(b) In the given figure, W represents deletion which
is a type of chromosomal aberration. It is the loss
of an intercalary segment of a chromosome which
is produced by a double break in the chromosome
followed by the union of remaining parts, e.g. ,
ABCDEFGH/ABCFGH (segment DE is missing). The
chromosomal aberration labelled as Y represents
inversion. In this type of aberration part of the
chromosome segment gets inverted by 180°. For
example, chromosome ABCDEFGH develops inversion
in the part CDE to form ABEDCFGH.
(c) Reciprocal translocation labelled as Z represents an
interchromosomal aberration.
CHAPTER-6 : molECulAR BAsIs of InHERITAnCE
- (b) 2. (d) 3. (d) 4. (d) 5. (c)
- (a) 7. (d) 8. (a) 9. (d) 10. (a)
- True
- false : The process of copying genetic information from one
strand of the DNA into RNA is termed as transcription. - True 14. True
- false : Induction is the switching on of an operon which
normally remains turned off. - false : A double stranded RNA is the genetic material in
reovirus. - false : Lagging strand require DNA ligase for joining
Okazaki fragments. - True 19. True 20. True
- A-(iii), B-(i), C-(ii), D-(v), E-(iv)
- A-(ii, iv), B-(i, v), C-(iii,vi), D-(vii, viii), E-(ix, x)
23.(A) (i) James Watson (ii) Francis Crick
(iii) 1953 (iv) X-ray diffraction
(v) Maurice Wilkins (vi) Rosalind Franklin
(vii) base pairing (viii) Erwin Chargaff
(ix) Thymine (x) Cytosine
(B) Translation refers to the process of polymerisation of
nucleotides amino acids to form aminoacids polypeptide.
The order and sequences of amino acids are defined by
the sequences of bases in the tRNA mRNA. Eukaryotic
translation occurs on 70S 80S ribosomes. It is a discontinuous
process as transcription occurs in cytoplasm nucleus while
translation takes place in nucleus cytoplasm.
- (c) 25. (a) 26. (d) 27. (a) 28. (b)
- (a) A – Repressor protein
B – Inducer
X – b-galactosidase
Y – Permease
Z – Transacetylase
(b) The given figure is of the lac Operon in the presence of
an inducer. A represents the repressor protein. It is meant
for blocking the operator gene so that the structural
genes are unable to form mRNAs (transcribe). It has two
allosteric sites, one for attaching to operator gene and
other for binding to the inducer. After coming in contact
with inducer the repressor undergoes conformational
change and is unable to combine with operator, which
allows the transcription of z, y and a gene.
(c) b-galactosidase (labelled part X) is involved in hydrolysing
lactose. It breaks lactose into glucose and galactose.- (a) A – DNA, B – H 1 Histone C – Histone octamer
(b) The given figure is of a nucleosome and the labelled
part C represents histone octamer. It is composed of
four type of histone proteins i.e., H 2 A, H 2 B, H 3 and
H 4. Each of these histones occur in pairs.
(c) Labelled part A represents DNA. Two functions of
DNA are as follows :
(i) Genetic information (Genetic Blue Print) : DNA is
the genetic material which carries all the hereditary
information. The genetic information is coded in the
arrangement of its nitrogen bases.
(ii) Replication: DNA has unique property of replication
or production of carbon copies. This is essential for
transfer of genetic information from one cell to its
daughters and from one generation to the next.
CHAPTER-7 : EvoluTIon - (a) 2. (c) 3. (a) 4. (b) 5. (b)
- (a) 7. (c) 8. (d) 9. (b) 10. (c)
- True 12. True
- false : When convergent evolution is found in closely
related species, it is called parallel evolution. - false : Heterozygotes for the sickle cell trait are exceptionally
resistant to malaria. - True