Radiobiology 4 MCQ
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Questions and Answers

Which of the following accurately describes the role of DNA in protein synthesis?

  • DNA produces enzymes that determine the structure of lipids.
  • DNA sequences dictate the arrangement of amino acids in proteins. (correct)
  • DNA is solely responsible for replicating genetic material.
  • DNA directly synthesizes proteins in the cytoplasm.

What is the consequence of a point mutation resulting in nonsense?

  • It does not affect the protein sequence.
  • It adds an amino acid causing longer proteins.
  • It leads to an incomplete protein due to premature termination. (correct)
  • It enhances the function of the protein.

Which of the following amino acids is coded for by the triplet CAA?

  • Leucine
  • Glutamine (correct)
  • Alanine
  • Valine

What role do enzymes play in biological reactions according to the provided content?

<p>They catalyze reactions and determine cellular function. (A)</p> Signup and view all the answers

What is the primary role of DNA in living organisms?

<p>It controls all the chemical changes in cells. (D)</p> Signup and view all the answers

Which of the following statements about deoxyribose is true?

<p>It lacks one oxygen atom compared to ribose. (B)</p> Signup and view all the answers

Which of the following statements about mutations is false?

<p>Silent mutations change the phenotype of an organism. (D)</p> Signup and view all the answers

Which of these is NOT one of the four common organic bases in DNA?

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

What defines a gene according to the provided information?

<p>A segment of DNA coding for a protein. (C)</p> Signup and view all the answers

How is a nucleotide formed?

<p>From deoxyribose, a phosphate group, and an organic base. (B)</p> Signup and view all the answers

In what way does an insertion mutation affect the reading frame?

<p>It shifts the entire reading frame downstream. (B)</p> Signup and view all the answers

What type of molecule is DNA primarily categorized as?

<p>A very large molecule made of nucleotides. (B)</p> Signup and view all the answers

Which pairing of nitrogenous bases is correct?

<p>Cytosine pairs with Guanine. (A)</p> Signup and view all the answers

In what way can low-energy electrons affect DNA?

<p>They can break a DNA strand by forming a transient molecular anion. (D)</p> Signup and view all the answers

Which type of mutation alters the DNA sequence by removing one or more bases?

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

Which of the following is not a function attributed to DNA?

<p>Directly participating in metabolic reactions. (A)</p> Signup and view all the answers

Why are some amino acids considered more radiosensitive than others?

<p>Due to structural differences that affect stability. (B)</p> Signup and view all the answers

What are the components of a nucleotide?

<p>A sugar, a phosphate group, and an organic base. (B)</p> Signup and view all the answers

What is a characteristic feature of ribose compared to deoxyribose?

<p>It contains an extra oxygen atom. (C)</p> Signup and view all the answers

How do transient molecular anions relate to the stability of DNA?

<p>They contribute to the degradation of DNA strands. (A)</p> Signup and view all the answers

What type of damage do low-energy electrons primarily cause within DNA?

<p>Indirect clustered damage (A)</p> Signup and view all the answers

What is the mean free path range of low-energy electrons in nanometers?

<p>0.1 to 10 nm (B)</p> Signup and view all the answers

Which type of bond is specifically formed between Adenine and Thymine in DNA?

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

Which component of DNA forms the backbone of its structure?

<p>Sugar-phosphate chains (D)</p> Signup and view all the answers

Cytosine forms bonds with which nitrogenous base?

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

What type of radicals contribute mostly to radiation damage?

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

Which of the following represents a primary structural feature of double-stranded DNA?

<p>Two intertwined strands (B)</p> Signup and view all the answers

Which functional groups allow Adenine and Thymine to pair effectively?

<p>-NH and -OH groups (D)</p> Signup and view all the answers

Clustered damage within DNA primarily results from which particle?

<p>Low-energy electrons (B)</p> Signup and view all the answers

Why do Adenine and Thymine specifically bond together?

<p>They have a favorable spatial configuration for bonding. (B)</p> Signup and view all the answers

Flashcards

What is DNA?

Deoxyribonucleic acid, a complex molecule found in the nucleus of all living cells, responsible for controlling the chemical processes within cells and determining the characteristics of an organism.

Describe the structure of a DNA molecule.

A very large molecule composed of a chain of sub-units called nucleotides.

What is a nucleotide?

A component of DNA, consisting of a sugar called deoxyribose, a phosphate group, and an organic base.

What is deoxyribose?

A five-carbon sugar found in DNA, similar to glucose but with one less oxygen atom.

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What are the organic bases in DNA?

Organic molecules that form part of nucleotides, contributing to DNA's genetic code.

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Name the four common organic bases in DNA.

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G) are the four common organic bases found in DNA.

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What is DNA damage?

The process by which DNA is damaged or altered, potentially leading to mutations and changes in a cell's function.

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How can low-energy electrons (LEEs) damage DNA?

Low-energy electrons (LEEs) are electrons with energy below 15 eV. They can damage DNA by breaking a DNA strand through a process involving transient molecular anions (TMAs).

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What is a transient molecular anion (TMA)?

A temporary negatively charged molecule formed when an LEE attaches to a DNA subunit such as a base, deoxyribose, phosphate, or water molecule.

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How do transient molecular anions (TMAs) decay and cause DNA damage?

The decay of a transient molecular anion (TMA) can lead to bond dissociation and DNA damage. This decay can occur either through autoionization or dissociation.

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Mean Free Path

The average distance a particle travels before interacting with something.

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Indirect Radiation Damage

A type of damage caused by radiation where free radicals and electrons directly interact with DNA.

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Nucleotide

The building blocks of DNA, composed of a sugar, a phosphate group, and a nitrogenous base.

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Sugar-Phosphate Backbone

The backbone of DNA, composed of alternating sugar and phosphate groups.

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Double-Stranded DNA

The two strands of DNA are held together by hydrogen bonds between the nitrogenous bases.

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Base Pairing Rules

Adenine always pairs with Thymine, and Cytosine always pairs with Guanine in DNA.

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Electron-Induced Damage

Damage to DNA caused by the direct interaction of electrons with DNA.

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Joining Nucleotides

The process of forming a long chain of nucleotides to create a DNA molecule.

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Bonding in DNA

The process of forming hydrogen bonds between complementary bases in DNA.

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Why Adenine Pairs with Thymine

The specific chemical structure of Adenine and Thymine allows them to form hydrogen bonds.

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What is the genetic code and how does it work?

The sequence of bases in a DNA molecule forms the genetic code. Each group of three bases, called a triplet, controls the production of a specific amino acid in the cell's cytoplasm.

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Describe the structure of DNA.

DNA is a double helix structure composed of two chains of nucleotides. Each nucleotide has a sugar (deoxyribose), a phosphate group, and a nitrogenous base. The bases pair up in a specific way: adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G).

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What is a mutation and how is it caused?

A mutation is a change in the DNA sequence of an organism. It can occur due to different factors like exposure to radiation or chemicals. It can be silent, meaning it doesn't affect the organism's phenotype, or it can result in a change in the organism's phenotype, like a disease.

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What is a point mutation?

A point mutation is a change in a single base in a DNA sequence. This can lead to a change in the amino acid sequence of the protein, affecting its function.

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What is a missense mutation?

A point mutation that changes the amino acid sequence but does not affect the function of the protein.

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What is a nonsense mutation?

A point mutation that changes the amino acid sequence and alters the protein function, often rendering it inactive or non-functional.

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What is an insertion mutation?

An insertion mutation occurs when one or more base pairs are added to a DNA sequence. This can shift the reading frame, leading to an incorrect amino acid sequence and altered protein function.

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What is a deletion mutation?

A deletion mutation occurs when one or more base pairs are removed from a DNA sequence. Like an insertion, it alters the reading frame, leading to a wrong amino acid sequence and aberrant protein.

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What is a gene?

A gene is a segment of DNA that codes for a specific protein. It contains a sequence of base triplets that are transcribed into mRNA and translated into a specific amino acid chain, resulting in a functional protein.

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How does DNA control cellular function?

DNA controls the production of enzymes, which in turn determine the chemical reactions within a cell. This control over enzymes ultimately determines what kind of cell it is and what function it performs.

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Study Notes

DNA Structure and Function

  • DNA stands for deoxyribose nucleic acid
  • DNA is a large molecule made of a long chain of subunits called nucleotides
  • Each nucleotide is composed of a sugar (deoxyribose), a phosphate group (-PO4), and an organic base
  • Ribose is a sugar similar to glucose but with only five carbon atoms
  • Deoxyribose is almost the same as ribose but lacks one oxygen atom
  • The most common organic bases are adenine (A), thymine (T), cytosine (C), and guanine (G)
  • Deoxyribose, phosphate, and a base combine to form a nucleotide
  • DNA is typically a double-stranded molecule
  • The sugar-phosphate chains are on the outside of the double helix and held together by chemical bonds between the bases
  • Adenine always pairs with Thymine, and Cytosine always pairs with Guanine

DNA Mutations

  • A mutation is a change in an organism's DNA
  • Mutations in germ cells (sperm and eggs) are passed on to offspring
  • Mutations in somatic (body) cells can be harmless or cause disease like cancer
  • Silent mutations don't affect the organism's phenotype
  • Chromosome mutations include deletion, duplication, inversion, insertion, and translocation
  • Point mutations are changes in a single nucleotide
    • Nonsense mutations create a premature stop codon, shortening the protein
    • Missense mutations change one amino acid to another, potentially affecting protein function
    • Insertion mutations add one or more nucleotides
    • Deletion mutations remove one or more nucleotides
  • These mutations alter the sequence of amino acids in a protein, which can lead to production of non-functional or faulty proteins

DNA and Enzymes

  • Proteins build cell structures and make enzymes
  • DNA controls which enzymes are made, and enzymes determine what reactions happen in the cell
  • DNA exerts control through the enzymes it codes for

Genes

  • A sequence of triplets in the DNA molecule may code for a complete protein.
  • Such a sequence forms a gene
  • A gene may contain thousands or more bases

Additional Information

  • In aqueous solutions, some amino acids (e.g., methionine, cystine) are more radiosensitive, compared to others (e.g., tyrosine, alanine)

  • The mean free path of the majority of LEEs (Low Energy Electrons) varies from 0.1 to 10 nm, potentially causing clustered damage within DNA

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Mutations 4th Lecture PDF

Description

Test your knowledge on the structure and function of DNA, including its components such as nucleotides and the double helix formation. Additionally, explore the concept of DNA mutations, their types, and implications for organisms. This quiz is essential for understanding fundamental genetics.

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