Genetics terminologies

Explains the basic terms used in Genetics

1. GENETICS - TERMINOLOGIES Dr. Valli Syam

2. HAPLOID - Haploid or monoploid is a cell or organism that has just a single copy of each chromosome DIPLOID - Diploid is a cell or organism that has paired or two sets of chromosomes, one from each parent. Homologous chromosome - Two pieces of DNA within a diploid organism which carry the same genes, one from each parental source. In simpler terms, both of your parents provide a complete genome. Each parent provides the same 23 chromosomes, which encode the same genes. So, our cells carry 46 total chromosomes, in two copies.  Father Father Father Mother Mother Mother

3. CHARACTER - Heritable feature that varies among individuals - an attribute or feature like Eye colour , Skin colour , Hair colour etc TRAIT - Specific manifestation of that particular character - Eye colour (Character) - Black, Blue, Brown (Traits) Skin colour (Character) - Tan, Brown, Black (Traits) Hair colour (Character) - Black, Blonde, Brunette (Traits)

4. GENE - Unit of heredity responsible for the expression and inheritance of particular characteristic – Eg. Eye colour ALLELE - Alternate forms of a gene – Eg. Black Eye colour , Blue Eye colour DOMINANT ALLELE – Allele which is expressed in both Homozygous and Heterozygous conditions – Denoted by Capital Letter RECESSIVE ALLELE – Allele which is expressed only in Homozygous condition – Denoted by Small Letter corresponding to dominant allele LOCUS - Specific place on a chromosome occupied by an allele

5. PHENOTYPE - Observable characteristic - Physical, Physiological, Biochemical or Behavioural - Eg. Flower colour (Purple or White) GENOTYPE - Genetic constitution of organism - A set of alleles that an organism possesses HOMOZYGOUS - a genotype consisting of two identical alleles for that locus - Flower colour (PP – Purple or pp - White) HETEROZYGOUS - a genotype consisting of two different alleles for that locus - Flower colour (Pp) - Purple CARRIER - a heterozygous individual not expressing a recessive trait but capable of passing it on to its offspring P P P p p p

6. PARENTAL GENERATION - The generation that supplies gametes to the filial generation. F1 GENERATION - First Filial Generation - the generation that receives gametes from the parental generation F2 GENERATION - Second Filial Generation - the generation that receives gametes from first filial generation

7. HYBRID - The progeny or offspring obtained from crossing two pure line plants with contrasting characters MONOHYBRID CROSS - A cross involving single pair of contrasting characters DIHYBRID CROSS - A cross involving two pairs of contrasting characters POLYHYBRID CROSS - A cross involving more than two pairs of contrasting characters

8. REFERENCES Genetics – VB Rastogi – 4th Edition – Medtech Publishers -2019 Cell Biology, Genetics, Molecular Biology, Evolution And Ecology - P.S. Verma &V.K. Agarwal - S. Chand & Company Ltd. 2005 Genetics A conceptual approach – Benjamin A Pierce – W.H. Freeman & Company – 2012 https://biologydictionary.net/homologous-chromosomes/ https://science.umd.edu/classroom/BSCI363/inouye/assignments/resources/glossary.htm https://microbenotes.com/diploid-vs-haploid/#:~:text=Diploid%20is%20a%20cell%20or%20organism%20that%20has%20paired%20or,single%20copy%20of%20each%20chromosome.&text=These%20cells%20are%20formed%20after%20mitotic%20cell%20division.