Mendelian Genetics and Inheritance Patterns

Selective Breeding

Selective Breeding

Intentional breeding to enhance desirable traits.

Particulate Inheritance

Traits remain intact during gamete formation.

Blending Inheritance

Traits mix, leading to intermediate offspring characteristics.

Gregor Mendel

Austrian monk known as the Father of Genetics.

True-Breeding Plants

Plants that produce identical offspring when self-fertilized.

F1 Generation

First filial generation from parental cross.

F2 Generation

Second filial generation from F1 self-pollination.

Dominant Trait

Trait expressed in the F1 generation.

Recessive Trait

Trait hidden in the F1 generation.

3:1 Ratio

Observed ratio of dominant to recessive traits in F2.

Genes

Hereditary determinants for traits.

Alleles

Different versions of a gene.

Genotype

Combination of alleles in an individual.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Phenotype

Expressed or measurable trait of an organism.

Law of Segregation

Alleles separate during gamete formation.

Monohybrid Cross

Cross between organisms differing in one character.

Punnett Square

Tool to predict genotype and phenotype ratios.

Independent Assortment

Alleles segregate independently during gamete formation.

Discrete Trait

Trait occurring in distinct categories.

Quantitative Trait

Trait occurring in a range of values.

Self-Pollination

Pollination of a flower by its own pollen.

Parental Generation

Original true-breeding plants in a cross.

Offspring

Descendants produced from a cross.

Hybrid

Offspring resulting from a cross of different pure lines.

Mendel's Experimental Design

Methodical approach to studying inheritance using peas.

Dihybrid Cross

Cross between two traits, resulting in 9:3:3:1 ratio.

Multiplication Rule

Probability of two independent events is multiplied.

Addition Rule

Probability of mutually exclusive events is added.

Multiple Alleles

More than two alleles exist for a gene.

Codominance

Both alleles express equally in heterozygotes.

Incomplete Dominance

Heterozygote shows intermediate phenotype.

Epistasis

One gene's expression affects another gene's expression.

Polygenic Inheritance

Multiple genes influence a single phenotype.

Crossing Over

Exchange of genetic material during meiosis I.

Linkage

Genes inherited together due to proximity on chromosome.

Sex-linked Inheritance

Traits associated with genes on sex chromosomes.

X-linked Genes

Genes located on the X chromosome.

Y-linked Genes

Genes located on the Y chromosome.

Nondisjunction

Chromosomes fail to separate properly during meiosis.

Aneuploidy

Abnormal number of chromosomes in a cell.

Monosomy

Condition of having one less chromosome (2n-1).

Trisomy

Condition of having one extra chromosome (2n+1).

Polyploidy

Condition of having multiple complete sets of chromosomes.

Barr Body

Inactivated X chromosome in female mammals.

Klinefelter Syndrome

XXY condition, phenotypically male with reduced traits.

Turner Syndrome

XO condition, phenotypically female with underdeveloped traits.

Deletion

Loss of a chromosomal segment.

Duplication

Repetition of a chromosomal segment.

Inversion

Reversal of a chromosomal segment's orientation.

Translocation

Movement of a chromosomal segment to another chromosome.

Philadelphia Chromosome

Translocation associated with chronic myelogenous leukemia.

Human ABO Blood Groups

Example of multiple alleles and codominance.