- (a) Draw a schematic representation of transcription units
showing its three components.
(b) Mention the function of promoter gene.
- "The sex of the child is determined by the father and not by
the mother." Justify the statement. - (a) State the "Theory of Spontaneous Generation".
(b) Name the scientists who experimentally disproved this
theory.
SECTION - D
- Ravi and Aabha are a happily married couple. A child
suffering from sickle cell anaemia is born to them, but only
Aabha was blamed by the family for delivering a sick child.
(a) What is sickle-cell anaemia?
(b) How would you counsel the family to not blame Aabha
for delivering a child suffering from sickle-cell anaemia?
What good values would your counselling propagate in the
family?
SECTION - E
- Describe the mechanism of inheritance of ABO blood groups
in humans.
OR
Explain the Hershey-Chase experiment. What inferences
can be drawn from the experiment? - (a) Who discovered coacervates? List the biological
properties of coacervates.
(b) Write short note on vestigial organs, giving example.
OR
Name the technique used for determining nucleotide
sequence unique to an individual. Who gave this technique?
Explain the procedure involved.
- (a) Refer to the given nucleotide sequence of mRNA strand
and polypeptide translated from it.
AUG UUU UCU ACU UCG UAG
Met – Phe – Ser – Thr – Ser –
List any four salient features of genetic code that you infer
from this?
(b) What are the three types of RNA? Mention their role in
protein synthesis.
OR
(a) Differentiate between adaptive radiation and adaptive
convergence.
(b) Explain reproductive isolation. What is its significance?
SOLUTIONS- The law of dominance and the law of segregation.
- Natural selection theory.
3. Theory of continuity of germplasm opposed the theory
of inheritance of acquired characters. It was proposed by
August Weismann.
4. Chromosome I has maximum genes, (2968 genes)
and chromosome Y have minimum genes (231 genes)
respectively.
5. Dihybrid cross is a cross involving two pairs of contrasting
characters. E.g., cross between plant with round and yellow
seeds with plant having wrinkled and green seeds.
6. Hardy-Weinberg equilibrium is affected by the following
factors:
(i) Gene migration (ii) Genetic drift (iii) Mutation
(iv) Genetic recombination (v) Natural selection
7. DNA packing of eukaryotes is carried out with help of lysine
and arginine rich basic proteins called histones. The unit of
compaction is nucleosome. There are five types of histone
proteins - H 1 , H 2 A, H 2 B, H 3 and H 4. Four of them (H 2 A, H 2 B,
H 3 and H 4 ) occur in pairs to produce histone octamer, called
nu body or core of nucleosome. Their positively charged
ends (due to basic amino acids) towards the outside
attract negatively charged strands of DNA. DNA connecting
two adjacent nucleosomes is called linker DNA. It bears
H 1 histone protein. Nucleosome chain gives 'a beads on
string' appearance under electron microscope. A typical
nucleosome contains 200 bp of DNA helix.
8. Differences between complete linkage and incomplete
linkage are as follows :
Complete linkage Incomplete linkage
(i) The genes located
very closely in the
same chromosome
remain linked, show
complete linkage and
are inherited together
over the generations
without disturbing
linkage groups.The genes are present
distantly in the same
chromosome and have a
tendency to occasionally
separate.(ii) There is no crossing
over between closely
linked genes.Crossing over occurs
to bring recombinants
alongwith parental types.
(iii) It produces parental
types and no
recombinants in the
progeny.It produces more
of parental types
(> 50%) alongwith few
recombinants (<50%) in
the progeny.- Incomplete dominance is the phenomenon where F 2
phenotypic ratio is similar to genotypic ratio of 1 : 2 : 1.
E.g., flower colour in Mirabilis jalapa.