Biology Chapter 9: What Genes Are
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Questions and Answers

What is the primary mechanism through which errors are minimized during DNA replication?

  • All mistakes are corrected after replication is complete.
  • DNA polymerase proofreads paired bases in real-time. (correct)
  • The replication process occurs in multiple locations simultaneously.
  • Replicated DNA segments are stored separately for comparison.

Which type of mutation involves the exchange of one nucleotide for another?

  • Deletion mutation
  • Insertion mutation
  • Substitution mutation (correct)
  • Frame shift mutation

How do repair proteins contribute to DNA integrity after replication?

  • They ensure that no mutations occur during replication.
  • They eliminate erroneous nucleotides without replacing them.
  • They correct about 99 percent of mismatched bases. (correct)
  • They create additional copies of the DNA for backup.

What effect does a single nucleotide change in DNA have on protein structure?

<p>It can potentially alter the shape and function of the protein. (A)</p> Signup and view all the answers

What type of mutation removal occurs when one nucleotide is deleted from a DNA sequence?

<p>Frame shift mutation (C)</p> Signup and view all the answers

What is the role of complementary base-pairing in DNA replication?

<p>It provides the template for building a new DNA strand. (A)</p> Signup and view all the answers

Which two nitrogenous bases pair together in the DNA double helix?

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

What structure forms the 'sides of the ladder' in a DNA molecule?

<p>Sugars and phosphate groups (C)</p> Signup and view all the answers

How do different alleles of a gene primarily differ from each other?

<p>In their nucleotide sequence. (D)</p> Signup and view all the answers

Which of the following accurately describes the structure of DNA?

<p>A double-stranded spiral structure composed of nucleotides. (D)</p> Signup and view all the answers

What causes mutations in DNA?

<p>Errors during DNA replication. (B)</p> Signup and view all the answers

Which type of mutation involves a substitution of one nucleotide for another?

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

What is the relationship between genes and proteins?

<p>Genes code for the creation of proteins. (A)</p> Signup and view all the answers

What is the primary function of DNA?

<p>To code for proteins (A)</p> Signup and view all the answers

Which of the following describes the correct sequence of structural organization from smallest to largest?

<p>Nucleotides, DNA, gene, chromosome (C)</p> Signup and view all the answers

What describes the process of DNA replication?

<p>The DNA double helix unwinds and new strands form from the original template (C)</p> Signup and view all the answers

Which statement accurately reflects the semi-conservative nature of DNA replication?

<p>Each new DNA molecule consists of one original strand and one newly synthesized strand (D)</p> Signup and view all the answers

How do slight differences in alleles affect the resulting protein product?

<p>They can change the function of the protein produced (D)</p> Signup and view all the answers

What is meant by complementary base pairing in DNA?

<p>The base pairs only match up with identical copies of themselves (A)</p> Signup and view all the answers

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

<p>Interphase - S phase (B)</p> Signup and view all the answers

What feature characterizes alleles for a particular gene?

<p>Alleles contain slightly different nucleotide sequences coding for the same protein (C)</p> Signup and view all the answers

Flashcards

DNA polymerase proofreading

A process where DNA polymerase corrects most errors during DNA replication by editing and fixing incorrect base pairs.

Mutation

A change in the sequence of nucleotides in an organism's DNA, leading to variation.

Point mutation

Mutation affecting only one nucleotide in a sequence.

Sickle cell disease

A blood disorder caused by a single nucleotide difference in the hemoglobin gene, leading to an abnormal hemoglobin shape and concave red blood cells.

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How mutations are minimized

DNA polymerase proofreading and repair proteins correct most errors during DNA replication which together minimizes mutations during DNA copying.

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DNA

Deoxyribonucleic acid; the genetic blueprint that codes for traits.

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Nucleotide

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

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Base Pairing

The specific way nitrogenous bases link up in DNA (A with T, and G with C).

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Allele

Different versions of a gene.

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DNA Sequence

The order of nucleotides (A, T, C, G) in a DNA molecule.

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Gene

A segment of DNA that codes for a protein and determines a specific trait.

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Double Helix

The twisted ladder-like shape of DNA.

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Complementary Base Pairing

A fundamental concept in DNA structure where A always pairs with T, and C always pairs with G.

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Genotype vs. Phenotype

Differences in DNA (genotype) lead to variations in physical traits (phenotype).

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Allele Differences

Slight DNA sequence variations within an allele (form of a gene) lead to protein differences, affecting the trait.

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Chromosome Structure

Chromosomes are DNA organized into a compact structure.

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DNA Replication

Creating identical copies of DNA.

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DNA Replication Timing

DNA replication occurs during the S phase of interphase, before cell division (mitosis).

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DNA Replication Steps

Unwinding, base-pairing, and new strand synthesis.

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Semiconservative Replication

Each new DNA molecule has one original and one new strand.

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Study Notes

Chapter 9: What Genes Are

  • DNA is deoxyribonucleic acid, our genetic blueprint, which codes for aspects of who we are.
  • DNA contains genes that code for proteins.
  • Alleles are different versions of a gene.
  • Nucleotides are the building blocks of nucleic acids.
  • DNA is a huge, double-stranded molecule made of nucleotides.

Nucleotides

  • Each nucleotide has three parts: a sugar (deoxyribose), a phosphate group, and a nitrogenous base.
  • Nitrogenous bases in DNA include Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
  • A pairs with T, and C pairs with G.

DNA Structure

  • The two strands of DNA are connected by bonds linking the nucleotide base pairs.
  • The DNA double helix is a twisted, ladder-like structure.
  • Nucleotides are linked together by covalent bonds to form one strand.
  • The two strands are held together by hydrogen bonds between the complementary bases.

DNA Sequencing

  • The sequence of bases on a DNA strand varies among species, subtypes within a species, and individuals within a species.

Gene Structure and Function

  • All genes are composed of just four nucleotides.
  • Information in genes is carried by the order of nucleotides.
  • Variations in the nucleotide order in different genes lead to different proteins and gene products.

DNA Replication

  • DNA replication is the duplication of a DNA molecule.
  • This happens during the S phase (synthesis phase) of interphase in the cell cycle.
  • DNA replication is semiconservative, meaning each new DNA molecule contains one strand from the original molecule and one newly synthesized strand.
  • The process begins at specific locations called "origins of replication".
  • DNA polymerase is the key enzyme involved.

Mutation Corrections

  • DNA polymerase proofreading is a system used to correct mistakes during replication.
  • Repair proteins correct the vast majority of mistakes in newly replicated DNA.

Mutations

  • A mutation is a change to the sequence of nucleotides in an organism's DNA.
  • Point mutations occur when a single base is altered in a sequence.
  • Types of point mutations include substitutions (one nucleotide is exchanged for another), insertions (one nucleotide is added), and deletions (one nucleotide is removed).
  • Sickle cell disease is an example of a point mutation affecting hemoglobin.

Review: Chromosome Structure

  • Chromosomes consist of a DNA strand wrapped up and organized into a compact structure.

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Chapter 9: What Genes Are - SCB 101 PDF

Description

Explore the fundamentals of genetics in Chapter 9, focusing on the structure of DNA and its key components like nucleotides and genes. Understand the roles of alleles and how base pairings contribute to the genetic blueprint of living organisms. This chapter delves into the DNA double helix and its importance in genetics.

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