BSCI 1510 EXAM
BSCI 1510 EXAM III QUESTIONS AND ANSWERS GRADED A+
The core histones are small proteins that have a globular domain and
long unstructured regions at the N-terminus. Which of the following is
NOT true of the N-terminal "tails" of these histones?
A. They can interact with neighbouring nucleosomes.
B. They extend out of the nucleosome core.
C. They bind to DNA in a sequence-specific manner.
D. They are subject to covalent modifications. ANS >> C. They bind to
DNA in a sequence-specific manner.
How are chromosomes organized in bacteria? ANS >> Circular
chromosome in which there is one site where DNA replication starts
called the origin of replication
Fission ANS >> Process through which prokaryotic cells divide in two by
pinching apart, although some is due to laying down of membrane and
cell wall in between two daughter cells
,BSCI 1510 EXAM
Why and how is it important that the two chromosomes move apart in
prokaryotes? ANS >> It is important to ensure that each daughter cell
gets a chromosome and may occur because chromosomes attach to
plasma membrane through protein attachments through possible
movement or growth, although this mechanism is not well understood
What are the reasons that cell division is more complicated in
eukaryotic cells? ANS >> 1. Nuclear envelope --> in most, needs to break
down during cell division
2. Large amount of DNA to replicate
3. DNA is organized in a different way --> multiple linear chromosomes
must be equally distributed to daughter cells
Centromere ANS >> Region of a chromosome where the two sister
chromatids attach; DNA site
Telomere ANS >> Protect ends of chromosome and facilitate complete
replication
Origins of replication ANS >> Many on a chromosome because eukaryotic
cells are much larger
Diploid ANS >> Two copies of each chromosome, each coming from one
parent (i.e., humans)
,BSCI 1510 EXAM
How many total chromosomes do humans have? Pairs? ANS >> 46 total
chromosomes, 23 pairs
How many chromosomes are 'autosomes'? Sex chromosomes? ANS >>
44 are autosomes and 2 are sex chromosomes (XX or XY)
Haploid ANS >> One copy of each chromosome (i.e., gametes)
Eukaryotic cell cycle ANS >> Interphase (G1, S phase, G2) --> M phase
(mitosis)
G1 phase (1st gap phase) ANS >> - Cell growth; ensures correct conditions
(i.e., signals and nutrients); can enter G0 (longer lasting G1 phase or
resting phase)
- One double-stranded DNA molecule --> homologs
S phase (synthesis phase) ANS >> DNA replication
G2 phase (2nd gap phase) ANS >> - Is DNA done replicating? Has DNA
damage been repaired? --> If the answer is no, mitosis can not occur
- 2 double-stranded DNA molecules; 2 sister chromatids (identical) that
are condensed
- Chromosome number stays the same
, BSCI 1510 EXAM
Mitosis ANS >> One cell divides into two
Characteristics of interphase ANS >> - 2 centrosomes (microtubule
organizing centres) --> daughter cell inherits 1 but duplicates during G1
phase; each consists of 2 centrioles
- Centrosomes begin to separate using microtubules
- Nuclear envelope is intact surrounding DNA which is in a condensed
state
- Interphase chromosomes occupy 'territories' --> sequences on the
same chromosomes are closer to each other but homologs have no
particular location
Characteristics of prophase (first events of mitosis) ANS >> - Nuclear
envelope still intact around chromosomes
- Chromosomes have been replicated and beginning to condense
- DNA becoming more tightly packaged
- Kinetochore forms are the centre of chromosomes
- 2 centrosomes moving apart in cytoplasm because eventually they're
going to have to be placed in opposite sides of cell
- Formation of the beginning of the mitotic spindle
- Breakdown of nuclear envelope signals next phase
BSCI 1510 EXAM III QUESTIONS AND ANSWERS GRADED A+
The core histones are small proteins that have a globular domain and
long unstructured regions at the N-terminus. Which of the following is
NOT true of the N-terminal "tails" of these histones?
A. They can interact with neighbouring nucleosomes.
B. They extend out of the nucleosome core.
C. They bind to DNA in a sequence-specific manner.
D. They are subject to covalent modifications. ANS >> C. They bind to
DNA in a sequence-specific manner.
How are chromosomes organized in bacteria? ANS >> Circular
chromosome in which there is one site where DNA replication starts
called the origin of replication
Fission ANS >> Process through which prokaryotic cells divide in two by
pinching apart, although some is due to laying down of membrane and
cell wall in between two daughter cells
,BSCI 1510 EXAM
Why and how is it important that the two chromosomes move apart in
prokaryotes? ANS >> It is important to ensure that each daughter cell
gets a chromosome and may occur because chromosomes attach to
plasma membrane through protein attachments through possible
movement or growth, although this mechanism is not well understood
What are the reasons that cell division is more complicated in
eukaryotic cells? ANS >> 1. Nuclear envelope --> in most, needs to break
down during cell division
2. Large amount of DNA to replicate
3. DNA is organized in a different way --> multiple linear chromosomes
must be equally distributed to daughter cells
Centromere ANS >> Region of a chromosome where the two sister
chromatids attach; DNA site
Telomere ANS >> Protect ends of chromosome and facilitate complete
replication
Origins of replication ANS >> Many on a chromosome because eukaryotic
cells are much larger
Diploid ANS >> Two copies of each chromosome, each coming from one
parent (i.e., humans)
,BSCI 1510 EXAM
How many total chromosomes do humans have? Pairs? ANS >> 46 total
chromosomes, 23 pairs
How many chromosomes are 'autosomes'? Sex chromosomes? ANS >>
44 are autosomes and 2 are sex chromosomes (XX or XY)
Haploid ANS >> One copy of each chromosome (i.e., gametes)
Eukaryotic cell cycle ANS >> Interphase (G1, S phase, G2) --> M phase
(mitosis)
G1 phase (1st gap phase) ANS >> - Cell growth; ensures correct conditions
(i.e., signals and nutrients); can enter G0 (longer lasting G1 phase or
resting phase)
- One double-stranded DNA molecule --> homologs
S phase (synthesis phase) ANS >> DNA replication
G2 phase (2nd gap phase) ANS >> - Is DNA done replicating? Has DNA
damage been repaired? --> If the answer is no, mitosis can not occur
- 2 double-stranded DNA molecules; 2 sister chromatids (identical) that
are condensed
- Chromosome number stays the same
, BSCI 1510 EXAM
Mitosis ANS >> One cell divides into two
Characteristics of interphase ANS >> - 2 centrosomes (microtubule
organizing centres) --> daughter cell inherits 1 but duplicates during G1
phase; each consists of 2 centrioles
- Centrosomes begin to separate using microtubules
- Nuclear envelope is intact surrounding DNA which is in a condensed
state
- Interphase chromosomes occupy 'territories' --> sequences on the
same chromosomes are closer to each other but homologs have no
particular location
Characteristics of prophase (first events of mitosis) ANS >> - Nuclear
envelope still intact around chromosomes
- Chromosomes have been replicated and beginning to condense
- DNA becoming more tightly packaged
- Kinetochore forms are the centre of chromosomes
- 2 centrosomes moving apart in cytoplasm because eventually they're
going to have to be placed in opposite sides of cell
- Formation of the beginning of the mitotic spindle
- Breakdown of nuclear envelope signals next phase
