Bio topic 4

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

  Similarities:

  • Both made of DNA nucleotides
  • Joined by phosphodiester bonds

  
  

  Differences:

  • Eukaryotic DNA is longer and linear
  • Prokaryotic DNA is circular
  • Eukaryotic DNA is associated with histones
• What is the structure of eukaryotic DNA?

  It is tightly coiled into chromosomes
• What is the function of DNA in mitochondria and chloroplasts?

  To transcribe and translate enzymes needed
• What is a gene?

  • A sequence of DNA
  • Codes for amino acid sequences
  • Codes for functional RNA
• What is the definition of locus in genetics?

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

  1. Degenerate code
  2. Universal
  3. Non-overlapping
• Why is the genetic code described as degenerate?

  More than one triplet codes for the same amino acid
• How many bases are needed to code for 20 amino acids?

  Three bases are needed
• 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 the function of exons in DNA?

  They code for amino acids
• 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 produced by a cell
• How does the genome differ between species?

  It varies in the number of DNA base pairs
• What is the structure of mRNA?

  Single stranded and shorter than DNA
• Where is mRNA found in the cell?

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

  To transfer amino acids during translation
• What is the shape of tRNA?

  Clover leaf shape
• What happens during transcription?

  DNA is copied into mRNA
• What are the key steps in transcription?

  1. DNA helix unwinds
  2. Template strand is used
  3. RNA nucleotides align
  4. RNA polymerase joins nucleotides
  5. mRNA is modified
  6. mRNA leaves the nucleus
• What is splicing in eukaryotes?

  Removing introns from pre-mRNA
• What are the key steps in translation?

  1. mRNA binds to ribosome
  2. tRNA aligns with codons
  3. Amino acids are joined by peptide bonds
  4. Ribosome moves along mRNA
  5. Translation ends at stop codon
• What is the role of the ribosome in translation?

  To hold tRNA and mRNA together
• What is a gene mutation?

  A change in the base sequence of DNA
• When do gene mutations commonly occur?

  During DNA replication in interphase
• What are mutagenic agents?

  Factors that increase mutation rates
• What is non-disjunction?

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

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

  Having multiple copies of every chromosome
• What is aneuploidy?

  Having an abnormal number of individual chromosomes
• How does Down syndrome occur?

  Due to non-disjunction of chromosome 21
• What happens during meiosis in non-disjunction?

  Chromosomes fail to separate equally
• What happens when chromosomes fail to separate during meiosis?

  It results in aneuploidy.
• How does Down syndrome occur?

  Through non-disjunction of chromosome 21.
• What is the difference between non-disjunction in meiosis I and meiosis II?

  Meiosis I affects homologous pairs; meiosis II affects chromatids.
• What does a haploid gamete with an extra chromosome represent?

  It is described as n plus one.
• What is the result of a haploid gamete missing a chromosome?

  It is described as n minus one.
• How can trisomy occur?

  By fusion of n plus one and n gametes.