Class XII Biology
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519 questions in this chapter
Question 161 of 519
π CLASS XII
The classic example of a disease caused by a point mutation that results in a change from Glutamic acid to Valine in the protein chain is:
Sickle-cell anemia is caused by a single point mutation (A β T transversion) in the Ξ²-globin gene, leading to the substitution of glutamic acid by valine.
Question 162 of 519
π CLASS XII
The Central Dogma of Molecular Biology describes the flow of genetic information as:
The Central Dogma states that genetic information flows from DNA (replication) to RNA (transcription) to Protein (translation).
Question 163 of 519
π CLASS XII
Which type of bond connects the sugar and phosphate groups to form the backbone of a DNA strand?
The sugar of one nucleotide is linked to the phosphate group of the next nucleotide via a covalent phosphodiester bond, forming the robust backbone of the DNA strand.
Question 164 of 519
π CLASS XII
According to Chargaff's rules, in a double-stranded DNA molecule, the amount of Adenine (A) is always equal to the amount of:
Chargaff's rules state that in DNA, the number of purines equals the number of pyrimidines β specifically, Adenine pairs with Thymine (A=T) and Guanine pairs with Cytosine (G=C).
Question 165 of 519
π CLASS XII
Which enzyme is primarily responsible for unwinding the DNA double helix during DNA replication?
Helicase is the enzyme that uses ATP energy to break the hydrogen bonds between the bases, separating the two strands of the DNA double helix to create a replication fork.
Question 166 of 519
π CLASS XII
If a coding strand of DNA has the sequence 5'-ATG-3', what is the sequence of the corresponding mRNA codon?
The coding strand has the same sequence as the mRNA, except that Thymine (T) in DNA is replaced by Uracil (U) in RNA. Since the DNA is 5'-ATG-3', the mRNA is 5'-AUG-3'.
Question 167 of 519
π CLASS XII
In eukaryotes, where does the process of transcription primarily occur?
Transcription, the synthesis of RNA from a DNA template, occurs in the nucleus where the DNA is located in eukaryotic cells.
Question 168 of 519
π CLASS XII
Which type of RNA carries the genetic code from the DNA to the ribosome for protein synthesis?
mRNA is synthesized during transcription and acts as the template, carrying the sequence of codons, which is then read by the ribosome during translation.
Question 169 of 519
π CLASS XII
What is the specific functional unit of the genetic code, consisting of three nucleotides on the mRNA?
A codon is a sequence of three nucleotides on the mRNA that specifies a particular amino acid or a stop signal during protein synthesis.
Question 170 of 519
π CLASS XII
The process of DNA replication is described as 'semi-conservative' because:
Semi-conservative replication means that after one round of replication, each of the two daughter DNA molecules consists of one parental strand and one new strand.
