Attitude is Everything

The process of human change begins within us. We all have tremendous potential. We all desire good results from our efforts. Most of us are willing to work hard and to pay the price that success and happiness demand.
Each of us has the ability to put our unique human potential into action and to acquire a desired result. But the one thing that determines the level of our potential, that produces the intensity of our activity, and that predicts the quality of the result we receive is our attitude.
Attitude determines how much of the future we are allowed to see. It decides the size of our dreams and influences our determination when we are faced with new challenges. No other person on earth has dominion over our attitude. People can affect our attitude by teaching us poor thinking habits or unintentionally misinforming us or providing us with negative sources of influence, but no one can control our attitude unless we voluntarily surrender that control.
No one else "makes us angry." We make ourselves angry when we surrender control of our attitude. What someone else may have done is irrelevant. We choose, not they. They merely put our attitude to a test. If we select a volatile attitude by becoming hostile, angry, jealous or suspicious, then we have failed the test. If we condemn ourselves by believing that we are unworthy, then again, we have failed the test.
If we care at all about ourselves, then we must accept full responsibility for our own feelings. We must learn to guard against those feelings that have the capacity to lead our attitude down the wrong path and to strengthen those feelings that can lead us confidently into a better future.
If we want to receive the rewards the future holds in trust for us, then we must exercise the most important choice given to us as members of the human race by maintaining total dominion over our attitude. Our attitude is an asset, a treasure of great value, which must be protected accordingly. Beware of the vandals and thieves among us who would injure our positive attitude or seek to steal it away.
Having the right attitude is one of the basics that success requires. The combination of a sound personal philosophy and a positive attitude about ourselves and the world around us gives us an inner strength and a firm resolve that influences all the other areas of our existence.

Solutions to Assignment 3 - BEL204

Clue to the assignment no.3

1. In these studies always look for the supplement that is + for all the mutants. In this case G. So, G is the final metabolite. Then work backward, like supplement that gives ++ and so on.
Sequence is
5 4 2 1 3
E -------- A -------- C--------- B -------- D ---------- G

2. Here, either trpB or trp A is closer to cys
In the first case, recipient is cys+trpA-. So, it may be cys+ trpA- trpB+ or cys+trpB+ trpA- and incoming DNA fragment is cys- trpA+ trpB- or cys- trpB- trpA+. In either case a double crossover event will form prototroph (all +ve).
In the second case, recipient is cys-trpB-. Now, depending upon the order among cys, trpA and trpB, the donor fragment will be cys+trpA-trpB+or cys+trpB+trpA-. Corresponding recipients will be cys-trpA+trpB- or cys-trpB- trpA+. In the first case where trpA is closer to cys, 4 crossover events will be required to get the prototroph, while 2 crossover events will be needed if trpB is close to cys. So, the sequence is cys-trpB-trpA.

Practice problems.....Asignment 3

1. In a biosynthetic pathway, A to E are intermediate metabolites and final product is G. Several mutants are isolated that are defective in one or the other step in the pathway. The order in which these intermediates are formed is not known. Each intermediate is tested for its ability to support the growth to each mutant (1 to 5). In the following table, + indicates growth and – indicates no growth.

A)What is the order of A to E in the pathway?
B) At which point in the pathway is each mutant blocked?
[ hint: approach followed by Tatum and Beadle with Neurospora arg- auxotrophs]

2. Two mutants at the tryptophan locus, trpA- and trpB-, are known to be close to a cysteine locus (cys). A bacterial strain of genotype cys+trpA-is conjugated to a donor strain that transfers cys-trpB-. The reciprocal cross in which donor transfers cys+trpA-to the strain that is cys-trpB-. In both the cases, the numbers of prototrophic recombinants are comparable. Determine the order of tryptophan loci relative to cysteine locus.

Bacterial Conjugation

Bacterial conjugation is the often regarded as the bacterial equivalent of sexual reproduction or mating; however it is not actually sexual as it does not involve the fusing of gametes and the creation of a zygote, it is merely the exchange of genetic information. In order to perform conjugation, one of the bacteria has to carry an F-plasmid, the other one must not.
The F-plasmid (also called F-factor) is an episome (a plasmid that can integrate itself into the bacterial chromosome by genetic recombination) of about 100 kb (kilo base pairs) length. It carries its own origin of replication, called oriV. There can only be one copy of the F-plasmid in a bacterium (which is then called F-positive), either free or integrated.
Among other genetic information, the F-plasmid carries a tra and a trb locus, which together are about 33 kb long and consist of about 40 genes. The tra locus includes the pilin gene and controlling genes, which together form pili on the cell surface, polymeric proteins that can attach themselves to the surface of F-negative bacteria and initiate the mating. The pili themselves do not seem to be the structures through which the actual exchange of DNA takes place; rather, some proteins coded in the tra or trb loci seem to open a channel between the bacteria.

BEL204 assignment on Mendelian Genetics

1. Black wool sheep is due to a recessive allele b and white wool sheep due to dominant allele B. A white ram (male) is crossed to white ewe (female), both animals carrying the allele for black. They produce a white lamb that is then backcrossed to the female parent. What is the probability of the backcross offspring being black?

2. The shape of radishes may be long (SL SL), round (SLSR) or oval (SRSR). If long radishes are crossed to oval radishes and F1 then allowed to cross at random among themselves, what phenotypeic ratio is expected in the F2?

3. Plumage colour in mallard ducks is dependent upon a set of 3 alleles: MR for restricted mallard pattern, M for mallard and m for dusky mallard. The dominance hierarchy is MR>M>m. Determine the genotype and phenotype ratios expected in F1 from the following crosses: a) MRX MRX MR, b) MR MR X MR M, c) MR MX MR M, d) MRmXMm and e) MmXmm.

4. In Drosophila, ebony body colour is produced by a recessive gene a and wild type (gray) colour by its dominant allele a+. Vestigial wings by recessive gene vg and normal wing (wild type) by vg+. If wild type dihybrid flies are crossed and produce 272 progenies, how many of these are expected in each phenotype class?

Use comments to post your answers and do discussions on the assignment.

(dbeb-iitd.blogspot.com)

BEL102 Assignment

Tutorial problems (from Text 1, unless specified otherwise):
Problem set 1: 3.27, 3.32, 3.53, 4.23
Problem set 2: 4.13, 4.18, 4.30, 4.75
Problem set 3:
(a) In example 4.4-2, what is the degree of freedom for (i) overall process (ii) first extractor(iii) second extractor (iv) extract mixing point (v) distillation column?
(b) Learn how to calculate equilibrium composition from example 4.6-2. What is the limiting reactant and why?

Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of the cell cycle - the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell.

Interphase
The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for cell division. Interphase is therefore not part of mitosis. Interphase is divided into three phases, G1 (first gap), S (synthesis), and G2 (second gap). During all three phases, the cell grows by producing proteins and cytoplasmic organelles. However, chromosomes are replicated only during the S phase. Thus, a cell grows (G1), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G2), and divides (M).

Preprophase

In plant cells only, prophase is preceded by a pre-prophase stage. In highly vacuolated plant cells, the nucleus has to migrate into the center of the cell before mitosis can begin. This is achieved through the formation of a phragmosome, a transverse sheet of cytoplasm that bisects the cell along the future plane of cell division. In addition to phragmosome formation, preprophase is characterized by the formation of a ring of microtubules and actin filaments (called preprophase band) underneath the plasma membrane around the equatorial plane of the future mitotic spindle. This band marks the position where the cell will eventually divide. The cells of higher plants (such as the flowering plants) lack centrioles: with microtubules forming a spindle on the surface of the nucleus and then being organized into a spindle by the chromosomes themselves, after the nuclear membrane breaks down. The preprophase band disappears during nuclear envelope disassembly and spindle formation in prometaphase.

Prophase

Prophase: The two round objects above the nucleus are the centrosomes. The chromatin has condensed.

Normally, the genetic material in the nucleus is in a loosely bundled coil called chromatin. At the onset of prophase, chromatin condenses together into a highly ordered structure called a chromosome. Since the genetic material has already been duplicated earlier in S phase, the replicated chromosomes have two sister chromatids, bound together at the centromere by the cohesion complex. Chromosomes are visible at high magnification through a light microscope.
Close to the nucleus are structures called centrosomes, which are made of a pair of centriole. The centrosome is the coordinating center for the cell's microtubules. A cell inherits a single centrosome at cell division, which replicates before a new mitosis begins, giving a pair of centrosomes. The two centrosomes nucleate microtubules (which may be thought of as cellular ropes or poles) to form the spindle by polymerizing soluble tubulin. Molecular motor proteins then push the centrosomes along these microtubules to opposite side of the cell. Although centrosomes help organize microtubule assembly, they are not essential for the formation of the spindle, since they are absent from plants, and centrosomes are not always used in meiosis.

Prometaphase

Micrograph showing condensed chromosomes in blue and the mitotic spindle in green during prometaphase of mitosis

Prometaphase: The nuclear membrane has degraded, and microtubules have invaded the nuclear space. These microtubules can attach to kinetochores or they can interact with opposing microtubules.

The nuclear envelope disassembles and microtubules invade the nuclear space. This is called open mitosis, and it occurs in most multicellular organisms. Fungi and some protists, such as algae or trichomonads, undergo a variation called closed mitosis where the spindle forms inside the nucleus or its microtubules are able to penetrate an intact nuclear envelope.
Each chromosome forms two kinetochores at the centromere, one attached at each chromatid. A kinetochore is a complex protein structure that is analogous to a ring for the microtubule hook; it is the point where microtubules attach themselves to the chromosome. Although the kinetochore structure and function are not fully understood, it is known that it contains some form of molecular motor. When a microtubule connects with the kinetochore, the motor activates, using energy from ATP to "crawl" up the tube toward the originating centrosome. This motor activity, coupled with polymerisation and depolymerisation of microtubules, provides the pulling force necessary to later separate the chromosome's two chromatids.
When the spindle grows to sufficient length, kinetochore microtubules begin searching for kinetochores to attach to. A number of nonkinetochore microtubules find and interact with corresponding nonkinetochore microtubules from the opposite centrosome to form the mitotic spindle. Prometaphase is sometimes considered part of prophase.

Metaphase

A cell in late metaphase. All chromosomes (blue) but one have arrived at the metaphase plate.

Metaphase: The chromosomes have aligned at the metaphase plate.

As microtubules find and attach to kinetochores in prometaphase, the centromeres of the chromosomes convene along the metaphase plate or equatorial plane, an imaginary line that is equidistant from the two centrosome poles. This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochores, analogous to a tug-of-war between people of equal strength. In certain types of cells, chromosomes do not line up at the metaphase plate and instead move back and forth between the poles randomly, only roughly lining up along the midline. Metaphase comes from the Greek μετα meaning "after."
Because proper chromosome separation requires that every kinetochore be attached to a bundle of microtubules (spindle fibres), it is thought that unattached kinetochores generate a signal to prevent premature progression to anaphase without all chromosomes being aligned. The signal creates the mitotic spindle checkpoint.

Anaphase

Early anaphase: Kinetochore microtubules shorten

When every kinetochore is attached to a cluster of microtubules and the chromosomes have lined up along the metaphase plate, the cell proceeds to anaphase (from the Greek ανα meaning “up,” “against,” “back,” or “re-”).
Two events then occur; First, the proteins that bind sister chromatids together are cleaved, allowing them to separate. These sister chromatids, which have now become distinct sister chromosomes, are pulled apart by shortening kinetochore microtubules and move toward the respective centrosomes to which they are attached. Next, the nonkinetochore microtubules elongate, pushing the centrosomes (and the set of chromosomes to which they are attached) apart to opposite ends of the cell. The force that causes the centrosomes to move towards the ends of the cell is still unknown, although there is a theory that suggests that the rapid assembly and breakdown of microtubules may cause this movement.
These two stages are sometimes called early and late anaphase. Early anaphase is usually defined as the separation of the sister chromatids, while late anaphase is the elongation of the microtubules and the microtubules being pulled farther apart. At the end of anaphase, the cell has succeeded in separating identical copies of the genetic material into two distinct populations.

Telophase

Telophase: The decondensing chromosomes are surrounded by nuclear membranes. Note cytokinesis has already begun, the pinching is known as the cleavage furrow.

Telophase (from the Greek τελος meaning "end") is a reversal of prophase and prometaphase events. It "cleans up" the after effects of mitosis. At telophase, the nonkinetochore microtubules continue to lengthen, elongating the cell even more. Corresponding sister chromosomes attach at opposite ends of the cell. A new nuclear envelope, using fragments of the parent cell's nuclear membrane, forms around each set of separated sister chromosomes. Both sets of chromosomes, now surrounded by new nuclei, unfold back into chromatin. Mitosis is complete, but cell division is not yet complete.

Cytokinesis

Cytokinesis is often mistakenly thought to be the final part of telophase, however cytokinesis is a separate process that begins at the same time as telophase. Cytokinesis is technically not even a phase of mitosis, but rather a separate process, necessary for completing cell division. In animal cells, a cleavage furrow (pinch) containing a contractile ring develops where the metaphase plate used to be, pinching off the separated nuclei. In both animal and plant cells, cell division is also driven by vesicles derived from the Golgi apparatus, which move along microtubules to the middle of the cell. In plants this structure coalesces into a cell plate at the center of the phragmoplast and develops into a cell wall, separating the two nuclei. The phragmoplast is a microtubule structure typical for higher plants, whereas some green algae use a phycoplast microtubule array during cytokinesis. Each daughter cell has a complete copy of the genome of its parent cell. The end of cytokinesis marks the end of the M-phase.