the
above indicates sickle cell anaemic condition?
b. Justify your
answer.
c. Describe what
is single base substitution.
ü Answer:
(a) The second b-chain.
(b) In the sixth position, glutamic acid replaced by
valine.
(c) Substitution of a single base in the sixth codon
GAG to GUG.
3. The blood group
of a child is ‘O’. His father is with 'A' blood group and mother with 'B' blood
group. Write down the genotype of the child and genotypes of parents. (2)
ü Answer:
Genotype of the child: ii (O group is always ii).
Genotype of the father: IAi
Genotype of the mother: IBi
2018
MARCH
1. ln a classroom
discussion, a student said that the sex of the baby is determined by father.
Analyse the statement and give reason for it. (2)
ü Answer:
This statement is true. Because male can produce two
types of gametes (sperms) – one with X chromosome and other with Y chromosome.
Y chromosome is responsible for the male sex of the baby. Female can produce
only gametes (Egg) containing X chromosome. X chromosome is responsible for
female sex of the baby.
2.
(a)
Observe the above cross and name the phenomenon.
(b)
Write down the theoretically given explanations of the phenomenon. (2)
ü Answer:
(a)
Incomplete dominance.
(b)
It is an inheritance in which heterozygous offspring shows intermediate
character b/w two parental characteristics.
3. Hemophilia,
Sickle cell anemia and Phenyl Ketonuria are Mendelian disorders. (3)
(a) What do you mean by Mendelian disorder?
(b) Which one of the above is an example of inborn error of
metabolism? Mention the cause of the disorder.
ü Answer:
(a)
Mendelian disorders are the disorders caused by the alteration or mutation in
the single gene.
(b)
Phenyl Ketonuria. It is due to mutation of a gene that codes for the enzyme phenyl
alanine hydroxylase. As a result, phenylalanine accumulates and converts
into phenyl pyruvic acid and other derivatives