Uations result from which of the following? a. breaks at or near the centromeres

Question

Uations result from which of the following? a. breaks at or near the centromeres of two acrocentric chromosomes followed by the reciprocal exchange of broken parts b. a part of one chromosome becomes attached to a non-homologous chromosome c, unequal crossing over during meiosis d. the fusion of two small chromosomes end-to-end such that a double centromere occurs 41. The condition of semisterility is most closely associated with a. chromosomal duplications b. chromosomal deletions c. translocation heterozygotes d. translocation homozygotes 42. Which type of chromosomal aberrations is a trisomic (2n+1) individual? a. polyploidy b. aneuploidy c. both a and b d. none of the above In humans, Down Syndrome can result from: a. three copies of chromosome 21 b. a translocation involving part of chromosome 21 and chromosome 14 . a reciprocal translocation between any two autnsomon

Explanation / Answer

Answer 41

Option C is correct i.e "Translocation heterozygote".

Explanation

Semi sterility condition is used as a diagnostic test for translocation hetrozygote.

Semi sterility or half sterility condition results if the gametes produced by the equality between alternate and adjacent segragation between two chromosomes in which one have N1T1 (N1 : normal ; T1 : translocation) and other chromosome have N2T2 (N2 : normal ; T2 : translocation). Half the gametes produced are inviable or fail to contribute to next generation.

Answer 42

Option B is correct i.e "Aneuploidy"

Explanation

Aneuploidy occurs if the cells have deleted or extra number of chromosomes. Example : 2n-1 (monosomic), 2n+1 (trisomic) etc. Whereas, polyploidy occurs due to the presence of more than two complete sets of chromosomes.

Answer 43

Trisomy of chromosome number 21 results in Down syndrome.

So option A is correct i.e " Three copies of chromosome 21".

Answer 38

Option D is correct i.e " Deletion loop".

Explanation

Deletion loop forms so that proper alignment of other portions of the homologous chromosomes can occus and proper alignment can cause recombination event in aligned portion of chromosomes in prophase-1 phase of meiosis.

Answer 39

Option A is correct i.e "Alternate".

Explanation

Crossover between two chromosomes i.e one chromosome have N1T1 (N1 : normal ; T1 : Translocation) and other chromosome have N2T2 (N2 : Normal ; T2 translocation) results in viable and balanced gametes only and only if alternative segregation occurs. Adjacent-1 and 2 results in inviable gametes.

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