DNA structure Flashcards
what are the nucleic acids?
DNA and RNA
what the the three components of nucleotides?
sugar, an aromatic nitrogenous base, and 1-3 phosphate group
DNA includes what type of sugar?
deoxyribose
RNA includes what type of sugar?
ribose
purines are which bases?
G and A
guanine and adenine
pyrimidine are which bases?
C, T, and U
(cytosine, thymine, and uracil)
*mnemonic = CUT the Py
which pyrimidine base does DNA use?
thymine
which pyrimidine base does RNA use?
uracil
nucleosides is a ribose with purine or pyrimidine linked to the?
1’ carbon in a b-N-glycosidic linkage
nucleotides are phosphate esters of nucleosides with 1, 2, or 3 phosphate groups joined to the?
ribose ring by the 5’ hydroxy group
the building block of DNA is the deoxyribonucleoside 5’ triphosphate (dNTP) where N represents one of the?
four basic nucleosides
(A, G, C, T for DNA)
(A, G, C, U for RNA)
the backbone of nucleic acids are the?
sugar and phosphate portion of the dNTP
the base is the variable portion
how are nucleotides in nucleic acids covalently linked? location?
by phosphodiester bond between the 3
hydroxy group of he sugar in one nucleotide and the 5’ phosphate group of the sugar in the next nucleotide?
nucleotide chains are written in which direction?
5’ to 3’
in the oligonucleotide, ACGT, which nucleotide has a free 3’ hydroxy group?
T because it is written last
the watson-crick models thats that DNA is in a?
right-handed double helix held together by hydrogen bonds and hydrophobic forces between bases
in the cell, DNA is doubled stranded and are in what orientation?
antiparallel, meaning that the 5’ end of one chain is paired with the 3’ end of the other
the hydrogen bonds of dsDNA are specific to which nucleotides?
A is always with T
G is always with C
*purine plus a pyrimidine
how many hydrogen bonds hold together GC pairs?
three hydrogen bonds
how many hydrogen bonds hold together AT pairs?
two hydrogen bonds
which component are on the exterior and interior of the double helix?
bases are on the interior
ribose/phosphate backbone on the exterior
how are bases stabilized by hydrophobic interactions?
once a purine is H-bonded to pyrimidine, most the polar nature of the individual bases disappears because the charge dipoles are occupied in H-bond
genome is the sum total of?
organism’s genetic information
each piece of dsDNA is called a?
chromosome
prokaryotic genomes are composed of?
single circular chromosome
prokaryotes use DNA gyrase enzyme to?
compact their single circular chromosome using ATP to twist the circular molecule by breaking the DNA and twisting the two sides of the circle around each other resulting in dsDNA
in eukaryotic genomes, packing is done by wrapping around globular proteins called?
histones
after being wrapped around histone and before being completely packed away, DNA has an appearance of beads on a string - those beads are called?
nucleosome and are composed of DNA wrapped around an octamer of histones (group of eight)
a fully packed DNA is called?
chromatin
when chromosomes are stained, the darker region are more dense and are called?
heterochromatin
when chromosomes are stained, the lighter region are less dense and are called?
euchromatin
it is known that the euchromatin (lighter regions) have higher rates of?
transcription and therefore higher gene activity because they are less dense so enzymes and proteins are more accessible
giemsa stains are used in what lab technqiue?
karyotypes for G-banding patterns
centromeres are a region of the chromosomes to which?
spindle fibers attach during cell division via kinetochores
centromeres are made up of?
heterochromatin and repetitive DNA sequences
metacentric centromere position is when?
centromere is at the center so chromatids are same length
submetacentric centromere position is when?
centromere is higher up so that there are short arms (p) and long arms (q)
acrocentric centromere position is when?
centromere is even higher up s that the short arms (p) are shorter than in submetacentric and long arms (q) are longer than in submetacentric
telocentric centromere position is when?
centromere is so high up that there are no short arm (p) chromatids, only long (q)
telomeres are the?
ends of linear chromosomes
telomeres are distinguishable by?
repeating unit 6-8 base pairs long and guanine-rich
in many vertebrates: 5’-TTAGGG-3’
telomeres function to?
prevent chromosome deterioration and prevent fusion with neighboring chromosomes
