Genetic information

• What are the definitions being reviewed in the video?

  Gene and allele
• How is a gene defined in A-level biology?

  A short section of DNA coding for polypeptides
• What does a gene code for besides polypeptides?

  Functional RNA
• How does the A-level definition of a gene differ from the GCSE definition?

  It specifies coding for polypeptides and RNA
• What is the primary structure of a protein?

  Polypeptide chain
• What role does the Golgi apparatus play in protein processing?

  It processes polypeptide chains into functional proteins
• What is the definition of locus?

  Location of a gene on a chromosome
• Why are humans not genetically identical despite having the same genes?

  They have different versions of those genes
• What is an allele?

  A different form of the same gene
• How do alleles affect traits in plants?

  Different alleles result in different traits
• How many pairs of chromosomes do humans have?

  23 pairs
• What is a homologous pair of chromosomes?

  A pair with identical genes but different alleles
• How do homologous pairs arise in humans?

  From the combination of sperm and egg DNA
• What is a human karyotype?

  An image of all chromosomes organized in pairs
• What do the dark and light bands on chromosomes indicate?

  They show the same genes in homologous pairs
• What determines biological sex in humans?

  The 23rd pair of chromosomes
• How is DNA stored in eukaryotic cells?

  In chromosomes within the nucleus
• What shape are eukaryotic chromosomes?

  Linear
• What helps DNA avoid tangling in eukaryotic cells?

  Histone proteins
• What is a nucleosome?

  DNA wrapped around histone proteins
• How does prokaryotic DNA differ from eukaryotic DNA?

  It is shorter and circular, not linear
• Where is prokaryotic DNA located?

  Free in the cytoplasm
• What type of DNA do mitochondria and chloroplasts contain?

  DNA similar to prokaryotic DNA
• Why is the DNA in mitochondria and chloroplasts significant?

  It codes for enzymes essential for reactions
• How is the length of DNA in a human muscle cell described?

  2.3 meters
• How do you calculate the mean length of DNA per chromosome?

  Divide total length by number of chromosomes
• What is the length of DNA in a human brain cell?

  2.3 meters
• How do you convert meters to millimeters?

  Multiply by 1000
• How many base pairs does the human genome contain?

  Approximately 3 billion
• How do you calculate base pairs per chromosome?

  Divide total base pairs by number of chromosomes
• What is the standard form of base pairs per chromosome?

  $6.5 \times 10^7$
• What are the key differences between eukaryotic and prokaryotic DNA?

  • Eukaryotic DNA is linear; prokaryotic DNA is circular.
  • Eukaryotic DNA is associated with histone proteins; prokaryotic DNA is not.
  • Eukaryotic DNA is stored in the nucleus; prokaryotic DNA is free in the cytoplasm.
• What are the main points about DNA and chromosomes covered in the video?

  • Genes are sections of DNA coding for polypeptides.
  • Alleles are alternative forms of a gene.
  • Humans have 23 pairs of homologous chromosomes.
  • Eukaryotic DNA is linear and histone-bound.
  • Prokaryotic DNA is circular and not histone-bound.
  • Mitochondria and chloroplasts contain DNA similar to prokaryotic DNA.
• Who is the presenter of the A Level Biology video?

  Miss Estrich
• What are the three key features of the genetic code?

  Degenerate, universal, and non-overlapping
• What is a start codon?

  Three bases at the start of a gene
• What does the start codon code for?

  Amino acid methionine
• What are the three bases of the start codon in DNA?

  TAC
• What is the function of a stop codon?

  It signals the end of translation
• How many stop codons are there?

  Three