Topic 4: Genetics, variation and relationships

• Who is the teacher in the video?

  Miss Estrich
• What is the purpose of the video?

  To provide revision for topic four
• How can viewers navigate to specific topics in the video?

  By using the time codes provided
• What has Miss Estrich been doing for over 10 years?

  Teaching and tutoring biology
• What resources has Miss Estrich prepared for revision?

  Essential revision resources
• What should students do if they struggle with timing in revision?

  Use the revision notes created by Miss Estrich
• What does the active recall workbook help students with?

  Testing knowledge and improving memory
• What is the purpose of the revision timetable maker?

  To help students manage their study time
• 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
  • Eukaryotic DNA is linear
  • Prokaryotic DNA is circular
  • Eukaryotic DNA associates with histones
• What is the structure of eukaryotic DNA?

  Linear and organized into chromosomes
• What is the function of histones in eukaryotic DNA?

  To associate with DNA and help coil it
• How does mitochondrial and chloroplast DNA compare to prokaryotic DNA?

  Similarities:

  • Both are circular
  • Both are short sequences
  • Neither is wrapped around histones

  
  

  Function:

  • Transcribe and translate enzymes for photosynthesis and respiration
• 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 is a triplet in the context of DNA?

  A sequence of three bases
• What are the three key features of the genetic code?

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

  Multiple triplets can code for the same amino acid
• How does a mutation affect the genetic code?

  It may not change the amino acid produced
• What is a codon?

  Three bases on mRNA coding for an amino acid
• 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 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?

  Cloverleaf shape held by hydrogen bonds
• What are the two main stages of protein synthesis?

  1. Transcription
  2. Translation
• What happens during transcription?

  A gene is copied into mRNA
• 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?

  To hold tRNA and mRNA together
• What is a peptide bond?

  A bond joining amino acids together
• What is the significance of non-overlapping codons?

  Each base is part of only one codon
• 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 exits nucleus
• What is 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