FRANK Solutions for Class 10 Biology Chapter 2 - Structure of Chromosomes
Chapter 2 - Structure of Chromosomes Exercise 20
During the developmental stage they also determine that the cells of the organism will give the animal or the plant, the characteristic features of its species.
Frederick Miescher discovered DNA.
(i) a pentose sugar,
(ii) nitrogenous bases
(iii) a phosphate
(a) Purines - Adenine and Guanine.
(b) Pyrimidines - Cytosine and Thymine.
(a) DNA consists of two strands which are spirally arranged around an axis. This is called a double helical arrangement.
(b) Each DNA strand is made up of nitrogenous bases, pentose sugar and phosphate.
(c) Sugars are pentose type; bases are adenine, guanine, cytosine and thymine.
(d) Both strands are connected with hydrogen bonds. There are two bonds between adenine and thymine and three bonds between guanine and cytosine.
(e) In the DNA, bases are inside and sugars are outside and two sugars are connected with phosphoric acid.
(f) Each DNA strand replicates and from each replicated DNA a new DNA is formed. This is called replication of DNA.
(a) DNA is most important because it is the hereditary material.
(b) It acts as the director of protein synthesis.
(c) Some DNA of chromosomes forms nucleolus.
(d) DNA in presence of enzymes forms mRNA which acts as messenger.
(i) Purines: Adenine and Guanine
(ii) Pyrimidines: Cytosine and Thymine.
(i) DNA replicates in the ______ of the cell cycle.
(ii) Chromatin fibre is made up of DNA and ______.
(iii) There are two nucleic acids ______ and ______.
(iv) DNA acts as director of ______ synthesis.
(v) DNA stands are made up of, pentose sugar and four types of ______ bases.
(ii) histone proteins
(iii) RNA, DNA
During metaphase, the chromosomes appear more distinct and clear and each consists of two parallel strands called chromatids joined by a centromere.
Chromosomes are so called because they take up certain basic dye and stain very rapidly. The word chromosome comes from two words "chromos" meaning colour and "soma" meaning body.
(iv) Sutton and Boveri
(ii) Balbiani - Described rod like structures in nucleus before cell division.
(iii) Waldeyer - Coined the term 'chromosomes'.
(iv) Sutton and Boveri - They described chromosomes as physical structures and transmitters of hereditary traits.
The chromosome consists of two symmetrical strands called chromatids. Each chromosome consists of a distinct constriction called centromere which gets attached to the spindle network.
(v) Secondary constriction
(ii) Matrix - It is a granular matter present inside the sheath.
(iii) Chromonemata - They are the subunits of chromatids.
(iv) Centromere - A constriction in the chromosome is called centromere.
(v) Secondary Constriction - A constriction other than primary constriction is called a secondary constriction.
(vi) Telomere - The ends of the chromosomes is termed as telomere.
22 pairs of autosomes are present in man.
Chapter - Exercise
Chapter 2 - Structure of Chromosomes Exercise 21
(i) Each spiral of the DNA has 12 nucleotides.
(ii) The two DNA chains are parallel to each other.
(iii) Genes are arranged in a linear order on a chromosome.
(iv) In any specimen of DNA, the total molar amount of A + G = T+ C.
(i) What does this diagram represent?
(ii) What is the importance of'd'?
(iii) What are the 'staining' properties of 'b' and 'c'?
(iv) Who gave the term used for this structure today?
(v) What is a?
(vi) Is 'e' present in all chromosomes?
(ii) 'd' is centromere which gets attached to the spindle fibres.
(iii) 'b' is heterochromatin which is darkly stained region when stained with acetocarmine and 'c' is euchromatin which when stained with acetocarmine or felugen gets lightly stained.
(vi) No, secondary constriction or 'e' is not present in all chromosomes.
(i) The network of fine threads in nucleus is called
(a) chromosome (b) chromonemata (c) chromatid (d) chromatin
(ii) The term 'chromosome' was coined by
(a) Balbiani (b) Darwin (c) Waldeyer (d) Sutton and Boveri
(iii) The primary constriction contains
(a) centromere (b) centriole (c) chromatid (d) telomere
(iv) This structure is not present in all chromosomes
(c) secondary constriction
(v) Chromosomes are thin and thread like at
(a) interphase (b) metaphase (c) anaphase (d) pachytene
(vi) Thick short chromosomes can be observed at (in mitosis)
(a) metaphase (b) telophase (c) anaphase (d) prophase
(vii) Chromosomes largely consist of
(a) DNA and histones
(b) DNA and RNA
(c) RNA and histones
(d) histones and ions
(viii) Chromosome number of man is
(ix) Telocentric chromosomes are
(a) I shaped (b) V shaped (c) J shaped (d) L shaped
(x) A 'V' shaped chromosomes has to
(xi) Sex chromosomes in man are
(a) XX (b) YY (c) XY (d) none of these
(xii) Sex of an individual is determined by
(b) sex chromosomes
(d) polytene chromosomes
(xiii) DNA model was given by
(a) Watson and Crick
(b) Sutton and Boveri
(c) Balbiani and Darwin
(d) Waldeyer and Carlson
(xiv) Adenine is a
(a) nitrogen base
(b) pentose sugar
(c) fatty acid
(xv) Which of these is not present in DNA?
(a) Adenine (b) Thymine (c) Uracil (d) Cytosine
(xvi) RNA has uracil instead of
(a) adenine (b) thymine (c) guanine (d) cytosine
(xvii) Spirally coiled double strands are observed in
(a) DNA (b) chromosome (c) RNA (d) chromatin
(ii) (c) Waldeyer
(iii) (a) centromere
(iv) (c) secondary constriction
(v) (a) interphase
(vi) (d) prophase
(vii) (a) DNA and histones
(viii) (a) 46
(ix) (a) I shaped
(xi) (c) XY
(xii)(b) sex chromosomes
(xiii) (a) Watson and Crick
(xiv) (a) nitrogen base
(xv) (c) Uracil
(xvi) (b) thymine
(xvii) (a) DNA
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