dna replication cytogen
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Questions and Answers

What is the full name of DNA?

  • Deoxyribonucleic acid (correct)
  • Chromosomal acid
  • Helix acid
  • Ribonucleic acid

    • What are the thread-like structures containing DNA and proteins within the cell?

  • Nucleotides
  • Chromosomes (correct)
  • Pentose sugars
  • Genes

    • What is the shape of the DNA molecule?

  • Square
  • Circle
  • Helix (correct)
  • Spiral

    • What are the specific sequences of nucleotides that encode instructions for the synthesis of proteins?

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

    Which of the following is NOT a nitrogenous base found in DNA?

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

    What is the function of the phosphate group in a nucleotide?

    <p>Forms the backbone of the nucleic acid structure</p> Signup and view all the answers

    What is the type of sugar found in DNA?

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

    What is the result of the base pairing in DNA?

    <p>A with T and C with G</p> Signup and view all the answers

    What is the structure of pyrimidines?

    <p>A six-membered single-ring structure</p> Signup and view all the answers

    Which nitrogenous bases are purines?

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

    What is the function of ribose in RNA?

    <p>To carry out cellular processes</p> Signup and view all the answers

    What is the difference between ribose and deoxyribose?

    <p>Ribose has a hydroxyl group at the 2' carbon, while deoxyribose has a hydrogen atom</p> Signup and view all the answers

    What is the process of forming a nucleotide?

    <p>Base + Sugar → Nucleoside, Nucleoside + Phosphate → Nucleotide</p> Signup and view all the answers

    What is the structure of purines?

    <p>A nine-membered double-ring structure</p> Signup and view all the answers

    Which nitrogenous bases are pyrimidines?

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

    What is the function of deoxyribose in DNA?

    <p>To carry genetic information</p> Signup and view all the answers

    What is the result of adding a phosphate group to a nucleoside?

    <p>A nucleotide</p> Signup and view all the answers

    What is the purpose of the hydroxyl group in ribose?

    <p>To make RNA more prone to hydrolysis</p> Signup and view all the answers

    What is the primary reason for the difference in stability between RNA and DNA?

    <p>The absence of a hydroxyl group in deoxyribose</p> Signup and view all the answers

    What is the key component that distinguishes a nucleoside from a nucleotide?

    <p>Phosphate group</p> Signup and view all the answers

    Which of the following is NOT a characteristic of pyrimidines?

    <p>Double-ring structure</p> Signup and view all the answers

    What is the purpose of the hydrogen bonds between nitrogenous bases in the DNA double helix?

    <p>To maintain the stability of the double helix</p> Signup and view all the answers

    Which of the following nitrogenous bases is found only in RNA?

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

    What is the consequence of the absence of a hydroxyl group in deoxyribose?

    <p>Increased stability of DNA</p> Signup and view all the answers

    Which of the following is a characteristic of purines?

    <p>Double-ring structure</p> Signup and view all the answers

    What is the result of adding a phosphate group to a nucleoside?

    <p>Formation of a nucleotide</p> Signup and view all the answers

    What is the primary function of ribose in RNA?

    <p>To provide structural support to the RNA molecule</p> Signup and view all the answers

    Which of the following is a characteristic of both RNA and DNA?

    <p>Presence of a pentose sugar</p> Signup and view all the answers

    What is the primary function of genes in the DNA molecule?

    <p>To encode instructions for the synthesis of proteins</p> Signup and view all the answers

    What is the term for the bond that forms between the phosphate group and the pentose sugar in a nucleotide?

    <p>Covalent bond</p> Signup and view all the answers

    What is the significance of the nitrogenous base in a nucleotide?

    <p>It determines the nucleotide's identity</p> Signup and view all the answers

    What is the term for the process of forming a nucleotide by linking the phosphate group, pentose sugar, and nitrogenous base together?

    <p>Dehydration synthesis</p> Signup and view all the answers

    What is the result of the base pairing in DNA?

    <p>A double helix structure</p> Signup and view all the answers

    What is the term for the five-carbon sugar found in RNA?

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

    What is the primary component of chromosomes?

    <p>DNA and proteins</p> Signup and view all the answers

    What is the term for the long chains of nucleic acids formed by linking nucleotides together?

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

    What is the primary component of a nucleoside?

    <p>A nitrogenous base and a pentose sugar</p> Signup and view all the answers

    Which of the following is an example of a ribonucleoside?

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

    What is the difference between a nucleoside and a nucleotide?

    <p>The presence of a phosphate group</p> Signup and view all the answers

    Which of the following is a characteristic of deoxyribonucleosides?

    <p>Contain deoxyribose as the pentose sugar</p> Signup and view all the answers

    What is the purpose of the phosphate group in a nucleotide?

    <p>To form a bond with the pentose sugar</p> Signup and view all the answers

    Which of the following is an example of a deoxyribonucleotide?

    <p>Deoxyadenylic acid</p> Signup and view all the answers

    What is the difference between ribose and deoxyribose?

    <p>The presence of a hydroxyl group on the 2' carbon</p> Signup and view all the answers

    Which of the following is a characteristic of nucleotides?

    <p>Contain a nitrogenous base, a pentose sugar, and a phosphate group</p> Signup and view all the answers

    What is the key difference between deoxyribose and ribose?

    <p>The presence or absence of a hydroxyl group at the 2' position</p> Signup and view all the answers

    What is the purpose of nucleoside triphosphates (NTPs) in cellular metabolism?

    <p>To provide energy for various biochemical processes</p> Signup and view all the answers

    What is the result of phosphorylating deoxythymidine diphosphate (dTDP)?

    <p>The formation of dTTP</p> Signup and view all the answers

    What is the directionality of the phosphodiester bond in a polynucleotide chain?

    <p>5' to 3'</p> Signup and view all the answers

    What is the primary component of deoxynucleoside diphosphates (dNDPs)?

    <p>A nitrogenous base, a deoxyribose sugar, and one or more phosphate groups</p> Signup and view all the answers

    What is the function of the phosphodiester bond in a polynucleotide chain?

    <p>To link nucleotides together to form a polynucleotide chain</p> Signup and view all the answers

    What is the result of the addition of another phosphate group to a deoxynucleoside diphosphate (dNDP)?

    <p>The formation of a deoxynucleoside triphosphate (dNTP)</p> Signup and view all the answers

    What is the characteristic of nucleoside triphosphates (NTPs) that distinguishes them from deoxynucleoside diphosphates (dNDPs)?

    <p>The number of phosphate groups</p> Signup and view all the answers

    What is the result of the linkage between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next?

    <p>The formation of a phosphodiester bond</p> Signup and view all the answers

    What is the primary function of ATP in cellular metabolism?

    <p>To provide energy for various biochemical processes</p> Signup and view all the answers

    What is the primary function of the phosphodiester bond in DNA?

    <p>To link the 3' carbon of one nucleotide's sugar to the 5' phosphate of the next nucleotide</p> Signup and view all the answers

    What is the significance of the 5' to 3' direction in DNA?

    <p>It indicates the sequence of nucleotides</p> Signup and view all the answers

    What is the main difference between the sugar molecules in DNA and RNA?

    <p>The presence or absence of a hydroxyl group</p> Signup and view all the answers

    What is the result of the base pairing in DNA?

    <p>The formation of the rungs of the DNA ladder</p> Signup and view all the answers

    What is the basis for the complementarity of DNA strands?

    <p>The specific A-T and C-G pairing</p> Signup and view all the answers

    What is the significance of the major and minor grooves in DNA?

    <p>They provide a site for protein binding</p> Signup and view all the answers

    What is the result of the proportionality of adenine and thymine residues in DNA?

    <p>The sum of the purines equals the sum of the pyrimidines</p> Signup and view all the answers

    What is the characteristic of the double helix model of DNA?

    <p>The bases of both chains are perpendicular to the axis</p> Signup and view all the answers

    What is the significance of the arrangement of sugars and bases along the axis in the double helix model?

    <p>It is a stabilizing factor for the DNA molecule</p> Signup and view all the answers

    What is the consequence of the antiparallel nature of the two chains in the double helix model?

    <p>The directionality of the DNA strand is reversed</p> Signup and view all the answers

    What is the difference between a nucleoside and a nucleotide?

    <p>A nucleotide has a phosphate group while a nucleoside does not</p> Signup and view all the answers

    Which of the following is an example of a ribonucleoside?

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

    What is the primary component of a nucleoside?

    <p>Nitrogenous base and pentose sugar</p> Signup and view all the answers

    Which of the following is an example of a deoxyribonucleotide?

    <p>Deoxyadenylic acid</p> Signup and view all the answers

    What is the type of sugar found in RNA?

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

    What is the difference between ribose and deoxyribose?

    <p>Ribose has a hydroxyl group on the 2' carbon, while deoxyribose has a hydrogen atom</p> Signup and view all the answers

    Which of the following is a characteristic of nucleotides?

    <p>They are composed of a nitrogenous base, a pentose sugar, and one or more phosphate groups</p> Signup and view all the answers

    Which of the following is a characteristic of deoxyribonucleosides?

    <p>They are composed of a nitrogenous base and deoxyribose sugar</p> Signup and view all the answers

    What is the direction of the polynucleotide chain?

    <p>5' to 3'</p> Signup and view all the answers

    What is the bond that links the 3' carbon of one nucleotide's sugar to the 5' phosphate of the next nucleotide?

    <p>Phosphodiester bond</p> Signup and view all the answers

    What is the composition of the backbone of DNA?

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

    What is the base pairing rule in DNA?

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

    What is the ratio of adenine to thymine residues in DNA?

    <p>1:1</p> Signup and view all the answers

    What is the orientation of the two chains in the DNA double helix?

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

    What is the distance between the bases in the DNA double helix?

    <p>3.4 Å</p> Signup and view all the answers

    What is the result of the base pairing in DNA?

    <p>The formation of a double helix</p> Signup and view all the answers

    What is the primary function of the phosphate group in a nucleotide?

    <p>To form the backbone of DNA</p> Signup and view all the answers

    What is the composition of a nucleotide?

    <p>Sugar, phosphate, and base</p> Signup and view all the answers

    What is the primary function of deoxynucleoside diphosphates (dNDPs)?

    <p>To act as intermediate forms in the synthesis of DNA</p> Signup and view all the answers

    What is the difference between deoxyribose and ribose?

    <p>The presence or absence of a hydroxyl group at the 2' position</p> Signup and view all the answers

    What is the result of phosphorylating deoxythymidine diphosphate (dTDP)?

    <p>The formation of deoxythymidine triphosphate (dTTP)</p> Signup and view all the answers

    What is the purpose of nucleoside triphosphates (NTPs) in cellular metabolism?

    <p>To provide energy for various biochemical processes</p> Signup and view all the answers

    What is the directionality of the phosphodiester bond in a polynucleotide chain?

    <p>From the 5' end to the 3' end</p> Signup and view all the answers

    What is the primary component of deoxynucleoside diphosphates (dNDPs)?

    <p>A combination of a nitrogenous base, a pentose sugar, and two phosphate groups</p> Signup and view all the answers

    What is the function of the phosphodiester bond in a polynucleotide chain?

    <p>To link nucleotides together to form a polynucleotide chain</p> Signup and view all the answers

    What is the primary function of adenosine triphosphate (ATP)?

    <p>To provide energy for various biochemical processes</p> Signup and view all the answers

    What is the difference between a nucleoside and a nucleotide?

    <p>The presence or absence of a phosphate group</p> Signup and view all the answers

    What is the result of the linkage between two nucleotides in a polynucleotide chain?

    <p>The formation of a phosphodiester bond</p> Signup and view all the answers

    What determines the order of the bases in one strand of DNA?

    <p>The order of the bases in the other strand</p> Signup and view all the answers

    What is the function of a gene in DNA?

    <p>To code for a unique protein</p> Signup and view all the answers

    What is the purpose of codons in DNA?

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

    What gives us a unique phenotype?

    <p>The combination of proteins produced by genes</p> Signup and view all the answers

    What is the relationship between the sequence of bases in a gene and the protein it codes for?

    <p>The sequence of bases determines the unique sequence of the protein</p> Signup and view all the answers

    What is the role of codons in DNA?

    <p>To arrange bases in triplets</p> Signup and view all the answers

    What determines the order of the bases in the other strand of DNA?

    <p>The sequence of bases in one strand</p> Signup and view all the answers

    What is the result of the unique sequence of bases in a gene?

    <p>A unique protein</p> Signup and view all the answers

    What is the relationship between genes and proteins?

    <p>A gene codes for a protein</p> Signup and view all the answers

    What is the role of genes in determining an organism's traits?

    <p>They code for unique proteins and combinations of proteins</p> Signup and view all the answers

    Study Notes

    DNA Structure

    • DNA's full name is Deoxyribonucleic acid.
    • The cell is the basic structural unit of living organisms.
    • Chromosomes within the cell contain DNA and proteins.

    DNA Helix

    • DNA has a double helix structure, composed of two strands forming a spiral.
    • The twisted ladder-like shape is composed of nucleotide bases.

    Genes and Nucleotides

    • Genes are specific sequences of nucleotides that encode instructions for protein synthesis.
    • Nucleotides are the building blocks of DNA, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.
    • A molecule of DNA is made up of millions of tiny nucleotides.

    Nucleotide Bases

    • The DNA helix is composed of four nucleotide bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
    • Base pairing occurs in a specific manner: A with T and C with G.

    Nucleotide Components

    • A phosphate group is attached to the pentose sugar and forms the backbone of the nucleic acid structure.
    • Pentose sugar can be either ribose (in RNA) or deoxyribose (in DNA).
    • Nitrogenous bases can be one of several types, including adenine (A), guanine (G), cytosine (C), thymine (T) in DNA, or uracil (U) in RNA.

    Nitrogenous Bases

    • There are two types of nitrogenous bases: Pyrimidines and Purines.
    • Pyrimidines have a six-membered single-ring structure and include cytosine (C), thymine (T), and uracil (U).
    • Purines have a nine-membered double-ring structure and include adenine (A) and guanine (G).

    Pentose Sugars

    • Ribose is found in RNA and has a hydroxyl group (-OH) at the 2' carbon.
    • Deoxyribose is found in DNA and lacks the hydroxyl group (-OH) at the 2' carbon, instead having a hydrogen atom (H).

    RNA and DNA

    • RNA (Ribonucleic Acid) contains ribose and is involved in protein synthesis and various cellular processes.
    • DNA (Deoxyribonucleic Acid) contains deoxyribose and carries genetic information crucial for inheritance and cellular function.

    Nucleotide Formation

    • A nucleoside is formed when a nitrogenous base is attached to a pentose sugar (ribose or deoxyribose).
    • A nucleotide is formed when a phosphate group is added to a nucleoside.
    • The process can be summarized as: Base + Sugar → Nucleoside, and Nucleoside + Phosphate → Nucleotide.

    DNA Structure

    • DNA's full name is Deoxyribonucleic acid.
    • The cell is the basic structural unit of living organisms.
    • Chromosomes within the cell contain DNA and proteins.

    DNA Helix

    • DNA has a double helix structure, composed of two strands forming a spiral.
    • The twisted ladder-like shape is composed of nucleotide bases.

    Genes and Nucleotides

    • Genes are specific sequences of nucleotides that encode instructions for protein synthesis.
    • Nucleotides are the building blocks of DNA, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.
    • A molecule of DNA is made up of millions of tiny nucleotides.

    Nucleotide Bases

    • The DNA helix is composed of four nucleotide bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
    • Base pairing occurs in a specific manner: A with T and C with G.

    Nucleotide Components

    • A phosphate group is attached to the pentose sugar and forms the backbone of the nucleic acid structure.
    • Pentose sugar can be either ribose (in RNA) or deoxyribose (in DNA).
    • Nitrogenous bases can be one of several types, including adenine (A), guanine (G), cytosine (C), thymine (T) in DNA, or uracil (U) in RNA.

    Nitrogenous Bases

    • There are two types of nitrogenous bases: Pyrimidines and Purines.
    • Pyrimidines have a six-membered single-ring structure and include cytosine (C), thymine (T), and uracil (U).
    • Purines have a nine-membered double-ring structure and include adenine (A) and guanine (G).

    Pentose Sugars

    • Ribose is found in RNA and has a hydroxyl group (-OH) at the 2' carbon.
    • Deoxyribose is found in DNA and lacks the hydroxyl group (-OH) at the 2' carbon, instead having a hydrogen atom (H).

    RNA and DNA

    • RNA (Ribonucleic Acid) contains ribose and is involved in protein synthesis and various cellular processes.
    • DNA (Deoxyribonucleic Acid) contains deoxyribose and carries genetic information crucial for inheritance and cellular function.

    Nucleotide Formation

    • A nucleoside is formed when a nitrogenous base is attached to a pentose sugar (ribose or deoxyribose).
    • A nucleotide is formed when a phosphate group is added to a nucleoside.
    • The process can be summarized as: Base + Sugar → Nucleoside, and Nucleoside + Phosphate → Nucleotide.

    Nucleotides and Nucleosides

    • Nucleotides consist of a nitrogenous base, a pentose sugar, and one or more phosphate groups.
    • Nucleosides consist of a nitrogenous base attached to a pentose sugar.
    • Examples of nucleosides:
      • Uridine (uracil + ribose)
      • Deoxyadenosine (adenine + deoxyribose)
    • Examples of nucleotides:
      • Deoxyadenylic acid (adenine + deoxyribose + phosphate group)
      • Adenylic acid (adenine + ribose + phosphate group)

    Classification of Nucleotides and Nucleosides

    • Ribonucleosides (RNA components):
      • Adenosine (adenine + ribose)
      • Cytidine (cytosine + ribose)
      • Guanosine (guanine + ribose)
      • Uridine (uracil + ribose)
    • Ribonucleotides (RNA components):
      • Adenylic acid (AMP)
      • Cytidylic acid (CMP)
      • Guanylic acid (GMP)
      • Uridylic acid (UMP)
    • Deoxyribonucleosides (DNA components):
      • Deoxyadenosine (adenine + deoxyribose)
      • Deoxycytidine (cytosine + deoxyribose)
      • Deoxyguanosine (guanine + deoxyribose)
      • Deoxythymidine (thymine + deoxyribose)
    • Deoxyribonucleotides (DNA components):
      • Deoxyadenylic acid (dAMP)
      • Deoxycytidylic acid (dCMP)
      • Deoxyguanylic acid (dGMP)
      • Deoxythymidylic acid (dTMP)

    Key Components and Structures of Nucleotides

    • Deoxynucleoside diphosphates (dNDPs):
      • Example: Deoxythymidine diphosphate (dTDP)
      • Components: Thymine (pyrimidine), deoxyribose, and two phosphate groups
      • Structure: Two phosphate groups attached to the 5' carbon of the deoxyribose sugar
    • Nucleoside triphosphates (NTPs):
      • Example: Adenosine triphosphate (ATP)
      • Components: Adenine (purine), ribose, and three phosphate groups
      • Structure: Three phosphate groups attached to the 5' carbon of the ribose sugar

    Functions of Nucleotides

    • Deoxynucleoside diphosphates (dNDPs):
      • Intermediate forms in the synthesis of DNA
      • Can be converted into deoxynucleoside triphosphates (dNTPs) by the addition of another phosphate group
    • Nucleoside triphosphates (NTPs):
      • Play critical roles in cellular metabolism
      • Example: ATP is the primary energy carrier in cells

    Phosphodiester Bonds and Polynucleotide Chains

    • Phosphodiester bonds:
      • Formed between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next nucleotide
      • Create a linkage from the 3' end of one nucleotide to the 5' end of the next, giving the DNA or RNA strand directionality (5' to 3')
    • Polynucleotide chain:
      • A sequence of nucleotides connected by phosphodiester bonds
      • Forms the structure of DNA or RNA
      • Directionality: 5' to 3' orientation

    Nitrogenous Bases and DNA Structure

    • Nitrogenous bases:
      • Four types: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G)
      • Pair up to form the rungs of the DNA ladder, adhering to specific pairing rules (A pairs with T, and C pairs with G)
    • DNA structure:
      • Backbone: made up of the phosphate and sugar molecules
      • Rungs: made up of nitrogenous bases
      • Base composition studies:
        • The amount of adenine residues is proportional to the amount of thymine residues in DNA
        • The amount of guanine residues is proportional to the amount of cytosine residues
        • The sum of the purines (A + G) equals the sum of the pyrimidines (C + T)

    The Watson-Crick Model

    • Two long polynucleotide chains are coiled around a central axis, forming a right-handed double helix
    • The two chains are antiparallel; that is, their (C-5') to (C-3') orientations run in opposite directions
    • The bases of both chains are flat structures, lying perpendicular to the axis; they are “stacked” on one another, 3.4 Å (0.34 nm) apart, and located on the inside of the structure
    • The nitrogenous bases of opposite chains are paired as the result of hydrogen bonds; in DNA, only A-T and C-G pairs occur
    • Each complete turn of the helix is 34 Å (3.4 nm) long; thus, 10 bases exist per turn in each chain
    • The double helix measures 20 Å (2.0 nm) in diameter

    Nucleotides and Nucleosides

    • Nucleotides consist of a nitrogenous base, a pentose sugar, and one or more phosphate groups.
    • Nucleosides consist of a nitrogenous base attached to a pentose sugar.
    • Examples of nucleosides:
      • Uridine (uracil + ribose)
      • Deoxyadenosine (adenine + deoxyribose)
    • Examples of nucleotides:
      • Deoxyadenylic acid (adenine + deoxyribose + phosphate group)
      • Adenylic acid (adenine + ribose + phosphate group)

    Classification of Nucleotides and Nucleosides

    • Ribonucleosides (RNA components):
      • Adenosine (adenine + ribose)
      • Cytidine (cytosine + ribose)
      • Guanosine (guanine + ribose)
      • Uridine (uracil + ribose)
    • Ribonucleotides (RNA components):
      • Adenylic acid (AMP)
      • Cytidylic acid (CMP)
      • Guanylic acid (GMP)
      • Uridylic acid (UMP)
    • Deoxyribonucleosides (DNA components):
      • Deoxyadenosine (adenine + deoxyribose)
      • Deoxycytidine (cytosine + deoxyribose)
      • Deoxyguanosine (guanine + deoxyribose)
      • Deoxythymidine (thymine + deoxyribose)
    • Deoxyribonucleotides (DNA components):
      • Deoxyadenylic acid (dAMP)
      • Deoxycytidylic acid (dCMP)
      • Deoxyguanylic acid (dGMP)
      • Deoxythymidylic acid (dTMP)

    Key Components and Structures of Nucleotides

    • Deoxynucleoside diphosphates (dNDPs):
      • Example: Deoxythymidine diphosphate (dTDP)
      • Components: Thymine (pyrimidine), deoxyribose, and two phosphate groups
      • Structure: Two phosphate groups attached to the 5' carbon of the deoxyribose sugar
    • Nucleoside triphosphates (NTPs):
      • Example: Adenosine triphosphate (ATP)
      • Components: Adenine (purine), ribose, and three phosphate groups
      • Structure: Three phosphate groups attached to the 5' carbon of the ribose sugar

    Functions of Nucleotides

    • Deoxynucleoside diphosphates (dNDPs):
      • Intermediate forms in the synthesis of DNA
      • Can be converted into deoxynucleoside triphosphates (dNTPs) by the addition of another phosphate group
    • Nucleoside triphosphates (NTPs):
      • Play critical roles in cellular metabolism
      • Example: ATP is the primary energy carrier in cells

    Phosphodiester Bonds and Polynucleotide Chains

    • Phosphodiester bonds:
      • Formed between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next nucleotide
      • Create a linkage from the 3' end of one nucleotide to the 5' end of the next, giving the DNA or RNA strand directionality (5' to 3')
    • Polynucleotide chain:
      • A sequence of nucleotides connected by phosphodiester bonds
      • Forms the structure of DNA or RNA
      • Directionality: 5' to 3' orientation

    Nitrogenous Bases and DNA Structure

    • Nitrogenous bases:
      • Four types: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G)
      • Pair up to form the rungs of the DNA ladder, adhering to specific pairing rules (A pairs with T, and C pairs with G)
    • DNA structure:
      • Backbone: made up of the phosphate and sugar molecules
      • Rungs: made up of nitrogenous bases
      • Base composition studies:
        • The amount of adenine residues is proportional to the amount of thymine residues in DNA
        • The amount of guanine residues is proportional to the amount of cytosine residues
        • The sum of the purines (A + G) equals the sum of the pyrimidines (C + T)

    The Watson-Crick Model

    • Two long polynucleotide chains are coiled around a central axis, forming a right-handed double helix
    • The two chains are antiparallel; that is, their (C-5') to (C-3') orientations run in opposite directions
    • The bases of both chains are flat structures, lying perpendicular to the axis; they are “stacked” on one another, 3.4 Å (0.34 nm) apart, and located on the inside of the structure
    • The nitrogenous bases of opposite chains are paired as the result of hydrogen bonds; in DNA, only A-T and C-G pairs occur
    • Each complete turn of the helix is 34 Å (3.4 nm) long; thus, 10 bases exist per turn in each chain
    • The double helix measures 20 Å (2.0 nm) in diameter

    DNA Structure

    • Complementary base pairing ensures that the order of bases in one strand determines the order of bases in the other strand.
    • The sequence of bases in DNA is crucial for cracking the genetic code.

    Codons

    • Bases are arranged in triplets called codons.
    • Example of codons: A G G - C T C - A A G - T C C - T A G, T C C - G A G - T T C - A G G - A T C.

    Genes and Proteins

    • A gene is a section of DNA that codes for a protein.
    • Each unique gene has a unique sequence of bases.
    • The unique sequence of bases in a gene codes for the production of a unique protein.
    • The combination of proteins produced by genes determines an individual's unique phenotype.

    DNA Structure

    • Complementary base pairing ensures that the order of bases in one strand determines the order of bases in the other strand.
    • The sequence of bases in DNA is crucial for cracking the genetic code.

    Codons

    • Bases are arranged in triplets called codons.
    • Example of codons: A G G - C T C - A A G - T C C - T A G, T C C - G A G - T T C - A G G - A T C.

    Genes and Proteins

    • A gene is a section of DNA that codes for a protein.
    • Each unique gene has a unique sequence of bases.
    • The unique sequence of bases in a gene codes for the production of a unique protein.
    • The combination of proteins produced by genes determines an individual's unique phenotype.

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    Learn about the basic components of a cell, including chromosomes, DNA, and genes. Understand the structure and function of DNA helix.

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