Flashcards in Lecture--Chapter 12 Deck (84)
Chromosomes have a DNA helix of 2 strands, which are complexed with _____.
The relaxed DNA molecule of a single chromosome is longer than the ________ of the cell.
Human genome (23 chromosomes) is about _____ long.
To fit into cells, DNA must be ____.
generally a single circular DNA helix
main chromosome + any plasmids:
Multiple copies of genome may be present during times of _____.
Genome is located as a _____, not in a nucleus.
bacterial "chromosome" (lacks chromatin)
Bacterial chromosome is a few million ____ in length.
E. coli has ~______ base pairs.
Haemophilus influenzae has ~_____ base pairs.
structural genes (encoding proteins)
transcribed gene sequences
intergenic regulatory regions
nontranscribed DNA segments
start site for DNA replication
origin of replication
Bacterial DNA must be packed about ______ smaller than its relaxed length.
Intergenic and repetitive sequences include regions with roles in ______.
With bacterial DNA. compaction is largely accomplished by ____ and ____.
additional coils due to twisting forces
different structural conformations of a molecule
Coiled coils form loops in response to _____.
_____ supercoiling is the ______ state.
Negative supercoiling creates tension which promotes _____.
Negative supercoiling: DNA replication in _____.
Negative supercoiling: DNA transcription for ______.
Supercoiling is _____.
enzymes that either create or reduce supercoiling
reduce ("relax") negative supercoiling
type I topoisomerases
break a single strand, allow rotation around the unbroken strand, and re-form phosphodiester backbone
type I topoisomerases
creates negative supercoiling
DNA gyrase plays a part in ____.
type II topoisomerases
makes a double strand break, redirects the broken strand, then re-seals
type II topoisomerases
essential for bacteria to survive
_______ is one way to cure some bacterial diseases.
inhibiting DNA gyrase
broad-spectrum antibiotics for UTIs, hospital-acquired pneumonia
drug-resistance, side effects issues
A eukaryotic genome is the complete set of _____ chromosomes.
Long ____ DNA molecules complexed with proteins.
Nearly all eukaryotic genomes have ______ of DNA.
3.1 billion nucleotides, 22,000 genes
human genome: initial draft completed in ____, final draft in ____.
human genome: useful for ____ research, _____, _____ studies.
biomedical; forensics; evolution
Large variation in genome size among _____.
many per chromosome, about every 100,000 base pairs
origins of replication
one per chromosome
defined DNA sequence of ~125 base pairs, yeast
long repetitive DNA sequences, most common
both ends, specialised repeated sequences
stabilise and protect the ends of the chromosomes
the number of times a particular motif appears throughout a genome
DNA sequence complexity
usually occur only once or a few times
encode proteins (gene exons)
100s to 1000s of copies
moderately repetitive sequences
Moderately repetitive sequences: _____ and ____ protein genes.
ribosomal RNA; histone
Moderately repetitive sequences: remnants of _____.
10s of thousands to millions of copies
highly repetitive sequences
Highly repetitive sequences: Alu and LINE ______.
clusters of highly repetitive sequences (satellites)
Tandem arrays: polymerase errors in ____.
Tandem arrays: _____ (chromosome pairing) and ____.
Eukaryotic DNA must be _____ packed to fit.
Eukaryotic DNA increased ___ and ____ makes compaction difficult.
size; complex structure
a double-stranded segment of DNA wrapped around an octamer of histone proteins
basic proteins that bind to negatively charged phosphates in the minor groove of the DNA backbone
Eukaryotic Chromosome Compaction: DNA is wrapped around the nucleosome (_____).
beads on a string
Eukaryotic chromosome compaction: nucleosomes coil to form ______.
30 nm fiber
Eukaryotic Chromosome Compaction: 30 nm fiber organised into ______.
radial loop domains
Eukaryotic Chromosome Compaction: MARs are:
matrix attachment regions
Eukaryotic Chromosome Compaction: Additional packing of radial loops and further packing is seen in ____ chromosomes.
discrete nuclear locations of each chromosome
Compaction state of ____ chromosomes is variable.
tightly compacted regions, generally not transcribed
always heterochromatic and inactive
chromatin that can interconvert between heterochromatin and euchromatin
less condensed regions capable of gene transcription
the entire chromosome is packed into heterochromatin
compacted radial loops remain anchored to a _____.
protein that coats individual chromosomes at the beginning of mitosis, then folds the strands.
loops on matrix fiber
matrix fiber folded
chromatin attached to scaffold proteins
family of ATPases that catalyse changes in chromosome structure (condensins and cohesins)
structural maintenance of chromosomes (SMC) proteins