Introduction
The inability to conceive or reproduce sexually is what is meant by infertility. Women aged 35 years are considered infertile if they can not reproduce until six months. The causes of infertility are due to genetic origin in 50 % of the cases. However, there are multiple causes of infertility influenced by genetic as well as environmental factors. With the help of genetic screening, genetic infertility can be detected. Genetic screening helps to detect the risk of experiencing early reproductive capacity loss in couples and the chances of inherited genetic disorders in their offspring. There are relevant studies that correlate genetics and human risk reproduction. However, discussions are still needed on the clinically and ethically acceptable procedures for how infertility can be cured.
What Is Infertility?
Infertility is the inability to reproduce without the use of contraception. The causes of infertility may be related to genetics and environmental factors. Several studies show the correlation between infertility and multiple gene defects. Chromosomal aberrations (a short form of genetic), monogenic diseases (a disease that is caused by a single gene), and phenotypes (traits) with multifactorial inheritance cause infertility. The mechanism of reproduction involves several paracrine, autocrine, and endocrine processes.
Fertility in men includes the complete sperm cycle, which is ejaculation (come out) through the reproductive organ, adequate secretion of seminal fluid, and the ability to deposit semen into the vagina (female reproductive system). Male infertility is mostly caused by chromosomal abnormalities, such as deletions on the Y chromosome (the male sex gene) and changes to the cystic fibrosis transmembrane receptors (CFTR) gene. In women, the cause of infertility is a premature secretion of the ovary, which does not let the woman be pregnant. Genetic testing helps to detect the causes of infertility. Recent advances in technology help in treating these conditions.
What Is Reproduction?
The biological process that allows the production of new organisms from existing organisms is called reproduction. It is one of the most fundamental characteristics of all living things because it is necessary for a species' survival. There are two different reproduction processes, and they are as follows:
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Asexual Reproduction -Asexual reproduction occurs without the fusion of gametes. Gamete formation is not needed for it to happen. There is an involvement of only one parent, so it is uniparental. Because the new organism created inherits all of its chromosomes from one parent, the individuals or offspring produced are identical replicas of each other and their parents. They are similar in morphology and genetics. Such types of offspring are known as clones. Asexual reproduction can occur through unspecialized or specialized parts of the parent. This type of reproduction is common in organisms with simple body organization, such as Monera, Protista, algae, sponges, etc. There are many different ways of asexual reproduction: binary fission, budding, sporulation, fragmentation, and vegetative propagation.
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Sexual Reproduction - In sexual reproduction, two gametes produced by the same or different individuals fuse together to form offspring. This reproduction type may involve one or two parents (biparental). Offsprings produced by this method are not identical to parents or amongst themselves as they inherit chromosomes or genetic material from two different gametes. It also produces variations. It involves meiosis and syngamy (fusion of gametes). The result of syngamy is the formation of a diploid zygote, which is the vital link that ensures the continuity of species between organisms of one generation to the next. This method is slow, elaborate, and has complex processes, so multiplication is not rapid in this type of reproduction.
This reproduction consists of different sequential events and processes that are exhibited by all sexually reproducing organisms. These are:
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Pre-fertilization- This event occurs just prior to the process of fertilization. In this event, gametogenesis and gamete transfer occur.
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Fertilization- The most vital event of sexual reproduction is the fusion of gametes, known as syngamy (fertilization). It leads to the formation of diploid zygotes. Fertilization itself is of two types:
1. External Fertilization- Syngamy occurs outside the organism's body in an external medium. This type of fertilization is shown by most aquatic organisms such as algae, fishes, and amphibians. A major disadvantage is that the young are very susceptible to predators, endangering their ability to survive until adulthood.
2. Internal Fertilization- Syngamy occurs inside the body of the organisms. It is present in the majority of plants and animals. The egg forms inside the female body, where syngamy or fertilization occurs.
3. Post-fertilization- In all sexually reproducing organisms, post-fertilization involves either embryogenesis or parthenogenesis.
4. Embryogenesis- The development of an embryo from the diploid zygote is known as embryogenesis. Cell division and cell differentiation are both important steps in the complex process of embryonic development. These events proceed according to the genetic information contained in the zygote and ultimately lead to the formation of mature organisms. The developing embryo grows in size at the expense of food derived from the outside.
5. Parthenogenesis- It is a specialized form of reproduction in which eggs develop without fertilization. It may be complete (that is there will be complete parthenogenesis), where it is the only one form of reproduction. It may be incomplete where it alternates.
What Is the Relation Between Genetics and Reproduction?
There is an interdependency between any individual organism's genetic configuration and reproduction. Both the terms are complementary to each other. Any alterations in the genetic figure of the sex chromosomes in the organism will lead to alteration in their reproductive phenomenon. Even the sex of an individual is decided based on chromosomes, known as sex chromosomes. In humans, there are two types of sex chromosomes: X and Y chromosomes. These two sex chromosomes form the basis of sex determination in human beings.
In humans, males are generally heterogametic, having both X and Y chromosomes, whereas females have only one type of sex chromosome: X chromosomes. It was believed earlier that the sex of a child or offspring depends totally upon females. However, according to this new basis of sex determination proposed by Wilson and Stevens, the sex of a child or offspring is decided by males only.
One pair of sex chromosomes and 22 pairs of autosomes make up the human genome. Males produce two types of sperm, and the remaining 50 % of the total sperm possess X-chromosomes, and the rest 50 % have Y-chromosomes besides the autosomes. If male gametes with X chromosomes fuse with the female ovum during the union of male and female gametes (sperm and ovum), the offspring would be female. During fusion, if male gametes having Y chromosomes fuse with the X chromosomes of the female ovum, the offspring would be a male.
The odds of the ovum being fertilized by sperm carrying either the X or the Y chromosomes are equal (22+x). Thus, the genetic makeup of the sperm determines the sex of a child. It is also clear that there is always a 50 % probability of either a male or a female child in each pregnancy.
Conclusion
Genetics and reproduction are interconnected to each other. Additionally, it is evident from the description above that a boy or girl child depends on the fusion, not just on the female. This stigma against women in society should be eliminated. Many recent studies in the field of genetics have mentioned the changes in gene, which will help in advancements that will cure infertility. Recent technological advances are already being used to investigate the underlying causes of male and female infertility and in genetic testing.
