BIOLOGY 1A03 Test #3 Questions and Answers Already Passed Latest Update 2025-2026
Annotation stage of genomic sequencing. - Answers Once all the DNA sequences are
assembled based on their contigs, the DNA can be analyzed with the 6 possible reading frames.
Computer programs scan the sequence of a genome in both directions and identify each
reading frame that is possible on both DNA strands.
- the longest stretch of codons that lacks a stop codon is a good reading frame and is therefore
indicative as a coding sequence.
- AUG is the start codon (ATG)
- UAA, UAG, and UGA are stop codons (TAA, TAG, TGA).
Cell cycle - Answers 1. Interphase (preparations for cell division, which includes growth of the
cell and replication of the DNA).
2. M Phase (mitosis + cytokinesis)
Interphase:
0. G0 phase (between M and S phase)
- can last from days to years.
- cells in G0 phase are non-dividing.
- e.g. muscle, lens, nerve cells.
1. G1 phase
2. S phase (DNA synthesis)
3. G2 phase
Mitosis (discovered by Walther Flemming. Composed of five distinct stages that are
morphometrically characterized based on the shapes of chromosomes)
,1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Binary Fission - Answers - Asexual reproduction
- Circular chromosome attach to cell membrane
- As the cell elongates so does the DNA
- DNA replication is complete when bacterium is double its original size
- Bacteria constricts along the midpoint of the cell
Stem cells - Answers - Adult stem cells are different from embryonic stem cells
- Embryonic stem cells can differentiate into all cell types in the organism whereas adult stem
cells can only replace non-reproducing specialized cells.
- When muscle tissue is damaged, quiescent (non-dividing) satellite stem cells present in the
basement membrane of the muscle tissue become activated and enable muscle regeneration.
- The activation of these stem cells leads to proliferation, differentiation and fusion of muscle
precursor cells (myoblast), which become mature muscle cells in muscle fibres (myofibres).
- Once the cells have differentiated into the myofibres, they can't divide.
- satillite stem cells that are in quiescence and are dormant in the G0 phase can be activated
and enter the cell cycle
Interphase - Answers - each chromosome is in long thin chromatin fibre.
- in S phase, two copies of DNA are created (sister chromatid).
- In S phase, centrosomes duplicate as well.
- 22 homologous chromosomes and 1 pair of sex chromosomes.
- chromsomes can't be identified from one another as they are not formed in the structures we
are used to seeing.
Mitosis - Answers - Beginning of M stage of cell division is following G2.
,Prophase
1. chromosomes condense (chromosomes are visible as sister chromatids)
2. centrosomes move to opposite poles of the cell.
3. centrosomes radiate microtubules, forming mitotic spindle (animal cells)
- microtubule organizing center (plant cells).
Prometaphase
1. The nuclear envelop disintegrates.
2. mitotic spindle can attach to special protein structures on the centromeres of chromosomes
called kinetochores.
- i) kinetechore microtubules move the chromosomes to the poles.
- ii) polar microtubules interact with each other to push the poles of the cell away from each
other.
Metaphase
1. marked by the alignment of chromosomes at the center of the cell in a region called the
metaphase plate.
- the kinetochore microtubules facilitate this alignment at the metaphase plate.
Anaphase
1. kinetochore microtubules shorten and sister chormatids move towards the opposite poles of
cell.
- disjunctional segregation occurs between the centromere where it is disjoined and segregated.
2. polar microtubules push each other to elongate the cell.
3. by the end of anaphase, the poles of the cell have equal amounts of chromosomes.
, Telophase
1. Nuclear envelop reforms
2. chromosomes decondense and spindle microtubules are depolymerized.
Cytokinesis
1. The cell divides
- i) in animal and fungi cells, the contractile ring made of motor proteins contract bundles of
actin fibers along the midline.
- this causes the cleavage furrow which separates into two identical cells.
- ii) in plant cells the cells lay down a newly developed cell wall along a cell plate region in the
middle of the cell.
- this forming cell wall fuses with the original cell wall and cytokinesis is complete.
Controlling progression of mitosis i) (Cyclin +CDK = MPF). - Answers - Tim hunt measured
changing levels of protein in sea urchin embryos.
- they added labelled methionine to the eggs and waited for the newly synthesized protein.
- they took samples of the embryos and examined the changing protein levels using gel
electrophoresis
- they noticed that most protein bands on the gel became darker as cell division and embryonic
division progressed.
- however one protein band oscilated.
- increaesd and decreaed with cell division.
- they called it cyclin.
Hunt discovered cyclin protein and cyclin dependent kinase (CDK) protein that controlled the
cell cycle.
Annotation stage of genomic sequencing. - Answers Once all the DNA sequences are
assembled based on their contigs, the DNA can be analyzed with the 6 possible reading frames.
Computer programs scan the sequence of a genome in both directions and identify each
reading frame that is possible on both DNA strands.
- the longest stretch of codons that lacks a stop codon is a good reading frame and is therefore
indicative as a coding sequence.
- AUG is the start codon (ATG)
- UAA, UAG, and UGA are stop codons (TAA, TAG, TGA).
Cell cycle - Answers 1. Interphase (preparations for cell division, which includes growth of the
cell and replication of the DNA).
2. M Phase (mitosis + cytokinesis)
Interphase:
0. G0 phase (between M and S phase)
- can last from days to years.
- cells in G0 phase are non-dividing.
- e.g. muscle, lens, nerve cells.
1. G1 phase
2. S phase (DNA synthesis)
3. G2 phase
Mitosis (discovered by Walther Flemming. Composed of five distinct stages that are
morphometrically characterized based on the shapes of chromosomes)
,1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Binary Fission - Answers - Asexual reproduction
- Circular chromosome attach to cell membrane
- As the cell elongates so does the DNA
- DNA replication is complete when bacterium is double its original size
- Bacteria constricts along the midpoint of the cell
Stem cells - Answers - Adult stem cells are different from embryonic stem cells
- Embryonic stem cells can differentiate into all cell types in the organism whereas adult stem
cells can only replace non-reproducing specialized cells.
- When muscle tissue is damaged, quiescent (non-dividing) satellite stem cells present in the
basement membrane of the muscle tissue become activated and enable muscle regeneration.
- The activation of these stem cells leads to proliferation, differentiation and fusion of muscle
precursor cells (myoblast), which become mature muscle cells in muscle fibres (myofibres).
- Once the cells have differentiated into the myofibres, they can't divide.
- satillite stem cells that are in quiescence and are dormant in the G0 phase can be activated
and enter the cell cycle
Interphase - Answers - each chromosome is in long thin chromatin fibre.
- in S phase, two copies of DNA are created (sister chromatid).
- In S phase, centrosomes duplicate as well.
- 22 homologous chromosomes and 1 pair of sex chromosomes.
- chromsomes can't be identified from one another as they are not formed in the structures we
are used to seeing.
Mitosis - Answers - Beginning of M stage of cell division is following G2.
,Prophase
1. chromosomes condense (chromosomes are visible as sister chromatids)
2. centrosomes move to opposite poles of the cell.
3. centrosomes radiate microtubules, forming mitotic spindle (animal cells)
- microtubule organizing center (plant cells).
Prometaphase
1. The nuclear envelop disintegrates.
2. mitotic spindle can attach to special protein structures on the centromeres of chromosomes
called kinetochores.
- i) kinetechore microtubules move the chromosomes to the poles.
- ii) polar microtubules interact with each other to push the poles of the cell away from each
other.
Metaphase
1. marked by the alignment of chromosomes at the center of the cell in a region called the
metaphase plate.
- the kinetochore microtubules facilitate this alignment at the metaphase plate.
Anaphase
1. kinetochore microtubules shorten and sister chormatids move towards the opposite poles of
cell.
- disjunctional segregation occurs between the centromere where it is disjoined and segregated.
2. polar microtubules push each other to elongate the cell.
3. by the end of anaphase, the poles of the cell have equal amounts of chromosomes.
, Telophase
1. Nuclear envelop reforms
2. chromosomes decondense and spindle microtubules are depolymerized.
Cytokinesis
1. The cell divides
- i) in animal and fungi cells, the contractile ring made of motor proteins contract bundles of
actin fibers along the midline.
- this causes the cleavage furrow which separates into two identical cells.
- ii) in plant cells the cells lay down a newly developed cell wall along a cell plate region in the
middle of the cell.
- this forming cell wall fuses with the original cell wall and cytokinesis is complete.
Controlling progression of mitosis i) (Cyclin +CDK = MPF). - Answers - Tim hunt measured
changing levels of protein in sea urchin embryos.
- they added labelled methionine to the eggs and waited for the newly synthesized protein.
- they took samples of the embryos and examined the changing protein levels using gel
electrophoresis
- they noticed that most protein bands on the gel became darker as cell division and embryonic
division progressed.
- however one protein band oscilated.
- increaesd and decreaed with cell division.
- they called it cyclin.
Hunt discovered cyclin protein and cyclin dependent kinase (CDK) protein that controlled the
cell cycle.
