Nucleic Acid & Protein Synthesis Quiz

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Questions and Answers

What is the primary phase during which DNA replication occurs?

  • G2 phase
  • M phase
  • S phase (correct)
  • G1 phase

DNA replication is a completely conservative process.

False (B)

What enzyme is responsible for forming the sugar-phosphate backbone during transcription?

RNA polymerase

During protein synthesis, the first 3 exposed bases on mRNA are known as the _____ codon.

<p>start</p> Signup and view all the answers

Match the following processes with their definitions:

<p>Transcription = Synthesis of mRNA from DNA Translation = Synthesis of protein from mRNA Replication = Duplication of DNA Base pairing = Matching of nucleotides according to A=T, C≡G</p> Signup and view all the answers

Which enzyme is responsible for unwinding DNA during replication?

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

What does it mean that the genetic code is degenerate?

<p>An amino acid can be coded by more than one codon. (C)</p> Signup and view all the answers

What role do tRNA molecules play in translation?

<p>tRNA molecules bring specific amino acids to the ribosome.</p> Signup and view all the answers

The Golgi body modifies and processes the amino acid sequence into its final 3D shape.

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

A base substitution will always lead to a frame shift mutation.

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

Define the term 'allele'.

<p>Different variant of a gene which originally arose by mutation.</p> Signup and view all the answers

A change in the DNA base sequence that can lead to an altered polypeptide is called a __________.

<p>mutation</p> Signup and view all the answers

Match the terms with their definitions:

<p>Gene = Part of DNA molecule coding for one polypeptide Base Insertion = Type of mutation causing a frame shift Base Deletion = Another mutation causing a frame shift Base Substitution = Mutation that may result in a silent effect</p> Signup and view all the answers

Which of the following is a key difference between DNA and RNA?

<p>DNA contains deoxyribose sugar, while RNA contains ribose sugar. (C)</p> Signup and view all the answers

RNA can replicate itself just like DNA.

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

What are the four nitrogen bases found in RNA?

<p>Adenine, Cytosine, Guanine, Uracil</p> Signup and view all the answers

In DNA, thymine pairs with __________.

<p>adenine</p> Signup and view all the answers

Match the nitrogen bases to their classification:

<p>Adenine = Purine Thymine = Pyrimidine Guanine = Purine Cytosine = Pyrimidine</p> Signup and view all the answers

What is the role of hydrogen bonds in the DNA molecule?

<p>They maintain the double helix structure of DNA. (B)</p> Signup and view all the answers

Semiconservative replication results in two new DNA molecules, each containing one parental and one newly synthesized strand.

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

Why is DNA considered stable compared to RNA?

<p>DNA is double-stranded and enclosed inside the nucleus.</p> Signup and view all the answers

What represents the change in the DNA sequence that leads to sickle cell anemia?

<p>Base substitution of 'A' for 'T' (B)</p> Signup and view all the answers

The primary structure of a protein does not change if sickle cell anemia occurs.

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

What is the role of mRNA in protein synthesis?

<p>mRNA codes for the amino acid sequence and brings the genetic information from DNA to the ribosome for translation.</p> Signup and view all the answers

During translation, tRNA carries specific _______ to the ribosome according to the codons on the mRNA.

<p>amino acids</p> Signup and view all the answers

Match the following components with their functions in red blood cell development:

<p>mRNA = Codes for amino acid sequence tRNA = Brings amino acids to the ribosome Golgi body = Modifies proteins Nucleus = Disappears as the cell matures</p> Signup and view all the answers

Which of the following proteins is found in red blood cells and is important for transporting carbon dioxide?

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

The ribosome is where mRNA is transcribed.

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

What happens to the polypeptide chain after its synthesis at the ribosome?

<p>It enters the Golgi body for chemical modification.</p> Signup and view all the answers

Flashcards

DNA

A type of nucleic acid responsible for storing and transmitting genetic information.

RNA

A type of nucleic acid that plays a crucial role in protein synthesis.

Nucleotide

The basic building block of DNA and RNA, composed of a sugar, a phosphate group, and a nitrogenous base.

Purines

Double-ringed nitrogenous bases found in DNA and RNA, including Adenine (A) and Guanine (G).

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Pyrimidines

Single-ringed nitrogenous bases found in DNA and RNA, including Cytosine (C), Thymine (T), and Uracil (U).

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Hydrogen bonds

Weak bonds that hold together the nitrogenous bases in DNA, forming base pairs (A-T and C-G).

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Semiconservative Replication

The process by which a DNA molecule replicates itself, producing two identical DNA molecules, each containing one original strand and one newly synthesized strand.

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Transcription

The process by which DNA's genetic information is copied into RNA, the first step in protein synthesis.

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DNA Replication

The process by which a cell creates an exact copy of its DNA molecule.

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DNA Helicase

The enzyme that unwinds the DNA helix by breaking the hydrogen bonds between complementary base pairs, allowing the strands to separate.

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Protein synthesis

The process by which a cell uses the information encoded in DNA to create a protein.

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Translation

The second stage of protein synthesis, where mRNA is used to assemble amino acids into a protein chain.

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Codon

The three-base sequence on mRNA that codes for a specific amino acid.

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Anticodon

The three-base sequence on tRNA that is complementary to a codon on mRNA.

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Peptidyltransferase

The enzyme that catalyzes the formation of peptide bonds between amino acids during translation.

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Degenerate Genetic Code

A genetic code where a single amino acid can be coded by more than one codon. This allows for some flexibility in the DNA sequence without altering the resulting protein.

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Gene Mutation

A change in the DNA sequence that can alter the amino acid sequence of a protein, potentially impacting its function.

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Base Substitution

A type of gene mutation where a single base is replaced with another. It can be silent (no change in amino acid), missense (change in amino acid), or nonsense (early stop codon).

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Frameshift Mutation

A change in the reading frame of a gene caused by insertions or deletions of bases. This leads to a completely different protein sequence.

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Red Blood Cell Development

Red blood cells (erythrocytes) are produced in the bone marrow through a process called erythropoiesis. This involves several stages:

  1. Hemoglobin Production: Genes responsible for hemoglobin production unwind, leading to the transcription of mRNA (messenger RNA). This mRNA carries the genetic code for hemoglobin. During translation, ribosomes use this mRNA to synthesize the polypeptide chains of hemoglobin, with the help of transfer RNA (tRNA) molecules that bring specific amino acids according to the codons on mRNA.

  2. Iron Incorporation: The polypeptide chains are then processed and chemically modified in the Golgi apparatus, where iron ions (Fe2+) are added to form functional hemoglobin.

  3. Formation of Carbonic Anhydrase: The gene coding for carbonic anhydrase also unwinds, producing mRNA for this important enzyme. Carbonic anhydrase, essential for transporting carbon dioxide in blood, is incorporated into the developing red blood cell.

  4. Nucleus Disintegration and Shape: Finally, as the red blood cell matures, its nucleus disintegrates, giving the cell its characteristic biconcave shape.

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Sickle Cell Anemia: Genetic Cause

Sickle cell anemia is a genetic disorder caused by a mutation in the gene that produces beta-globin, a protein component of hemoglobin. This mutation, a single nucleotide change, leads to a change in the amino acid sequence of the beta-globin chain, altering the structure of hemoglobin.

The specific mutation is a substitution of adenine (A) for thymine (T) at a particular position in the DNA sequence. This changes the codon (coding for a specific amino acid) from 'CTT' to 'CAT'. During transcription, the mRNA will have a different codon 'GUA' instead of 'GAA'. During translation, this results in the replacement of glutamic acid (glutamine) with valine.

This change in the amino acid sequence of the beta-globin chain affects the overall structure of hemoglobin, causing it to fold into a sickle shape under low oxygen conditions. Sickle cells are rigid and can clog blood vessels, leading to various health complications.

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Role of Messenger RNA (mRNA)

Messenger RNA (mRNA) plays a crucial role in protein synthesis by carrying the genetic information from DNA to the ribosomes, where proteins are made. Here's its key role:

  1. Codes for Amino Acid Sequence: mRNA carries the genetic code for a specific protein, dictating the order of amino acids in the polypeptide chain, which will fold into the final protein structure.

  2. Transcription: During transcription, mRNA is synthesized as a complementary copy of a gene in the DNA, with the same sequence but with uracil (U) replacing thymine (T) in the base pairing.

  3. Translation: mRNA binds to ribosomes, where the codons on mRNA are recognized by tRNA molecules carrying the correct amino acids, leading to the creation of a polypeptide chain.

  4. Start and Stop Codon: Each mRNA molecule has a start codon (AUG) and stop codon, signaling the beginning and end of the protein sequence.

  5. Production of Multiple Proteins: One mRNA molecule can be translated many times, allowing the production of multiple protein molecules.

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Study Notes

Nucleic Acid and Protein Synthesis

  • DNA and RNA Similarities: Both have four types of bases and pentose sugars in their structure. Both are long polymers made of nucleotides bonded by phosphodiester bonds.

  • DNA and RNA Differences: DNA has deoxyribose sugar (less oxygen), is double-stranded, can replicate, and is more stable. DNA bases are A, G, C, and T. RNA has ribose sugar (more oxygen), is single-stranded, cannot replicate, and is less stable. RNA bases are A, G, C, and U (uracil replaces thymine).

Nitrogen Bases

  • Type 1: Purines (double rings) - Adenine and guanine.
  • Type 2: Pyrimidines (single ring) - Thymine, uracil, and cytosine.

Hydrogen Bonds and Base Pairing

  • Importance: Maintain the 3D shape of DNA (double helix) and make it stable. Responsible for genetic stability and the formation of two genetically identical daughter cells. Base pairing allows DNA replication.

DNA Stability

  • Double-stranded structure: DNA's double helix is stabilized by the base pairing rule (A-T, C-G)
  • Protection: DNA is protected and enclosed within the nucleus.

DNA's Role in Genetic Information Storage

  • Stability enables replication: The stability of DNA allows it to replicate and produce proteins.

Semiconservative Replication

  • Template strands: Each parental strand acts as a template for the formation of a new complementary DNA strand. Resulting in two identical copies of the original DNA.

Protein Synthesis

  • Transcription: DNA is transcribed to produce mRNA (messenger RNA), which is a single-stranded nucleotide sequence containing the genetic code for making a protein. This occurs in the nucleus.
  • Translation: The mRNA, carrying the genetic code, moves to ribosomes to direct protein synthesis. Ribosomes assemble the amino acids specified by mRNA codons in the cytoplasm. This process is known as translation.

DNA Replication

  • Semiconservative replication: DNA replication proceeds through a semiconservative process where an original double-stranded DNA molecule replicates into two new double-stranded DNA molecules with one parental DNA strand in each new DNA molecule.
  • Enzymes: Enzymes like DNA helicase and DNA polymerase are involved in unwinding and building the new complementary strands.

Importance of Base Pairing Rule

  • Replication: Allows DNA to replicate and store genetic information.
  • Stability: Maintains the structure and stability of DNA.

Why DNA Can Be Coded by More Than One Codon

  • Degenerate code: The genetic code is degenerate, meaning that more than one codon can code for the same amino acid.

Properties of the Genetic Code

  • Universal: The same triplet genetic code is used in all living organisms.
  • Degenerate: Amino acids can be coded by more than one codon.

Mutations and Gene Effects

  • Gene Mutation: Random and spontaneous changes in the nucleotide sequence. Mutations alter the resulting polypeptide sequence and can affect the protein's function.
  • Effects of gene mutations: Changes in the amino acid sequence of a protein can alter the protein's function and lead to disease (e.g., sickle cell anemia).
  • Frame-shift mutations: These mutations (insertions or deletions) alter the reading frame of mRNA resulting in a different protein and can have significant effects on the protein.

Red Blood Cell Development

  • Hemoglobin synthesis: Genes code for protein synthesis like hemoglobin and other required molecules that allow red blood cells to develop in the bone marrow.
  • mRNA and tRNA: mRNA directs the translation of specific amino acids in the correct order using ribosomes. tRNAs bring the required amino acids to form the protein.

Sickle Cell Anemia

  • Base substitution: A point mutation in the beta-globin gene causes a change in the DNA sequence that results in abnormal hemoglobin.
  • Protein structure: This abnormal hemoglobin affects the shape of red blood cells, making them sickle-shaped.

mRNA Role

  • Coding: mRNA carries the genetic code for a specific protein from DNA to the ribosomes.

tRNA Role

  • Amino acid transport: tRNA molecules transport the correct amino acid to the ribosome during protein synthesis.
  • Anticodon: tRNA has an anticodon that pairs with a complementary codon on mRNA.

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