Mendel’s law of dominance states that a dominant allele expresses itself in a monohybrid cross and suppresses the expression of recessive allele. However, this recessive allele for a character is not lost and remains hidden or masked in the progenies of F1generation and reappears in the next generation.

For example, when pea plants with round seeds (RR) are crossed with plants with wrinkled seeds (rr), all seeds in F₁ generation were found to be round (Rr). When these round seeds were self fertilized, both the round and wrinkled seeds appeared in F₂ generation in 3: 1 ratio. Hence, in F₁ generation, the dominant character (round seeds) appeared and the recessive character (wrinkled seeds) got suppressed, which reappeared in F₂ generation.

Linkage and recombination are phenomena that describe the inheritance of genes. A linkage is a phenomenon where two or more linked genes are always inherited together in the same combination for more than two generations. The recombination frequency of the test cross progeny is always lower than 50%. Therefore, if any two genes are completely linked, their recombination frequency is almost 0%. The phenomenon of linkage was studied by the scientist T.H. Morgan using the common fruit fly or Drosophila melanogaster.

Alec Jeffreys developed this technique in which he used satellite DNAs also called VNTRs (Variable Number of Tandem Repeats) as a probe because it showed the high level of polymorphism.

Following are the steps involved in DNA fingerprinting:

Isolating the DNA.

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Digesting the DNA with the help of restriction endonuclease enzymes.

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Separating the digested fragments as per the fragment size by the process of electrophoresis.

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Blotting the separated fragments onto synthetic membranes like nylon.

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Hybridising the fragments using labelled VNTR probes.

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Analysing the hybrid fragments using autoradiography.

Tetanus antitoxin is given as prophylaxis to the persons at risk with infected wounds, wounds contaminated with soil or mud, deep or punctured wounds and wounds with devitalising tissue damages. A dose of 1,500 IU should be given subcutaneously or intramuscularly as early as possible after the wound is received.  The tetanus vaccine doesn't provide lifelong immunity. Protection begins to decrease after about 10 years, which is why doctors advise booster shots every decade. A doctor may recommend children and adults get a booster shot earlier if there's a suspicion they may have been exposed to tetanus-causing spores.

Signs and symptoms of tetanus appear anytime from a few days to several weeks after tetanus bacteria enter your body through a wound. The average incubation period is seven to 10 days. Common signs and symptoms of tetanus include: Spasms and stiffness in your jaw muscles (trismus). There's no cure for tetanus. Treatment consists of wound care, medications to ease symptoms and supportive care.

One evolutionary hypothesis suggests the hymen arose because it was a desirable trait, due to the common societal preference for virgin wives. But that explanation fails for other species. Instead, some scientists speculate that the hymen helps keep bacteria out of the ******.

Amniocentesis is a procedure used to diagnose fetal defects in the early second trimester of pregnancy. A sample of the amniotic fluid, which surrounds a fetus in the womb, is collected through a pregnant woman's abdomen using a needle and syringe. Amniocentesis is a prenatal test in which a small amount of amniotic fluid is removed from the sac surrounding the fetus for testing. The sample of amniotic fluid (less than one ounce) is removed through a fine needle inserted into the uterus through the abdomen, under ultrasound guidance.

Probes are small (15-30 bases long) nucleotide (DNA/RNA) sequences used to detect the presence of complementary sequences in nucleic acid samples. They are single stranded and consist of a tagged radioactive label which helps in detection.

Progesterone belongs to a group of steroid hormones called progestogens. It is mainly secreted by the corpus luteum in the ovary during the second half of the menstrual cycle. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. The menstrual cycle is regulated by hormones. Luteinizing hormone and follicle-stimulating hormone, which are produced by the pituitary gland, promote ovulation and stimulate the ovaries to produce estrogen and progesterone.

A genotype is an individual's collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the genes' DNA is used to make protein and RNA molecules. An organism's genotype is its specific combination of alleles for a given gene. So, for example, in the pea plants above, the possible genotypes for the flower-color gene were red-red, red-white, and white-white. The phenotype is the physical manifestation of an organism's allellic combination (genotype).

Diphtheria is a severe communicable and bacterial infectious disease that causes inflammation of the mucous membranes by forming a false membrane in the throat which creates a problem while swallowing food and during breathing. It can also damage nerves by a bacterial toxin present in the blood. Currently, this syndrome is rare in developed countries. This disease spreads easily from one person to another but can be prevented by the use of vaccines.

The female reproductive system provides several functions. The ovaries produce the egg cells, called the ova or oocytes. The oocytes are then transported to the fallopian tube where fertilization by a sperm may occur. The fertilized egg then moves to the uterus, where the uterine lining has thickened in response to the normal hormones of the reproductive cycle. Once in the uterus, the fertilized egg can implant into thickened uterine lining and continue to develop. If implantation does not take place, the uterine lining is shed as menstrual flow. In addition, the female reproductive system produces female *** hormones that maintain the reproductive cycle.

Multiplication Phase: During sexual maturity, the division of undistinguishable primordial germ cells occurs several times due to mitosis. This is majorly to produce a large count of spermatogonia. These are of two kinds: type A and type B. Type A spermatogonia act as the stem cells that divide to create additional spermatogonia. On the other hand, Type В spermatogonia can be thought as the prototypes of male *** cells.

Creation of Spermatids

This procedure covers three stages; namely:

• Multiplication Phase: During sexual maturity, the division of undistinguishable primordial germ cells occurs several times due to mitosis. This is majorly to produce a large count of spermatogonia. These are of two kinds: type A and type B. Type A spermatogonia act as the stem cells that divide to create additional spermatogonia. On the other hand, Type В spermatogonia can be thought as the prototypes of male *** cells.
• Growth Phase: Do remember that, every type В spermatogonium dynamically grows to form a superior primary spermatocyte through nourishment received from the nursing cells. This phase further concludes in the maturation stage.
• Maturation Phase: Under this, primary spermatocyte experiences two successive divi­sions. These are termed as maturation divisions, and meiotic is the first maturation disunion. Therefore, the primary spermatocyte segregates into two haploid daughter cells known as secondary spermatocytes. Further, both the secondary spermatocytes suffer second maturation separation that is a regular mitotic division. It leads to the creation of four haploid spermatids.

Parapodia are lateral appendages. They help in locomotion. Example: Nereis

Components of the Cardiac Conduction System:

1. Sinoatrial Node: The sinoatrial (SA) node is a collection of specialized cells (pacemaker cells), and is located in the upper wall of the right atrium, at the junction where the superior vena cava enters. These pacemaker cells can spontaneously generate electrical impulses. The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles.
2. Atrioventricular Node (AV Node) - The AV Node receives the signal from the SA Node with the help of Bachmann's Bundle. It takes a 0.1s delay for the signal to transmit from the AV node to the Bundle of His.
3. Atrioventricular Bundle:  The atrioventricular bundle (bundle of His) is a continuation of the specialized tissue of the AV node, and serves to transmit the electrical impulse from the AV node to the Purkinje fibers of the ventricles. It descends down the membranous part of the interventricular septum, before dividing into two main bundles: Right bundle branch – conducts the impulse to the Purkinje fibres of the right ventricle. Left bundle branch – conducts the impulse to the Purkinje fibers of the left ventricle.
4. The Purkinje fibers (sub-endocardial plexus of conduction cells) are a network of specialized cells. They are abundant with glycogen and have extensive gap junctions. These cells are located in the subendocardial surface of the ventricular walls and are able to rapidly transmit cardiac action potentials from the atrioventricular bundle to the myocardium of the ventricles. This rapid conduction allows coordinated ventricular contraction (ventricular systole) and blood is moved from the right and left ventricles to the pulmonary artery and aorta respectively.

During intra-erythrocytic development, malaria trophozoites digest hemoglobin, which leads to parasite growth and asexual replication while accumulating toxic heme. To avoid death, the parasite synthesizes insoluble hemozoin crystals in the digestive vacuole through polymerization of β-hematin dimers.

Meiosis is a type of cell division that results in the formation of four daughter cells each with half the number of chromosomes as the parent cell.