What are the significance of crossing over ?

Crossing over results in the production of recombinants (new gene combinations) and allows the expression of new traits not visible in the parents. It had shown a linear arrangement of linked genes present in the chromosome of an individual. Genetic maps are prepared with the help of the crossing over. It also results in genetic diversity due to the production of gene combinations.

What is sex-linked inheritance? Give one example.

Sex linked are the traits that are found on the sex chromosomes. X-linked chromosomes are inherited for females and Y-linked chromosomes are inherited for males. Some of the more familiar sex-linked traits are hemophilia, red-green color blindness, congenital night blindness, Duchenne muscular dystrophy, Fragile X syndrome, etc.

Describe about the Pedigree analysis.

Pedigree analysis is a graphical representation of the inheritance of a particular trait that is inherited from one generation to another. It represents a family tree, which displays the members of the family who are affected by a genetic disorder or maybe a carrier of the disease. It can be studied as follows: The rows represent the generations of a family Squares represent the males. Circles represent the females. The pedigree analysis helps to know the trait of inheritance for a particular trait, and also know whether the trait is getting inherited or not. It is a strong tool in human genetics that helps to predict the pattern of inheritance of traits. Also helps in studying the pattern in the family that can be studied concerning a particular trait or the disease which is carried on to the next generation.

Write differences between linkage and crossing over.

Feature Linkage Crossing over Definition The linkage is the association of genes or any DNA sequences on the same chromosome. Crossing over is the exchange of genetic material during sexual reproduction between non-sister chromatids of two homologous chromosomes that form recombinants. Feature Linkage Crossing over Relation of the distance The strength of the genetic linkage between two genes is inversely proportional to the distance between them in the chromosome. The probability of two genes crossing over is directly proportional to the distance between them in a chromosome.

Write differences between Down's syndrome and Klinefelter's syndrome.

Features Down's Syndrome Klinefelter's syndrome. Chromosome It is genetic disorder that occurs due to the trisomy of an autosome, i.e. chromosome 21. It occurs due to the trisomy of the sex chromosome. i.e. X-chromosome. Karyotype The karyotype for Down's syndrome is 47, XY The karyotype for Klinefelter's syndrome is 47, XXY.

Define chromosomal theory of inheritance.

Chromosomal theory of inheritance was proposed by Sutton and Boveri (1904). It states that: The gametes have all the hereditary characters. These are the genetic link between two generations. The genetic material is present within the nucleus in the form of chromosomes and the chromosomes occur in pairs. During gamete formation, the homologous chromosome pair segregate independently by a process called meiosis. Thus, each gamete contains only one set of chromosomes. The fusion of sperm and ovum happens during fertilization due to which the diploid number of chromosomes is retained.