Chromosomes and DNA structure

• What is a gene?

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

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

  It specifies coding for polypeptides
• What is a polypeptide chain?

  The primary structure of a protein
• What is the role of the Golgi apparatus in protein processing?

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

  The location of a gene
• 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?

  They result in different proteins being created
• How many pairs of chromosomes do humans have?

  23 pairs
• What is a homologous pair?

  A pair of chromosomes with identical genes
• What is a human karyotype?

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

  They show the same genes in homologous pairs
• What is the shape of DNA in eukaryotic cells?

  Linear in shape
• How is DNA compacted in eukaryotic cells?

  Wrapped around histone proteins
• What is the structure of prokaryotic DNA?

  Circular and shorter than eukaryotic DNA
• Where is prokaryotic DNA located?

  Free within the cytoplasm
• What two organelles contain their own DNA?

  Mitochondria and chloroplasts
• How is the DNA in mitochondria and chloroplasts similar to prokaryotic DNA?

  It is short, circular, and not histone-bound
• How is the length of DNA in a human muscle cell described?

  2.3 meters
• How do you calculate the mean length of DNA in each 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 3 billion?

  3 times 10 to the 9
• 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 longer; prokaryotic DNA is shorter.
• What are the main points about DNA and chromosomes covered in the video?

  • Genes code for polypeptides and functional RNA.
  • Alleles are alternative forms of genes.
  • Humans have 23 pairs of homologous chromosomes.
  • Eukaryotic DNA is stored in chromosomes and tightly coiled.
  • Prokaryotic DNA is shorter, circular, and free in the cytoplasm.
  • Mitochondria and chloroplasts have DNA similar to prokaryotic DNA.