Biology 1124 EXAM III Questions And All
Correct Answers.
True or False: The number of chromosomes differs from species to species. - Answer True
What happens if an individual has too many copies of a chromosome? Too few? Which is more
problematic? What type of error during gametogenesis could lead to gametes with n+1 or n-1
chromosomes? - Answer - If an individual has too many or too few copies of a chromosome,
they are not likely to survive.
- However, having too few copies of a chromosome is more problematic than having too many.
- An organism may be able to survive with three copies of a particular chromosome (e.g. trisomy
21 causes Down syndrome), but they cannot survive with only one copy of a particular
chromosome.
- Nondisjunction during gametogenesis could lead to gametes with too many or too few
chromosomes.
What is chromatin? - Answer Chromatin is a condensed form of DNA consisting of DNA
wrapped around histone proteins.
How are chromosomes further condensed for mitosis? Why do chromosomes need to be more
condensed for mitosis? - Answer Chromosomes are further condensed for mitosis by attaching
chromatin to a protein scaffold and then wrapping up the protein scaffold to form
chromosomes that can be seen under a microscope.
Chromosomes need to be as condensed as possible for mitosis for efficient and accurate
separation.
What are homologous chromosomes? - Answer Homologous chromosomes are pairs of
chromosomes that code for the same genes but may have slightly different information for
those genes.
What are sister chromatids? - Answer Sister chromatids are two copies of a replicated
chromosome held together at the centromere.
In a pair of replicated homologous chromosomes, there are _____ sister chromatids. - Answer
4
, Put the following phases of the cell cycle in order: cytokinesis, G1, G2, M, S. Describe what
happens during each phase. - Answer G1 → S → G2 → M → cytokinesis.
- During G1 phase, the cell grows, performs its function, and prepares for DNA replication.
- During S phase, DNA replication occurs.
- During G2 phase, the cell continues to grow and perform its function while preparing for
mitosis.
- During M phase, mitosis occurs.
- Cytokinesis is the splitting of the cell into two daughter cells.
What is G0 phase? - Answer G0 phase is a stationary phase where cells continue to perform
their function, but they are not growing nor preparing for replication. Cells may enter this phase
from G1, and if signaled to do so, they may reenter G1 to continue through the cell cycle.
Put the following phases of mitosis in order: anaphase, metaphase, prometaphase, prophase,
telophase. Describe what happens during each phase - Answer Prophase → prometaphase →
metaphase → anaphase → telophase.
PROPHASE: the chromosomes condense, the spindle fibers begin to form, and the nuclear
envelope breaks down.
PROMETAPHASE: the microtubule spindles connect to the chromosomes at the kinetochores
and the chromosomes begin to move to the equator of the cell.
METAPHASE: the chromosomes are aligned at the equator of the cell and the chromosomes are
attached to each pole of the cell via microtubules.
ANAPHASE: the proteins holding the centromeres of the sister chromatids together are
degraded so that the chromosomes can be pulled to opposite poles and the poles move further
apart.
TELOPHASE: the chromosomes are clustered at opposite poles, the nuclear envelope reforms,
the chromosomes decondense, and the spindle microtubules are dissembled.
There are three checkpoints during the cell cycle. Describe when they occur and what must
Correct Answers.
True or False: The number of chromosomes differs from species to species. - Answer True
What happens if an individual has too many copies of a chromosome? Too few? Which is more
problematic? What type of error during gametogenesis could lead to gametes with n+1 or n-1
chromosomes? - Answer - If an individual has too many or too few copies of a chromosome,
they are not likely to survive.
- However, having too few copies of a chromosome is more problematic than having too many.
- An organism may be able to survive with three copies of a particular chromosome (e.g. trisomy
21 causes Down syndrome), but they cannot survive with only one copy of a particular
chromosome.
- Nondisjunction during gametogenesis could lead to gametes with too many or too few
chromosomes.
What is chromatin? - Answer Chromatin is a condensed form of DNA consisting of DNA
wrapped around histone proteins.
How are chromosomes further condensed for mitosis? Why do chromosomes need to be more
condensed for mitosis? - Answer Chromosomes are further condensed for mitosis by attaching
chromatin to a protein scaffold and then wrapping up the protein scaffold to form
chromosomes that can be seen under a microscope.
Chromosomes need to be as condensed as possible for mitosis for efficient and accurate
separation.
What are homologous chromosomes? - Answer Homologous chromosomes are pairs of
chromosomes that code for the same genes but may have slightly different information for
those genes.
What are sister chromatids? - Answer Sister chromatids are two copies of a replicated
chromosome held together at the centromere.
In a pair of replicated homologous chromosomes, there are _____ sister chromatids. - Answer
4
, Put the following phases of the cell cycle in order: cytokinesis, G1, G2, M, S. Describe what
happens during each phase. - Answer G1 → S → G2 → M → cytokinesis.
- During G1 phase, the cell grows, performs its function, and prepares for DNA replication.
- During S phase, DNA replication occurs.
- During G2 phase, the cell continues to grow and perform its function while preparing for
mitosis.
- During M phase, mitosis occurs.
- Cytokinesis is the splitting of the cell into two daughter cells.
What is G0 phase? - Answer G0 phase is a stationary phase where cells continue to perform
their function, but they are not growing nor preparing for replication. Cells may enter this phase
from G1, and if signaled to do so, they may reenter G1 to continue through the cell cycle.
Put the following phases of mitosis in order: anaphase, metaphase, prometaphase, prophase,
telophase. Describe what happens during each phase - Answer Prophase → prometaphase →
metaphase → anaphase → telophase.
PROPHASE: the chromosomes condense, the spindle fibers begin to form, and the nuclear
envelope breaks down.
PROMETAPHASE: the microtubule spindles connect to the chromosomes at the kinetochores
and the chromosomes begin to move to the equator of the cell.
METAPHASE: the chromosomes are aligned at the equator of the cell and the chromosomes are
attached to each pole of the cell via microtubules.
ANAPHASE: the proteins holding the centromeres of the sister chromatids together are
degraded so that the chromosomes can be pulled to opposite poles and the poles move further
apart.
TELOPHASE: the chromosomes are clustered at opposite poles, the nuclear envelope reforms,
the chromosomes decondense, and the spindle microtubules are dissembled.
There are three checkpoints during the cell cycle. Describe when they occur and what must
