Cat-cry syndrome (Cri du chat syndrome) is caused by a partial deletion of the short arm of chromosome 5 (5p-). The total chromosome count remains 46, and affected individuals are typically female (XX) in the classic description, though it affects both sexes.
The correct formula is: 46, XX, 5p-
This represents:
- 46 total chromosomes (no change in number)
- XX sex chromosomes
- 5p- deletion of the short arm of chromosome 5
The other options are wrong because:
- 46, XX, 9p+ = partial trisomy 9p (different syndrome)
- 46, XX, 18p- = partial deletion of chromosome 18 (Edwards-related variant)
- 45, XO = Turner syndrome
- 47, XXY = Klinefelter syndromeThe correct answer is There is no body cavity.
Tapeworms (Class Cestoda, Phylum Platyhelminthes) are acoelomate organisms - they have no body cavity at all. Their interior is filled with a solid mass of parenchyma (loose mesenchymal tissue) between the body wall and internal organs.
Here's why the other options are wrong:
- Primary body cavity (pseudocoelom) - found in roundworms (Nematoda), not flatworms
- Secondary body cavity (coelom) - found in higher invertebrates and vertebrates (annelids, molluscs, arthropods, etc.)
- Mixed body cavity (mixocoelom) - found in arthropods (combination of blastocoel + reduced coelom)
- Tertiary body cavity - not a standard zoological classification
Key point: All Platyhelminthes (flatworms), including tapeworms, flukes, and planarians, are acoelomate - they lack any true body cavity. This is one of the defining characteristics of the phylum.The answer is triatomine (also called kissing bug or Triatoma).
The vector of Chagas disease (Trypanosoma cruzi) is the triatomine bug - a blood-sucking insect from the family Reduviidae. Common genera include Triatoma, Rhodnius, and Panstrongylus.
How transmission occurs:
- The bug bites (usually near the mouth/eyes at night)
- It defecates near the bite wound while feeding
- The infected feces contain T. cruzi trypomastigotes
- The person scratches and rubs the feces into the wound or mucous membranes
Acceptable answer forms:
- triatomine
- kissing bug
- Triatoma
- Rhodnius
The most concise and universally accepted single-word answer for this type of question is triatomine.The correct answers are XO and XY.
The rule for sex chromatin (Barr bodies):
The number of Barr bodies = number of X chromosomes - 1
A "clump of sex chromatin" (Barr body) is absent when there are zero Barr bodies, meaning only 1 X chromosome is present.
| Karyotype | X chromosomes | Barr bodies | Chromatin present? |
|---|---|---|---|
| XXX | 3 | 2 | Yes |
| XXYY | 2 | 1 | Yes |
| XX | 2 | 1 | Yes |
| XO | 1 | 0 | No |
| XY | 1 | 0 | No |
- XY = normal male - 1 X, so 0 Barr bodies
- XO = Turner syndrome - 1 X, so 0 Barr bodies
Both XO and XY have only one X chromosome, so sex chromatin (Barr body) is absent in both.
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