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The correct ANSWER is (a) Maternal Igf2 is methylated to prevent expression

To elaborate: It is true that the maternal Igf2 is not expressed in MICE but the mechanism is via blockage of the ENHANCER by an insulator called CTCB binding to the CCCTC sequence in between the two adjacent genes. Rest of the OPTIONS is correct.

Right choice is (d) It occurs when the region containing SPECIFIC genes in the maternal chromosome are missing

For explanation: In case of PADER Willi SYNDROME the genes 15q11-q13 contained in the paternal chromosome are missing which LEADS to the defects. It is not DUE to the maternal factors missing.

Right option is (a) True

To explain: Expressivity means that the individual is able to MAKE the PROTEIN DUE to the penetrance and the genotype. But the DEGREE of functionality of that encoded protein may VARY giving different expressivity.

Right answer is (B) Osteoporosis imperfectica

For explanation I would say: In CASE of PEA seed colour the penetrance and expressivity are both 100%. In case of brachydactyly and polydactyly the penetrance varies as WELL as the expressivity. But in the case on osteoporosis imperfectica it is ALMOST 100% penetrant but the expressivity is different.

Right option is (b) OOGENESIS, activated

To explain: The genomic imprinting has to be RESET in every generation. This is achieved VIA the MEANS that the genes that are MATERNALLY inherited are activated during oogenesis and paternally inherited genes are inactivated during the same and reverse for spermatogenesis. H19 is maternally inherited.

The correct choice is (c) The 3’ OH is methylated

The BEST explanation: The 2’-OH groups of some bases are MODIFIED in the tRNA and not the 3’-OH. White the remaining modifications of the tRNA TRANSCRIPT are necessary.

The CORRECT choice is (c) The INTRONS are seen in YEAST and they are larger than exons

Explanation: It is true that the intron is seen in the yeast tRNA primary transcript. But it is very SHORT about 14bp and the introns in tRNA are generally much shorter than the mRNA.

Right answer is (a) UPD

Explanation: This condition gives rise to UPD or uni parental disomy. Here as the imprinting RELATION will be HAMPERED, the individual may LACK any active copy of the gene leading to DEVELOPMENTAL defects.

Correct answer is (c) Imprinting

To elaborate: Genomic imprinting STATES that the ALLELES of some genes vary in their or EXPRESSION depending on the fact that they are INHERITED from the MOTHER or the father.

The correct CHOICE is (d) 100% penetrant with 100% expressivity

The best I can explain: The 7 sets of pea genes that Mendel worked with showed 100% penetrance and 100% expressivity. Due to this the dominant and recessive genes always expressed the different phenotype to the FULL degree of expression.

Right option is (d) Rnase P

To EXPLAIN I would say: RNase P removes the 5’ nucleotide sequence or the tRNA transcript. This GENERATES a 5’ end that is shorter than the 3’ end.

Right choice is (d) Proteins modulating the cleavage

To EXPLAIN: In CASE of rRNA the SNORNA along with proteins making snoRNP aids in cleavage and modifications, and not just proteins as seen in case of tRNA primary TRANSCRIPT.

Correct ANSWER is (c) The EMBRYO cells shows that maternal ALLELE XIST is active over paternal

The best I can explain: XIST allele in case of the embryo doesn’t show any imprinting. Imprinting is seen in case of the extra-embryonic cells.

Right answer is (b) False

The best EXPLANATION: In addition to methylation the CONTROL is achieved by the presence of an insulator CTCB that HELPS by PREVENTING the enhancer interaction of IGF2 in the maternal chromosome.

The CORRECT option is (c) No major change

For explanation: In mice the IGF2 genes from the female parent is methylated and inactivated by imprinting and only the male one is expressed. THUS, ABSENCE of the respective gene in mother shows no significant effect. However, if it were male hen the PROGENY would be smaller.

The CORRECT answer is (b) If penetrance is 100% the expressivity is 100%

Best EXPLANATION: In case of penetrance being 100% it makes sure that a particular phenotype that is determined by the genotype is expressed in all individuals. But the limit to which it is expressed in the different individuals can vary so the expressivity MAY not ALWAYS be 100%.

Correct OPTION is (b) Angelman SYNDROME

Explanation: In Angelman syndrome the gene in the maternal chromosome 15 REGION 15q11-q13 is MISSING which leads to the absence of any FUNCTIONAL copy of the gene at all as paternal copy is methylated and inactivated.

Correct option is (b) 16S 4S 23S 5S

For EXPLANATION I would say: The pre-rRNA transcript of PROKARYOTES is 30S, it has 16S 4S 23S and 5S subunits in sequence where the 4S subunit codes for the TRNA.

Correct choice is (d) Paternal, MATERNAL

To explain I would say: The insulin like growth factor Igf for human SHOWS that there only the paternal allele is expressed, but in its RECEPTOR, in case of mice the maternal allele is expressed. Thus both the alles must be PRESENT for proper function of the signal.

The CORRECT option is (d) Expressivity, penetrance

To explain: The formation of coloured cones is sure that the cones are penetrant, it is variation in the expressivity that GIVES them different colour. The uncoloured cone shows no penetrance.

The correct answer is (B) 5S

Best explanation: White the 18S, 5.8 S and the 28S subunits are present in the pre rRNA transcript, the 5S subunit comes from another region that is TRANSCRIBED by the RNA pol III.

Right CHOICE is (c) Overeating urge

Easiest explanation: The urge to overeat is a symptom of the Pader Willi syndrome and it is not seen in case of Angelman syndrome. While the REMAINING OPTIONS are seen in Angelman syndrome due to lack of a FUNCTIONAL copy of maternally imprinted gene.

Right option is (c) Igf2 SHOWS paternal imprinting, H19 shows maternal imprinting

The BEST explanation: It is much of a surprise although both the genes can be ENHANCED by the same enhancer element located downstream of H19 both are not enhanced at once. In maternal gene the H19 is expressed and in paternal gene the Igf2 is expressed.

Right OPTION is (b) The person’s children are not likely to EXPRESS that phenotype

To explain: If the gene is non-penetrant for an individual it is not mandatory that it will also be non-penetrant for his offspring. As a result, the pedigree could appear to skip a GENERATION with the parent being a CARRIER.

The correct option is (C) Sometimes

Easiest explanation: It is not that the HOMOZYGOUS genotype will always express the required phenotype. It MAY or may not express it depending on some FACTORS. This gives the concept of PENETRANCE.

The correct option is (b) False

The explanation is: The snRNA helps in the splicing of MRNA, however the cleavage of the RRNA is DONE via the small nucleolar restricted RNA or snoRNAs INSTEAD.

The correct option is (C) Two

The explanation is: In running a whole RNA EXTRACT you will get 2 bands each corresponding to 60S rRNA and 40S rRNA for eukaryotes and corresponding 30S and 50S for prokaryotes.

The CORRECT choice is (a) True

To explain I would say: PENETRANCE doesn’t depend on EXPRESSIVITY, i.e. it is considered penetrant for an individual even if the expressivity varies among individuals, but it is not possible to measure the expressivity UNLESS the GENE is penetrant. So the expressivity depends on penetrance.