2. Genes & Chromosomes Flashcards
current definition of a gene
all of the DNA that encodes the primary sequence of some final product
former definitions of a gene
portion of a chromosome that gave rise to a phenotype
one gene, one enzyme
genome content
1.5% exons
28.5% introns/non-coding elements
45% transposons
25% miscellaneous
within transposons, *% is what?
retrovirus-like DNA
3 macrostructures within chromosomes?
- centromeres
- telomeres
- multiple origins of replication
centromeres
structures in the middle of the chromosome where spindle fibers attach during cell division
telomeres
ends of chromosomes
thousands of TTTAGG repeats
serves as extension of the area of replication
used as markers for mortality
premature shortening associated w/obesity, smoking
elongation associated w/running
multiple origins of replication
allows for faster, more efficient replication
supercoiling
stored from of DNA
coiled coils
result of intentional unwinding
topology
study of properties of an object that do not change under continuous deformation (such as supercoiling)
Lk=?
topological linkage number
defines # of times DNA strands cross an imaginary plane (number of helix turns altered)
cannot be defined in situations where strand is broken
if negative, right handed supercoil
if positive, left handed supercoil
topoisomerases
break 1 or both strands of DNA in order to alter Lk
type 1: break only one of the two strands (Lk=1)
type 2: break both strands of DNA (Lk=2)
decreasing the Lk value means?
removing supercoils
nucleosome
basic DNA packaging
DNA wraps around histone core
50bp linker region connects two nucleosomes
progression of DNA packaging
30nm fibers to coiled loops to rosettes to coiled coils to chromatids to chromosomes
