Which was the last human chromosome to be completely sequenced?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Chromosome 1
• Chromosome 11
• Chromosome 21
• Chromosome X
Correct Option: A  [ Chromosome 1 ]

Remark: Chromosome 1 was finished last.

Which of the following are the functions of RNA?

[Molecular-Basis-of-Inheritance] [class-xii ]

• It is a carrier of genetic information from DNA to ribosomes synthesizing polypeptides
• It carries amino acids to ribosomes
• It is a constituent component of ribosomes
• All of the above
Correct Option: D  [ All of the above ]

Remark: mRNA carries info, tRNA carries AAs, rRNA makes ribosomes.

While analyzing the DNA of an organism, a total number of 5386 nucleotides were found out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff's rule it can be concluded that _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• It is a double stranded circular DNA
• It is single stranded DNA
• It is a double stranded linear DNA
• No conclusion can be drawn
Correct Option: B  [ It is single stranded DNA ]

Remark: A!=T and G!=C, so it must be single stranded.

In some viruses, DNA is synthesized by using RNA as template. Such a DNA is called _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• A - DNA
• B - DNA
• cDNA
• rDNA
Correct Option: C  [ cDNA ]

Remark: Complementary DNA (cDNA) is made from RNA.

If Meselson and Stahl's experiment is continued for four generations in bacteria, the ratio of N15/N15 : N15/N14 : N14/N14 containing DNA in the fourth generation would be _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• 1:1:0
• 1:4:0
• 0:1:3
• 0:1:7
Correct Option: D  [ 0:1:7 ]

Remark: After 4 generations: 0 heavy, 2 hybrid, 14 light. Ratio 0:1:7.

If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is: 5' - A T G A A T G - 3', the sequence of bases in its RNA transcript would be _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• 5' - A U G A A U G - 3'
• 5' - U A C U U A C - 3'
• 5' - C A U U C A U - 3'
• 5' - G U A A G U A - 3'
Correct Option: A  [ 5' - A U G A A U G - 3' ]

Remark: Coding strand is same as RNA (T becomes U).

The RNA polymerase holoenzyme transcribes _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• The promoter, structural gene and the terminator region
• The promoter and the terminator region
• The structural gene and the terminator region
• The structural gene only
Correct Option: D  [ The structural gene only ]

Remark: The polymerase transcribes the structural gene; promoter/terminator regulate.

If the base sequence of a codon in mRNA is 5' - AUG - 3', the sequence of tRNA pairing with it must be _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• 5' - UAC - 3'
• 5' - CAU - 3'
• 5' - AUG - 3'
• 5' - GUA - 3'
Correct Option: B  [ 5' - CAU - 3' ]

Remark: Anticodon is antiparallel. AUG -> CAU (reading 5'->3'). 3' UAC 5' = 5' CAU 3'.

The amino acid attaches to the tRNA at its _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• 5' - end
• 3' - end
• Anticodon loop
• DHU loop
Correct Option: B  [ 3' - end ]

Remark: Amino acids bind to the 3' end.

To initiate translation, the mRNA first binds to _______

[Molecular-Basis-of-Inheritance] [class-xii ]

• The smaller ribosomal subunit
• The larger ribosomal subunit
• The whole ribosome
• No such specificity exists
Correct Option: A  [ The smaller ribosomal subunit ]

Remark: mRNA binds to the small subunit first.