Dr. Valli Syam's document defines several key genetics terms: Haploid cells have a single copy of each chromosome, while diploid cells have two sets of chromosomes, one from each parent. Homologous chromosomes are pairs that carry the same genes. A gene is the unit of heredity responsible for traits, while alleles are alternate forms of a gene. Dominant alleles are expressed in both homozygous and heterozygous conditions, while recessive alleles require the homozygous condition. Phenotype is an observable trait, and genotype is the genetic makeup. Monohybrid and dihybrid crosses involve one or two pairs of contrasting traits.

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.h
tm
• https://microbenotes.com/diploid-vs-
haploid/#:~:text=Diploid%20is%20a%20cell%20or%20organism%20that%20has%2
0paired%20or,single%20copy%20of%20each%20chromosome.&text=These%20cell
s%20are%20formed%20after%20mitotic%20cell%20division.