LEHNINGER PRINCIPLES OF BIOCHEMISTRY
2026 MOCK PAPER COMPREHENSIVE REVIEW
NOTES ANALYTICAL SUMMARY
◉ Human genomic DNA.
Answer: Less than 1.5% encodes proteins, with less than one-third
consisting of genes
◉ Transposons.
Answer: Nucleic acid parasites accounting for about half of the
human genome
◉ Centromeres.
Answer: Special-function repetitive DNA sequences serving as
attachment points for the mitotic spindle
◉ Telomeres.
Answer: Repetitive DNA sequences located at the ends of
chromosomes
◉ Supercoiled DNA.
, Answer: Underwound state of DNA that is either a closed circle or
bound to protein
◉ Linking number (Lk).
Answer: Topological parameter quantifying underwinding of DNA
◉ Superhelical density (σ).
Answer: Measure of underwinding, typically -0.05 to -0.07 for
cellular DNAs
◉ Topoisomers.
Answer: DNAs that differ only in linking number
◉ Topoisomerases.
Answer: Enzymes that underwind and/or relax DNA, changing
linking number
◉ Type I topoisomerases.
Answer: Enzymes that change linking number in increments of 1 per
catalytic event
◉ Type II topoisomerases.
2026 MOCK PAPER COMPREHENSIVE REVIEW
NOTES ANALYTICAL SUMMARY
◉ Human genomic DNA.
Answer: Less than 1.5% encodes proteins, with less than one-third
consisting of genes
◉ Transposons.
Answer: Nucleic acid parasites accounting for about half of the
human genome
◉ Centromeres.
Answer: Special-function repetitive DNA sequences serving as
attachment points for the mitotic spindle
◉ Telomeres.
Answer: Repetitive DNA sequences located at the ends of
chromosomes
◉ Supercoiled DNA.
, Answer: Underwound state of DNA that is either a closed circle or
bound to protein
◉ Linking number (Lk).
Answer: Topological parameter quantifying underwinding of DNA
◉ Superhelical density (σ).
Answer: Measure of underwinding, typically -0.05 to -0.07 for
cellular DNAs
◉ Topoisomers.
Answer: DNAs that differ only in linking number
◉ Topoisomerases.
Answer: Enzymes that underwind and/or relax DNA, changing
linking number
◉ Type I topoisomerases.
Answer: Enzymes that change linking number in increments of 1 per
catalytic event
◉ Type II topoisomerases.