Lecture 13- Terminologies gene, allele, locus, homozygous, heterozygous, hemizygous, genotype, phenotype,.ppt

erminologies gene, allele, locus, homozygous, heterozygous, hemizygous, genotype, phenotype

1. Lecture 13- Terminologies: gene, allele, locus,
homozygous, heterozygous, hemizygous,
genotype, phenotype, monohybrid, dihybrid,
trihybrid, polyhybrid.

2. •Basic unit of inheritance/heredity
•Sequence of DNA nucleotides which coded for a
functional product of RNA or a ploypeptide
•Factors which are responsible for the inheritance of
characters from one generation to another
Genes

3. Allele
•An allele is an alternate form of a gene, which are located at
the same position or genetic locus, on a chromosome

4. Contrasting characters
•Features of an individual with marked (observable)
phenotypic difference

5. Phenotype
•The observable characteristics of an individual resulting from
the interaction of its genotype with the environment (or) the
actual appearance of an individual. eg.colour, height etc
Genotype
•The genetic constitution of an individual such as RR, Rr or rr

7. •F1:The first filial generation or offspring of two distinct parents.
•F2: The progeny of F1 plants obtained by selfing.
•Dominance: Masking effect of one allele of a gene over the other.
•Dominant: The character which is expressed in F1.
•Recessive: The character whose effect is suppressed or masked in
F1.
•Gene symbol: Various symbols which are used to represent genes
or alleles.
•Homozygous: Individuals having identical alleles on the
corresponding locus of homologous chromosomes.
•Heterozygous: Individuals having dissimilar alleles on the
corresponding locus of homologous chromosomes

9. •Locus: A position on chromosome which is occupied by an
allele.

10. Hemizygous
Having only a single copy of a gene instead of the customary
two copies. All of the gene on the single X chromosome in
the male are in the hemizygous state.

11. •Hybridization / crossing: The process through which
the hybrids are produced involving parents having
contrasting characters.
•Monohybrid cross: Crossing of the two individuals
differing in one pair of gene affecting one character.
•Dihybrid cross: Crossing of the two individuals
differing in two pairs of gene affecting two
characters.
•Polyhybrid cross: Crossing of the two individuals
differing in three or more pairs of genes, each
affecting a different character.

12. •Direct cross: A cross between two genotypes.
•Backcross: Crossing F1 with any one of the parents.
•Testcross: Crossing F1 with homozygous recessive parent.
•Punnett Square
•Developed by Reginald Punnett.
• The Punnett square is a square diagram that is used to
predict the genotypes of a particular cross.
•The diagram is used by biologists to determine the
probability of an offspring having a particular genotype.

13. Punnett Square