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Chapter 14: Problem 23

The ends of the linear chromosomes are maintained by what? a. DNA polymerase b. helicase c. primase d. telomerase

Short Answer

Expert verified
d. telomerase

Step by step solution

01

Understand the terminology

Chromosomes are structures within cells that contain DNA. Linear chromosomes refer to the DNA molecules that are linear in shape, as found in eukaryotic cells.
02

Identify the problem

The question asks about the enzyme responsible for maintaining the ends of linear chromosomes. These ends are known as telomeres.
03

Review enzyme functions

Review the functions of the given enzymes: a. DNA polymerase synthesizes new DNA strands. b. Helicase unwinds the DNA helix. c. Primase synthesizes RNA primers. d. Telomerase adds repetitive sequences to the ends of chromosomes (telomeres) to prevent them from getting shorter.
04

Determine the correct enzyme

Based on the functions, telomerase is the enzyme that maintains the ends of linear chromosomes by adding telomere sequences.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

DNA polymerase
DNA polymerase is a crucial enzyme in DNA replication. It synthesizes new DNA strands by adding nucleotides to a pre-existing chain. This enzyme reads the existing DNA strand as a template and creates a complementary strand.

Key points to remember about DNA polymerase:
  • It synthesizes DNA in a 5鈥� to 3鈥� direction.
  • It requires a primer to start the synthesis process.
  • It plays a vital role in DNA repair and proofreading mechanisms.

DNA polymerase ensures that genetic information is accurately copied during cell division, which is essential for maintaining genetic integrity.
Helicase
Helicase is another critical enzyme in the DNA replication process. Its primary function is to unwind and separate the double-stranded DNA helix into two single strands. This creates the necessary template strands for DNA replication.

Important features of helicase:
  • Uses energy from ATP to unwind the helix.
  • Creates replication forks where DNA replication can proceed.
  • Ensures that the DNA strands are accessible for the replication machinery, including DNA polymerase.

By unwinding DNA, helicase helps the cell prepare for accurate DNA synthesis and distribution to daughter cells.
Primase
Primase plays a key role in initiating DNA synthesis. It is an RNA polymerase that creates short RNA primers complementary to the DNA template strands. These RNA primers provide a starting point for DNA polymerase to begin adding DNA nucleotides.

Essential points about primase:
  • Generates RNA primers during DNA replication.
  • Works on both leading and lagging strands of DNA.
  • Helps in the formation of Okazaki fragments on the lagging strand.

Primase is critical because DNA polymerase cannot start DNA synthesis from scratch and needs these RNA primers.
Telomeres
Telomeres are repetitive nucleotide sequences at the ends of linear chromosomes. They protect chromosome ends from degradation and prevent the loss of genetic information during cell division.

Key functions of telomeres:
  • Shield chromosome ends from being mistaken for broken DNA.
  • Facilitate complete replication without losing essential DNA sequences.
  • Maintain chromosome stability and integrity.

Telomeres are extended by the enzyme telomerase, which adds specific sequences to the ends of chromosomes, thus preventing them from shortening with each replication cycle.

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Most popular questions from this chapter

Which type of point mutation would have no effect on gene expression? a. frame shift b. missense c. nonsense d. silent

What happens when a dideoxynucleotide is added to a developing DNA strand? a. The chain extends to the end of the DNA strand. b. The DNA stand is duplicated. c. The chain is not extended any further. d. The last codon is repeated.

Meselson and Stahl鈥檚 experiments proved that DNA replicates by which mode? a. conservative b. converse c. dispersive d. semi-conservative

Explain how the components of DNA fit together. a. DNA is composed of nucleotides, consisting of a 5 carbon sugar, a phosphate, and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with thymine and guanine pairs with cytosine. Adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run anti parallel to each other. b. DNA is composed of nucleotides, consisting of a 5 carbon sugar, a phosphate, and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with cytosine and guanine pairs with thymine. Adenine and cytosine form two hydrogen bonds and guanine and thymine form three hydrogen bonds. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run anti parallel to each other. c. DNA is composed of nucleotides, consisting of a 5 carbon sugar, a phosphate, and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with cytosine and guanine pairs with thymine. Adenine and cytosine form three hydrogen bonds and guanine and thymine form two hydrogen bonds. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run antiparallel to each other. d. DNA is composed of nucleotides, consisting of a 5 carbon sugar, a phosphate, and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with cytosine and guanine pairs with thymine. Adenine and cytosine form three hydrogen bonds and guanine and thymine form two hydrogen bonds. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run parallel to each other.

What can be the result of DNA failing to undergo repair after too much UV exposure? a. second degree burns b. a malignant melanoma c. a breakdown of deep layers of the skin d. a sun burn
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