Category «Genetics»

The study of heredity and the variation of inherited characteristics and the genetic properties or features of an organism and their characteristics.

Gene Linkage Groups

Linkage group • A linkage group is a linearly arranged group of linked genes which are normally inherited together except for crossing over during cell division. They act and move as a unit rather than independently. • Because the two homologous chromosomes possess either similar or allelic genes on the same loci, they constitute the …

Gene Linkages and Their Types

• Linkage has been found to be complete or incomplete depending upon the absence or presence of nonparental or new combinations of linked genes. Complete linkage • Complete linkage is a linkage or grouping of genes on a chromosome which is not altered and is inherited as such from generation to generation without any cross-over. …

AIPMT PMT Post-Mendelian Genetics

• Although Gregor Mendel developed his ground : breaking principles of inheritance in the mid-1800s, the importance of his work went largely unnoticed by the scientific community until the early 1900s. • At that time, numerous researchers began to conduct experiments that upheld many of Mendel’s ideas; however, they also discovered several situations that represented …

Laws or Principles of Inheritance

Principles or laws of Inheritance (I) Law of Dominance When two homozygous individuals with a contrasting characters are crossed the character that appear in the F, hybrids is dominant character and that does not appear in F, is recessive character. (II) Law of segregation The law of segregation states that when a pair of contrasting …

Monohybrid cross

Mendel’s Experiment – Monohybrid Cross Monohybrid cross is a cross made to study simultaneous inheritance of a single pair of Mendelian factors. In other words, the cross in which only alternate forms of a single character are taken into consideration is called monohybrid cross. Mendel crossed tall and dwarf pea plants to study the inheritance …

Mendel’s Laws of Inheritance – Terminology and Symbols

• Character is a well defined morphological or physiological feature of an organism. • Trait is the distinguishing feature of a character. • Gene is the inherited factor that determine the biological character of an organism. • A pair of contrasting characters is called allelomorph or allele. •  Term allele was given by W. Bateson …

Gregor Johann Mendel

Gregor Mendel Biography Gregor Johann Mendel (1822-84) was born to a peasant family in the Central European village of Heinzendorf. The poverty his family experienced meant that Mendel had to work to support himself in his studies from an early age. It placed a strain on his health throughout his schooling. From the age of …

Pleiotropy

In general, one gene affects a single character. But many genes are known to affect more than one character. Such genes are called pleiotropic genes and the condition is called Pleiotropy. An example of a gene in human beings is the recessive gene s ( sometimes denoted as Hbs) which produces sickle cell anemia in …

Modified dihybrid ratios with codominant and lethal alleles

The classical phenotypic ratio resulting from the mating of dihybrid genotypes is 9:3:3:1. This ratio appears whenever the alleles at both loci display dominant and recessive relationships. The classical dihybrid ratio may be modified if one or both loci have codominant alleles or lethal alleles. A summary of these modified phenotypic ratios in adult progeny …

Mendel’s Hypothesis

Mendel studied the pattern of inheritance using several true-breeding varieties of garden peas. He concentrated on transmission of seven easily identified traits, and crossed plants showing alternate aspects of each of these(e.g., tallness and dwarfness; yellowness or greenness of peas; smooth; rounded versus crinkled versions of seeds; and so on). Mendel’s application of probability methods …