MCQ
Down’s syndrome in humans is due to
- Athree $‘X’$ chromosomes
- ✓three copies of chromosome $21$
- Cmonosomy
- Dtwo $‘Y’$ chromosomes.
✓
Answer
Correct option: B.
three copies of chromosome $21$
b
(b): Down’s syndrome is the trisomy of $21$ stchromosome in man. Down’s syndrome ischaracterized by short stature, warty skin, protrudingtongue, slanting eyes, with folded eyelids. The affectedperson’s face presents a typical mongoloid look. Henceit is also called as mongoloid idiocy. It occurs due tothe phenomenon of nondisjunction.Non disjunction occurs when a pair of homologous chromosomes donot separate in meiosis but migrate to the same poleof the cell resulting in an uneven number ofchromosomes in the daughter cells $(45$ in one and $47$ in other) This numerical abnormality results in trisomy $(2n + 1)$ and monosomy $(2n -1)$. Nondisjunctionismore common in sex chromosomes.
(b): Down’s syndrome is the trisomy of $21$ stchromosome in man. Down’s syndrome ischaracterized by short stature, warty skin, protrudingtongue, slanting eyes, with folded eyelids. The affectedperson’s face presents a typical mongoloid look. Henceit is also called as mongoloid idiocy. It occurs due tothe phenomenon of nondisjunction.Non disjunction occurs when a pair of homologous chromosomes donot separate in meiosis but migrate to the same poleof the cell resulting in an uneven number ofchromosomes in the daughter cells $(45$ in one and $47$ in other) This numerical abnormality results in trisomy $(2n + 1)$ and monosomy $(2n -1)$. Nondisjunctionismore common in sex chromosomes.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Hypersensitivity towards any foreign material or particle is known as
Make correct pair.
→$\begin{array}{|l|l|} \hline Column-I & Column-II \\ \hline 1.\,\,Osculum & p.\,\,Fasciola \\ \hline 2.\,\,Hypostom & q.\,\,Ctenoplana \\ \hline 3.\,\,Comb\,\,jellies & r.\,\,Spongilla \\ \hline 4.\,\,Hook\,\,and\,\,sucker & s.\,\,Meandrina \\ \hline \end{array}$
Microbe used for biocontrol of pest butterfly caterpillars is
Acrosome is a part of
Hugo de Vries's experimental organism was
Humoral immunity is due to
In the given reaction identify $X , Y , Z$ respectively:
→Which one of the following statements about morula in humans is correct?
Spongilla is....
- They are pathogens
- They attack insects and other arthropods.