Principles of Inheritance & Variation

Flashcards on Principles of Inheritance & Variation, Mendel's Laws, Non-Mendelian Inheritance, Chromosomal Theory, Sex Determination, Mutation, Pedigree Analysis, Genetic Disorders, and Mendelian Disorders.

Inheritance

Transmission of characters from parents to progeny.

Heredity

Resemblance between offspring and their parents.

Variation

Difference between parents and offspring.

Genetics

Study of heredity and variation.

Alleles

Alternative forms of a gene.

Homozygous

Condition in which chromosome carries similar alleles for a character.

Heterozygous

Condition in which chromosome carries dissimilar alleles for a character.

Dominant character

The character which is expressed in heterozygous condition.

Recessive character

The character which is suppressed in heterozygous condition.

Phenotype

Physical (visible) expression of an individual.

Genotype

Genetic make-up of an individual.

Punnett square

A grid that enables us to calculate the probability of all possible genotypes of offspring in a genetic cross.

Cross

Deliberate mating of 2 parental types.

Backcross

Crossing of F1 hybrid with its any of parent.

Testcross

Crossing of an F1 hybrid with its recessive parent. It is used to find out the unknown genotype.

Monohybrid cross

A cross involving 2 plants differing in one character pair.

Law of Dominance

When a pair of contrasting characters combines, only one is expressed (dominant character) and the other remains hidden (recessive character).

Law of Segregation

During gamete formation, the factors (alleles) of a character pair present in parents do not mix each other, but separate and segregate from each other such that a gamete receives only one of the 2 factors.

Dihybrid cross

A cross between two parents differing in 2 pairs of contrasting characters.

Law of Independent Assortment

When more than one pair of characters is involved in a cross, factor pairs independently segregate (separate) from the other pair of characters.

Incomplete Dominance

Inheritance where heterozygous offspring shows intermediate character between two parental characteristics.

Co-dominance

Inheritance in which both alleles of a gene are expressed in a hybrid.

Multiple allelism

Inheritance in which more than 2 alleles govern the same character.

Pleiotropy

Inheritance in which a single gene governs multiple phenotypic expressions; such a gene is called pleiotropic gene.

Polygenic Inheritance

Inheritance in which traits are controlled by 3 or more genes.

Linkage

Physical association of 2 or more genes on a chromosome; they do not show independent assortment.

Recombination

Generation of non-parental gene combinations.

Genetic map

Linear graphic representation of the sequence and relative distances of the genes present in the chromosome.

Autosomes

Chromosomes determining the somatic characters of an individual.

Sex chromosomes

Chromosomes that involve in sex determination.

Mutation

Sudden heritable change in DNA sequences resulting in changes in the genotype and the phenotype of an organism.

Frame-shift mutation

Loss (deletions) or gain (insertion/ duplication) of a DNA segment.

Point mutation

Mutation due to change in a single base pair of DNA.

Pedigree Analysis

Analysis of inheritance of a particular trait through several generations in a family (pedigree).

Mendelian Disorders

Caused by alteration or mutation in the single gene.

Chromosomal disorders

Caused due to absence or excess or abnormal arrangement of one or more chromosomes.

Aneuploidy

The gain or loss in a subset of chromosomes due to failure of segregation of chromatids during cell division.

Monosomy

One chromosome is lost from diploid set; 2n-1.

Trisomy

One chromosome is added to diploid set; 2n+1.

Polyploidy (Euploidy)

It is an increase in a whole set of chromosomes due to failure of cytokinesis after telophase stage of cell division.