short note

: 4) *Codominant markers* are markers for which both alleles are expressed when co-occurring in an individual. Therefore, with codominant markers, heterozygotes can be distinguished from homozygotes, allowing the determination of genotypes and allele frequencies at loci.

 *genetic marker* is a DNA sequence with a known physical location on a chromosome. Genetic markers can help link an inherited disease with the responsible gene. DNA segments close to each other on a chromosome tend to be inherited together.

 1)pure line. noun. a breed or strain of animals or plants in which certain characters appear in successive generations as a result of inbreeding or self-fertilization.

 2) *Backcrossing* is a crossing of a hybrid with one of its parents or an individual genetically similar to its parentto achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and production of gene knockout organisms.

: 5) *Quantitative trait loci* are regions of the genome at which genetic variation is associated with a particular quantitative trait - for example, height, weight or blood pressure.

 7) *Gene mapping* is the process of establishing the locations of genes on the chromosomes. Early gene maps used linkage analysis.

*Male sterility* These techniques help much to reduce the cost of hybrid seed production. Male sterility. Male sterility refers to a condition in which pollen is either absent or non-functional in flowering plants, while female gametes function normally.

*fruit breeding* refers to the purposeful genetic improvement of fruit crops through various techniques including selection, hybridization, mutation induction, and molecular techniques.

Examples of physical mutagens* are ultraviolet (UV) and gamma radiation.

*chemical mutagens* are alkylating agents and azides

*conventional plant breeding also has its limitations.* First, breeding can only be done between two plants that can sexually mate with each other. This limits the new traits that can be added to those that already exist in a particular species.

*Marker-assisted selection (MAS)* is a method of selecting desirable individuals in a breeding scheme based on DNA molecular marker patterns instead of, or in addition to, their trait values.

: Molecular breeding, or MAS, refers to the technique of using DNA markers that are tightly linked to phenotypic traits to assist in a selection scheme for a particular breeding objective.

*Molecular breeding advantages* genetic transformation, genetic diversity assessment, large-scale transcriptome and proteome studies, identification of candidate genes for trait improvement, and whole genome sequencing

*Quality Genetic markers* have to be easily identifiable, associated with a specific locus, and highly polymorphic, because homozygotes do not provide any information. Detection of the marker can be direct by RNA sequencing, or indirect using allozymes

 *micropropagation can be divided into four stages:* 

Initiation stage. A piece of plant tissue (called an explant) is (a) cut from the plant, (b) disinfested (removal of surface contaminants), and (c) placed on a medium. ... 

Multiplication stage. ... 

Rooting or preplant stage. ... 

Acclimatization.

: *molecular marker* is defined as any DNA sequence which shows polymorphism and can be detected using a molecular technique.

: PCR Based

1)RAPD- Random amplification of polymorphic DNA.

२)AFLP-Amplified fragment length polymorphism.

३)SCAR-Sequence characterize amplified region.

४)STS-Sequence tagged sites.

५)EST-Express sequence tags.

६)SNP-Single nucleotide polymorphism.

७)SSR-Simple sequence repeats

8)CAPS-Cleaved amplified polymorphic sequences.

*explant* is a part of the plant by which a whole plant can be produced through plant tissue culture technique.

 *CpG islands* are regions of the genome that contain a large number of CpG dinucleotide repeats.