Meiosis It is one of the ways of cell reproduction. This process is performed in the cells in the sex cells. It is a process of cell division in which a diploid cell (2n) undergoes two successive divisions, with the ability to generate four haploid cells (n). This process is carried out in two nuclear and cytoplasmic divisions, called first and second meiotic division or simply meiosis I and meiosis II
Phases of Meiosis
Two successive cell divisions occur in meiosis, Meiosis I (Reduction) and Meiosis II (Division). Meiosis produces 4 haploid cells. Meiosis is also known as reduction division.
In Meiosis I, the level of ploidy is reduced from 2n to n while in Meiosis II the "set" of remaining chromosomes is divided into a process similar to mitosis (division). The biggest difference in the process occurs during Meiosis I.
- MEIOSIS I: Prophase I
During mating, a key event occurs in the matching of homologous chromosomes.
- Metaphase I
In Metaphase I the tetrads line the equator of the cell. The spindle fibers "stick" to the centromere of each homologous pair and subsequent events are similar to mitosis.
- Anaphase I
During Anaphase I the tetrads separate and the chromosomes are dragged to the opposite poles by the spindle fibers. The centromeres in Anaphase I remain intact.
- Telophase I
Telophase I is similar to mitosis, except that in the end each "cell" has only one group of replicated chromosomes. Depending on the species, the new nuclear membrane can be formed (or not). Some animals can divide their centrioles during this phase.
Telophase may be absent in some species. If there is, it is followed by an interface called interkinesis; Unlike the mitotic interface, there is no duplication of genetic material since each chromosome already has two chromatids. The other difference is that these sister chromatids are no longer genetically identical, due to the cross-linking phenomenon.
- MEIOSIS II: Prophase II
During Prophase II, the nuclear membrane (if formed during Telophase I) dissolves, and the spindle fibers appear, as in the prophase of mitosis. Actually, Meiosis II is very similar to mitosis.
- Metaphase II
Metaphase II is similar to that of mitosis, with chromosomes in the equatorial plane and spindle fibers sticking to the opposite faces of the centromere in the kinetochore region.
- Anaphase II
During Anaphase II, the centromere divides and the then chromatids, now chromosomes, are secreted to the opposite poles of the cell.
- Telophase II
Telophase II is identical to Telophase of mitosis. Cytokinesis separates the cells.
Comparison of Mitosis and Meiosis :
- Mitosis maintains the level of ploidy while meiosis reduces it.
- Meiosis can be considered as a phase of chromosome number reduction followed by a slightly different mitosis.
- Meiosis only occurs in relatively few cells of a multicellular organism, while mitosis is more common.
A--When someone hike, how will the altitude affect your body?
The maintenance of the body's physiology is important for the living organisms.The metabolism of the human body affects with the temperature, altitude and with the other external and internal conditions of the body.
In case of higher altitudes, the partial pressure of the oxygen is low. This causes the increase in the breathing rates so the oxygen amount in the body can be increased. The dehydration of the body may also occur for the few hours as the individual reaches the altitude. The body's metabolism also increased with the increase in the altitude.
The domains Archaea and Eubacteria are similar in thatall
A. live in extreme environments
B. carry on photosynthesis
C. lack a nucleus
D. carry on aerobic respiration
Would the answer be C. lack a nucleus?
The correct answer is C. lack a nucleus
Eubacteria are bacteria which is different from archaea but both archaea and bacteria are considered to be in prokaryotes however they both are divided into two different domain that is bacteria and archaea.
Bacteria and archaea are prokaryotes because they lack membrane-bound nucleus so their genetic material is scattered in the cytoplasm. Eukaryotes are organism which have their genetic material enclosed in a membrane-bound nucleus. So the similarity in archaea and eubacteria is that they both lack a nucleus.
Based on what is known about cell division, what woul happen if colchicine was administered at the S phase of interphase and why?
Colchicine is a drug obtained from the Colchicum autumnale which is used to induce polyploidy in the cell by preventing the segregation of the chromosomes during anaphase. The colchicine act by preventing the depolymerisation of the microtubules thus the chromosomes become condensed at the equatorial plate.
Since during S phase, the DNA gets replicated where no involvement of the microtubules is observed therefore the Colchicine will show no effect during the S phase on the DNA.
Thus, no effect is the correct answer.
A--What do you get if you add the number of maternal chromosomes in a somatic cell to the number of autosomes in a sex cell, then subtract the number of Barr bodies in a somatic cell of a person with kleinfelter's syndrome?
A somatic cell is diploid - it has 46 chromosomes. Half of these are from the mother, so there are 23 maternal chromosomes
A sex cell (gamete) is haploid - it has 23 chromosomes. There are (usually) two sex chromosomes in a diploid genome, either XX or XY, so there is one 1 in a haploid cell, giving a total of 22 autosomes
Barr bodies are inactive X chromosomes in a female somatic cell. This occurs to control dosage compensation (otherwise all the genes on the X in females would be expressed twice as much as they are in males). In a healthy female, there is normally one Barr body
A person with Kleinfelter's syndrome has two X chromosomes and one Y (XXY). They are biologically male, but have two X chromosomes. Therefore, one of these becomes a Barr body, as in females.
23 + 22 - 1 = 44
During DNA replication, the short sections of new DNA, known as Okazaki fragments, which are eventually linked together by ligase. What are these strands called?
The correct answer is- lagging strand
During the DNA replication both the strands acts as template strand and DNA polymerase replicated both the strand. During this replication, one strand is replicated continuously which is called the leading strand and another strand is not synthesized in a continuous manner.
So small DNA fragments are formed due to discontinuous replication of DNA which is called Okazaki fragments. These fragments are then joined by DNA ligase and the strand is called lagging strand.
Therefore the strand which is synthesized in a discontinuous manner is called lagging strand.
True or False 1.Reproductive potential is the same for every generation
2. The rawmaterial for evolutionary change are mutations.
3. Microevolution refers to change of microbial populations.
4. Thebiological definition of a species refers to those
individuals thatcan interbreed and produce fertile offspring.
5. The level ofecological study that involves organisms of the same
species livingin an area is a population.
6. Populationdistribution is largely determined by limiting
7. Events suchas floods or fires are density-independent factors
because theyaffect population size regardless of the population
8. A communityconsists of organisms of various species interacting
with eachother in a particular area.
9. One outcomeof a situation in which 2 species occupy the same
10. Coastalregions generally have greater temperature fluctuations
between dayand night.
true i think becuase i checked it out i already had that question before
A--What do you get if you add the number of maternal chromosomesin a somatic cell to the number of autosomes in a sex
cell, thensubtract the number of Barr bodies in a somatic cell of a
personwith kleinfelter's syndrome?
• Men with Klinefelter's syndrome have an extra X chromosome.
• Of the 23 pairs of chromosomes, one pair is called the sex chromosomes because they determine a person's sex. One sex chromosome is inherited from the mother and the other from the father. Mothers always pass on an X chromosome, but fathers can pass on an X or a Y chromosome. -
•The normal male chromosome arrangement is 46XY, but men with Klinefelter's syndrome have 47XXY. The extra X chromosome can come from either parent.
Describe what RNA splicing is and how it explains that the humangenome can be approximately the same size as a far
RNA splicing is the intron removal and exon binding in the mRNA before leaving the nucleus.
Alternative splicing of identical RNA transcripts into different cell types can produce different mature mRNA molecules that translate into different polypeptides.
The genetic information encoded in the AND is transcribed to a copy of RNA (primary transcript). This copy is then modified with the addition of the 5 ’cap (CAP) and the poly-A tail, the excision of the introns and the union of the exons (splicing). The mature mRNA then goes to the cytoplasm, where it is translated into proteins.
What are the main differences and similarites between the radioimmunodiffusion (rid) and oucterlony plate technique?
- Similarities both are diffusion process
- wells are involved.
Radial Immunodiffusion (RID) Quantitative test technique quantitative radial immunodiffusion is based upon the reaction between an Ag, and a specific Ab during a diffusion period.
• Ag placed in a well diffuses into an agar containing the Ag (anti-IgG looking for serum IgG).
• The Ag-Ab interaction is manifested by well-defined ring of precipitation around the Ag well.
While Ouchterlony double diffusion (Immunodiffusion) Qualitative test It is based upon the simultaneous application of Ag and Ab in separate but adjacent wells of an agar plate.
• As the materials diffuse toward one another, ppt. lines form resulting from the Ag-Ab interactions.
• If multiple wells of Ag are positioned around an Ab well on the same plate, several patterns of reactivity may be observed.
In eukaryotes, numerous transcription factors are involvedin the synthesis of mRNA. Outline
the sequence of events (the order in which the
variousproteins bind to form the complex)
leading up to the binding of RNA polymerase II to
thepromoter, and subsequent synthesis of
Answer: check explanation.
Transcription is a process in which protein is being produced or synthesized. Transcription can also be defined as the transfer of genetic instructions in DNA to RNA. Transcription uses the DNA in the nucleus to make an RNA molecule. Then, the RNA will now leave the nucleus for ribosome(cytoplasm).
Transcription takes place in three steps and they are;
(1). INITIATION STEP: in this step, the RNA polymerase(an enzyme) binds to the promoter.
(2). ELONGATION STEP: in this step, we have the addition of nucleotides to the mRNA strand.
(3). TERMINATION STEP: In this step, we have the RNA polymerase crosses a terminating sequence in the gene. Here, the mRNA strand detaches itself from the DNA.
After the three steps above, we have the processing of the mRNA. This additional processing include, Splicing(removal of introns from mRNA), Editing( changes in nucleotides in mRNA) and Polyadenylation(addition of tail).
Explain the relationship of entropy and disorder in the context of Shannon's formula.
In information theory, entropy is a measure of uncertainty in a random variable. In this context, the term refers to Shannon's entropy, which quantifies the expected value of the information contained in a message.
The entropy defined by Shannon, referring to the theory of information, refers to the average amount of information contained in a random (psychological) variable or, in particular, a binary transmission source. The information that provides a certain value, xi, of a discrete random variable X, is defined as:
I (xi) = log2 (1 / p (xi))
whose unit is the bit if the logarithm is used in base 2 (for example, when the natural or natural logarithm is used, we speak of nats).
The entropy or average information of the discrete random variable, X, is determined as the average information of the set of discrete values that can be adopted (also measured in bits):
H (x) = Σip (xi) • log2 (1 / p (xi))
In addition to its definition and study, Shannon demonstrated analytically that entropy is the maximum limit to which a source can be compressed without any loss of information.
If several people got sick after eating cheese from a particulargrocery store, describe how you would demonstrate
whichmicroorganism had caused the problem.
Through Microbial Culture test
If after eating cheese from a particular grocery store, several people got sick, it will be very important to conduct a microbial test on food poisoning to ascertain the particular microorganism that is responsible for it.
To do this, a sample stool test is carried out and cultured in a particular media to determine its growth rate, this is then matched with the categories of organisms responsible for food poisoning.
A--When someone hike, how will the altitude affect your body? Its affect on these systems are concern ofthis question:
nervous system, kidneys and urinary system,endocrinesystem .
When someone hike and goes to a higher altitude than usual, it affects the heart rate and it becomes more difficult to breath. In higher altitude there is less oxygen and so this affects breathing. People get more tired because the source of oxygen is less in higher altittudes.
Sympatetic nervous system increases its activity, that is why heart and blood presure rate increases. There is also a pulmonary vasconstriction and during excercise it may lead to pulmonary hipertension.
Altitude can increase urinary output. The bodys kidneys respond to lower oxygen by producing more red blood cells to increasing oxygen. To make room for the new cells the body eliminates through urine.
When hiking in high altitudes, while people try to breathe heavily to get more oxygen they fail because there is a lack of it. Threre is less oxygen throughout the respiratory system and this afects the muscles and limits excersise preformance.
Compare and contrast the evolutionary ideas of gradulism and punctuated equilibrium and name thier originators.
1. GRADUALISM VERSUS 2. PUNCTUATED EQUILIBRIUM
1. Hypothesis that evolution proceeds by imperceptibly small, cumulative steps over long periods of time rather than by abrupt, major changes
2.Hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between periods of little or no change
1. Brings small variation to a particular species
2. Emphasizes consistent and cumulative changes to species
1 Occurs over a long period of time
2.Occurs within a short period of time
1. Describes evolution as a slow process
2. Brings short events, which speed up the slow evolution
1. Not proven by fossil records
2. Better model to describe evolution
It is a term coined by Stephen Jay Gould and Niles Eldredge to contrast with their model of punctuated equilibrium, which is gradualist itself, but argues that most evolution is marked by long periods of evolutionary stability (called stasis), which is punctuated by rare instances of branching evolution.
Based on geology and the findings of James Hutton and Charles Lyell, gradualism states that large changes are actually the culmination very small changes that build up over time. Scientists have found evidence of gradualism in geologic processes, which the Prince Edward Island Department of education describes as the
"...processes at work in the earth's landforms and surfaces. The mechanisms involved, weathering, erosion, and plate tectonics, combine processes that are in some respects destructive and in others constructive."
Proponents of punctuated equilibrium included such scientists as William Bateson, a strong opponent of Darwin's views, who argued that species do not evolve gradually. This camp of scientists believes that change happens very rapidly with long periods of stability and no change in between.
The_ of an element tells how many particles are in the nucleus of each atom.
Answer: The mass number of an element tells us about the number of particles present in the nucleus of an atom
Nucleons are defined as the sub-atomic particles which are present in the nucleus of an atom. Nucleons are protons and neutrons.
Atomic number is defined as the number of protons or electrons that are present in a neutral atom.
Atomic number = number of protons = number of electrons
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons
For Example: Taking an isotope of chlorine, Cl-35
Atomic number = Number of protons = 17
Mass number = Nucleons = 35
Hence, the mass number of an element tells us about the number of particles present in the nucleus of an atom
Can the terms homozygous and heterozygous be usedwith autosomal genomically imprinted genes? Explain your
Genomic imprinting is an inheritance process independent of the classical Mendelian inheritance. It is an epigenetic process that involves DNA methylation and histone methylation without altering the genetic sequence. These epigenetic marks are established in the germline of the parents and are maintained through mitotic cell divisions. The genes do not change to be either homozygous or heterozygous.
What is the difference between Gibbs Free Energy and Helmholtz Free Energy, and which is more applicable to biological systems?
The Gibbs free energy (G) of a system is a measure of the amount of usable energy (energy that a job can do) in that system. Changing Gibbs free energy during a reaction provides useful information about the energy and spontaneity of the reaction while Helmholtz free energy is a thermodynamic property that can be used to predict whether a process occurs spontaneously at constant volume and temperature.
Gibbs free energy is the most used for biological systems since it allows to relate the enthalpy change of the reactions occurred in the system and determine for example if they occur spontaneously or not, if they produce heat or absorb heat.
On the other hand, Helmholtz energy (also called Helmholtz function, Helmholtz free energy or work function) is an extensive quantity, thermodynamic potential and state function, of a thermodynamic system that measures the work obtainable in a closed system, in constant temperature conditions. . It does not depend on the process suffered, but on the final and initial state of the system
What was Darwin's dilemma with micro and macro evolution? Contrastthe evolutionary changes in light of Darwin's proposed
mechanismfor evolution. Compare speciation with the evolution of
Answer:The contrast of the difference between what is called "microevolution", and "macroevolution".
Microevolution concerns the transformation of traits in a population of a given species.
Macroevolution concerns evolution above the species level: it includes the diversification of high level taxa, (mass) extinctions, origin and diversification of clades, etc.
Speciation – the arising of new species, and the main processes likely to produce it stands at the boundary between those evolutions.
Notably, when people of the term "evolution" they typically think of macroevolution (think of Darwin's focus on species their origins and transformation).
Darwin's focused on species their origins and transformation.
Darwin on evolution proposed natural selection as the mechanism of evolution
- Note these important points he outlined:
• Individuals do not evolve: populations evolve
• Natural selection can amplify or diminish only heritable traits; acquired characteristics cannot be passed on to offspring
• Evolution is not goal directed and does not lead to perfection; favorable traits vary as environments change.
Contrast the significance of the cone of increasing diversity withthe pattern representing decimation and diversification. Can
youalso give an example of evolution at the phylotypic level
thatconforms to each of these patterns?
The history of human cultures is frequently marked by a distinctive pattern of evolution that paleobiologists term diversification and decimation. Under this process, fundamentally new socioeconomic systems appear during periods of dramatic cultural diversification,typically through cultural cladogenesis. Significant diversification episodes come about under conditions that favor group economic success under effective or geographic isolation.Typically short-lived, they are often followed by abrupt decimation under more competitive economic conditions. Regional archaeological sequences, viewed from this perspective, suggest that cultural evolutionary trends are strongly conditioned by historical contingency, though general evolutionary processes are continuously active; the emergence of new systems may be contingent on economic opportunities associated with niche reorganization; and severe competition such as that associated with demographic stress will generally favor decimation.
Thalidomide was a druggiven to pregnant women in the early 1960's to reduce morningsickness. Unfortunately, the drug caused
irreparable damage to thedeveloping fetus.Thalidomide inhibited
proper limb formation. Manychildren were born without arms and
legs. Explain how he ames testcould have prevented this
Thalidomide may be defined as a type of the sedative drug that in the earlier time referred for the pregnant ladies. This drug causes the world wide tragedy and acts as a teratogen.
This drug causes mutation in the fetus. The Ames test is effective to understand the mutagenicity of the drug. In this test, if the auxotrophic strain of the bacteria is grown on the the deficient media containing thalidomide drug. The bacteria growth indicates the positive Ames test and the substance is considered as mutagen.