Practicals

• What is the main topic of the notes by @biologywitholivia?

  Genetic information, variation, and relationships
• What are the main sections covered in Topic 4 of AQA A Level Biology?

  • 4.1 DNA, genes, and chromosomes
  • 4.2 DNA and protein synthesis
  • 4.3 Genetic diversity from mutation or meiosis
  • 4.4 Genetic diversity and adaptation
  • 4.5 Species and taxonomy
  • 4.6 Biodiversity within a community
  • 4.7 Investigating diversity
• What is the structure of DNA in eukaryotic cells compared to prokaryotic cells?

  Eukaryotic DNA is linear; prokaryotic DNA is circular
• What is a chromosome?

  Long, linear DNA with associated histone proteins
• What is a gene?

  A sequence of DNA bases coding for proteins
• What is a locus?

  Fixed position a gene occupies on DNA
• Describe the nature of the genetic code.

  • Triplet code: 3 DNA bases code for an amino acid
  • Universal: Same triplets code for same amino acids in all organisms
  • Non-overlapping: Each base is part of only one triplet
  • Degenerate: An amino acid can be coded by multiple triplets
• What are non-coding base sequences?

  DNA that does not code for amino acids
• Where are non-coding base sequences found?

  Between genes and within genes as introns
• What are introns and exons?

  Introns do not code; exons code for amino acids
• What are common mistakes regarding chromosomes and prokaryotic DNA?

  • Bacteria have small, circular DNA, not chromosomes
  • Prokaryotic DNA is double-stranded, not single-stranded
  • Triplets code for amino acids, not produce them
• What is a genome?

  The complete set of genes in a cell
• What is a proteome?

  The full range of proteins a cell can produce
• Describe the two stages of protein synthesis.

  1. Transcription: mRNA is produced from DNA in the nucleus
  2. Translation: Polypeptides are produced from mRNA at ribosomes
• Compare and contrast the structure of tRNA and mRNA.

  Similarities:

  • Both are single polynucleotide strands

  
  

  Differences:

  • tRNA is clover leaf shaped; mRNA is linear
  • tRNA has hydrogen bonds; mRNA does not
  • tRNA is shorter; mRNA is longer
  • tRNA has anticodons; mRNA has codons
• How is mRNA formed by transcription in eukaryotic cells?

  RNA polymerase joins RNA nucleotides to form mRNA
• How does mRNA production differ in eukaryotic and prokaryotic cells?

  Eukaryotes produce pre-mRNA; prokaryotes produce mRNA directly
• Describe the process of translation leading to polypeptide production.

  1. mRNA attaches to ribosome at start codon
  2. tRNA brings specific amino acids
  3. tRNA anticodon binds to mRNA codon
  4. Ribosome moves to next codon, forming peptide bonds
  5. tRNA is released after amino acid joins polypeptide
  6. Process continues until stop codon is reached
• What are the roles of ATP, tRNA, and ribosomes in translation?

  • ATP: Provides energy for peptide bond formation
  • tRNA: Transports specific amino acids to ribosome
  • Ribosomes: Catalyze peptide bond formation and move along mRNA
• How can the base sequence of nucleic acids relate to the amino acid sequence of polypeptides?

  tRNA anticodons are complementary to mRNA codons
• What is a gene mutation?

  A change in the base sequence of DNA
• What is a mutagenic agent?

  A factor that increases the rate of gene mutation
• How can a mutation lead to a non-functional protein?

  It changes the amino acid sequence in the polypeptide
• What are the possible effects of a substitution mutation?

  It may change one amino acid in the polypeptide
• What are the possible effects of a deletion mutation?

  It changes the sequence of amino acids in the polypeptide
• Describe features of homologous chromosomes.

  • Same length
  • Same genes at the same loci
  • May have different alleles
• What is the difference between diploid and haploid cells?

  • Diploid: 2 complete sets of chromosomes (2n)
  • Haploid: 1 set of unpaired chromosomes (n)
• Describe how a cell divides by meiosis.

  1. Interphase: DNA replicates
  2. Meiosis I: Separates homologous chromosomes
  3. Meiosis II: Separates sister chromatids
• What is the sequence of amino acids represented by TAC GTC AAC GGC ATC?

  Met His Leu Ala Val
• What are the features of homologous chromosomes?

  • Same length
  • Same genes at same loci
  • May have different alleles
• What are monomers?

  Smaller, repeating molecules that form polymers
• What is the difference between diploid and haploid cells?

  Diploid has 2 sets, haploid has 1 set
• What are polymers?

  Molecules made from many identical monomers
• What occurs during a condensation reaction?

  Two molecules join, releasing a water molecule
• Describe the process of meiosis.

  1. Interphase: DNA replicates
  2. Meiosis I: separates homologous chromosomes

  • Crossing over occurs
  • Independent segregation occurs

  1. Meiosis II: separates sister chromatids
  2. Outcome: 4 genetically varied daughter cells
• What happens in a hydrolysis reaction?

  Two molecules separate, using a water molecule
• What is a nucleotide?

  A monomer that makes up polynucleotides
• What is the outcome of meiosis?

  4 genetically varied daughter cells
• What is a monosaccharide?

  A monomer from which larger carbohydrates are made
• Why is the number of chromosomes halved during meiosis?

  Homologous chromosomes are separated in meiosis I