UNIT TEST-I (Answer
Key)
Dt.22/07/2013
Subject: Biology
Attempt all the
following questions:
I.
Name the
following:
a) The stage of Mitosis where sister
chromosomes separate from their paired condition
Ans. Anaphase
b) The dominant trait of flower
position in pea plant
Ans. Axillary
c) Type of cell division which occur in
meristamatic tissue of the plant body
Ans. Mitosis
d) The complementary base pair of Thymine in a
DNA molecule
Ans. Adenine
e) The only condition in which the recessive
character can be expressed
Ans. Homozygous
II.
Fill
up the blanks with appropriate words:
a) Removal of anthers of a bisexual flower to
carry out artificial cross pollination is known as emasculation.
b) Scientific name of Pea plant is Pisum sativum.
c) A phase of Mitosis which is reverse of
prophase is Telophase.
d) The repeating small and similar components
of each strand of DNA are known as Nucleotides.
III.
Define
the following terms:
a) Karyotype
The diagrammatic representation
of all the chromosomes of an individual according to their size and shapes is known as karyotype.
b) Allelomorph
The alternative form of a gene which occupy the same position on the
chromosome but alters the character in a different way.
c) Homologous chromosomes
A pair of chromosomes which are similar in all respects such as size,
shape, length etc. and each of them are derived from a parent.
d) Mutations
The sudden changes which occur in the genetic constitution of an
individual or in the number or structure of chromosomes are known as mutations.
e) Cell Cycle
The sequence of events which occur between one cell division and other is
known as Cell cycle.
IV.
Write
the difference between the following pairs of terms:
a) Phenotype and Genotype
Ans. Phenotype: The
external appearance of an individual irrespective of its genetic constitution
is known as Phenotype.
Genotype: The genetic constitution of an individual is known as
genotype.
b) Character and Trait
Ans. Character: Any heritable feature of an individual is
known as Character.
Trait:
The alternative form of a character is known as Trait.
C) Gene and
Genome
Gene:
Gene is a specific part of the chromosome which decides a particular character
in the individual.
Genome:
All the genes present in a haploid set of chromosomes of an individual is known
as Genome.
d)Pure Breed
and Hybrid
Pure
Breed: Plants bred true for the same
feature for several generations without any change through controlled breeding.
Hybrid:
Offspring obtained by crossing two genetically
different plants.
E)Karyokinesis
and Cytokinesis
Karyokinesis:
The division of nucleus into two daughter nuclei is known as Karyokinesis.
Cytokinesis:
The division of cytoplasm into two daughter cells is known as cytokinesis.
V.
Answer the following questions on Mitosis Cell
division:
I)
Why
mitosis is known as “equational division”?
Ans. The two
daughter cells formed are exact similar copies of the parent cell
with the same number of chromosomes.
ii) Draw a
neat labeled diagram of an animal cell in Anaphase of Mitosis starting with a
cell of six chromosomes. Label the parts centromere, chromatid, spindle fibers,
aster in your drawn diagram.
iii) State
four important features which occur in prophase of mitosis.
Ans. 1. Chromatin
get resolved and condensed to form
visible chromosomes.
2. Centrosome
split into two bits and move to opposite poles to form asters.
3.
Chromosomes split longitudinally to form two chromatids and which are held
together by centromere.
4. Nuclear
membrane and nucleolus disappear.
iv) Write any
two differences between mitotic cell
division of a plant cell and animal cell.
Ans. Plant
Cell: 1. Aster formation do not occur in cell division.
2.
Cytokinesis occur by cell plate formation
Animal
cell: 1. Aster formation occur in
cell division.
2.
Cytokinesis occur by furrow formation.
VI) The
following diagram represents an important event which occur in Meiotic Cell
division. Study the same carefully and answer the questions that follow:
a) What is the important event that was
depicted in the above diagram? Define it.
Ans. The
event that was depicted in the diagram is Crossing over.
Crossing
over: The overlapping of non-sister chromatids along the length of the homologous pair
of chromosomes in meiosis is known as crossing over.
b) What do you understand by the term
“Chiasma” and mention its importance.
Ans. The ‘X’
shaped marking formed due to overlapping of non-sister chromatids during
crossing over in meiosis is known as chiasma.
Chiasma is the region where exchange of genetic materials occur.
c) “Gametes must be produced through meiosis
for sexual reproduction.” Why is it so?
Ans. The
original chromosome number will be halved during gamete formation in meiosis.
When gametes with haploid number fuse in fertilization, the original number of
chromosomes will be restored.
d) Write
any two differences between Mitosis and Meiosis cell division.
Ans. Mitosis: 1. In mitosis full set of chromosomes are
passed on to the daughter cells.
2. Mitosis
occurs in somatic cells.
3. Mitosis
cell division results in two daughter cells.
Meiosis: 1. In
meiosis, only half set of chromosomes are passed on to the daughter cells.
2. Meiosis occurs in reproductive cells.
3. Meiosis cell division results in four
daughter cells.
e) What are diploid and haploid cells? Give an
example of each.
Ans. A cell with two sets of chromosome is
known as diploid cell. Ex: Zygote cell, somatic cell.
A cell
with one set of chromosomes is known as haploid cell. Ex: Unfertilized egg
cell, sperm cell
VI)A pea
plant having pure round seeded nature is crossed with a pea plant having
wrinkled seeded nature
a) Give a phenotype of F1 progeny by using Punnet checker board.
Ans. F1 Progeny:
r
|
r
|
|
R
|
Rr
|
Rr
|
R
|
Rr
|
Rr
|
All the
progeny of F1 generation are phenotypically round in nature.
b) Give the F2 progeny produced upon by the self pollination of F1 progeny with the
help of Punnet checker board.
F2 Progeny:
R
|
r
|
|
R
|
RR
|
Rr
|
r
|
rR
|
rr
|
c) Give the Phenotypic and genotypic ratio of
F2 generation.
Ans. Phenotypic
ratio: 3(Round)
: 1(Wrinkled)
Genotypic
Ratio: 1(Pure Round):2(Mixed Round):1(Wrinkled)
d) Name and explain the laws induced by Mendel
on the basis of the above experiments conducted by him.
Ans. 1.
Law of Dominance: Every character is
influenced by a pair of factors. Of
these, the dominant factor gets expressed and the recessive factor gets
suppressed. This is known as Law of
dominance.
2. Law of
segregation or Law of Purity of Gametes: Every
character is influenced by a pair of factors. These factors they get separated during the formation of gametes and move into two different gametes
without blending or mixing.
