How is DNA categorized
Not all of it serves the same purpose, so it’s divided based on primary roles into coding regions and non-coding regions
what is in coding regions
genes
genes
specific sequences of DNA that contain the instructions for building proteins that determine traits
Non-coding regions
perform critical regulatory functions and structural functions (telomeres/caps at the end of chromosomes)
what do regulatory functions do
act as switches that turn genes on or off, ensuring that the right proteins are made in the right cells at the right time
transcription
when a specific gene in the DNA is copied/rewritten into messenger RNA (mRNA) so the code can leave the nucleus
Erwin Chargaff
Discovered that the percentage of A and T bases are almost equal in any sample, the same for C and G
Determined the base pair rules A=T and G=C
Senescence
the process of deterioration with age; loss of a cell’s power of division or growth.
Rosalind Franklin
Showed that nitrogen bases are toward the center of DNA
Used x-ray diffraction (crystallography)
Showed that the DNA is a helix
Pieces of DNA
adenine, guanine, cytosine, thymine, deoxyribose, phosphate
what are the steps of the ladder made out of
nitrogenous bases
what are the sides of the ladder made out of
sugars and phosphates
what holds the nitrogenous bases together
hydrogen bonds
what do complementary pairs always involve
one purine and one pyrimidine base
trinucleotide repeat expansions
a mutation in DNA replication that results in an increased number of copies in the same codon (3 bases)
why is dna called “semi conservative”
it contains one old strand and one new strand
One-half of the old strand is saved/conserved, reducing the chance of errors
