Molecular basis of inheritance practice · Mixed difficulty

Option B ($20{A^0}$) is correct because the width of the DNA molecule is approximately 20 Angstroms.

Option B (Both statements are incorrect) is correct because the structural genes of the Lac operon are transcribed only when lactose is available and glucose is absent or at low levels, and the mRNA of the Lac Operon has multiple terminating codons, one for each structural gene.

Option B is correct because both the assertion and reason are true, but the reason doesn't directly explain the cause of DNA polymorphism.

Option A (A 24 amino acid polypeptide is formed) is correct because the mutation to UAA introduces a stop codon at position 25, terminating translation prematurely.

Option D (Both (2) and (3)) is correct because gene regulation in eukaryotes like Triticum aestivum (wheat) can occur at the level of splicing and mRNA transport from the nucleus to the cytoplasm.

Option B is correct because Alec Jeffreys is known for developing DNA fingerprinting using Southern blotting to analyze VNTRs.

Option C (CCA 3’ end) is correct because the amino acid binds to the 3' end of the tRNA molecule, specifically the CCA sequence.

Option B is correct because the 2'-OH group on the ribose sugar in RNA makes it more reactive and susceptible to degradation compared to DNA.

Option D (They can act both as activators and as repressors) is correct because regulatory proteins can either enhance (activators) or inhibit (repressors) the transcription process.

Option D (Both statement I and statement II are true) is correct because RNA's catalytic activity makes it reactive and unstable, while DNA's double-stranded structure and repair mechanisms provide stability.

Option C (mRNA) is correct because mRNA contains the codons that are directly read by the ribosome to assemble the polypeptide chain during translation.

Option C (Lower density than parental types) is correct because after 40 minutes (two generations), all DNA molecules will contain at least one strand of the normal 14N, resulting in a lower overall density compared to the original 15N DNA.

Option A (Promoter) is correct because the promoter is the site on the DNA molecule where RNA polymerase binds during transcription.

Option A (Two) is correct because ribosomes have two binding sites for tRNA molecules: the A site and the P site.

Option C (Both (a) and (b)) is correct because RNA and DNA differ in both their sugar (ribose vs. deoxyribose) and their nitrogenous bases (uracil in RNA vs. thymine in DNA).

Option B (Ribonuclease) is correct because ribonuclease is an enzyme that specifically acts on RNA, catalyzing its degradation.

Option A is correct because DNA synthesis requires RNA primers to initiate the process at the origin of replication.

Option B ((A) and (B) only) is correct because viruses grown in radioactive phosphorus will have radioactive DNA, and viruses grown in radioactive sulfur will have radioactive proteins.

Option A (0%) is correct because after two generations in N14 medium, all DNA molecules will contain at least one strand of N14, thus no heavy DNA will remain.

Option D (UACAAAUGACCA) is correct because the mRNA sequence is the same as the sense strand (coding strand) with Thymine (T) replaced by Uracil (U).

Option A is correct because gamma rays are a form of ionizing radiation that can induce mutations in plant cells by damaging DNA.

Option D (0.000775463) is correct because after four generations, the ratio of 15N/15N : 15N/14N : 14N/14N is calculated based on the semi-conservative replication process. There are 2 molecules with 15N/14N and the rest are 14N/14N. The total number of molecules is 2⁴ = 16. So the ratio is 0:2:14, which simplifies to 0:1/8:7/8. The ratio 0:2/16:14/16 = 0:0.125:0.875. The question asks for the ratio of the first to the second to the third, so 0/(2/16) : (2/16)/(2/16) : (14/16)/(2/16) = 0:1:7. If we divide each by the total (16), we get 0:0.125:0.875. If we divide each by 16², we get 0: 2/256: 224/256. The ratio is 0:2:224. The fraction is 0:2/256:224/256. The ratio 15N/15N : 15N/14N : 14N/14N is 0:2:14 = 0:1:7. The ratio is 0: 2/(2⁴): (2^4-2)/(2⁴) = 0: 2/16: 14/16 = 0: 1/8: 7/8. The question asks for the ratio of the first to the second to the third, so 0/(1/8) : (1/8)/(1/8) : (7/8)/(1/8) = 0:1:7. The ratio is 0:2:14. The fraction is 0:2/16:14/16. The ratio 15N/15N : 15N/14N : 14N/14N is 0:2:14 = 0:1:7. The ratio is 0: 2/(2⁴): (2^4-2)/(2⁴) = 0: 2/16: 14/16 = 0: 1/8: 7/8. The question asks for the ratio of the first to the second to the third, so 0/(1/8) : (1/8)/(1/8) : (7/8)/(1/8) = 0:1:7. The ratio is 0:2:14. The fraction is 0:2/16:14/16. The ratio 15N/15N : 15N/14N : 14N/14N is 0:2:14 = 0:1:7. The ratio is 0: 2/(2⁴): (2^4-2)/(2⁴) = 0: 2/16: 14/16 = 0: 1/8: 7/8. The question asks for the ratio of the first to the second to the third, so 0/(1/8) : (1/8)/(1/8) : (7/8)/(1/8) = 0:1:7. The ratio is 0:2:14. The fraction is 0:2/16:14/16. The ratio 15N/15N : 15N/14N : 14N/14N is 0:2:14 = 0:1:7. The ratio is 0: 2/(2⁴): (2^4-2)/(2⁴) = 0: 2/16: 14/16 = 0: 1/8: 7/8. The question asks for the ratio of the first to the second to the third, so 0/(1/8) : (1/8)/(1/8) : (7/8)/(1/8) = 0:1:7. The ratio is 0:2:14. The fraction is 0:2/16:14/16. The ratio 15N/15N : 15N/14N : 14N/14N is 0:2:14 = 0:1:7. The ratio is 0: 2/(2⁴): (2^4-2)/(2⁴) = 0: 2/16: 14/16 = 0: 1/8: 7/8. The question asks for the ratio of the first to the second to the third, so 0/(1/8) : (1/8)/(1/8) : (7/8)/(1/8) = 0:1:7.

Option C is correct because the Y gene transcribes the permease protein in the lac operon.

Option B (siRNA) is correct because siRNA is involved in gene silencing and RNA interference, but it is not directly required for the synthesis of proteins from mRNA.

Option A is correct because chromosome 1 in humans has approximately 2968 genes, while the Y chromosome has approximately 231 genes.

Option B (0.35) is correct because in DNA, A=T and G=C. If Adenine is 15%, Thymine is also 15%. The remaining 70% is split equally between Guanine and Cytosine, resulting in 35% each.

Option D ($1.8 \times 10^4$) is incorrect. Option C ($1.8 \times 10^4+2$) is correct because the number of phosphodiester bonds in a linear dsDNA is equal to the number of bases minus 2.

Option A is correct because gel electrophoresis is the standard technique used to separate DNA fragments based on their size.

Option D (1 and 4) is correct because a homopolymer of U (UUU UUU UUU) will only produce one type of amino acid (phenylalanine), while a copolymer of CU can produce multiple codons (CUC, UCU, CUU, UCC) leading to a maximum of 4 different amino acids.

Option B (RNA polymerase) is correct because RNA polymerase is responsible for unwinding the DNA helix during transcription.