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प्रश्न
What is Down’s syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?
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उत्तर
Down’s syndrome is a human genetic disorder caused due to trisomy of chromosome no. 21. Such individuals are aneuploid and have 47 chromosomes. (2n + 1) The symptoms include mental retardation, growth abnormalities, constantly open mouth, dwarfness etc. The reason for the disorder is the non-disjunction (failure to separate) of homologous chromosome of pair 21 during meiotic division in the ovum. The chances of having a child with Down’s syndrome increase with the age of the mother (+ 40) because ova are present in females. since their birth and therefore older cells are more prone to chromosomal non-disjunction because of various physico-chemical exposures during the mother’s life-time.
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संबंधित प्रश्न
Klinefelters’ syndrome is characterized by a karyotype of ____________.
Pataus’ syndrome is also referred to as ____________.
Define aneuploidy. How is it different from polyploidy? Describe the individuals having following chromosomal abnormalities.
- Trisomy of 21st Chromosome
- XXY
- XO
Which of following organisms cannot fix nitrogen?
- Azotobacter
- Oscillatoria
- Anabaena
- Volvoх
- Nostoc
Choose the correct answer from the options given below:
Given below are two statements:
Statement I: Transfer RNAs and ribosomal RNA do not interact with mRNA.
Statement II: RNA interference (RNAi) takes place in all eukaryotic organisms as a method of cellular defence.
In the light of the above statements, choose the most appropriate answer from the options given below:
In the above represented plasmid an alien piece of DNA is inserted at EcoRI site. Which of the following strategies will be chosen to select the recombinant colonies?
Name the class of enzyme that usually catalyse the following reaction:
S − G + S# → S + S# − G
where, G → a group other than hydrogen
S → a substrate
S# → another substrate
Which are correct:
- Computed tomography and magnetic resonance imaging detect cancers of internal organs.
- Chemotherapeutics drugs are used to kill noncancerous cells.
- α-interferon activate the cancer patients' immune system and helps in destroying the tumour.
- Chemotherapeutic drugs are biological response modifiers.
- In the case of leukaemia blood cells counts are decreased.
Choose the correct answer from the option given below:
Match List - I with List - II.
| List - I | List - II |
| A. Centromere | I. Mitochondrion |
| B. Cilium | II. Cell division |
| C. Cristae | III. Сell movement |
| D. Cell membrane | IV. Phospholipid Bilayer |
Choose the correct answer from the options given below:
Find the correct statements:
- In human pregnancy, the major organ systems are formed at the end of 12 weeks.
- In human pregnancy, the major organ systems are formed at the end of 8 weeks.
- In human pregnancy, heart is formed after one month of gestation.
- In human pregnancy, limbs and digits develop by the end of second month.
- In human pregnancy, the appearance of hair usually observed in the fifth month.
Choose the correct answer from the options given below:
Which of the following diagrams is correct with regard to the proximal (P) and distal (D) tubule of the Nephron.
Assertion (A): A typical unfertilised, angiosperm embryo sac at maturity is 8 nucleate and 7-celled.
Reason (R): The egg apparatus has 2 polar nuclei. In the light of the above statements, choose the correct answer from the options given below:
In the light of the above statements, choose the correct answer from the options given below:
A specialised membranous structure in a prokaryotic cell which helps in cell wall formation, DNA replication and respiration is ______.
Which of the following are the post-transcriptional events in an eukaryotic cell?
- Transport of pre-mRNA to cytoplasm prior to splicing.
- Removal of introns and joining of exons.
- Addition of methyl group at 5' end of hnRNA.
- Addition of adenine residues at 3' end of hnRNA.
- Base pairing of two complementary RNAs.
Choose the correct answer from the options given below:
Each of the following characteristics represent a Kingdom proposed by Whittaker. Arrange the following in increasing order of complexity of body organisation.
- Multicellular heterotrophs with cell wall made of chitin.
- Heterotrophs with tissue/organ/organ system level of body organisation.
- Prokaryotes with cell wall made of polysaccharides and amino acids.
- Eukaryotic autotrophs with tissue/organ level of body organisation.
- Eukaryotes with cellular body organisation.
Choose the correct answer from the options given below:
Match List - I with List - II.
| List - I | List - II |
| A. Alfred Hershey and Martha Chase | I. Streptococcus pneumoniae |
| B. Euchromatin | II. Densely packed and dark-stained |
| C. Frederick Griffith | III. Loosely packed and light-stained |
| D. Heterochromatin | IV. DNA as genetic material confirmation |
Choose the correct answer from the options given below:
Neoplastic characteristics of cells refer to:
- A mass of proliferating cell.
- Rapid growth of cells.
- Invasion and damage to the surrounding tissue.
- Those confined to original location.
Choose the correct answer from the options given below:
Match List - I with List - II.
| List - I | List - II |
| A. Adenosine | I. Nitrogen base |
| B. Adenylic acid | II. Nucleotide |
| C. Adenine | III. Nucleoside |
| D. Alanine | IV. Amino acid |
Choose the option with all correct matches.
Assertion (A): All vertebrates are chordates but all chordates are not vertebrate.
Reason (R): The members of subphylum vertebrata possess notochord, during the embryonic period, the notochord is replaced by a cartilaginous or bony vertebral column in adults.
In the light of the above statements, choose the correct answer from the options given below:
Match List I with List II.
| List I | List II | ||
| A. | Down’s syndrome | I. | 11th chromosome |
| B. | α-Thalassemia | II. | ‘X’ chromosome |
| C. | β-Thalassemia | III. | 21st chromosome |
| D. | Klinefelter’s syndrome | IV. | 16th chromosome |
Choose the correct answer from the options given below:
