4) Genetic information

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

  • Both are made of DNA nucleotides
  • Both contain deoxyribose, phosphate group, nitrogenous base
  • Nucleotides 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?

  • It is a degenerate code
  • It is universal
  • It is non-overlapping
• Why is the genetic code considered degenerate?

  More than one triplet codes for the same amino acid
• How many possible triplet combinations are there?

  64 possible combinations
• What is a codon?

  A sequence of three bases on mRNA
• What is the role of introns in DNA?

  They do not code for polypeptides
• 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
• What is the structure of mRNA?

  It is single-stranded and shorter than DNA
• Where is mRNA found in the cell?

  In both the cytoplasm and the nucleus
• What is the role of tRNA?

  To transfer amino acids during translation
• What shape does tRNA have?

  A clover leaf shape
• What are the key steps in transcription?

  1. DNA helix unwinds
  2. One strand acts as a template
  3. RNA nucleotides align opposite DNA bases
  4. RNA polymerase joins nucleotides
  5. mRNA is modified and exits nucleus
• What are the key steps in translation?

  1. mRNA binds to ribosome
  2. tRNA aligns with complementary codons
  3. Amino acids are joined by peptide bonds
  4. Ribosome moves along mRNA
  5. Translation ends at stop codon
• What is a gene mutation?

  A change in the base sequence of DNA
• What can increase the likelihood of gene mutations?

  Exposure to mutagenic agents
• What is non-disjunction?

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

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

  A change in whole sets of chromosomes
• What is aneuploidy?

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

  Due to non-disjunction on chromosome 21
• What are the effects of non-disjunction during meiosis?

  • Can lead to polyploidy
  • Can lead to aneuploidy
  • Can result in genetic disorders
• What is aneuploidy?

  Changes in the number of individual chromosomes
• How does non-disjunction lead to Down syndrome?

  It causes three copies of chromosome 21
• What happens during non-disjunction in meiosis I?

  Homologous chromosomes fail to separate
• What is the result of non-disjunction in meiosis I?

  One gamete has n+1 chromosomes
• What does n+1 represent in gametes?

  Haploid with an extra chromosome
• What is trisomy?

  Three copies of one particular chromosome
• How can non-disjunction occur in meiosis II?

  Chromatids fail to separate equally
• What is the outcome of meiosis?

  Four genetically different haploid gametes
• What are the two mechanisms that introduce variation in meiosis?

  • Independent segregation of homologous chromosomes
  • Crossing over between homologous chromosomes
• What is independent segregation in meiosis?

  Homologous pairs line up randomly at the equator