Week 1, Lecture 2: Structure of Nucleic Acids Flashcards
What are the Monomeric Units of Nucleic acids, DNA and RNA?
Nucleotides
Nucleotides consist of what ?. How are they linked?
nitrogenous base, a five-carbon sugar, and a phosphate….linked by phosphodiester bonds between the 3 -sugar of one nucleotide and the 5 -sugar of the next nucleotide
DNA contains the sugar ____? RNA contains ?
2 -deoxyribose; ribose
DNA and RNA contain the purine bases
adenine (A) and guanine (G)
DNA contains the pyrimidine bases ?
cytosine (C) and thymine (T)
RNA contains the pyrimidine bases ?
C and uracil (U)
transcription of a gene generates ?
single-stranded RNA
the three major types of RNA?
are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
What RNAs are required for protein sythesis?
rRNA and tRNA
rRNA is complexed with proteins to form ribonucleoprotein particles called? what does this bind?
ribosomes, which bind mRNA and tRNAs during translation
What does tRNA contain and where does it bind?
anticodon that binds to a complementary codon on mRNA, ensuring insertion of the correct amino acid into the protein being synthesized
DNA is complexed with proteins called ?
histones to form nucleosomes that are further condensed into wound chromatin
where is DNA found in the Eukaryote?
nucleus and mitochondria
nucleosides lack …?
inorganic phosphates of nucleotides
deoxyribonucleotides are abbreviated?
dNMP, dNDP
what is the backbone of DNA made of?
sugar-phosphate backbone, created by phosphodiester bonds
what charge does DNA have? how does this help?
negative die to oxygen. aids in the binding of specific proteins.
DNA has three conformations?
B-DNA (right-handed helix) , A-DNA (right-handed helix), Z-DNA (left-handed helix)
found in DNA-RNA hybrids and is more compact than B-DNA?
A-DNA
DNA conformation that is formed briefly during transcription?
Z-DNA
the genome is all of an organism’s ??
DNA (nuclear and mitochondrial)
the nuclear genome of a human haploid cell (sperm or egg) contains # of chromosomes?
23
all mitotic progeny of the diploid zygote have a homologous pair of ….?
22 autosomes and one pair of sex chromosomes (male = X,Y; female = X,X) for a total of 46 chromosomes in a single diploid cell
the display of the 46 human chromosomes is called ?
Karyotype
How can chromosomes be distinguished?
size, staining patterns, and FISH color
each DNA molecule that forms a linear chromosome must contain what?
a centromere, two telomeres (ends) and a replication origin
Ex. what is this event: a piece of chromosome 4 that had become attached to chromosome 12 through an abnormal recombination event.
chromosomal translocation
what does FISH stand for and when is it used?
This technique is called spectral karyotyping and it is a form of of fluorescent in situ hybridization (FISH).
The banding patterns of human chromosomes are made by what stain?
Giemsa stain, then light microscope.
specific location on a chromosome/
genetic locus
alternate gene versions are called?
alleles, two for each gene, one obtained maternally and one paternally
if the alleles functionally differ then the gene is called what?
heterozyous
a correlation exists between the complexity of an organism and the number of what?
genes in its genome
two species have essentially the same set of genes, and that in many cases the genes are found in the same order (mouse and human)? what is this called?
conserved synteny
Mobile genetic elements in our genome?
LINES, SINES, retroviral-like elements, and DNA-only transposons
short nucleotide sequences that are repeated for long stretches?
Simple sequence repeats
large blocks of the genome (100K -200k) that are present at two or more locations in the genome?
Segmental suplications
describe Prokaryote DNA? how is it packaged?
single circular chromosome of double-stranded DNA, DNA is supercoiled and attached to an RNA-protein core
histones that contain large amounts what AA’s?
histones that contain large amounts of arginine and lysine
further compaction of chromatin occurs as the strings of nucleosomes wind into helical, tubular coils called?
solenoids
this higher order chromatin structure is mediated by ?
H1 histones, but also, especially by the “tails” of the core histones
each of the core histones has what?
long N-terminal amino acid “tail” which extends out from the core
How are the tails of histones modified?
acetylation of lysines( added by HATs) (removed by HDACs), methylation of lysines and phosphorylation of serines
what is the critical role of histone acetylation?
destabilizing chromatin structure , removing positive charge from lysine
chromatin that is loose or “open” for transcription and replication is called ?
euchromatin
chromatin that is most highly condensed, and thus closed to processes such as transcription is called ?
heterochromatin
acetylation of tail histones is associated with ? de-acetylation is associated with?
euchromatin, heterochromatin
What is often upregulated in cancer cells? what does this lead to ?
HDACs, to silencing of expression of tumor suppressor genes (such as p53
how do ; uracil & thymine differ?
the presence of a methyl group in thymine at position 5 of the ring
What is it called:RNAs can also act as enzymes ?
ribozymes
mRNA processing?
introns, poly-a-tail and cap
where is mRNA processed?
nucleus
what are the subunits in prokaryotyic ribosomes? Eukaryotic?
Prokaryotic ribosomes have 50S and 30S subunits and eukaryotic ribosomes have 60S and 40S subunits
RNA molecules that carry amino acids to ribosomes and ensure they are incorporated into the correct positions in the polypeptide chain are what?
tRNA
pairing of three bases in the tRNA with mRNA are what?
anti-codons and codons
serve as primers for DNA replication?
oligonucleotides
what are the key functions of miRNAs?
development, cell differentiation, regulation of the cell cycle & apoptosis. regulate mRNA degradation, translation, chromatin condensation
What happens when microRNAs are mutated?
can act as either an oncogene or tumor suppressor gene in human cancers
