Biology Chapter: DNA Structure and Function
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Questions and Answers

What role do the nitrogenous bases play in DNA?

  • They bind to water molecules.
  • They form the sugar backbone.
  • They act as the energy source.
  • They determine the genetic code. (correct)

Which sugar is present in the backbone of the DNA molecule?

  • Deoxyribose (correct)
  • Glucose
  • Fructose
  • Ribose

Which bases are classified as purines in DNA?

  • Cytosine and Thymine
  • Adenine and Guanine (correct)
  • Cytosine and Guanine
  • Adenine and Thymine

What type of bond holds the two strands of DNA together?

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

According to Chargaff's rules, which of the following ratios is accurate?

<p>A=T; C=G (A)</p> Signup and view all the answers

What is the overall shape of a DNA molecule?

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

How many nucleotides make up a single turn of the DNA helix?

<p>10 nucleotides (C)</p> Signup and view all the answers

In the DNA structure, what components form the backbone?

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

What fundamental structure of DNA was discovered by Watson and Crick in 1953?

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

What are the building blocks of DNA composed of?

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

Which nitrogen bases pair together in DNA?

<p>A with T (D)</p> Signup and view all the answers

What significant discovery did Barbara McClintock make?

<p>Mobility of genes (D)</p> Signup and view all the answers

What did Rosalind Franklin contribute to DNA research?

<p>X-ray crystallography images of DNA (B)</p> Signup and view all the answers

Which component of a nucleotide is absent?

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

What aspect of DNA did Chargaff's Rules reveal?

<p>The same quantity of adenine and thymine (A)</p> Signup and view all the answers

What is the visual representation of DNA structure commonly likened to?

<p>A twisted ladder (C)</p> Signup and view all the answers

Who first discovered DNA?

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

Which of the following correctly lists the bases identified by Phoebus Levene in DNA?

<p>Adenine, thymine, cytosine, guanine (D)</p> Signup and view all the answers

What did Oswald Avery first outline about DNA in 1944?

<p>It is the transforming principle of cells. (D)</p> Signup and view all the answers

What major contribution did Erwin Chargaff make regarding DNA?

<p>He proved that DNA varies between species. (D)</p> Signup and view all the answers

In which year did Sir Archibald Edward Garrod publish his findings on recessive inheritance?

<p>1902 (B)</p> Signup and view all the answers

Which sugar molecule is a component of DNA?

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

Which scientist was known for associating Mendel's theories with a human disease?

<p>Sir Archibald Edward Garrod (B)</p> Signup and view all the answers

Which of the following statements about Watson and Crick is true?

<p>They discovered DNA's double helix structure. (A)</p> Signup and view all the answers

What conclusion can be drawn from the similarity in nitrogenous base proportions in thymus and sperm DNA?

<p>Certain DNA characteristics are conserved across different tissues (C)</p> Signup and view all the answers

Which statement best reflects the implications of the findings about DNA in different tissues?

<p>DNA from different sources can behave in the same way (C)</p> Signup and view all the answers

What might be a reason to explore more about DNA proportions in human tissues?

<p>To understand cancer development better (B)</p> Signup and view all the answers

Which type of publication did the content refer to for a deeper understanding of DNA?

<p>Biological textbooks and research articles (B)</p> Signup and view all the answers

What comprises the backbone of a DNA structure?

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

What is a key focus of the references mentioned in the content?

<p>Historical perspective on the discovery of DNA's structure (D)</p> Signup and view all the answers

Which of the following are the four bases that make up a DNA molecule?

<p>Adenine, Thymine, Cytosine, Guanine (A)</p> Signup and view all the answers

What three structures make up a nucleotide?

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

Why is the sequence of bases in DNA significant?

<p>It encodes genetic information (C)</p> Signup and view all the answers

What describes the base pairing rules in DNA?

<p>A pairs with T, and C pairs with G (D)</p> Signup and view all the answers

In a DNA molecule where one strand has a sequence of 5' ATG CAG TCT GAT CAT 3', what would be the complementary strand?

<p>3' TAC GTC AGA CTA TAG 5' (B)</p> Signup and view all the answers

If a double-stranded DNA molecule is found to contain 30% adenine, what is the percent composition of guanine?

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

Which statement reflects Chargaff's data about DNA composition?

<p>The proportions of adenine and thymine equal those of guanine and cytosine. (D)</p> Signup and view all the answers

Flashcards

Mendel's Laws and Human Disease

Sir Archibald Edward Garrod, in 1902, was the first to connect Mendel's theories with a human disease by studying recessive inheritance.

DNA Components

Phoebus Levene, in 1939, identified the building blocks of DNA: adenine (A), thymine (T), cytosine (C), guanine (G), deoxyribose sugar, and a phosphate group.

DNA as Transforming Principle

Oswald Avery, in 1944, proved that DNA, not proteins, is responsible for transforming cell properties.

DNA's Role in Heredity

Erwin Chargaff, between 1944 and 1950, discovered that DNA is responsible for heredity and that its composition varies between different species.

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Describe the DNA structure.

DNA's structure is a twisted ladder-like shape, resembling a double helix. It consists of two strands of nucleotides that are intertwined.

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What are nucleotides and their components?

Nucleotides are the building blocks of DNA. Each nucleotide consists of three parts: a sugar molecule, a phosphate group, and a nitrogen base.

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What are the base pairing rules in DNA?

Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C). This specific pairing is crucial for maintaining the DNA structure.

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How are nucleotides connected in DNA?

The sugar and phosphate groups link nucleotides together to form the backbone of each DNA strand. The nitrogen bases link the two strands together.

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What was Rosalind Franklin's contribution to discovering DNA's structure?

Rosalind Franklin's X-ray diffraction images provided crucial evidence for the helical structure of DNA, later confirmed by Watson and Crick.

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Who discovered DNA's double helix structure?

James Watson and Francis Crick are renowned for their groundbreaking discovery of DNA's double helix structure in 1953. This discovery revolutionized our understanding of genetics.

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What are Chargaff's rules?

Erwin Chargaff's research revealed that the amount of adenine (A) always equals the amount of thymine (T), and the amount of guanine (G) always equals the amount of cytosine (C). This is known as Chargaff's rules.

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What are "jumping genes" and who discovered them?

Barbara McClintock discovered "jumping genes", also known as transposons, which are segments of DNA that can move around on a chromosome. This discovery challenged conventional understanding of gene stability.

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DNA Base Proportions in Different Tissues

The proportions of nitrogenous bases in DNA are generally consistent across different tissues within the same organism. This supports the idea that DNA is a universal blueprint for all cells in an organism.

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Chargaff's Rule

Chargaff's rule states that in DNA, the amount of adenine (A) is always equal to the amount of thymine (T), and the amount of guanine (G) is always equal to the amount of cytosine (C). This rule is based on the pairing of bases in the double helix.

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DNA Structure Discovery

The discovery of DNA's structure, specifically the double helix model, revolutionized our understanding of how genetic information is stored and transmitted.

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What are the four nitrogenous bases in DNA?

Adenine (A), thymine (T), cytosine (C) and guanine (G) are the four nitrogenous bases that make up DNA. They are the building blocks of the genetic code.

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What are purines?

Purines are double-ringed nitrogenous bases found in DNA, including adenine (A) and guanine (G).

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What are pyrimidines?

Pyrimidines are single-ringed nitrogenous bases found in DNA, including cytosine (C) and thymine (T).

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What forms the backbone of the DNA molecule?

The sugar molecule, deoxyribose, forms the backbone of the DNA molecule, providing structural support for the genetic code.

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In what direction do the two DNA strands run?

The two strands of DNA run in opposite directions, with one strand oriented from 5' to 3' and the other from 3' to 5'.

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What holds the two strands of DNA together?

Hydrogen bonds form between the complementary nitrogenous bases (A-T and C-G) on the opposite strands of DNA, holding the two strands together.

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What did Erwin Chargaff discover about the nitrogenous bases in DNA?

Erwin Chargaff discovered that the amounts of adenine (A) and thymine (T) are equal in DNA, as are the amounts of cytosine (C) and guanine (G).

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What determines the DNA's instructions?

The order of the nitrogenous bases along the DNA strand determines the genetic code, which provides instructions for building and maintaining an organism.

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What makes up the backbone of DNA?

The backbone of a DNA molecule is made up of alternating sugar (deoxyribose) and phosphate groups. These two components bind together to form a long chain.

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What are the four bases of DNA?

The four nitrogenous bases that make up DNA are adenine (A), thymine (T), guanine (G), and cytosine (C).

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What makes up a nucleotide?

A nucleotide is made up of three parts: a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base.

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Why is the order of bases important?

The order of bases in a DNA molecule is important because it determines the genetic code and the sequence of amino acids in proteins, which are essential for all biological functions.

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Explain the base pairing rules.

The base pairing rules state that adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). This is due to the specific hydrogen bonds that can form between these bases.

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What would be the complementary DNA strand?

The complementary strand would have a sequence of 3' TAC GTC AGA CTA GTA 5'. The base pairing rules are flipped on the complementary strand - A pairs with T and G pairs with C.

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What would be the percentage composition of other bases in a DNA molecule with 30% Adenine?

If a double stranded molecule of DNA contains 30% Adenine, then it would also contain 30% Thymine. Since the total percentage is 100%, the remaining 40% would be equally divided between Guanine and Cytosine, each having 20% composition.

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What did Chargaff discover?

Erwin Chargaff discovered that the amount of adenine in DNA is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine. This is known as Chargaff's rule.

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Study Notes

Biotechnology - DNA History, Structure and Chemistry

  • DNA was discovered by Friedrich Miescher in 1869, but its structure wasn't fully understood until much later.
  • Gregor Mendel, considered the "Father of Genetics", proposed that traits are passed down through generations.
  • Albrecht Kossel identified DNA as a nucleic acid, isolating the nitrogenous bases (adenine, cytosine, guanine, and thymine) crucial to DNA and RNA.
  • Walther Flemming's research on cytology, the study of chromosomes, highlighted the significance of chromosomes in inheritance.
  • The Boveri-Sutton chromosome theory explains how chromosomes carry genetic information across generations.
  • Phoebus Levene identified the components of DNA: deoxyribose sugar, phosphate group, and the bases adenine, guanine, cytosine, and thymine.
  • Oswald Avery highlighted DNA as the transforming principle, establishing DNA as the carrier of genetic information.
  • Erwin Chargaff's rules demonstrated that the base pairings (adenine with thymine, guanine with cytosine) amount to roughly the same ratio in DNA.
  • Rosalind Franklin and Maurice Wilkins used X-ray diffraction to generate images of DNA's structure.
  • Watson and Crick's model utilized Franklin's and Wilkins' data to propose the double helix structure of DNA in 1953.
  • DNA's structure is a double helix, formed from a sugar-phosphate backbone connecting nitrogen base pairs (adenine-thymine, guanine-cytosine). The sequence of these bases carries the genetic code.
  • The order of bases (A, T, C, G) determines the genetic code, and these bases pair up to form the DNA structure.
  • The base ratio (A=T and G=C) is consistent across various living organisms.

Activity 1: Trace and You Will Know

  • The provided text outlines the historical discoveries related to DNA. Scientists like Miescher, Chargaff, Watson, and Crick were key contributors to our understanding of DNA's composition and structure.

Activity 2: DNA Structure - Mastery Unit

  • A diagram of DNA might be included. Students need to label the components (Adenine, Guanine, Cytosine, Thymine, Sugar, Phosphate Backbone, Base Pair, Nitrogenous base).
  • The letters DNA stand for Deoxyribonucleic Acid

Activity 3: Fact or Bluff

  • The activity presents data on base composition in DNA for various organisms and asks students to determine whether statements about the data are correct or not.

Reflection and References

  • The reflection section allows students to reflect on what they have learned.
  • Listed are some of the references used in the material.

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Biotechnology Learning Activity Sheets - DNA History, Structure, and Chemistry - PDF

Description

Test your knowledge of DNA's structure and function with this quiz. Explore the roles of nitrogenous bases, the components of the DNA backbone, and the contributions of key scientists in the discovery of DNA. Challenge yourself with questions about the helical shape and bonding in DNA!

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