Chapter 10: Chromosome Organization & Molecular Structure (Exam 3)

Question 1

chromosome

Answer 1

structures that contain genetic material, composed of DNA and proteins

Question 2

genome

Answer 2

comprises all genetic material an organism possesses

Question 3

main function of genetic material

Answer 3

store information required to produce an organism:
sythesis of RNA and proteins
replication, segregation, compaction of chromosomes

Question 4

nucleoid

Answer 4

region of bacterial cell where chromosome is found, not membrane bound

Question 5

properties of bacterial chromosomes

Answer 5

circular, few million nucleotides in length
majority of gene sequences encode for proteins, do not have introns, nontranscribed regions referred to as intergenic regions
contain one origin of replication

Question 6

compaction of bacterial chromosomes

Answer 6

compacted 1000-fold
formation of loop domains (microdomains) ~10k bp

Question 7

nucleoid associated proteins (NAPs)

Answer 7

form micro and macro domains:
facilitate compaction and organization
bend DNA
facilitate segregation
help gene regulation

Question 8

DNA supercoiling

Answer 8

second layer of DNA compaction, in bacteria negatively supercoiled (less tight than positive, creates tension that may be released by DNA strand separation)

Question 9

supercoiling enzymes

Answer 9

DNA gyrase: introduces negative supercoils using ATP, can relax positive supercoils, untangle DNA molecules
DNA topoisomerase I: relaxed negative supercoils

Question 10

eukaryotic chromosomes

Answer 10

contain one or more sets of chromosomes
linear
much more DNA than bacteria
located in nucleus, highly compacted
DNA-protein complex in chromosomes: chromatin
vary in size
contain repetitive DNA sequences that do not encode proteins
noncoding regions called introns
average genome 1 billion bp

Question 11

types of DNA sequences in eukaryotes used for DNA replication and segregation

Answer 11

origins of replication, centromeres, telomeres

Question 12

types of eukaryotic genome sequences

Answer 12

unique/ non-repetitive
moderately repetitive
highly repetitive

Question 13

unique sequences

Answer 13

found once or twice in genome, includes structural genes and intergenic areas
41% of genome

Question 14

moderately repetitive sequences

Answer 14

found 100s-1000s of times
includes: rRNA and histone genes, origins of replication, sequences for expression and translation, transposable elements

Question 15

highly repetitive sequences

Answer 15

found 10s of thousands to millions of times
each copy relatively short
can be interspersed throughout genome
examples: Alu family, AATAT in drosophila
found in centromeric and telomeric regions
make up 50% of genome

Question 16

nucleosome

Answer 16

repeating structural unit of a chromatin
composed of double stranded DNA segment wrapped around an octamer

Question 17

octamer

Answer 17

composed of two copies each of four histone proteins

Question 18

histone proteins

Answer 18

made of many positively charges amino acids (lysine and arginine) which bind to DNA backbone
H2A. H2B, H3, H4 make up octamer
H1 linker histone

Question 19

30 nm fiber

Answer 19

structure of compacted nucleosomes
H1 compacts them
beads on a string morphology
shortens DNA 7 fold

Question 20

loop domains in chromatin

Answer 20

uses proteins CTCF and SMC
contain genes cell is using, remains accessible

Question 21

CCCTC binding factor (CTCF)

Answer 21

binds 3 regularly spaced repeats of CCCTC

Question 22

structural maintenance of chromosome (SMC) proteins

Answer 22

wrap around themselves and 2 DNA segments to form loop

Question 23

euchromatin

Answer 23

less condensed, transcriptionally active, made of loop domains

Question 24

heterochromatin

Answer 24

tightly compacted, transcriptionally inactive

Question 25

types of heterochromatin

Answer 25

constitutive and faculatative

Question 26

constitutive heterochromatin

Answer 26

always heterochromatic
permanently inactive
highly repetitive sequences

Question 27

facultative heterochromatin

Answer 27

regions that convert between euchromatin and heterochromatin

Question 28

compaction of chromatin during cell divison

Answer 28

end of prophase: entirely heterochromatic
interphase: entirely euchromatic

Question 29

metaphase chromosomes

Answer 29

loop domains highly compacted, anchored to scaffold
uses two proteins: condensin and cohesion (both SMCs)