DNA, Genes & Chromosomes

• What type of DNA do prokaryotes usually possess?

  Single, circular chromosomal DNA
• What are plasmids?

  Very small circular DNA molecules
• Why are plasmids more accessible for proteins?

  They contain genes required often
• What do eukaryotic DNA associate with?

  Histone proteins
• What forms when eukaryotic DNA coils around histone proteins?

  Chromatin
• Where is mitochondrial DNA found?

  In the matrix of mitochondria
• What is the role of mitochondrial DNA and ribosomes?

  Needed for replication
• What does the chloroplast contain?

  Small circular pieces of DNA
• What is the function of ribosomes in the chloroplast?

  To synthesize proteins needed for replication
• What are genes?

  Sections of DNA that code for proteins
• What is a locus?

  The position of a gene on a chromosome
• What are alleles?

  Different forms of the same gene
• What does each codon code for?

  One amino acid
• What do some triplets of bases code for?

  Start and stop signals
• What are the characteristics of the genetic code?

  Non-overlapping, triplet code, universal, degenerate
• What does 'degenerate' mean in the context of the genetic code?

  Multiple codons can code for the same amino acid
• What is a genome?

  The complete set of genes in a cell
• What do introns represent in eukaryotic DNA?

  Non-coding sections of DNA
• What are exons?

  Sections of DNA that code for a protein
• What happens during transcription?

  The whole gene is transcribed to produce pre-mRNA
• What is splicing in the context of mRNA processing?

  Introns are removed and exons are joined together
• What is the final product of splicing?

  mRNA with only exons
• What is the process of translation in protein synthesis?

  • mRNA is translated into a polypeptide
  • Ribosomes read codons on mRNA
  • tRNA brings corresponding amino acids
  • Amino acids are linked to form proteins
• What are the differences between introns and exons?

  • Introns: non-coding sections of DNA
  • Exons: coding sections of DNA that produce proteins
• What are the steps involved in gene expression?

  1. Transcription: DNA to pre-mRNA
  2. Splicing: introns removed, exons joined
  3. Translation: mRNA to protein