Molecular Genetics- DNA Replication MCQ Test

1.

____________ are highly repetitive DNA that allow the ends of chromosomes to be replicated; also protect the ends of chromosomes as being mistaken as broken

Explanation
Telomeres are highly repetitive DNA sequences that play a crucial role in the replication and protection of chromosome ends. They provide a protective cap at the ends of chromosomes, preventing them from being recognized as broken DNA strands and triggering unnecessary repair mechanisms. Telomeres also allow for the complete replication of chromosomes during cell division by preventing the loss of genetic material from the ends. Overall, telomeres ensure the stability and integrity of chromosomes, allowing cells to divide and function properly.

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2.

_________ are repetitive DNA that forms the spindle attachment in mitosis.

Explanation
Centromeres are repetitive DNA sequences that play a crucial role in cell division, specifically in the formation of the spindle attachment during mitosis. They are responsible for ensuring the proper segregation of chromosomes by connecting them to the spindle fibers. Centromeres are essential for the accurate distribution of genetic material to daughter cells during cell division.

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1

3.

________________ are special sequences where duplication of the DNA begins; each chromosome will have many.

Explanation
Origins of replication are specific sequences in DNA where the process of DNA duplication begins. Each chromosome contains multiple origins of replication, which allow for the replication of the entire DNA molecule. These origins are essential for ensuring that the genetic information is accurately and efficiently copied during cell division.

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4.

______________ replication means that each new DNA molecule produced in replication contains one of the original strands of DNA and one new strand.

Explanation
Semiconservative replication refers to the process in which each new DNA molecule produced during replication contains one original strand of DNA and one newly synthesized strand. This means that the DNA molecule is composed of both old and new strands, ensuring the preservation of genetic information. The term "semiconservative" is commonly used in molecular biology to describe this type of replication.

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5.

Name the enzyme responsible for DNA synthesis.

Explanation
DNA polymerase is the enzyme responsible for DNA synthesis. It catalyzes the formation of phosphodiester bonds between nucleotides, resulting in the synthesis of a new DNA strand complementary to the template strand. DNA polymerase also proofreads the newly synthesized DNA strand, correcting any errors in nucleotide incorporation. This enzyme is essential for DNA replication, repair, and other DNA-dependent processes in all living organisms.

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6.

True or False: DNA synthesis occurs in a 5' to 3' direction.

A.

True
B.

False

Correct Answer
A. True

Explanation
DNA synthesis occurs in a 5' to 3' direction because DNA polymerase, the enzyme responsible for synthesizing new DNA strands, can only add nucleotides to the 3' end of the growing strand. This means that the template strand is read in the 3' to 5' direction, and the new complementary strand is synthesized in the 5' to 3' direction. This directionality is important for the accurate replication of DNA during cell division.

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7.

True or False: RNA polymerase is more accurate than DNA polymerase.

A.

True
B.

False

Correct Answer
B. False

Explanation
FALSE.
DNA polymerase is actually more accurate than RNA polymerase.

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0

8.

Name the enzyme involved in 'proofreading' DNA by removing nucleotides from the 3' end of a polynucleotide chain.

Correct Answer
Exonuclease
Exonucleases

Explanation
Exonuclease and Exonucleases are enzymes involved in the proofreading process of DNA by removing nucleotides from the 3' end of a polynucleotide chain. They play a crucial role in maintaining the integrity and accuracy of DNA replication and repair mechanisms. These enzymes help in removing any incorrect or damaged nucleotides from the growing DNA strand, ensuring the fidelity of genetic information.

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9.

DNA replication is bidirectional, resulting in the formation of ___________________.

Correct Answer
replication bubbles
A replication bubble

Explanation
During DNA replication, the double-stranded DNA molecule unwinds and separates into two strands. The replication process occurs bidirectionally, meaning that replication proceeds in opposite directions on each strand. As the replication forks move along the DNA strands, they create "bubbles" where the DNA is unwound and actively being replicated. These replication bubbles are formed as a result of the bidirectional replication process and are essential for the synthesis of new DNA strands. Therefore, the correct answer is replication bubbles.

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10.

True or False: Bacterial DNA contains histone proteins.

A.

True
B.

False

Correct Answer
B. False

Explanation
Bacterial DNA does not contain histone proteins. Histones are proteins that help in packaging and organizing DNA in eukaryotic cells, but they are not present in bacteria. Bacterial DNA is typically organized and compacted by other mechanisms, such as supercoiling and the presence of nucleoid-associated proteins. Therefore, the statement that bacterial DNA contains histone proteins is false.

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2

11.

Name the short, newly synthesised DNA fragments found on the lagging template during DNA synthesis...

Correct Answer
Okazaki fragments
Okazaki

Explanation
Okazaki fragments are short, newly synthesized DNA fragments that are found on the lagging template during DNA synthesis. They are formed during the replication of the lagging strand, which occurs in short segments due to the antiparallel nature of DNA. The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments. These fragments are then joined together by DNA ligase to form a complete DNA strand. Okazaki fragments were named after the Japanese scientist Reiji Okazaki, who first discovered and characterized them.

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12.

Name the enzyme that prevents base pairing until DNA polymerase arrives.

Correct Answer
Single stranded binding protein
Single-stranded binding protein
SS Binding protein
SS-binding protein

Explanation
The enzyme that prevents base pairing until DNA polymerase arrives is the single-stranded binding protein (SSBP). This protein binds to the single-stranded DNA during DNA replication and prevents it from reannealing or forming secondary structures. By keeping the DNA single-stranded, the SSBP ensures that the DNA polymerase can effectively bind and synthesize the complementary strand. The various variations of the name (Single stranded binding protein, Single-stranded binding protein, SS Binding protein, SS-binding protein) all refer to the same enzyme.

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13.

What is the name given to proteins that load histones onto newly synthesised DNA?

Correct Answer
Histone chaperones

Explanation
Histone chaperones are proteins that are responsible for loading histones onto newly synthesized DNA. Histones are proteins that help in organizing and packaging DNA into a compact structure called chromatin. During DNA replication, histone chaperones bind to newly synthesized DNA strands and facilitate the assembly of histones onto the DNA, ensuring proper chromatin formation. This process is crucial for maintaining the integrity and stability of the genome. Therefore, the term "histone chaperones" accurately describes the proteins involved in this process.

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14.

Helicase unwinding of DNA causes supercoiling (“twists”) ahead of the replication fork which need to be unwound by enzymes called _____________.

Correct Answer
topoisomerases
topoisomerase

Explanation
During DNA replication, helicase unwinds the double helix structure of DNA, causing supercoiling or twisting ahead of the replication fork. This supercoiling needs to be resolved or unwound in order for the replication process to continue smoothly. Enzymes called topoisomerases are responsible for this task. They are able to cut the DNA strands, allowing them to rotate and relieve the tension caused by supercoiling. Once the tension is released, the topoisomerases reseal the DNA strands, ensuring the proper unwinding and replication of the DNA.

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15.

_______________ proteins detect and correct incorrect base pairing in newly-synthesised DNA.

Correct Answer
Mismatch repair
MutS

Explanation
Mismatch repair proteins, such as MutS, play a crucial role in detecting and correcting incorrect base pairing in newly-synthesized DNA. These proteins recognize and bind to mismatches or errors in the DNA sequence. Once bound, they recruit other proteins to remove the incorrect base and replace it with the correct one. This process helps to maintain the integrity and fidelity of the DNA sequence, preventing the accumulation of mutations that can lead to genetic disorders or diseases.

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