Who is the father of genetics?

Gregor Mendel is known as the Father of Genetics. He experimented on pea plants and discovered the basic inheritance rules. Gregor Johann Mendel  was a meteorologist, mathematician, biologist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire (today's Czech Republic) and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.

Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. Taking seed color as an example, Mendel showed that when a true-breeding yellow pea and a true-breeding green pea were cross-bred their offspring always produced yellow seeds. However, in the next generation, the green peas reappeared at a ratio of 1 green to 3 yellow. To explain this phenomenon, Mendel coined the terms "recessive" and "dominant" in reference to certain traits. In the preceding example, the green trait, which seems to have vanished in the first filial generation, is recessive and the yellow is dominant. He published his work in 1866, demonstrating the actions of invisible "factors"—now called genes—in predictably determining the traits of an organism.

The profound significance of Mendel's work was not recognized until the turn of the 20th century (more than three decades later) with the rediscovery of his laws. Erich von Tschermak, Hugo de Vries and Carl Correns independently verified several of Mendel's experimental findings in 1900, ushering in the modern age of genetics.

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HOW DO HUMAN BABIES DEVELOP?


Human beings are mammals, which mean that their young develop inside the mother until they are ready to be born. This development takes place inside the womb or uterus, where the baby gains the nutrients and oxygen it needs for growth from its mother’s own blood, supplied through the umbilical cord.



A woman’s ovaries usually release one egg each month. As it travels through the fallopian tube towards the uterus, it may be fertilized by a sperm that has enter her bady during sexual intercourse.



As soon as it is fertilized, the egg call begins to divide, until it becomes a ball of cells called a blastocyst. This ball then implants itself in the wall of the uterus.



After four weeks, the blastocyst has become an embryo. Its brain, spin and limbs are already forming and its heart will soon begin to beat.



At 12 week, the embryo is now called a foetus. All its organs are formed. For the rest of the time before it is born, it simply has to grow.



From 38 weeks onwards, the baby is ready to be born. It moves down into the pelvis. At birth, the cervix gradually opens and the baby is born through the vagina.










HOW ARE CHARACTERISTICS PASSED FROM ONE GENERATION TO THE NEXT?

The characteristics of individual human beings are passed from one generation to the next in their chromosomes. Each of our parents gives us 23 chromosomes, making 46 in all. That means that we have two versions of each of our genes, but one is often dominant. We see the effect of the dominant gene, but the other (recessive) gene is still there and can be passed to our children.



The Law of Inheritance – Mendel’s Law, is significant in comprehending how characteristics or traits are genetically passed from one generation to the next. Heredity is the process through which a new individual acquires traits from its parents during the event of reproduction.



Every individual has 23 pairs of chromosomes, each of which comes from the father and the mother. As genes are present on chromosomes, we receive two copies of each gene from paternal and maternal side respectively and one pair of sex chromosomes from each parent to form 46 chromosomes on the whole.



Traits acquired through inheritance are determined by rules of heredity. These traits are coded in our DNA and hence can be passed to the offspring (eye color, hair color, height etc.). Thus for each trait, there are two versions in a child. During the cell division process, genetic information (DNA structure) containing chromosomes are transferred into the cell of the new individual, therefore, passing traits to the next generation.








WHAT IS GESTATION?


Gestation is the length of time between conception — the fertilization of an egg by a sperm — and the birth of the baby that grows from the fertilized egg. The length of gestation varies according to the species.



Gestation, in mammals, the time between conception and birth, during which the embryo or fetus is developing in the uterus. This definition raises occasional difficulties because in some species (e.g., monkeys and man) the exact time of conception may not be known. In these cases the beginning of gestation is usually dated from some well-defined point in the reproductive cycle (e.g., the beginning of the previous menstrual period).



The length of gestation varies from species to species. The shortest known gestation is that of the Virginian opossum, about 12 days, and the longest that of the Indian elephant, about 22 months. In the course of evolution the duration of gestation has become adapted to the needs of the species. The degree of ultimate growth is a factor, smaller animals usually having shorter periods of gestation than larger ones. Exceptions are the guinea pig and related South American rodents, in which gestation is prolonged (averaging 68 days for the guinea pig and 111 days for the chinchilla). The young of these species are born in a state of greater maturity than are those of the rat with its period of 22 days. Another factor is that, in many species with restricted breeding seasons, gestation is adjusted so that birth coincides with the period when food is most abundant. Thus the horse, a spring breeder with 11 months’ gestation, has its young the following spring, as does the sheep, a fall breeder with a five months’ gestation. Animals that live in the open tend to have longer gestations and to bear young that have reached a state of greater maturity than do animals that can conceal their young in underground burrows or in caves. Marsupials generally have short gestations—e.g., 40 days for the largest kangaroos. The young, born in an extremely immature state, transfer to the pouch in which gestation may be said to continue.



Embryos of some species experience an arrest in development that greatly prolongs gestation. This is especially true of the fur-bearing carnivores the martens and weasels. Embryos of the European badger and American marten, which breed in July and August, develop for a few days, and then lie dormant in the uterus, being implanted in January. Birth occurs in March. Of the total gestation period of 250 days, growth occurs during only 50. Delayed implantation also occurs in mice and other small rodents that become pregnant while they are still suckling a litter.



Either a single factor or a great number of minor factors, all culminating at or near one date, determine the length of gestation. Several minor variations are known: in man, gestation for males is three to four days longer than that for females; and in cattle, bulls are carried about one day longer than heifers. In both species gestation of twins is five to six days less than for singlet’s. In animals such as the rabbit or pig, which bear many young at a time, gestation is shorter for larger litters than for smaller ones. Heredity also influences gestation; in cattle the mean gestation period for Holstein-Friesians is 279 days; for Brown Swiss, 290 days; other breeds fall between these extremes. When hybrids are produced by crossing two species with different gestation periods, the hybrid is carried for a period lying somewhere between those of the two parents and tending toward the mother’s species. Thus a mare carries a mule foal (fathered by a jackass) about 10 days longer than the normal period for the horse (about 337 days). For human gestation, see pregnancy.






HOW DO LIVING THINGS GROW AND AGE?


Two things affect the way in which living things grow and age. The first is their genetic make-up — the genes that they have inherited from their parents. The DNA in their chromosomes controls the way that cells divide to cause the growth of the young organism, its coming to maturity and its aging. The other important factor is the environment and conditions that the organism experiences — how much of the right kind of food it eats, where it lives, the climate and the kinds of events and accidents that happen to it.



Every living organism begins life as a single cell. Unicellular organisms may stay as one cell but they grow too. Multicellular organisms add more and more cells to form more tissues and organs as they grow.



The Growth and development of living organisms are not the same things. Growth is the increase in size and mass of that organism. Development involves the transformation of the organism as it goes through the growth process.



Think of a newly born baby. It has all the features of a fully-grown adult, but they are very tiny. As the years go by, they become big and become a young person like you, and later on, into a fully grown adult, maintaining all the features that they are born with. This is growth. But in their mummy’s tummy, they started off as a single cell and transformed into a zygote and into a foetus before transforming into a tiny baby.



In some organisms, growing involves drastic transformation. Think of a butterfly for instance. It starts off as a cell (egg). Then it transforms into a caterpillar, then into a pupa (chrysalis), and then pops out as a beautiful butterfly.



Plants often start from a tiny seed, and grow into a big tree. One thing common to all organisms is that they grow or develop to look just like their parent species, even though there may be some slight variations resulting from the mixing of cells by the parents. 



Cell growth and development include its repair. As cells grow old, they wear off. Sometimes they suffer injury and bruises, but they are able to repair themselves by growing new cells in a process called Mitosis.



As living things grow, they undergo a process called aging (age). As they get close to the end of their lifespan, their ability to carry out life functions reduces. Eventually, they die to end the process of life.





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