Nucleic Acids and DNA Replication
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Which of the following base pairing rules did Erwin Chargaff establish?

  • [A] = [G] and [C] ≡ [T]
  • [A] = [C] and [T] ≡ [G]
  • [G] = [T] and [A] ≡ [C]
  • [A] = [T] and [C] ≡ [G] (correct)

Which type of DNA is characterized as a right-handed double helix and is the most common form?

  • Z DNA
  • A DNA
  • X DNA
  • B DNA (correct)

Under what conditions is A DNA typically found?

  • In acidic solutions only
  • Low salt concentration with no alcohol
  • High salt concentration or with alcohol added (correct)
  • At room temperature without any additives

What is the structural characteristic of Z DNA?

<p>Its bases seem to zigzag (C)</p> Signup and view all the answers

What feature of B DNA relates to the orientation of its strands?

<p>Strands are anti-parallel (A)</p> Signup and view all the answers

Which statement correctly describes the structure of nucleotides?

<p>Nucleotides are the basic units of nucleic acids, consisting of three covalently-linked units. (A)</p> Signup and view all the answers

Which of the following pairs of bases are correctly matched as complementary base pairs in DNA?

<p>Adenine and Thymine (C)</p> Signup and view all the answers

What characterizes purine bases compared to pyrimidine bases?

<p>Purines have two hydrogen-carbon rings while pyrimidines have one. (C)</p> Signup and view all the answers

Which sugar is found in RNA, and how does it differ from the sugar in DNA?

<p>Ribose; it has an oxygen atom at carbon 2. (C)</p> Signup and view all the answers

How many pairs of chromosomes are present in a typical human genome?

<p>22 autosome pairs and 1 sex chromosome pair. (A)</p> Signup and view all the answers

What accurately describes the function of the phosphate group in nucleotide structure?

<p>It contributes to the formation of the DNA backbone. (C)</p> Signup and view all the answers

Which of the following correctly identifies the number of phosphate groups that can be present in a nucleotide?

<p>Nucleotides can have up to three phosphate groups. (C)</p> Signup and view all the answers

Which best describes the overall construction of DNA?

<p>DNA is a double-stranded helix made of nucleotides with a consistent backbone. (D)</p> Signup and view all the answers

How many hydrogen bonds are formed between adenine and thymine?

<p>2 (C)</p> Signup and view all the answers

What is the distance covered by one full helical turn of DNA?

<p>3.4 nm (D)</p> Signup and view all the answers

Which nitrogenous base forms three hydrogen bonds with its complementary base?

<p>Guanine (A)</p> Signup and view all the answers

What is the complementary sequence of 5’-GTAGCCTA-3’?

<p>3’-CATCGGAT-5’ (C)</p> Signup and view all the answers

How many base pairs per turn of the DNA helix are observed?

<p>10 bp's (C)</p> Signup and view all the answers

What is the chemical composition of deoxyadenosine monophosphate (dAMP)?

<p>Deoxyribose, Adenine, 1 Phosphate (A)</p> Signup and view all the answers

What type of proteins do histones represent in DNA packaging?

<p>Structural Proteins (A)</p> Signup and view all the answers

What is the correct numbering for the nitrogenous base pairing where adenine pairs with thymine?

<p>N6 to N3 (C)</p> Signup and view all the answers

What is the primary function of topoisomerase in the context of DNA?

<p>Prevents tangling of DNA strands. (D)</p> Signup and view all the answers

Which component of chromatin is directly associated with the DNA-protein complex structure?

<p>Nucleosomes (D)</p> Signup and view all the answers

In eukaryotic cells, where does transcription occur?

<p>In the nucleus (D)</p> Signup and view all the answers

What role do condensins play during cell division?

<p>They compact chromosomes. (A)</p> Signup and view all the answers

What is the correct sequence of the central dogma of molecular biology?

<p>DNA → RNA → Protein (C)</p> Signup and view all the answers

Which type of chromatin is characterized as tight and inactive?

<p>Heterochromatin (D)</p> Signup and view all the answers

What is the primary role of linker DNA in the context of chromatin?

<p>To connect nucleosomes. (D)</p> Signup and view all the answers

What is the function of messenger RNA (mRNA) in the central dogma?

<p>To serve as a template for protein synthesis. (B)</p> Signup and view all the answers

What initiates protein synthesis in the process of translation?

<p>AUG codon (A)</p> Signup and view all the answers

In which cellular component does translation occur?

<p>Ribosome (B)</p> Signup and view all the answers

Which of the following statements is true regarding prokaryotic transcription and translation?

<p>They occur simultaneously. (C)</p> Signup and view all the answers

What characterizes the transcriptional region of a gene?

<p>Part of DNA that is transcribed to mRNA (A)</p> Signup and view all the answers

What is the role of tRNA during translation?

<p>To match amino acids with corresponding codons (B)</p> Signup and view all the answers

Which of the following modifications can occur after protein synthesis?

<p>Glycosylation (D)</p> Signup and view all the answers

How many protein-coding genes are estimated to exist in the human genome?

<p>20,000 (C)</p> Signup and view all the answers

Which sequence is classified as a stop codon?

<p>UGA (C)</p> Signup and view all the answers

What is the primary characteristic of semi-conservative DNA replication?

<p>Each new DNA molecule contains one original and one new strand. (C)</p> Signup and view all the answers

In DNA replication, what is the role of specific enzymes?

<p>They assist in the separation of DNA strands. (B)</p> Signup and view all the answers

During the Meselsohn-Stahl experiment, what was observed after one round of replication in the presence of heavy nitrogen?

<p>The DNA exhibited an intermediate density. (D)</p> Signup and view all the answers

Which model of DNA replication suggests both strands contain mixed old and new DNA?

<p>Dispersive model (C)</p> Signup and view all the answers

What defines the specific start point of DNA replication?

<p>Designated origins in the chromosome. (C)</p> Signup and view all the answers

What was a key finding in the Meselsohn-Stahl experiment regarding the DNA of E.coli after switching from heavy to light nitrogen?

<p>One strand contained heavy nitrogen and the other light nitrogen. (C)</p> Signup and view all the answers

In which direction does DNA replication occur at the replication fork?

<p>Bidirectionally from the origin. (D)</p> Signup and view all the answers

What is DNA polymerase primarily responsible for during DNA replication?

<p>Driving the synthesis of the new DNA strand. (A)</p> Signup and view all the answers

Flashcards

Nucleotide

Basic unit of nucleic acids (e.g., DNA, RNA), composed of a nitrogenous base, a pentose sugar, and a phosphate group.

Nitrogenous Base

A molecule with nitrogen atoms that form the essential parts of a nucleotide and helps in storing genetic information.

Purine

A type of nitrogenous base with a double-ring structure.

Pyrimidine

A type of nitrogenous base with a single-ring structure.

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Base Pair

A pair of complementary nitrogenous bases that bond together in the double helix of DNA.

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DNA

A nucleic acid that carries genetic information, composed of a double helix of nucleotides.

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Genome

Complete set of genetic instructions/hereditary information for an organism.

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Chromosome

A long strand of DNA tightly coiled around proteins, carrying genes.

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Chargaff's Rules

The observation that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of cytosine (C) is equal to the amount of guanine (G).

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What are the three forms of DNA?

The three major forms of DNA are B-DNA (right-handed double helix), A-DNA (right-handed and found in high salt or alcohol), and Z-DNA (left-handed and found in alternating G-C sequences).

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Glycosidic Bond

A covalent bond that connects the sugar molecule to the nitrogenous base in a nucleotide. It links the 1' carbon of the sugar to the N9 of purines or N1 of pyrimidines.

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Pentose Sugar

A 5-carbon sugar that is a key component of nucleotides. It forms the backbone of DNA and RNA, providing structure and stability.

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How many H-bonds between A and T?

Adenine (A) forms 2 hydrogen bonds with Thymine (T).

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How many H-bonds between G and C?

Guanine (G) forms 3 hydrogen bonds with Cytosine (C).

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Distance between Base Pairs

The distance between two adjacent base pairs in a DNA double helix is 0.34 nm.

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Helical Turn (Pitch)

The distance covered by one complete turn of the DNA helix is 3.4 nm.

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Base Pairs per Turn

There are approximately 10.4 base pairs in one complete turn (pitch) of the DNA helix.

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Base Pair Rotation

Each base pair rotates approximately 35.4 degrees relative to the adjacent base pair in the DNA helix.

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Chromatin

A complex of DNA and proteins, found in the nucleus of eukaryotic cells. It exists in two forms: euchromatin (loose, active) and heterochromatin (tight, inactive).

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Linker DNA

The DNA segment that connects nucleosomes. It's bound by histone H1, a protein that helps organize DNA.

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Topoisomerase

An enzyme that prevents DNA tangling during replication and transcription. It works by cutting and reattaching the DNA strands.

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Condensins

Proteins responsible for compacting chromosomes during mitosis. They play a key role in cell division.

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Scaffold Proteins

Structural proteins that support chromatin loops and contribute to the organization of chromosomes. They provide a framework for DNA.

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What is the central dogma of molecular biology?

The central dogma of molecular biology describes the flow of genetic information within a biological system. It starts with DNA, which stores genetic instructions, then moves to RNA, which acts as the messenger, and finally to proteins, which carry out the instructions.

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How does DNA become RNA?

Through a process called transcription, a segment of DNA is copied into mRNA by the enzyme RNA polymerase. This happens in the nucleus of eukaryotic cells.

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DNA Replication

The process of producing two identical DNA molecules from one original DNA molecule.

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Semi-conservative Replication

Each new DNA molecule contains one original strand and one newly synthesized strand.

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Origin of Replication

The specific location on a chromosome where DNA replication starts.

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Replication Fork

The Y-shaped structure formed during DNA replication, where the parental DNA strands are unwound and new strands are synthesized.

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DNA Polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to a pre-existing strand.

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Promoter

A region of DNA where RNA polymerase binds to initiate transcription.

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Transcription Start Site

The specific nucleotide sequence where transcription begins.

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RNA Polymerase

An enzyme that synthesizes RNA from a DNA template.

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Translation

The process of converting mRNA into a protein by matching codons on mRNA to specific amino acids using tRNA in the ribosome.

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Codon

A sequence of three nucleotides on mRNA that corresponds to a specific amino acid during translation.

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Post-Translation

The process of folding and modifying proteins after they have been synthesized on the ribosome, resulting in a fully functional protein.

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Transcription

The process of copying genetic information from DNA to RNA.

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Intron

Non-coding regions of DNA that are removed during RNA processing in eukaryotes.

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Exon

Coding regions of DNA that are translated into proteins.

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Gene Expression

The process by which genetic information is used to create a functional protein.

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Study Notes

Nucleic Acids

  • Nucleic acids are the genetic material
  • Found in all living organisms
  • Consist of nucleotides
  • Nucleotides are composed of three parts: nitrogenous base, pentose sugar, and phosphate group.
  • Nitrogenous bases can be either purines (Adenine, Guanine) or pyrimidines (Cytosine, Thymine, Uracil).
  • Pentose sugar is either ribose (in RNA) or deoxyribose (in DNA)
  • DNA is a double helix made of two strands of nucleotides paired in a specific manner (A with T, and C with G).
  • RNA is a single stranded structure.
  • Chromosomes are long strands of DNA
  • DNA and RNA carry the instructions for creating and maintaining life.
  • Genes are segments of DNA that carry hereditary information.
  • DNA replication: creates a new double-stranded DNA molecule from an existing one.
  • Transcription: produces an RNA (mRNA) molecule from a DNA template.
  • Translation: uses mRNA to create a protein.

DNA Replication

  • DNA replication happens during cell division
  • Using semi-conservative principle (one original strand and one new strand)
  • Process involves several enzymes and proteins to unwind, separate, copy and assemble new strands.
  • Starts at specific sites on DNA called origins of replication.
  • Proceeds bidirectionally away from the origin, creating replication forks, to copy the entire DNA molecule.
  • DNA polymerase is the main enzyme responsible for synthesizing new DNA strands.
  • Replication occurs in a 5' to 3' direction.
  • Leading strand is synthesized continuously; lagging strand is synthesized in short fragments (Okazaki fragments), joined by DNA ligase

DNA Transcription

  • DNA transcription uses the information in a DNA strand to create an RNA molecule
  • RNA polymerase is the main enzyme that performs DNA transcription.
  • The process initiates at specific DNA regions called promoters , with the enzyme starting at the 3' → 5'.
  • During transcription, a DNA strand serves as a template, which gets copied into an RNA molecule, one nucleotide at a time (5' →3').
  • After transcription, the enzyme detaches from the DNA molecule.

DNA Translation

  • DNA translation is the synthesis of proteins from the information encoded in an mRNA molecule, using ribosomes and transfer RNA molecules, to read the language of mRNA.
  • The mRNA molecule is a transcript for the DNA molecule.
  • Ribosomes read three nucleotides on the mRNA , translating into amino acids.
  • tRNAs bring the needed amino acids to the ribosome, using the mRNA as a guide, to assemble into a protein.

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Description

This quiz covers the essential concepts of nucleic acids, including their structure and function, as well as the processes of DNA replication. It explores the components of nucleotides, the roles of DNA and RNA, and the mechanisms of transcription and translation. Test your understanding of how genetic material is preserved and expressed in living organisms.

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