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Respiration and Circulation — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYRespiration and Circulation4 Marks
Question
Distinguish between : Single circulation and Double circulation.
✓

Answer

Single circulationDouble circulation
1. Blood flows only once through the heart in a complete cycle.1. Blood flows twice through the heart during one complete circulation. Systemic – to and fro ‘ from heart to body and pulmonary – to and fro from heart to lungs.
2. Heart pumps deoxygenated blood only.2. Heart pumps both deoxygenated and oxygenated blood to lungs and body respectively.
3. Blood is oxygenated in gills.3. Blood is oxygenated in lungs.
4. Occurs only in fishes.4. Occurs in amphibians, reptiles, birds and mammals.

 

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Read the following and answer any four questions from (i) to (v) given below:
The process of translation requires transfer of genetic information from a polymer of nucleotides to synthesise a polymer of amino acids. The relationship between the sequence of amino acids in a polypeptide and nucleotide sequence of DNA or mRNA is called genetic code. George Gamow suggested that in order to code for all the 20 amino acids, code should be made up of three nucleotides.
  1. What is a codon?
  1. A length of DNA which codes for a particular protein.
  2. A part of the tRNA molecule to which a specific amino acid is attached.
  3. A part of the tRNA molecule which recognises the triplet code on the messenger RNA.
  4. A part of the messenger RNA molecule that has a sequence of bases coding for an amino acid.
  1. Three consecutive bases in the DNA molecule provide the code for each amino acid in a protein molecule. What is the maximum number of different triplets that could occurs?
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  1. Listed below are some amino acids and their corresponding mRNA triplets.
Amino acid
mRNA triplet
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  4. $\text{CGU}\ \ \ \text{GCU}\ \ \ \text{UUC}\ \ \ \text{TTT}$
  1. Identify the non-sense codons among the following.
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  1. A polypeptide is made using synthetic mRNA molecules as shown.
Synthetic mRNA used
Polypeptide produced
UUUAAAUUUAAA
Phenylalanine-Iysine-phenylalanine-Iysine
What are the DNA codes for the amino acids phenylalanine and lysine?
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TTT
(b)
AAA
UUU
(c)
GGG
CCC
(d)
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GGG
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Read the following and answer any four questions from (i) to (v) given below:
Translation is the process of polymerisation of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence bases in the mRNA. The amino acids are joined by a bond called peptide bond. Ribosome is the site of protein synthesis.
  1. Which ion is essential for association of both units of ribosome at the time of protein formation?
  1. $Mg^{2+}$
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  1. During translation, how many initiation factors are required in eukaryotes for initiation reactions?
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  1. Which part of mRNA contains untranslated regions (UTR)?
  1. 3' end
  2. 5' end
  3. Either 3' or 5' end
  4. Both 5' end and 3' end
  1. Name the enzyme that helps in combining amino acid to its particular tRNA?
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  4. Both (a) and (b)
  1. From the given list, select the translation machinery.
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Gene regulation is the mechanism of switching off and switching on of the genes depending upon the requirement of cells and the state of development. Gene regulation is of two types : negative and positive. In negative generegulation the genes continue expressing their effect till their activity is suppressed. Positive gene regulation is the one in which the genes remain non-expressed unless and until they are induced to do it. Operon model is a co-ordinated group of genes such as structural gene, operator gene, promoter gene, regulator gene which function together and regulate a metabolic pathway as a unit, e.g., lac operon, trp operon, ara operon, etc.
  1. Regulation of gene expression occurs at the level of.
  1. Transcription
  2. Processing/splicing
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  4. All of these.
  1. Inducible operon system usually occurs in A pathways. Nutrient molecules serve as B to stimulate production of the enzymes necessary for their breakdown. Genes for inducible operon are usually switched C and the repressor is synthesised in an D form.
S.no
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C
D
(a)
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corepressor
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(b)
anabolic
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(c)
catabolic
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(d)
catabolic
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  1. An mRNA molecule transcribed from the lac operon contains nucleotide sequences complementary to.
  1. Structural genes coding for the enzymes.
  2. the operator region
  3. the promotor region
  4. the repressor gene.
  1. Which statement correctly describes the control of transcription of the genes involved in the breakdown of lactose in Estherichia coli?
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  2. A repressor protein binds to the operator and the genes are switched off.
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  1. To form mRNA
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Mutation explains the relationship between gene and DNA. The effects of large deletions and rearrangement in a segment of DNA results in loss or gain of gene and its function. Insertion or deletion of one or two bases changes the reading frame from the point of insertion or deletion. A classical example of point mutation is a change of single base pair in the gene for beta globin chain that results in change of amino acid residue glutamate to valine and results into a diseased condition called sickle cell anaemia.
  1. A mutation is a change produced by an alteration in the genetic mechanism and.
  1. May arise spontaneously.
  2. Is always induced by the environment.
  3. Is never advantageous.
  4. Is not inherited.
  1. The DNA code for glutamic acid is CTC or CTT. The code for valine is CAA or CAT. In sickle cell haemoglobin, valine is present instead of glutamic acid.
Assuming a single base pair substitution has occurred, what is the mRNA code in the affected mutant?
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  2. GAA
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  4. GUA
  1. A mutation involving the substitution of one nitrogenous base for another has altered the base sequence of a DNA molecule, coding for four amino acids, as shown below.
Normal A-G-C-A-T-G-G-A-T-C-C-T

Mutant A-G-C-A-T-G-C-A-T-C-C-T
The table shows six codons and the corresponding amino acids into which each is translated.
mRNA codon
Amino acid
AAG
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GGA
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GUA
Valine
UAC
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Serine
The mutation has changed the amino acid.
  1. Leucine to valine.
  2. Lysine to glycine.
  3. Serine to leucine.
  4. Tyrosine to lysine.
  1. Assertion : Insertion or deletion of three or its multiple bases, insert or delete one or multiple codons and so one or multiple amino acids.
Reason: Reading frame remains unaltered with insertion or deletion of three or its multiple bases.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
  1. Part of the amino acid sequences in normal and sickle cell haemoglobin are shown.
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Prashant wanted to find the genotype of a pea plant bearing purple coloured flowers in his kitchen garden. For this, he crossed purple flowered plant with white flowered plant. As a result, all plants which were produced had purple flower only. Upon selfing these plants, 75 purple flower plants and 25 white flower plants were produced. Now, he can determine the genotype of a purple flowered plant by crossing it with a white flowered plant.
  1. Which of the following cannot be derived from the crosses done by Prashant?
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  2. Mendel's law of dominance.
  3. Mendel's law of independent assortment.
  4. Both (a) and (c).
  1. To determine the genotype of a purple flowered plant, Prashant crossed this plant with a white flowered plant. This cross represents a?
  1. Test cross.
  2. Dihybrid cross.
  3. Reciprocal cross.
  4. Trihybrid cross.
  1. In white flowered plant, allele is expressed in?
  1. Heterozygous condition only.
  2. Homozygous condition only.
  3. F3 generation.
  4. Both homozygous and heterozygous condition.
  1. The character, i.e., purple colour of the flowers that appeared in the first filial generation is called?
  1. Recessive character.
  2. Dominant character.
  3. Dominant character.
  4. Lethal character.
  1. Assertion: A geneticist crossed two plants and he obtained 50% purple flowered plants and 50% white flowered plants.
Reasons: Purple coloured flower plant might be heterozygous.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
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