Lecture 1 Flashcards
What was the chemical structure of a gene?
- passed from cell to daughter cell mostly unchanged
- undergoes accurate and unlimited replication
- must direct development of a cell and the daily life of the cell
the information- containing elements that determine the characteristics of a species
genes
Chromosomes contain
DNA and protein
building blocks of DNA
nucleic acids
What is DNA made up of
polynucleotides have POLARITY 5' phosphoryl end 3' hydroxyl end phasphate group, sugar group and a base... hooked together by hydroxly polariy linkage. always 5-3 prime
What has 2 long …. with 4 types of …. subunits
DNA has polynucleotide chains with nucleotide
what is a nucleotide?
5-carbon sugar and nitrogenous base covalently linked via glycosidic bonds
What is the sugar in DNA?
deoxyribose
What are the 4 bases?
adenine, cytosine, guanine, and thymine
What is the 3D structure of DNA?
double helix, 1 turn every 10 bp
each strand’s sequence is complementary to partner
antiparallel, helps DNA function the way it does.. allows for replication
Whare are the purines?
adenine and guanine
What are pyrimidines?
cytosine and thymine
What does adenine pair with?
thymine… 2 hydrogen bonds
What does guanine pair with?
cytosine (3 hydrogen bonds)
complete set of information in a an organims’s DNA
genome
At replication, the entire genome must be
duplicated and passed to the daughter cell
allow for the genome to be replicated
complimentary strands, each strand serves as the template
Dna has Minor and major groves
….
single long linear DNA molecular associated with proteins that fold and pack it into compact structre
chromosome
autosomes and sex chromsomes
22 pairs and 2 sex
Each chromosome is a
single long linear DNA molecular associated with protiens that fold and pack it into compact structure
What information is found on chromosomes?
encoding proteins
encoding RNA molecules
Information that does not contain DNA in a chromosomes is for?
regulatory information
“Junk” DNA
2 copies are called
homologs
Little of genome is
protein coding
most DNA is
transposable elements
lots of intonic sequences
regulatory sequences
region of gene that codes for proteins
exons
typically 145 bp floating in sea of lg introns, the sequence of which is of little consequence
coding regions (exons)
sequences are relatively conserved during evolution
functional
sequences mutate randomly wo consequnces
non functional
not only do we share the same genes, but large blocks of
them are conserved in the same order on the chromosome “conserved synteny”
chomosomes are replicated; they are decondensed and ccant be easily distinguished
interphase
become highly condensed and separated into two duaghter nuclei
mitosis
where duplication of the DNA begins
DNA replication origin
allows one copy of each duplicated and condensed chromosmes to be pulled into each daughter cell when the cell divides
centromere
at the end of a chromsomes, contain repetitive sequences that enable the end to be efficiently replicated
telomere
must allow rapid localized access to DNA for gene expression
dynamic situation
DNA binding protines involved in forming chromosomes
histones and non-histone chromosomal proteins
Protein + nuclear DNA=
chromatin
most basic unit of chromosome packing
nucleosome
beads on a string
linker DNA and DNA wrapped around histones
nucleosome is made up of
histone octomer
8 histone protiens
-2 molecules each of H2A, H2B, H3, H4
- And 2x stranded DNA that is 147 nucleotide pairs long
what break down DNA by cutting btw nucleosomes and degrading the exposed DNA btw nucelosome core particles?
nucleases
small proteins with common structural motif called histone fold
histones
What are N terminal amino acid tail that extends out from the core of nucleosome improtant for?
Covalent modifications important for chromatin regulation
interactions btw DNA and histone
142 H bonds are formed btw DNA and histone core in each nucleosome
Hydrophobic interactions
salt linkages
histones are highly conserved; most changes would be lethal
specialized variant histone proteins add to vaious possiblechromatin sturctures
lysine and arginine (positive charges) comprise more than 1/5 of histone residues; effectively neutralize negatively charged DNA backbone
salt linkages
Chromatin remodeling complexes
allow further loosening of DNA/ histone contact
proteins are related to….
helicases and are ATP dependent; bind to both protein core and DNA
stacking may be facilited by histone tails (esp H4)
H1 “linker histone” is present in 1:1 ratio with nucleosome cores
zig zag model… nucleosome packing- a dense fibrous structure w diameter of 30 nm
linker histone
larger than other histone proteins- also less well conserved
contacts both DNA and protein
changes the path of the DNA as it exits the nucleosome
Histone H1
