Roots, shoots, and leaves all contain three basic types of tissues:
1. dermal tissues
2. ground tissues
3. vascular tissue
Dermal tissue includes the epidermis. The epidermis forms an outer protective covering for the plant. It is one cell layer thick in most plants.
Ground tissue includes the cortex of the stem and mesophyll of leaves. Ground tissue cells function in storage, photosynthesis, and secretions.
Vascular tissue conducts fluids and dissolved substances throughout the plant body.
A vascular plant consists of a root system and a shoot system.
Root System
The root system anchors the plant into the soil, from which it absorbs water and ions. Roots evolved as an adaptation to living on land.
Shoot System
The shoot system consists of the stem, leaves, flowers, and ultimately, fruits and seeds. Stems serve as an attachment surface for leaves. leaves are the principal sites of photosynthesis. Flowers are the reproductive organs of the plant.
The shoot also consists of repeating internode, node, and axillary bud. An axillary bud is a lateral shoot apex that gives rise to new branches or replaces the main shoot if it is eaten by an herbivore.
Roots and shoots grow at their tips, called apices (singular, apex).
Sex determination in drosophila
In Drosophila, males are XY, but sex not only depends on the presence of a Y chromosome. Drosophila is a diploid organism with a pair of sex chromosomes (XX or XY) and three autosomal pairs of chromosomes (two autosomal sets). Sex depends on the ratio of the number of X chromosomes to the number of autosome sets.
An X: A ratio of 1.00 or higher produces a female whereas an X: A ratio of 0.5 or lower produces a male. The X: A between 0.5 and 1.0 produces intersex.
Basic Definitions
Inheritance: Inheritance is the process of character transmission from individuals of one generation to the next. It is regulated by the genes present on chromosomes.
Genetics: The branch of biology concerned with the study of inheritance, or the transmission and expression of genetic information.
Character: Any heritable feature or characteristic of an organism is known as a character e.g. Height, Intelligence, blood group, and hair color.
Trait: A Variant of a character is called a trait e.g. black or brown hair color, and short or tall stature. These are characteristics that an organism displays. Also include the organism’s behavior (behavioral traits).
Gene: Gene is the unit of heredity. It is a segment of DNA that contains the information to make a functional protein.
Allele: Alleles are the alternative form of a specific gene. Alleles Control the same characteristics (e.g. hair color) but produce different effects (e.g black or red)
Back cross: Back cross refers to a cross of F 1 hybrids to individuals with genotypes of the parental generation or with its parents.
Test cross: A cross between a recessive individual and a dominant individual whose genotype is unknown (Homozygous or heterozygous) is known as a test cross.
Pure breeding: An individual with two identical alleles of a particular gene or an individual that when self-crossed produces progeny of its own type.
Hybrid: An individual that has two different alleles of a particular gene A progeny individual from any cross involving parents of different alleles.
Dominant Allele: An allele that determines the phenotype in the heterozygous condition. For example, if a plant is Tt and has a tall phenotype, the T (tall) allele is dominant over the t (dwarf) allele.
Recessive allele: A gene that is masked by the presence of a dominant gene is called recessive.
Reciprocal Crosses: A pair of crosses in which the traits of the two parents differ about gender. For example, one cross could be a red-eyed female fly and a white-eyed male fly, and the reciprocal cross would be a red-eyed male fly and a white-eyed female fly.
