1.
What are the characteristics of rough pneumococci strain?
Correct Answer
B. Non-capsulated and non-pathogenic
Explanation
Rough pneumococci strains are characterized by being non-capsulated and non-pathogenic. This means that they do not have a protective capsule surrounding them and they do not cause disease or infection.
2.
In Griffith’s experiment which of the following strains of pneumococci was isolated from dead mice?
Correct Answer
C. Living smooth cells
Explanation
In Griffith's experiment, living smooth cells of pneumococci were isolated from dead mice. This suggests that the transformation of the rough strain into the smooth strain occurred, as the smooth strain was able to cause disease and kill the mice. The rough strain alone did not cause disease, indicating that the transformation of the rough strain was responsible for the lethal effects.
3.
Which of the following things was identified as the transforming principle in Griffith experiment?
Correct Answer
A. DNA
Explanation
The transforming principle in Griffith's experiment was identified as DNA. In his experiment, Griffith observed that when he injected a mixture of heat-killed disease-causing bacteria and live harmless bacteria into mice, the mice died. This showed that something in the heat-killed bacteria was able to transform the harmless bacteria into disease-causing ones. Later research by Avery, MacLeod, and McCarty confirmed that the transforming principle was DNA. This discovery played a crucial role in establishing DNA as the genetic material and paved the way for further understanding of genetics.
4.
When DNA replication starts, .......
Correct Answer
D. The hydrogen bonds between the nucleotides of two strand break.
Explanation
When DNA replication starts, the hydrogen bonds between the nucleotides of the two strands break. This is necessary for the separation of the DNA strands and allows for the replication process to occur. Breaking the hydrogen bonds allows the DNA helix to unwind and exposes the nucleotides on each strand, which serve as templates for the synthesis of new complementary strands. The breaking of the hydrogen bonds is a crucial step in DNA replication as it enables the formation of new DNA strands through the pairing of nucleotides.
5.
The elongation of the produced strand during DNA replication .......
Correct Answer
D. Depends on the action of DNA polymerase.
Explanation
During DNA replication, the elongation of the produced strand depends on the action of DNA polymerase. DNA polymerase is responsible for adding nucleotides to the growing DNA strand in a complementary manner to the template strand. It catalyzes the formation of phosphodiester bonds between the nucleotides, allowing for the continuous elongation of the new DNA strand. Therefore, the correct answer is that the elongation of the produced strand depends on the action of DNA polymerase.
6.
During DNA replication ....
Correct Answer
A. The lagging strand requires a slight delay before undergoing replication.
Explanation
The lagging strand requires a slight delay before undergoing replication because it is synthesized discontinuously in short fragments called Okazaki fragments. These fragments are then joined together by DNA ligase to form a continuous strand. This process requires the lagging strand to undergo a slight delay in order to allow for the synthesis and joining of these fragments.
7.
Hershey and Chase experiment confirms that ......
Correct Answer
B. DNA is the genetic material and not protein.
Explanation
The Hershey and Chase experiment involved the use of bacteriophages to confirm that DNA is the genetic material and not protein. In the experiment, the bacteriophages were labeled with either radioactive sulfur (which labels proteins) or radioactive phosphorus (which labels DNA). After infecting the bacteria, it was found that only the radioactive phosphorus was transferred to the bacterial cell progeny, indicating that DNA is the genetic material responsible for inheritance. This experiment provided strong evidence to support the idea that DNA carries the genetic information, not proteins.
8.
Which of the following has the self-repairing mechanisms?
Correct Answer
C. Only DNA
Explanation
DNA has the self-repairing mechanism because it contains enzymes called DNA repair enzymes that can detect and correct errors in the DNA sequence. These enzymes can identify and remove damaged or incorrect nucleotides and replace them with the correct ones, ensuring the integrity of the DNA molecule. RNA and proteins do not have this self-repairing capability.
9.
How did Rosalind Franklin take pictures of the shape of DNA?
Correct Answer
A. X-Ray diffraction
Explanation
Rosalind Franklin used X-Ray diffraction to take pictures of the shape of DNA. X-Ray diffraction is a technique that involves directing X-rays at a crystal and analyzing the pattern of the diffracted X-rays to determine the structure of the crystal. By using this technique, Franklin was able to capture images of the DNA molecule and provide crucial insights into its helical structure.
10.
How did Rosalind Franklin's photo of DNA affect the work of Watson and Crick?
Correct Answer
A. It was used to determine the pHysical structure of DNA
Explanation
Rosalind Franklin's photo of DNA, known as Photo 51, played a crucial role in determining the physical structure of DNA. This photo provided key insights into the helical nature of DNA and the arrangement of its components. Watson and Crick used this information to develop their double helix model of DNA, which revolutionized our understanding of genetics and molecular biology.
11.
When a DNA molecule is described as replicating bidirectionally, that means that it has two ......
Correct Answer
D. Replication forks.
Explanation
When a DNA molecule is described as replicating bidirectionally, it means that the replication process occurs in two opposite directions from a central point. This results in the formation of two replication forks, which are the points where the DNA strands separate and new nucleotides are added to each strand. The replication forks move in opposite directions along the DNA molecule, allowing for the simultaneous synthesis of both strands.
12.
A nucleotide of DNA may contain ________.
Correct Answer
C. Deoxyribose, thymine, and a pHospHate group
13.
In double helix of DNA, the two DNA strands are .......
Correct Answer
B. Coiled around a common axis
Explanation
The correct answer is "Coiled around a common axis". In the double helix structure of DNA, the two DNA strands are twisted around each other in a helical shape. This coiling occurs around a common axis, with the two strands running in opposite directions. This arrangement allows for the complementary base pairing between the strands, where adenine pairs with thymine and guanine pairs with cytosine, forming the genetic code. The coiling around a common axis also helps to stabilize the DNA structure and protect the genetic information it carries.
14.
A segment of DNA has 120 adenine and 120 cytosine bases. The total number of nucleotides present in the segment is .....
Correct Answer
D. 480
Explanation
The total number of nucleotides present in a DNA segment can be calculated by adding the number of adenine (A) bases and the number of cytosine (C) bases together. In this case, there are 120 adenine bases and 120 cytosine bases, so the total number of nucleotides is 120 + 120 = 240.
15.
Nucleotides have a nitrogenous base attached to a sugar at the …....
Correct Answer
A. 1' carbon
Explanation
Nucleotides have a nitrogenous base attached to a sugar at the 1' carbon. This is because the carbon atoms in the sugar molecule are numbered, with the 1' carbon being the carbon atom closest to the nitrogenous base. The attachment of the nitrogenous base to the 1' carbon is important for the formation of the phosphodiester bond that links nucleotides together in a DNA or RNA strand.
16.
A nucleotide has ……….
Correct Answer
C. One pentose sugar
Explanation
A nucleotide is composed of three main components: a nitrogenous base, a sugar molecule, and a phosphate group. The sugar molecule in a nucleotide is a pentose sugar, which is a type of sugar with five carbon atoms. Therefore, the correct answer is "One pentose sugar."
17.
Each half turn of DNA molecule contains _______ nitrogenous bases.
Correct Answer
B. 10
Explanation
Each half turn of a DNA molecule contains 10 nitrogenous bases. The DNA molecule consists of two strands that are twisted together in a double helix structure. Each strand is made up of a sequence of nitrogenous bases, which are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair up with each other, with A always bonding with T and C always bonding with G. In each half turn of the DNA molecule, there are 10 pairs of nitrogenous bases, resulting in a total of 10 bases.
18.
How many turns does a molecule of DNA consist of 2000 base pairs have?
Correct Answer
C. 200
Explanation
A molecule of DNA consists of two strands that are twisted around each other in a double helix structure. Each turn of the helix contains approximately 10 base pairs. Therefore, a molecule of DNA with 2000 base pairs would have 200 turns, since 2000 divided by 10 is equal to 200.
19.
For a DNA molecule, which is not true?
Correct Answer
C. (A +T) / (G + C) = 1
Explanation
The statement (A + T) / (G + C) = 1 is not true for a DNA molecule. The correct ratio for the base pairs in DNA is A + T = G + C, not (A + T) / (G + C) = 1.
20.
DNA is composed of repeating units of ………
Correct Answer
D. Deoxyribonucleotides.
Explanation
DNA is composed of repeating units called nucleotides. These nucleotides consist of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. Therefore, the correct answer is deoxyribonucleotides, as they contain the deoxyribose sugar molecule that is characteristic of DNA. Ribonucleosides and ribonucleotides contain ribose sugar and are components of RNA, not DNA.
21.
Which of the following nucleotide sequences contains 4 different types of bases?
Correct Answer
B. GCCAGAUAA
Explanation
The nucleotide sequence "GCCAGAUAA" contains 4 different types of bases because it includes the nucleotides G, C, A, and U. The other sequences do not contain all 4 types of bases.
22.
Which of the following is true about the linkage between two adjacent nucleotides?
Correct Answer
A. 5’-pHospHate group of one nucleotide unit is joined to the 3’-hydroxyl group of the other nucleotide.
Explanation
The correct answer is that the 5'-phosphate group of one nucleotide unit is joined to the 3'-hydroxyl group of the other nucleotide. This is known as a phosphodiester bond and it forms the backbone of DNA and RNA molecules. The phosphate group of one nucleotide is covalently bonded to the hydroxyl group of the sugar of the adjacent nucleotide, creating a strong and stable linkage between the nucleotides. This linkage allows for the formation of a linear chain of nucleotides, which is essential for the structure and function of DNA and RNA.
23.
In the transcription of RNA from DNA, which of the following statements is true?
Correct Answer
B. The template strand DNA is complementary to the sequence of the RNA transcript.
Explanation
The correct answer is that the template strand DNA is complementary to the sequence of the RNA transcript. This means that the RNA transcript is formed by pairing complementary nucleotides to the template strand of DNA. The RNA transcript will have a sequence that is complementary to the template strand, but it will not be identical to it.
24.
What is the complementary DNA strand that is created from this template during replication?
3’ T A C C G A T T G C A 5’
Correct Answer
D. 5’ATGGCTAACGT 3’
Explanation
The complementary DNA strand is created by pairing each nucleotide with its complementary base. In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Therefore, the complementary DNA strand for the given template sequence is 5’ATGGCTAACGT 3’.
25.
Which association between complementary bases would require the most energy to break?
Correct Answer
C. G:C
Explanation
The association between complementary bases G:C would require the most energy to break because it is connected by three hydrogen bonds, whereas A:T and A:U are connected by only two hydrogen bonds. The additional hydrogen bond in G:C makes it stronger and more stable, hence requiring more energy to break the bond.
26.
In a sample of double-stranded DNA, 20% of the nitrogenous bases are guanine (G). What is the percentage of the nitrogenous bases adenine (A) in the sample?
Correct Answer
B. 30%
Explanation
In a double-stranded DNA, the percentage of guanine (G) is 20%. Since DNA consists of two strands, the percentage of cytosine (C) would also be 20% as it pairs with guanine. This means that the total percentage of guanine and cytosine combined is 40%. As DNA follows the base pairing rule, the percentage of adenine (A) would be equal to the percentage of thymine (T). Therefore, the percentage of adenine would also be 40%. However, since the question specifically asks for the percentage of adenine (A) alone, we need to divide the 40% by 2, resulting in 20%. Therefore, the correct answer is 30%.
27.
Where is DNA NOT found?
Correct Answer
A. In red blood cells
Explanation
Red blood cells do not contain a nucleus, which means they do not contain DNA. Unlike other cells in the body, red blood cells lose their nucleus during development in order to make space for more hemoglobin, the protein responsible for carrying oxygen. Therefore, DNA is not found in red blood cells.
28.
One of the following statements describing the similarities between ribose and deoxyribose, is not correct …..
Correct Answer
D. Both have an OH group attached to C2’
Explanation
Both ribose and deoxyribose are pentoses, meaning they both have five carbon atoms. They also both enter into the structure of nucleotides, which are the building blocks of DNA and RNA. Additionally, they are both monosaccharides, which means they are simple sugars composed of a single sugar unit. However, the statement that both ribose and deoxyribose have an OH group attached to C2' is incorrect. Deoxyribose lacks the OH group at the C2' position, which is replaced by a hydrogen atom.
29.
A molecule of DNA consists of 300 base pair. If the number of thymine base is 150. What is the number of the triple hydrogen bonds found in the molecule?
Correct Answer
B. 150
Explanation
The number of triple hydrogen bonds in a DNA molecule is equal to the number of adenine-thymine base pairs. Since the number of thymine bases is given as 150, it means that there are 150 adenine bases in the molecule as well. Therefore, the number of triple hydrogen bonds in the molecule is also 150.
30.
A molecule of DNA consists of 200 base pair. What is the number of the free phosphate groups found in the molecule?
Correct Answer
D. 2
Explanation
A molecule of DNA consists of two strands, each made up of a long chain of nucleotides. Each nucleotide contains a phosphate group, a sugar molecule, and a nitrogenous base. Therefore, for a molecule of DNA with 200 base pairs, there would be 200 phosphate groups. However, since each phosphate group is shared between two nucleotides, there would be half as many free phosphate groups. Therefore, the number of free phosphate groups found in the molecule would be 2.
31.
In the DNA molecule, the width of the A=T is always …….. ring/(s)
Correct Answer
C. 3
Explanation
The width of the A=T ring in the DNA molecule is always 3.
32.
In the figure below, if A is a phosphate group, B is a ribose sugar and C is a nitrogenous base, then D have to be …..
Correct Answer
D. C = H
Explanation
In a DNA molecule, the phosphate group (A) is attached to the ribose sugar (B) and the nitrogenous base (C). The ribose sugar has a hydroxyl group (-OH) attached to it. Since the question asks for the identity of D, it can be deduced that D refers to the hydrogen atom (H) attached to the carbon atom (C) in the ribose sugar. Therefore, the correct answer is C = H.
33.
If you know that the percentage of (A) in one strand of a DNA molecule is 10% and that of (T) on the same strand is 20%. What is the percentage (C) in the double helix molecule?
Correct Answer
C. 35%
Explanation
The percentage of (A) and (T) in a DNA molecule always add up to 100%. Since the percentage of (A) is 10% and the percentage of (T) is 20%, the remaining percentage must be allocated to (C) and (G). Therefore, the percentage of (C) in the double helix molecule is 35%.
34.
True replication of DNA is possible due to ……….
Correct Answer
C. Complementary base pairing rule
Explanation
True replication of DNA is possible due to the complementary base pairing rule. This rule states that adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). This allows for the accurate and precise replication of DNA during cell division. Each strand of the double helix acts as a template for the synthesis of a new complementary strand, ensuring that the genetic information is faithfully passed on to the next generation of cells.
35.
What is the correct mode of DNA replication?
Correct Answer
B. Semi-conservative
Explanation
In DNA replication, the correct mode is semi-conservative. This means that during replication, each new DNA molecule consists of one original strand and one newly synthesized strand. This was proven by the Meselson-Stahl experiment, where they labeled the parental DNA with a heavy isotope and the newly synthesized DNA with a light isotope. After multiple rounds of replication, the DNA was analyzed and it was found that the DNA molecules were a mix of heavy and light isotopes, supporting the semi-conservative mode of replication.
36.
What is the reaction in DNA replication catalyzed by DNA ligase?
Correct Answer
A. Formation of a covalent bond between the 3’-OH of one DNA fragment and the 5’-pHospHate of the next fragment
Explanation
DNA ligase catalyzes the formation of a covalent bond between the 3'-OH of one DNA fragment and the 5'-phosphate of the next fragment. This process is crucial in DNA replication as it joins the Okazaki fragments on the lagging strand and seals any nicks or gaps in the DNA backbone. By forming this bond, DNA ligase helps to ensure the integrity and continuity of the newly synthesized DNA strand.
37.
What does the following mathematical equation mean? A/T = G/C =1
Correct Answer
C. (A + C) / (G + T) = 1
Explanation
The equation (A + C) / (G + T) = 1 means that the sum of the occurrences of adenine (A) and cytosine (C) in a DNA molecule is equal to the sum of the occurrences of guanine (G) and thymine (T). This equation is based on Chargaff's rules, which state that in DNA, the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine. Therefore, the ratio of (A + C) to (G + T) is always equal to 1.
38.
For the following figure to be the building unit of DNA and not of RNA, The structure ……. Should be …….
Correct Answer
D. C / Thymine
Explanation
The structure that should be present in the building unit of DNA and not RNA is Thymine. Thymine is one of the four nucleotide bases found in DNA, while RNA contains Uracil instead of Thymine. Therefore, the presence of Thymine indicates that the structure is specific to DNA and not RNA.
39.
In the following figure, write the sequence of the structural letters with respect to each of the following: leading strand / cannot work from 3`end toward 5`end / lagging strand / joins the short pieces of DNA.
Correct Answer
B. C / B / D / A
Explanation
The correct answer is C / B / D / A. In DNA replication, the leading strand is synthesized continuously in the 5' to 3' direction, so the structural letter C represents the leading strand. The lagging strand is synthesized in short fragments called Okazaki fragments, which are later joined together. Therefore, the structural letter B represents the lagging strand. The short pieces of DNA on the lagging strand are joined by an enzyme called DNA ligase, so the structural letter D represents the joining of the short pieces. Finally, the structural letter A represents the inability to work from the 3' end toward the 5' end, which is a characteristic of DNA replication.
40.
Some Mice were killed in Griffith’s experiment after injection with ….
Correct Answer
D. Living R-type + nonliving S-type
Explanation
In Griffith's experiment, some mice were killed after injection with a combination of living R-type bacteria and nonliving S-type bacteria. This suggests that the living R-type bacteria were able to transform the nonliving S-type bacteria into a deadly form. This transformation is known as bacterial transformation and was a key discovery in understanding how genetic material can be transferred between bacteria.
41.
The ratio between the amount of DNA in the uterine cells and that in the kidney cells is ….
Correct Answer
B. 1 : 1
Explanation
The ratio between the amount of DNA in the uterine cells and that in the kidney cells is 1 : 1. This means that both types of cells have the same amount of DNA.
42.
During DNA replication, a separation occurs between …..
Correct Answer
A. Cytosine and guanine
Explanation
During DNA replication, a separation occurs between cytosine and guanine. This is because during replication, the DNA double helix unwinds and the two strands separate. Cytosine and guanine are complementary base pairs, meaning they always pair together. Therefore, during replication, the cytosine on one strand will pair with guanine on the other strand, and vice versa. This separation allows for the synthesis of new DNA strands using the separated strands as templates.
43.
……. was the first to isolate the material that was capable of inducing genetic transformation in the non-virulent bacteria.
Correct Answer
B. Avery
Explanation
Avery was the first to isolate the material that was capable of inducing genetic transformation in the non-virulent bacteria.
44.
The enzyme deoxyribonuclease hydrolyses ……… completely.
Correct Answer
D. DNA
Explanation
The correct answer is DNA because deoxyribonuclease is an enzyme that specifically hydrolyzes DNA. It breaks down the DNA molecule into smaller fragments by breaking the phosphodiester bonds between the nucleotides. This enzyme does not hydrolyze proteins, RNA, or any other molecule besides DNA. Therefore, the correct answer is DNA.
45.
The nitrogenous base of the nucleotide is linked to the sugar molecule at its carbon atom number ……
Correct Answer
A. 1’
Explanation
The nitrogenous base of the nucleotide is linked to the sugar molecule at its carbon atom number 1. This is because carbon atom number 1 in the sugar molecule is attached to the nitrogenous base, forming a covalent bond. This bond is important for stabilizing the structure of the nucleotide and allowing it to participate in the formation of DNA and RNA molecules.
46.
…… is a pyrimidine base that makes a triple hydrogen bond.
Correct Answer
C. Cytosine
Explanation
Cytosine is a pyrimidine base that forms a triple hydrogen bond. Adenine and guanine are purine bases, while thymine is also a pyrimidine base but it forms only a double hydrogen bond. Therefore, the correct answer is cytosine.
47.
The enzyme ……… adds a new nucleotide in the direction of 5`to 3` of the strand which is synthesizing.
Correct Answer
B. DNA polymerase
Explanation
DNA polymerase is the correct answer because it is the enzyme responsible for adding new nucleotides during DNA synthesis. It adds nucleotides in the 5' to 3' direction, meaning it adds them to the growing strand in the same direction as the replication fork is moving. DNA helicase unwinds the DNA strands, reverse transcriptase synthesizes DNA from an RNA template, and DNA ligase joins together Okazaki fragments during DNA replication.
48.
Which of the following is untrue for a DNA molecule?
Correct Answer
C. G + C = A + T
Explanation
The equation A + G / C + T = 1 represents the fact that the sum of the adenine (A) and guanine (G) nucleotides is equal to the sum of the cytosine (C) and thymine (T) nucleotides in a DNA molecule. The equation A + G = C + T indicates that the total number of adenine and guanine nucleotides is equal to the total number of cytosine and thymine nucleotides. The equation G = C states that the number of guanine nucleotides is equal to the number of cytosine nucleotides. Therefore, the only statement that is untrue for a DNA molecule is G + C = A + T.
49.
How many nucleotides are there in a DNA strand that comprises 150 nitrogenous bases?
Correct Answer
C. 150
Explanation
The number of nucleotides in a DNA strand is equal to the number of nitrogenous bases. Since the question states that the DNA strand comprises 150 nitrogenous bases, the correct answer is 150.
50.
Which of the following DNA segments is complement to the segment 5’-G-T-C-3?’
Correct Answer
C. 5’-C-A-G-3’
Explanation
The complementary strand of DNA is formed by pairing the nucleotides in a specific way. Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C). Therefore, the complementary strand to 5'-G-T-C-3' would be 5'-C-A-G-3'.