Chapter 16 (DNA) Flashcards
Who discovered the structure of DNA?
Rosalind Franklin, Maurice Wilkins, James Watson, and Francis Crick
What kind of structure is DNA?
double helix
What does Adenine pair with?
thiamine
What does cytosine pair with?
guanine
What was the width like when pairing the nitrogenous bases?
a uniform width
What did Erwin Chargaff notice?
no matter what piece of DNA was taken, number of A = number of T, number of G = number of C via HYDROGEN bonding
Why must DNA be copied?
to conserve genetic material in cells
What is the mechanism for replication?
specific base pairing that happens between nitrogenous bases
What does it mean for DNA to be complementary?
if you pull DNA strands apart into parent strands, those parents strands act as templates for new daughter strands
What does it mean for DNA to be semi-conservative?
one strand is old and the other is new
What is the “origin of replication”?
a location where replication is initiated
Can there be multiple origins of replication on DNA?
yes
What is a replication bubble?
unwound and open region of the double helix where the replication occurs and contains 2 replication forks
What is a replication fork?
separation strands of DNA create Y shape
What does DNA polymerase do?
the enzyme that creates a new strand of DNA by adding nucleotides
What do helicase enzymes do?
untwist double helix at replication forks, unzip the genes
What does the single-strand binding protein do?
stabilize single-stranded DNA
What does topoisomerase do?
enzyme that corrects any overwinding or underwinding due to double-helix nature
What are the enzymes that are used in the actual process of replication?
Primase, DNA polymerase III, DNA polymerase I, DNA ligase (paul probably put little)
What does primase do?
synthesizes short RNA sequences as primers for DNA polymerase
What does DNA polymerase III do?
synthesizes DNA strands in a leading and lagging fashion by adding nucleotides to 3’ end of template strand ONLY , proofreads
What does DNA polymerase I do? (think of it, first to do all)
adds DNA nucleotides to the primers creates from primase AND extracts primers
What does DNA ligase do?
joins the Okazaki fragments into strand one of DNA
Is DNA parallel or anti-parallel?
anti-parallel
if there is a d in front of atp or nucleotide name, what does it indicate?
a dna nucleotide and ATP
What sugar does DNA nucleotides have?
deoxyribose on 2’ carbon (no oxygen)
ATP is a nucleotide of what?
RNA
As the nucleotides join the DNA strand, what happens to the phosphates?
it loses two phosphate groups cuz energy is used for the process and that energy is within phosphate groups
What is the leading strand?
replication going in the same direction as the fork in 3’ to 5’ direction and away from origin of direction (as the fork keeps opening, the replication keeps happening)
New DNA only grows in which direction?
5’ to 3’
What is the lagging strand?
replication in the chunks that get joined togehther that go in the opposite direction of the fork (5’ to 3’) and towards the origin of replication
What are the chunks in lagging strands called?
Okazaki fragments
What is the purpose of an RNA primer?
anchored at the end of a DNA strand so that DNA polymerase has something to hold onto when adding nucleotides
What are telomeres? (in chromosome structure of a eukaryote)
repeating nucleotide sequences that don’t hold any genetic significance at the ends of DNA that prevent the shortening of DNA molecules and genetic erosion, like shoelaces
What is telomerase? (telo-end) (in chromosome structure)
adds a repetitive sequence of nucleotides at the end of DNA sequence in the case that telomeres are degraded too much
Does telomerase work in all cells? (chromosome structure)
no, only ones that replicate often
What makes up a chromosome?
DNA and proteins (histones)
What do histone proteins do?
proteins that can undergo chemical change and allow dna to wind around them to make nucleosomes
What are nucleosomes?
DNA wound around a series of histone 8 proteins (octomer)
What is euchromatin?
regions where important genetic code is packed, loosely packed (e for easy to transcribe)
What is heterochromatin?
tightly packed areas of chromatin that include telomeres and centromeres and aid in structural support (H for hard to transcribe)
Which does not have any genes on it, euchromatin or heterochromatin?
heterochromatin
What is a dNTP?
nucleotide added to new DNA strand
What does dATP do?
provides adenine to DNA, similar to regular ATP
What loosens histones?
acetylation
What tightens histones?
deacetylation or demethylation
What does histone acetylation do?
acetyl groups attatch to lysine histone tails and loosens chromatin structure
What process can also loosen histones?
methylation and phosphorylation
What does DNA methylation do?
gene slicing (permanent binding) that involves adding methyl groups to cytosine-guanine areas, regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA
What is an example of DNA methylation?
genomic imprinting and X-inactivation
What happens in genomic imprinting?
methylation of DNA to silence either maternal or paternal gene
