Topic 4

• What do both DNA and RNA carry?

  genetic Information
• What is the primary function of DNA?

  To hold genetic information
• What is the role of RNA in relation to DNA?

  To transfer genetic information from DNA to ribosomes
• What are the two types of nucleic acids mentioned?

  DNA and RNA
• What are nucleotides composed of?

  Pentose sugar, nitrogen base, and phosphate group
• What sugar is found in DNA nucleotides?

  Deoxyribose
• What are the organic bases found in DNA?

  Adenine, cytosine, guanine, and thymine
• How are adenine and guanine classified?

  As purine bases
• What sugar is found in RNA nucleotides?

  Ribose
• What are the organic bases found in RNA?

  Adenine, cytosine, guanine, and uracil
• How are thymine, uracil, and cytosine classified?

  As pyrimidine bases
• How do nucleotides join together?

  By phosphodiester bonds formed in condensation reactions
• What structure does a DNA molecule form?

  A double helix
• How are the two polynucleotides in DNA held together?

  By hydrogen bonds between complementary bases
• What is the structure of RNA compared to DNA?

  RNA is a relatively short polynucleotide chain
• What is the order of bases on DNA called?

  The genetic code
• What does each triplet of bases on DNA code for?

  A particular amino acid known as a codon
• What is a gene?

  A sequence of bases on a DNA molecule coding for a sequence of amino acids
• What is the location of a gene called?

  The locus
• What are introns and exons?

  Introns are non-coding sections of DNA, while exons are coding regions
• How many nucleotide bases code for how many different amino acids?

  Four nucleotide bases code for 20 different amino acids
• What conclusion did scientists reach regarding amino acids and triplets?

  Each amino acid is coded for by one or more combinations of triplets
• How many possible triplets are there?

  64 possible triplets
• What does it mean that the genetic code is non-overlapping?

  Each triplet is only read once and does not share bases
• How are genes separated in the genetic code?

  By non-coding repeats of bases
• What does it mean that the genetic code is degenerate?

  More than one triplet codes for the same amino acid
• What are mutations?

  Changes in the base sequence of DNA
• What can a change in the base sequence of DNA affect?

  The amino acid sequence and the protein
• What are two examples of harmful mutations?

  Cystic fibrosis and sickle cell anemia
• What do start and stop codons indicate in the genetic code?

  The beginning and end of protein synthesis
• Where is DNA found in eukaryotic cells?

  In the nucleus
• How is eukaryotic DNA structured?

  Long and linear, associated with histones to form chromosomes
• What are chromosomes visible during?

  Cell division
• What is the role of histones in eukaryotic cells?

  To associate with DNA and form chromosomes
• How many chromosomes do humans have in each cell?

  46 chromosomes
• What is a homologous pair of chromosomes?

  Two chromosomes that carry the same genes but may have different alleles
• What determines the sex of an individual in humans?

  The 23rd chromosome
• What are alleles?

  Alternative forms of the same gene
• How many alleles does an individual inherit from their parents for each gene?

  Two alleles
• What are the two stages of protein synthesis?

  Transcription and translation