DNA (exam 2 q 2) Flashcards
DNA was discovered by
Rosalind Franklin
what did Rosalind Franklin do?
Took x ray photos of DNA.
Discovered double helix structure and measured many more DNA parameters
Watson and Crick:
made a model that fit data using some of Franklin’s work. they got credit for discovering DNA structure.
DNA is composed of
sugar backbones and there are 4 nitrogenous bases: A, T, G, C
base pair between DNA strands
A and T
C and G
* Forms 3 rings across middle
combination of bases and sugar is called a
nucleotide
5’ end has
phosphate
3’ end has
hydroxyl
new nucleotides are always added to the ___ end.
3’
direction of strand:
5’ to 3’
complementary strands
each strand has letters that fit with the other strand
antiparallel strands
strands run in opposite directions
*5’ and 3’ are on opposite ends for each strand
genes are instructions to make
proteins and useful RNA
linked genes:
on same chromosome
DNA replication
making a DNA copy
DNA replication is accomplished by
DNA polymerase
since DNA cannot start itself…
you cannot copy the first section of information on the strand and DNA gets shorter each time it is copied
telomeres
sections of DNA at end of chromosomes that act as pointless information that is okay to be lost
telomeres prevent…
loss of important information
when telomeres are used up…
cells may lose ability to divide
how are mistakes made as DNA is copied handled?
- Proteins search for mistakes in DNA
- Tags are added to mistakes
- Repair polymerase cuts out damaged section of strand
- Damaged section is discarded
- Repair polymerase recreates damaged section
how are long stands of DNA handled?
they are packed into chromosomes to take up less space
DNA is wrapped around spools called
histones
histones twist around each other to form
a chromatin fiber
chromatin fiber (formed from twisted histones) twist around
other structures
DNA compacts into ___ ____ if cell is dividing
sister chromatids
