eChapters

7.1 Gel Electrophoresis
    
7.2 Polymerase Chain Reaction (PCR)
    
7.3 Restriction Fragment Length Polymorphisms (RFLPs)
    
7.4 Random Amplification of Polymorphic DNA (RAPD)
    
7.5 Amplified Restriction Fragment Length Polymorphism (AFLP)

6.1 Prokaryotic Gene Expression
    
6.2 The lac  Operon
    
6.3 The trp  Operon

5.1 Replication
    DNA Replication in Bacteria
    DNA Replication in Eukaryotes
    
5.2 Transcription

5.3 Translation

4.1 DNA: The word means
    
4.2 Double Helical Structure: The Watson and Crick Model
    
4.3 Family of DNA 
    
4.4 The Chromosomes

DNA (deoxyribonucleic acid), the giant molecule that carries genetic information in living things, is made up of just a few chemical building blocks that bond together in very particular ways. A typical molecule of DNA consists of two strands that are linked together. A segment can be visualized as a ladder-like structure:

The DNA as made of two strands, a left and a right, which are linked in the middle. In reality, since the ladder is twisted, there really is no “right” or “left,” but we use that terminology here since it applies to the model graphs. The square shapes and diamonds you see in the middles of the “rungs” are the links, which are meant to represent the different chemical bonds between the two strands of DNA.

2.1     Regulation of the Cell Cycle 
    
2.2     Mitosis
    
2.3     Meiosis

1.1     Prokaryotic 
    
1.2     Eukaryotic
    
1.3     Cell orgenellie

Castration means removal of the testicles and there are two methods of castration in domestic animals viz. closed and open method.

1. Closed method

In closed method, without incision, the spermatic cord is crushed where thrombus is formed which arrest blood flow to the testicles resulting in gradual atrophy of the testicles. ex. Burdizzo method

Artificial insemination technology is a valuable tool to inseminate 2000 to 3000 does by frozen semen instead of breeding 40 to 50 does by natural service in a year. Goat semen may be stored and frozen more successfully than ram semen. The buck will be sexually mature at 6-7 months of age.

Artificial insemination Technology is a high cost and labour intensive technique in sheep and In India, sheep are reared by economically weaker sections of the society and any advanced technique may take much time to reach their flocks.  Considerably more research work has been done in AI with sheep than with goats. However, the equipment and techniques are very similar for the two species. Goat semen may be stored and frozen more successfully than ram semen.

Artificial insemination (AI) technique in pigs is being performed since several decades in many countries but not widely accepted technology as in cattle due to reasons like sub-standard method of semen cryopreservation and lower fertility rate. The main idea is to increase the breeding efficiency by utilization of superior boars. The number of boars needed for breeding purposes can be reduced by use of AI and reduced transmission of infectious diseases. A minimum of 15 to 20 sows can be inseminated after dilution over a 2 days period with an ejaculate from a boar. Artificial insemination had considerable impact worldwide in its application to commercial pig production. The main advantage of using fresh liquid boar semen is that fertility is maintained even with low number of spermatozoa in the inseminate. AI provides unique opportunity for the genetic improvement of pig industry. Using fewer than 1 million sperm cells per breeding unit can achieve conception rates with liquid semen similar to those with frozen thawed semen containing approximately 15 million sperm and reduced fertility makes cryopreservation an uneconomical option in boars.

Artificial insemination in horses is being practiced since many years in Russia and China for genetic up-gradation. The equine artificial insemination industry has evolved a system in which mares are inseminated with fresh or cooled semen (500 million motile sperm) every 48 hours until estrus is no longer detected or until ovulation is detected by trans-rectal palpation or ultrasonography of ovaries respectively. The advantages of AI include:

The first buffalo AI progeny is reported at Allahabad in August 1943. Although AI is commonly used as a tool of breeding in buffaloes and complaints have appended that conception rate is not satisfactory. There are differences in the anatomy of the sexual organs, sexual physiology and general breeding behaviour that have to be known and taken into consideration when the same technique of AI used in cattle is applied in buffalo breeding. It explains the lower semen production capacity of male buffaloes compared to the cattle bulls. The buffalo bull’s penis is shorter and thinner than penis of the cattle bull. There is a pronounced tapering of the penile end and glans penis is rather poorly developed. The thrust is shorter and less forceful than the bulls. The sheath is tighter and closer to the abdomen than zebu cattle. These anatomical differences are of significance in the semen collection work and type of artificial vagina to be used. The weight of testis and epididymidis in the male buffalo is only ¼ of what it is in cattle. In addition, the seminal vesicles and the prostate are considerably smaller.

Breeding soundness examination can be used as a diagnostic aid in herd fertility problems. After breeding soundness examination, a bull is classified as a satisfactory potential breeder, a questionable potential breeder or an unsatisfactory potential breeder. Members of the Society for Theriogenology developed the concept of a breeding soundness examination as mentioned below.

Immediately after use, all sorts of items are thoroughly washed with water and the rubber catheters are washed with the force of tap water to remove the residual diluted semen. The glass wares are kept in 1% chromic acid solution for overnight to remove cloudiness of glass surface. Then the articles are washed with lukewarm laboratory grade detergent (ex. Labolene®) with a brush to make the articles grease free. All the items are thoroughly washed several times under distilled water and kept inverted position in a clean trough then the openings of glassware wrapped with aluminum foil / paper.

The information in respect of reproductive parameters and events are recorded in respect of following points.
    
1.    Date of semen collection, evaluation, preservation and semen distribution from different bulls 
    
2.    Fertility status of semen 
    
3.    Reproductive performance of females 
    
4.    Work of inseminators

The progress of AI organization depends upon the type of service over and above that initially expected by the members. A well-conducted field service is very important in expanding the growth of any breeding organization. It includes activities as publicity, cooperation in health control, production testing and culling and progeny appraisal, the holding of demonstrations and open house and participation in cattle shows. The salary of a technician with bonus incentive encourages to do work of a high order. The semen costs per inseminated cow can be reduced by maintaining highest quality standards in producing, processing and shipping, by increasing number of cow serviced and by cutting all unnecessary costs. When breeding efficiency is high, the required amount of semen is kept at a minimum. An increase in cows inseminated is a key factor in keeping an organization in the back.

The spermatogenesis is a continuous process in male animals but affected by following factors. 
    
1.     Genetic makeup of male animal: Certain sperm defects like Diadem defect, knobbed sperm, decapitated sperm, sterilizing tail stump, corkscrew mid piece and narrow head are inherited defects and reported in certain males. Few inherited genetic factors are also associated with poor libido and poor fertility. Inherited sperm defects affect sperm motility, fertilization and embryo formation.

The reproductive efficiency in dairy herd is one of the important factor in determining total production and profitability. To remain profitable, dairy cows must reproduce at greatest efficiency and should calve every year (12-13 months). The measure of fertility in a herd is the calving rate (percentage of live, normal calves born). However, it is also necessary to measure fertility based on services per conception. In a healthy herd in which fertile bulls are used, an average of about 1.6 to 1.7 services is required per conception. The number of services per conception is particularly useful for analyzing costs and in comprising the A.I. quite similar to that obtained through natural service in well managed herds. Another measure of fertility is the non-return rate that is calculated from insemination records. Non-return rate is the percentage of cows that are not subsequently rebred within a defined period (60 to 90 days) following an insemination. On an average, about 70% percent of cows inseminated fail to return for service after first service on a 60 to 90 days non-return basis.

1. AI with liquid semen

The ampoule is thawed in ice water for 6-7 minutes. Then, the ampoule is dried and cut. The semen is drawn in a sterilized glass pipette (40-42 cm x 5 mm length diameter) fitted to a sterile glass/plastic syringe (2-5 mL) filled with 1 mL of semen with a rubber connecter. Artificial insemination is done by recto-vaginal method after securing cow/buffalo in standing position in the trevis.