Best Ways to Face Medical Entrance Exams

Hello Students, hope you must be preparing hard for the medical entrance tests. AIPMT and AIIMS test dates have already been declared; and this obviously means that you’ve a very limited time frame to revise the syllabus and prepare yourself for the final day of the test. It is important for you to get disciplined, motivated and organized in order to achieve realistic goals. Besides, a good planning is essential, which must include a balanced routine and effective time management. Your routine must include activities like sleeping, studying and relaxing at intervals. There are a few basic things that you need to consider while preparing for the medical entrance exams.

Do’s

·         Make a timetable and adhere to it

·         Read NCERT Books everyday, especially in Biology subject

·         Learn the concept rather than mugging up

·         Revise chapters for at least three times

·         Take short breaks and revise effectively

·         Solve previous year question papers

·         Use a stopwatch to check the speed with which you solve the questions

·         Practice, practice and practice

·         Listen to toppers on YouTube to get motivated

·         Stay positive and confident

Don’ts

·         Do not buy unnecessary books

·         Do not hesitate to ask your friends or mentors to understand a concept

·         Do not try to cover the entire syllabus at a time

·         Do not take stress about too many things at a time

·         Do not neglect or skip chapters that you already know

Your aim is to succeed in the entrance tests and this could only be possible if you don’t get too much anxious about the exams. The possibility of success or failure depends on how you prepare yourself for the test. Practice as many questions as you can; if you mark incorrect to some questions, solve them again at certain intervals. 

Besides hard work, you also need to maintain your physical and mental wellness. It, is, therefore, important to follow a light, balanced diet to remain active, always. Say no to junk food as it may cause health problems. A minimum 8 hours of sleep is essential; and follow the golden rule, ‘’early to bed and early to rise, makes a man, healthy, wealthy and wise.’’ Best of Luck to all.

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What is the Difference Between hnRNA and mRNA?

RNA synthesis takes place in the nucleus in eukaryotes. However, when RNA is formed, it is transferred from the nucleus to the cytoplasm. The physiological environment in the nucleus is quite different than than of the cytoplasm. This physiological difference may harm newly formed RNA in the cytoplasm. In order to prevent RNA from any damage, it is processed first and then transferred to the cytoplasm.

A newly formed RNA before processing is called heterogenous RNA (hnRNA) and RNA after processing is called mRNA (messenger RNA). Processing involves capping and tailing of RNA. Capping is done by adding 5-methyl guanosine, and tailing is done by adding polyA to the 3'-OH using poly A polymerase enzyme.

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What is Chargaff's Rule of DNA?

Erwin Chargaff was an Australian biochemist who analyzed nucleic acids of many organisms. From his research, he concluded that the number of purine bases (A, G) equals the pyrimidine bases (C, T) in any double stranded DNA of an organism.

It means,

•  A+G / T+C = 1; 
• A+T / C+G may vary from organism to organism.
• % A = % T, and % G = % C

Based on Chargaff's rule, many questions are asked in various competitive exams including AIPMT, CSIR NET, GATE, etc.

Q1. One of the strands of a double stranded DNA has the following number of bases:
A= 3800; T= 2600. What would be the base composition of the double stranded DNA?

Solution:

From the question, it is a double stranded DNA (Chargaff's rule is valid for only double stranded DNA), and only one strand with its base composition is given. So, the total number of bases would be 20k (10k bases on each strand).

Now, A and T bases with their numbers are given on one strand, so A will have T and T will have A on their complementary DNA. It means, on one strand, the total number of A would be 3800+2600 because % A = % T. Similarly, the total number of T would be 2600 + 3800 = 6400

The total number of A and T on both strands would be 6400 + 6400 = 12800

The remaining bases would be G and C = 20,000 - 12800 = 7200

Since % G =  % C; G = 7200/2 = 3600; C = 3600

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Find the Gender on the Basis of Genic Balance Theory?

Find the gender of the following combinations based on Genic Balance Theory:

1. 3A+XXX

2. 3A+XXY

3. 2A+XX

4. 2A+XY

5. 3A+XX

6. 3A+XY

7. 2A+XXX

8. 2A+XXY

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What Is Genic Balance Theory?

C.B. Bridges in 1922 proposed the Genic Balance Theory for sex determination while working on his experimental model, Drosophila.

Like mammals, XX sex chromosome determines female character and XY as males in Drosophila. However, unlike humans, Y chromosome is not responsible for maleness in Drosophila, as Y chromosome is heterochromatic in nature and thus not active in sex determination.

According to Bridges, sex determination in Drosophila depends on the X/A sex index ratio. Following are the sex index ratios for maleness and female characters:

If X/A = 1.0 it means normal female
If X/A = 0.5, it means normal male
If X/A = <0.5, it means super male
If X/A = 0.5 to 1.0, it means intersex
If X/A = >1.0, it means super female

For example, 3A+XXX: X/A = 3/3 = 1.0 => Normal female
                     2A+XO: X/A = 1/2 = 0.5 => Normal male

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What are the different properties of water?

What is called as the universal solvent. Water has many special properties that enable it to act as a solvent. These features are due to the polar structure of water molecule. Polarity of water molecules gives rise to hydrogen bonds.

The chemical formula of water is H₂O. It means, two hydrogen atoms get attached to an oxygen atom. Since oxygen is electronegative in nature, it carries a partial negative charge. Hydrogen atoms, on the other hand, get a partial positive charge. Since the magnitude of these positive and negative charges are equal, water molecule carries no net charge.

However, these partial charges on H₂O molecule attract other water molecules. This weak electrostatic attraction between H₂O molecules is called HYDROGEN BOND. This hydrogen bond is responsible for many of the unusual physical properties of H₂O. Some of the properties are mentioned below:

H₂O is an excellent solvent:

The polarity of water molecule makes it an excellent solvent. Hydrogen bonding between water molecules and ions and between water and polar solutes in solution effectively decreases the charged substances and thereby increases their solubility.

H₂O has high specific heat

Specific heat is defined as the energy required to raise the temperature of a substance by a specific amount. Unlike other liquids, water requires a relatively large energy input to raise its temperature. This large energy input is essential for plants because it helps buffer temperature fluctuations.

H₂O has high latent heat of vaporization

Latent heat of vaporization is defined as the energy required to separate molecules from the liquid phase and move them into the gas phase at constant temperature – a process that occurs during transpiration. Due to high latent heat of vaporization – water enables plants to cool themselves by evaporating water from leaf surfaces.

Cohesive and adhesive properties of water

Cohesive means attraction between similar molecules and adhesive means attraction between different molecules. Due to these properties, water creates surface tension at an air-water interface. Cohesion, adhesion and surface tension give rise to a phenomenon, called CAPILLARY, the movement of H₂O along a capillary tube

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AIPMT DISCUSSION QUESTIONS ON GENETIC CODE

Q1. Which of the following is a characteristic of genetic code?

a)      The genetic code is non overlapping

b)      The genetic code is unambiguous

c)       The genetic code is degenerative

d)      All of the above

Explanation:

The correct answer is‘d’. The genetic code is non overlapping means that the successive triplets are read in order.

The genetic code is unambiguous means each codon or triplet specifies a particular amino acid and only one amino acid.

The genetic code is degenerative means each amino acid can be specified by more than one triplet codon.

Q2. Which of the following is a nonsense codon?

a)      UAG

b)      UGA

c)       UAA

d)      All of the above

Explanation:

The correct answer is‘d’. Out of 64 triplet codons, three codons are called nonsense codons because they terminate the process of translation. UAG is amber, UGA is opal and UAA is ochre.

Q3. Which of the following poly bases could not form any amino acid in Nirenberg’s experiment?

a)      Poly U

b)      Poly A

c)       Poly G

d)      Poly C

Explanation:

The correct answer is ‘c’ i.e., Poly G because it formed triple stranded structure and thus no translation occurred.

Q4. Hargobind Khorana chemically synthesized amino acids:

a)      Cysteine/valine 50:50 percent

b)      Proline/Cysteine 50:50 percent

c)       Phenyalanine/ Proline 50:50 percent

d)      All of the above

Explanation:

The correct answer is ‘a’ i.e., cysteine/valine. He used UGUGUGUGU poly nucleotide bases to synthesize the same.

Q5. Which one represents serine?

a)      CUU, CUC, CUA, and CUG

b)      UAU, UAC, UGU, and UGC

c)       UCU, UCC, UCA, and UCG

d)      UGU, UGC, UGA, and UAG

Explanation:

The correct answer is ‘c’. In order to remember which triplet codon codes for which amino acid, one needs to see the codon chart. If we reference Proline which falls on the second row and second column of the codon chart, we can remember the codons. However, a practice is needed for the same.

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