genetic variation

• What are the key similarities between eukaryotic and prokaryotic DNA?


  • Both made of DNA nucleotides
  • Contain deoxyribose, phosphate group, nitrogenous base
  • Joined by phosphodiester bonds
• What are the key differences between eukaryotic and prokaryotic DNA?

  • Eukaryotic DNA is longer
  • Eukaryotic DNA is linear; prokaryotic is circular
  • Eukaryotic DNA is associated with histones; prokaryotic is not
• Where is eukaryotic DNA organized?

  In chromosomes within the nucleus
• What is the structure of DNA in mitochondria and chloroplasts?

  They have circular loops of DNA
• What is a gene?

  A sequence of DNA coding for proteins
• What does the term locus refer to?

  The exact position of a gene on a chromosome
• What are the features of the genetic code?

  • Degenerate: multiple triplets for one amino acid
  • Universal: same triplet codes for same amino acid in all organisms
  • Non-overlapping: each base is part of one triplet only
• Why is the genetic code considered degenerate?

  More than one triplet codes for the same amino acid
• How many bases are needed to code for one amino acid?

  Three bases
• What is a codon?

  Three bases on mRNA coding for an amino acid
• What is a start codon?

  Three bases that initiate translation
• What is a stop codon?

  Three bases that end translation
• What is a genome?

  An organism's complete set of genes
• What is a proteome?

  The full range of proteins a cell can produce
• How does the genome differ between species?

  It varies in the number of DNA base pairs
• How many DNA base pairs do humans have?

  Three billion
• What is mRNA?

  A short copy of one gene from DNA
• What is the structure of tRNA?

  It has a clover leaf shape
• What is the role of tRNA in translation?

  Brings specific amino acids to the ribosome
• What are the two main stages of protein synthesis?

  1. Transcription: DNA is copied into mRNA
  2. Translation: mRNA is used to assemble amino acids
• What happens during transcription?

  A complementary mRNA copy of DNA is created
• What enzyme is involved in transcription?

  RNA polymerase
• What is splicing in eukaryotes?

  Removing introns from pre-mRNA
• What is the role of the ribosome in translation?

  Holds tRNA and mRNA together
• What is a peptide bond?

  A bond joining amino acids together
• What is non-disjunction?

  Failure of chromosomes to separate properly
• What are the two types of chromosome mutations?

  1. Polyploidy: change in whole sets of chromosomes
  2. Aneuploidy: change in number of individual chromosomes
• What is polyploidy?

  Change in whole sets of chromosomes
• What is aneuploidy?

  Change in number of individual chromosomes
• How does Down syndrome occur?

  Non-disjunction on chromosome 21
• What happens during non-disjunction in meiosis?

  Chromosomes fail to separate equally
• What is the effect of a frame shift mutation?

  Shifts the reading frame of codons
• What can cause gene mutations?

  Exposure to mutagenic agents
• What are mutagenic agents?

  Agents that increase mutation rates
• What is the role of the Golgi body in protein synthesis?

  Modifies and folds polypeptide chains
• What is the significance of the genetic code being universal?

  Same triplet codes for the same amino acid in all organisms
• What is the advantage of the genetic code being non-overlapping?

  Minimizes harm from point mutations
• What is the role of histones in eukaryotic DNA?

  They help package DNA into chromosomes
• What is the difference between introns and exons?

  Introns do not code for proteins; exons do
• What is the function of a spliceosome?

  To remove introns from pre-mRNA