Protein Synthesis Overview

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Questions and Answers

What characterizes necrosis compared to apoptosis?

  • Necrosis is a controlled process.
  • Necrosis is beneficial for tissue regeneration.
  • Necrosis occurs during normal development.
  • Necrosis usually involves inflammation. (correct)

What is the primary outcome of meiosis?

  • Formation of stem cells for tissue regeneration.
  • Reduction of chromosome number to diploid.
  • Production of two genetically identical cells.
  • Production of four genetically diverse gametes. (correct)

Which phase of meiosis is characterized by the separation of homologous chromosomes?

  • Meiosis II
  • Anaphase II
  • Prophase I
  • Meiosis I (correct)

What role does p53 play in cancer cells with mutations?

<p>p53 regulates the cell cycle and prevents apoptosis in mutated cells. (A)</p> Signup and view all the answers

Which of the following is NOT a result of apoptosis?

<p>Potential tissue damage. (A)</p> Signup and view all the answers

Which option best describes apoptosis?

<p>A programmed and controlled mechanism. (A)</p> Signup and view all the answers

What happens during the elongation stage of translation?

<p>Peptide bonds are formed between amino acids. (A)</p> Signup and view all the answers

During which checkpoint do cells assess DNA integrity before proceeding to division?

<p>G1 Checkpoint (B)</p> Signup and view all the answers

What is the primary role of RNA in protein synthesis?

<p>To facilitate the translation of DNA into proteins (B)</p> Signup and view all the answers

During which stage of protein synthesis does RNA polymerase synthesize a growing mRNA strand?

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

What modification is added to the 5' end of mRNA during processing?

<p>A modified guanine nucleotide (A)</p> Signup and view all the answers

What is the function of the poly-A tail that is added to the 3' end of mRNA?

<p>To enhance mRNA stability and export (B)</p> Signup and view all the answers

Which of the following components is NOT part of a nucleotide in DNA?

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

What signifies the start of transcription in the DNA process?

<p>The binding of RNA polymerase to the promoter (A)</p> Signup and view all the answers

Which stage of transcription involves RNA polymerase synthesizing mRNA by adding complementary RNA nucleotides?

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

Which nitrogenous base is found in RNA but not in DNA?

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

What occurs during the splicing of mRNA?

<p>Introns are removed and exons are joined together. (A)</p> Signup and view all the answers

Which of the following accurately describes the initiation phase of translation?

<p>The small ribosomal subunit binds to the mRNA at the start codon. (A)</p> Signup and view all the answers

What is the function of release factors during translation termination?

<p>To facilitate the release of the polypeptide chain from the ribosome. (B)</p> Signup and view all the answers

In which phase of the cell cycle does DNA replication occur?

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

What role does DNA helicase play in DNA replication?

<p>It unwinds the DNA double helix at origins of replication. (C)</p> Signup and view all the answers

During elongation in translation, where do tRNAs carrying amino acids enter the ribosome?

<p>At the A site. (D)</p> Signup and view all the answers

What is the main outcome of the elongation phase of DNA replication?

<p>New DNA strands are synthesized in a 5' to 3' direction. (D)</p> Signup and view all the answers

What happens to tRNAs after delivering their amino acids in the ribosome?

<p>They move to the E site for exit from the ribosome. (C)</p> Signup and view all the answers

What is the primary difference between the leading and lagging strands during DNA replication?

<p>The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments. (C)</p> Signup and view all the answers

During which phase of mitosis do chromosomes align at the metaphase plate?

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

What occurs in anaphase of mitosis?

<p>Chromatids are pulled apart to opposite poles. (A)</p> Signup and view all the answers

Which checkpoint verifies that DNA replication is complete before entering mitosis?

<p>G2 Checkpoint (C)</p> Signup and view all the answers

What is the role of cyclins and cyclin-dependent kinases (CDKs) in cell division?

<p>They regulate check points for cell division. (A)</p> Signup and view all the answers

Which phase of mitosis is characterized by the reformation of the nuclear envelope?

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

What results from the termination phase of DNA replication?

<p>Two identical DNA molecules, each with one original and one new strand. (C)</p> Signup and view all the answers

At which checkpoint does the cell ensure that all chromosomes are properly aligned before anaphase begins?

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

Flashcards

Protein Synthesis

The process by which cells produce proteins, the building blocks of life that perform countless functions within the body.

DNA (Deoxyribonucleic Acid)

The molecule that carries the genetic blueprint of the cell. It consists of two strands forming a double helix, with each strand made up of nucleotides containing a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases (adenine, thymine, cytosine, guanine).

RNA (Ribonucleic Acid)

A single-stranded molecule that helps translate the genetic code from DNA into proteins. RNA differs from DNA by having ribose as its sugar and uracil instead of thymine.

Transcription

The process of copying a segment of DNA into messenger RNA (mRNA). This occurs in the nucleus.

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Initiation (Transcription)

RNA polymerase binds to the promoter region of the gene, signaling the start of transcription.

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Translation

The process of translating mRNA into a protein, which occurs in the cytoplasm.

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Transcription

The process of converting a segment of DNA into messenger RNA (mRNA). It involves initiation, elongation, and termination.

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Translation

The process of converting messenger RNA (mRNA) into a protein. It takes place in the ribosome.

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DNA Replication

The process of replicating DNA, resulting in two identical DNA molecules.

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Leading Strand

The new strand of DNA that is synthesized continuously during DNA replication.

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Lagging Strand

The new strand of DNA that is synthesized in short fragments called Okazaki fragments during DNA replication.

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Okazaki Fragments

Short fragments of DNA synthesized on the lagging strand during DNA replication.

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DNA Ligase

An enzyme that joins the Okazaki fragments together on the lagging strand during DNA replication.

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Mitosis

The process of cell division that produces two genetically identical daughter cells.

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Prophase

The stage of mitosis where chromosomes condense and become visible, the nuclear envelope breaks down, and the mitotic spindle forms.

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Metaphase

The stage of mitosis where chromosomes line up at the middle of the cell, attached to spindle fibers.

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Splicing

The process of removing non-coding regions (introns) from a pre-mRNA molecule and joining together the coding regions (exons) to produce a mature mRNA molecule.

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Initiation (Translation)

The first stage of translation, where the ribosome, mRNA, and the initiator tRNA converge to form a complex.

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Elongation (Translation)

The second stage of translation, where the existing polypeptide chain at the 'P' site is extended by adding new amino acids to the 'A' site.

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Termination (Translation)

The final stage of translation, where a stop codon signals the completion of protein synthesis, and the ribosome, mRNA, and the protein separate.

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Initiation (DNA Replication)

The initial step of DNA replication, involving the unwinding of the DNA double helix and separation of the two strands.

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Elongation (DNA Replication)

The main stage of DNA replication where DNA polymerase adds complementary nucleotides to each template strand, growing new DNA strands in a specific direction.

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Apoptosis: What is it?

A programmed cell death mechanism that allows a cell to die in a controlled manner, preventing damage to its neighbors.

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Apoptosis: What is its role?

Apoptosis plays a crucial role in development, tissue balance, and eliminating damaged or harmful cells.

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Necrosis: What is it?

The uncontrolled death of cells caused by injury, infection, or toxins, leading to inflammation and damage to surrounding tissues.

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What unwinds DNA?

DNA Helicase is the enzyme responsible for unwinding the DNA double helix during DNA replication.

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Chromosomes aligning during mitosis:

During Metaphase of mitosis, chromosomes line up at the metaphase plate, ensuring equal distribution to daughter cells.

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What delivers genetic information to ribosomes?

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes for protein synthesis.

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How does cell damage affect mitosis?

Apoptosis can be triggered when a G1 checkpoint detects damaged DNA, preventing damaged cells from dividing.

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Apoptosis and Cancer: What is the connection?

The failure of apoptosis in cancer cells allows them to grow uncontrollably, leading to tumor formation. Mutations in the p53 gene can make cancer cells resistant to apoptosis.

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Study Notes

Protein Synthesis

  • Protein synthesis is the process cells use to create proteins.
  • It occurs in two stages: transcription and translation.
  • DNA (Deoxyribonucleic Acid) carries genetic information in a double helix structure with four nitrogenous bases: adenine, thymine, cytosine, and guanine.
  • RNA (Ribonucleic Acid) translates DNA's genetic code into proteins. RNA has ribose sugar instead of deoxyribose and uracil instead of thymine.
  • Transcription: a process of copying a DNA segment into messenger RNA (mRNA).
    • Initiation: RNA polymerase binds to the gene's promoter region.
    • Elongation: RNA polymerase moves along the DNA, adding complementary RNA nucleotides.
    • Termination: RNA polymerase reaches a termination sequence, releasing mRNA.
  • Translation: mRNA is decoded into a polypeptide chain, forming a protein.
    • Initiation: Small ribosomal subunit binds to mRNA near the start codon (AUG), initiator tRNA binds.
    • Elongation: tRNA carrying amino acids enter ribosome; peptide bonds form; ribosome moves along mRNA.
    • Termination: Ribosome reaches a stop codon; polypeptide chain released; ribosome subunits dissociate.

mRNA Processing

  • Before translation, mRNA undergoes modifications:
    • 5' capping: protecting from degradation and aiding ribosome binding.
    • Polyadenylation: adding a poly-A tail; enhancing stability and export.
    • Splicing: removing introns (non-coding regions) and joining exons (coding regions).

Cell Division

  • Cell division creates more cells for growth, development, and repair.
  • Two main types: mitosis (somatic cell division) and meiosis (reproductive cell division).

DNA Replication

  • DNA replication creates identical copies of DNA during the S phase.
  • Initiation: DNA helicase unwinds DNA; single-strand binding proteins stabilize.
  • Elongation: DNA polymerase adds complementary nucleotides to each strand; leading strand synthesized continuously; lagging strand in Okazaki fragments.
  • Termination: replication continues until the whole DNA molecule is copied, resulting in two identical DNA molecules.

Mitosis

  • Mitosis is somatic cell division forming two genetically identical daughter cells.
  • Stages: prophase, metaphase, anaphase, telophase, and cytokinesis.
  • Prophase: chromatin condenses, nuclear envelope breaks down, spindle fibers form.
  • Metaphase: chromosomes align at the metaphase plate.
  • Anaphase: sister chromatids separate.
  • Telophase: chromosomes reach poles, decondense, nuclear envelope reforms.
  • Cytokinesis: cytoplasm divides, two daughter cells formed.

Control of Cell Division

  • Cell division is tightly regulated by checkpoints (G1, G2, and M) to ensure proper replication and alignment.
  • G1 checkpoint: ensures the cell is ready for DNA replication.
  • G2 checkpoint: ensures DNA replication was complete.
  • M checkpoint: ensures chromosomes are correctly aligned for separation.

Necrosis and Apoptosis

  • Necrosis: uncontrolled cell death that damages surrounding tissues.
  • Apoptosis: programmed cell death that eliminates damaged or unwanted cells in a controlled manner.

Meiosis

  • Meiosis is reproductive cell division, producing four genetically unique haploid cells from one diploid cell.
  • Meiosis occurs in two rounds (Meiosis I and Meiosis II).
  • Meiosis I: homologous chromosomes separate, reducing the chromosome number from diploid to haploid.
  • Meiosis II: sister chromatids separate, similar to mitosis, resulting in four haploid gametes.

Multiple Choice Questions (MCQs)

  • Question 1: The enzyme responsible for unwinding DNA during replication is DNA helicase.
  • Question 2: Chromosomes align at the metaphase plate during metaphase.
  • Question 3: mRNA carries genetic information from DNA to ribosomes.
  • Question 4: Peptide bond formation between amino acids occurs during translation elongation.
  • Question 5: The G1 checkpoint prevents cells with damaged DNA from entering mitosis.

Clinical Cases (Case 1: Apoptosis and Cancer)

  • p53 gene mutations can lead to cancer cell resistance to apoptosis, causing uncontrolled growth.
  • Apoptosis is essential to prevent uncontrolled cell growth.

Clinical Cases (Case 2: Meiosis and Genetic Disorders)

  • Chromosomal translocations during meiosis disrupt chromosome numbers, leading to miscarriages and genetic disorders.
  • Proper chromosomal segregation during meiosis is crucial to maintain genetic stability.

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Protein Synthesis and Cell Division Notes PDF

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