Prokaryotes, Bacteria, and cell division
What is binary fission?
A form of asexual reproduction in which the parent divides into two approximately equal parts Bacterial binary fission is the process that bacteria use to carry out cell division.
Centrioles can be found in:
Centrioles help organize the mitotic spindle. Centrioles are found in centrosomes, which are organelles. Only eukaryotes have membrane-bound organelles, so only eukaryotes can have membrane-associated structures such as centrioles.
What are the two cell division in Eukaryotas?
There are two ways cell division can happen in humans and most other animals, called mitosis and meiosis.
Problem Which of the following is not a reason cancer is hard to treat? (Choice A) A Increased growth rate (Choice B) B Increased contact inhibition (Choice C) C Increased metastasis (Choice D) D Increased mutation rate
Contact inhibition in cells is a growth control mechanism that is often damaged or turned off in cancerous growths.
A karyotype can be used to check for certain chromosomal mutations. In what cell cycle phase can cells be karyotyped?
Sister chromatids split in anaphase, meaning that a karyotype is taken of cells arrested in metaphase.
Which of the following would you expect to see in a cancerous mass? Choose 1 answer: Choose 1 answer: (Choice A) A Decreased ATP use (Choice B) B Increased time in G_0 0 start subscript, 0, end subscript (Choice C) C Gain of function mutations in checkpoint proteins (Choice D) D Loss of function mutations in apoptosis-controlling proteins
A cancer is an uncontrolled, quickly dividing cellular mass. Cellular division is an energy intensive process, and cancer cells tend to use an increased amount of ATP. Loss of function mutations in the mechanisms that protect the cell, such as the apoptosis mechanisms, are often seen in cancerous masses.
A hybridization probe is a fragment of genetic material that is used to to detect the presence of nucleotide sequences that are complementary to the sequence of the probe. Which infectious agent could not be detected with a probe? (Choice A) A A retrovirus (Choice B) B A virus with double-stranded RNA material (Choice C) C A virus with single-stranded DNA material (Choice D) D A prion
A hybridization probe would not detect a prion, because prions are made of proteins. They have no genetic material for the probe to bind to.
Colchicine is a drug used to treat gout. It also happens to arrest cells in anaphase. Which cytoskeletal protein does colchicine effect? Choose 1 answer: Choose 1 answer: (Choice A) A Tubulin (Choice B) B Keratin (Choice C) C Myosin (Choice D) D Actin
Anaphase is the stage where sister chromatids are pulled apart. Microtubules from centrosomes bind chromosomal kinetochores to separate the genetic material. Microtubules are made from tubulin, a protein that can be bound by colchicine. By binding the tubulin, colchicine inhibits tubulin polymerization, and so prevents microtubules from being formed.
Which factor may help determine the antigenicity of a virus?
Antigenicity refers to the part of the virus that stimulates white blood cells. Internal proteins are not in direct contact with white blood cells, and therefore would not express antigenicity of any kind. The whole capsid is not entirely recognized by white blood cells. The capsomers are recognized by white blood cells, and therefore determine the virus antigenicity.
What is a chromosome?
Chromosomes made of chromatin. a chromosome is as one very long strand of DNA, with a bunch of histone proteins stuck to it like beads on a string. Chromosomes are stored in the nuclei of cells.
How does copying of DNA replication occur in bacteria?
Copying of DNA by replication enzymes begins at a spot on the chromosome called the origin of replication. The origin is the first part of the DNA to be copied. s replication continues, the two origins move towards opposite ends of the cell, pulling the rest of the chromosome along with them. The cell also gets longer, adding to the separation of the newly forming chromosomes.
What are the characteristics of virus?
Doesn't maintain homeostasis It has level of organization It adapts to their environment
Oogenesis, the process that creates female gametes, is halted at prophase I until puberty. Which of the following describes the DNA content of a female's gametes during her childhood?
In prophase I the cell has undergone DNA replication, but has yet to divide, leaving it with 46 chromosomes and 92 chromatids.
Oncoviruses are a type of animal virus that can cause a neoplasm - an abnormal, often excessive, growth of tissue. Which type of virus is likely to be an oncovirus?
Lysogenic Virus Bacteriophage viruses attack bacteria. Presence of an envelope does not determine tissue growth. All lytic viruses destroy the cell while lysogenic viruses may be replicated with the cell. Thus the host will generate new daughter cells infected with the virus, eventually leading to a neoplasm, also known as tumor.
Certain types of arthritis, or inflammation of the joints, could be caused by viruses. In some cases, infected individuals experience an acute, rapid degradation of the chondrocytes that make up the articular capsule upon infection. Which type of virus is likely to cause such acute symptoms? Choose 1 answer: Choose 1 answer: (Choice A) A A lysogenic virus, because its virulence tends to be expressed immediately (Choice B) B A lysogenic virus, because it would specifically target and quickly destroy the chondrocytes (Choice C) C A lytic virus, because it has a brief latent phase and immediately attacks the joints (Choice D) D A lytic virus, because it would cause a rapid destruction of the articular capsule
Lysogenic viruses have a dormant period. This means that although they are being replicated by the host, their virulence will not be expressed for some time. Hint #22 / 3 Because their virulence is temporarily repressed, a lysogenic virus would not act so quickly upon infection. Hint #33 / 3 Lytic viruses do not have a dormant or latent phase. In other words, they are fast-acting and cause immediate damage to the host cells. Therefore, lytic viruses are much more likely to be the cause of this specific viral arthritis.
Retinoblastoma protein, RB, is an important cell cycle checkpoint protein that prevents the transition from G1 to S phase. The presence of the cyclin/CDK complex releases it from the genes that it binds. Which of the following mutation scenarios is least likely to lead to the formation of a neoplasm?
No RB mutation and CDK that cannot bind to cyclin An RB loss of function mutation would result in fewer checkpoints for the cell to pass through in its division cycle. A neoplasm is an uncontrolled growth. In a CDK loss of function mutation would be there was no way for the cell to pass through the G1 to S phase checkpoint, and the cell would be stuck. While this could lead to cell death and atrophy, it would not lead to uncontrolled growth.
Reverse transcriptase is known for having poor proofreading activity. What would be a consequence of this? (Choice A) A It could add to the virulence and transmission of the virus (Choice B) B It could cause the host cell to incorrectly proofread as well (Choice C) C It establishes lifelong infection in the host (Choice D) D It makes each new viral generation more viable
Poor proofreading will typically result in mutations. Mutations in the viral genome could cause it to become nonfunctional. Therefore, it would not always make each new viral generation more viable. However, mutations can also allow the virus to become drug-resistant or increase virulence. Therefore, if the mutation occurs at the right spot, it can increase transmission of the virus.
What distinguishes prions from viruses?
Presence of genetic material Not all viruses have an envelope, and prions don't need one. Both viruses and prions contain protein. Both viruses and prions can cause infection. Prions, as opposed to viruses, do not contain any genetic material.
What is a hallmark characteristic of reverse transcriptase? Choose 1 answer: Choose 1 answer: (Choice A) A It reads the genetic material backwards (3' → 5') (Choice B) B It allows the virus to infect bacteria through endocytosis (Choice C) C It is encoded in the host cell's genome (Choice D) D It challenges the central dogma of biology (DNA → RNA → Protein)
Retroviruses don't infect bacteria. They infect animals. This is due to the fact that bacteria don't perform endocytosis on account of their rigid cell walls. The retrovirus produces the DNA from 3' → 5', but it reads the template RNA from 5' → 3'. Reverse transcriptase must be encoded for in the virus' genetic material. Hosts never create DNA from RNA, so they would have no need to have that material stored. The last two hints should give you the answer. The reverse transcriptase makes DNA from RNA, challenging the central dogma of biology.
An antiviral drug specifically modifies viral receptors on a eukaryotic host cell. How might this affect the viral reproductive cycle? Choose 1 answer: Choose 1 answer: (Choice A) A It would prevent the virus from attaching to the host cell (Choice B) B It would enhance the process of viral apoptosis (Choice C) C It would facilitate the process of viral endocytosis (Choice D) D It would result in the degeneration of the viral capsid
Since the virus depends on specific receptors on the host cell to attach, this process would be prevented when these specific receptors are modified by the antiviral drug.
Problem Which central dogma of genetics had to be revisited after the discovery of a retrovirus? Choose 1 answer: Choose 1 answer: (Choice A) A Messenger RNA does not always code for proteins (Choice B) B DNA makes RNA that makes protein (Choice C) C Transcriptase assists in the formation of proteins (Choice D) D RNA replication cannot occur prior to translation
The genetic material of retroviruses is RNA. Hint #22 / 4 Retroviruses use reverse transcriptase. Hint #33 / 4 Reverse transcriptase transforms RNA into DNA Hint #44 / 4 The central dogma of genetics is that DNA makes RNA, which in turn makes protein. Retroviruses are an exception to this dogma because they use RNA to make DNA, which makes protein.
Which statement best describes chromosomal movement during mitosis? Choose 1 answer: Choose 1 answer: (Choice A) A Each centrosome binds an individual chromatid to ensure equal division. (Choice B) B Microtubules bind tubulin polymers on centromeres to initiate homologous chromosome separation. (Choice C) C Centrioles send out asters, which bind to kinetochores to pull chromatids apart. (Choice D) D Centrioles on chromatids bind kinetochores to rays sent by the asters.
The kinetochore is a protein structure centered around a chromosome's centromere. Centromeres are found on chromosomes, centrosomes are found towards the poles of cells during cell division. Asters are microtubules sent out by centrioles to bind kinetochores, and microtubule contraction helps pull chromatids apart.
During which phase does the nuclear envelope begin to disappear?
The nuclear envelope is responsible for protecting the genetic material from the rest of the cellular contents. In anaphase, chromosomes move to opposite sides of the cell. In order to allow for proper metaphase alignment and chromosomal division, the nuclear envelope dissolves in prometaphase.
Interphase
The stage of the cell cycle when a cell is preparing itself to duplicate is called interphase. Since so many things are happening in the cell at this time, most of the cell's life is spent in this stage.
A scientist is investigating a specimen in a laboratory. She is attempting to determine whether it is a virus or not. Which of the following would allow her to conclude that it is not a virus? Choose 1 answer: Choose 1 answer: (Choice A) A The specimen has a protein coat (Choice B) B The specimen has no organelles (Choice C) C The specimen is extremely small (Choice D) D The specimen contains DNA and RNA
Viruses are extremely small, so this would not allow her to eliminate the possibility. Viruses are not living cells, and as such do not have organelles. They rely entirely on host cell machinery. Viral nucleic acid is either single-stranded DNA, single-stranded RNA, double-stranded DNA, or double-stranded RNA. It would not have both DNA and RNA, as its size would not allow them to carry that much genetic information
Meiosis
When a cell divides by way of meiosis, it produces four cells, called gametes. Gametes are more commonly called sperm in males and eggs in females. Unlike in mitosis, the gametes produced by meiosis are not clones of the original cell, because each gamete has exactly half as many chromosomes as the original cell.
Mitosis
When a cell divides by way of mitosis, it produces two clones of itself, each with the same number of chromosomes.
What does bacterial cell look like?
bacterial cells usually have a single, circular chromosome and always lack a nucleus. However, the bacterial chromosome is found in a specialized region of the cell called the nucleoid.
