Exam 1 Flashcards
the fundamental properties of genetic material
must…
-contain complex information
-encode a phenotype
-replicate faithfully
-have the capacity to vary
Before the discovery of DNA people knew there was a source of heritable information and called it…
genetic information (will later be known as genes)
the word genetic means…
traits
genes reside where
chromosomes
chromosomes contain both __ and __
DNA and proteins
DNA contains nucleotides with …
bases which have pairing rules
Flow of genetic information
-DNA replication
-DNA to RNA
-RNA to proteins
nucleotides are the __ and contain three things which are…
building blocks
-phosphate (left), sugar (middle), base (right)
nucleotides have locations called primes: where are they…
-on the sugar
0 top
1top right
2 bottom right
3 bottom left
4 top left
5 outside by four
what prime if the phosphate and base on?
-phosphate: 5`
-base: 1’
what part of the nucleotide gives the DNA backbone a negative change
phosphate
the base of the nucleotide is either a …
purine or a pyrimidine
purine
nitrogenous base with a 6 member and 5 member ring (2 parts)
-has A and G
-each nucleotide is a monomer used to make a nucleotide
pyrimidine
nitrogenous base with only a six member ring (1 parts)
-has C, T, an U
-only have one phosphate
-called monophosphate
-make up nucleic acids
each DNA strand is a polymer meaning…
chain of repeating units
a polynucleotide strand (single strand of DNA or RNA) has…
polarity
polarity is referred to as…
5-> 3
each strand has a…
5 end and a 3
end
incoming nucleotides are always added on the __ end of the strand
3`
properties of double stranded DNA
-antiparallel (5 end of one strand is opposite the 3
end of the other strand)
-complementary (base pairs follow the rules)
-5 to 3
(each strand is directional (polar))
-negatively charger
DNA strands are held together by 2 natural forces
-hydrogen bonds (base to base )
-stacking forces (base rings stack on each other)
base pairing rules
-purine to pyrimidine
-A-T, C-G
the 3 forms of DNA
A, B, and Z
form of DNA: A
-less stable and more condensed
-right handed helix
form of DNA: B
-most stable with random nucleotides under physiological conditions
-right handed helix
-most common
form of DNA: Z
-zig-zag
-less stable
-left handed helix (counter clockwise)
difference between RNA and DNA
-ribose as -OH on 3` end of sugar wile deoxyribose only has H
topoisomerases
induces and removes supercoiling
-by nicking the DNA and turning is a certain way
-2 types
topoisomerases 1
-one strand of the DNA nicked
topoisomerases 2
-both strands of the DNA nicked
packaging DNA in chromosomes (bacteria)
-looping proteins
packaging DNA in chromosomes (bacteria)
-histones (proteins) with 2 strands of DNA wrapped around them
3 parts of the chromosome structure
-centromeres
-telomers
-arms
Chromosome structure: centromeres
-center of chromosome
Chromosome structure: Telomers
-ends of the arms
Chromosome structure: Arms
Arms (4)
All DNA is contained and regulated in …
chromosomes
Histone
-predominant protein in chromatin
Chromatin is…
DNA/ protein complex
-makes up chromosomes
The 3 levels of chromatin organization
-Euchromatin
-Heterochromatin
-Higher level DNA packaging into metaphase chromosome
level of chromatin (Euchromatin)
-1st level
-DNA wraps around histone octamers forming nucleosomes
-less condensed, expressed
-loose packaging
nucleosomes are also called…
beads on a string
level of chromatin (heterochromatin)
-multiple histones wrap into nucleosome arrays into their compact form
-condensed, few genes, not really expressed
-tight packaging
most basic level of chromatin is…
the nucleosome
chromatin
-a DNA/ protein complex that is able to be packaged into chromosomes
primary protein component of chromatin that compacts the DNA is called…
histones
the core unit of chromatin
nucleosome
unbound DNA in between nucleosomes is called __ DNA
linker
core nucleosomes
-2 of each
-all octameric
-H2A, H2B, H3, H4
additional histone (name and function)
-H1
-clamps onto the nucleosome
each core histone has a…
flexible tail that holds the DNA either tighter or looser
the charge of nucleosomes
- positively charged so interacts with the negatively charged DNA backbone
replication is __ -> ___
DNA to DNA
4 fundamental properties of genetic information
-contain complex information
-replicate faithfully
-encode a phenotype
-have the capacity to vary
properties of DNA
-5 to 3
polarity
-antiparallel strands
-complementary base pairs
the 3 proposed models of DNA replication
-conservative replication
-dispersive replication
-semiconservative replication
proposed model of DNA (conservative replication)
R1: P and N
R2: P:P +N, N: N+N
proposed model of DNA (dispersive replication)
R1:P makes hybrids (the DNA molecule has fragments of new and parent DNA)
R2: hybrids from the last 2 created
proposed model of DNA (semiconservative replication)
R1: DNA molecule has 1 strand of the parent and one of the new
R2: 2 completely new molecules and 2 with half new and half parent
-this makes the most sense
The Meselson and Stahl experiment
-wanted to test between the 3 models of DNA replication
-label the original DNA and follow it through the rounds of replication
-along the rounds the new DNA molecules will lift to the top of the test tube