Genetics-notes

             Allele : Various or slightly different forms of a gene, having same position on chromosomes.

Phenotype : The observable or external characteristics of an organism

Genotype : The genetic constitution of an organism.

Monohybrid cross : A cross between two individuals of species, considering the inheritance of single pair of contrasting character e.g., a cross between pure tall (TT) and Dwarf (tt).

Dihybrid cross : A cross between two individuals of a species, considering the inheritance of two pairs of contrasting traits/characters e.g., a cross between Round and Yellow (RRYY) and wrinkled and green (rryy) pea seeds

Co-dominance : When two alleles of a gene are equally dominant and express themselves even when they are together.

Multiple allelism : When a gene exists in more than two allelic forms e.g., gene for blood group exist in three allelic forms, IA, IB and i.

Aneuploidy : The phenomenon of gain or loss of one or more chromosome(s), that results due to failure of separation of homologous pair of chromosomes during meiosis.

Trisomy : The condition in which a particular chromosome is present in three copies in a diploid cell/ nucleus.

Male heterogamety : When male produces two different types of gametes/ sperms e.g., In human beings X and Y.

Mutation : The sudden heritable change in the base sequence of DNA, or structure of chromosome or a change in the number of chromosomes.

Pedigree Analysis : The analysis of the distribution and movement of trait in a series of generations of a family.

Female heterogamety : When female produces two different types of gametes/ova e.g., female bird produces Z and W gametes.

Law of Dominance : When two individuals of a species differing in a pair of contrasting characters/traits are crossed, the trait that appears in the F1 hybrid is dominant and the alternate from that remain hidden, is called recessive.

Law of Segregation : The members of allelic pair that remained together in the parent, segregate/separate during gamete formation and only one of the factors enters a gamete.

Law of Independent Assortment : In the inheritance of two pairs of contrasting characters, the factors of each pair of characters segregate independently of the factors of the other pair of characters.

Test Cross : When offspring or individual with dominant phenotype, whose genotype is not known, is crossed with an individual who is homozygous recessive for the trait.

The progeny of monohybrid test cross ratio is 1 : 1 while the dihybrid test cross ratio is 1 : 1 : 1 : 1.

                                                                                SUPPORT MATERIAL

Chapter-1

Clone : A group of organism derived from a single individual and hence morphologically and genetically similar.

Embryogenesis : The process of development of embryo from zygote.

Juvenile Phase : It is the period of growth before maturity when sex organs are not functional.

Meiocytes : These are specialized cells of diploid organisms which undergo meiosis.

Pericarp : It is the protective covering of fruit, may be divided into epicarp, mesocarp and endocarp.

Parthenogenesis : Development of an egg into an embryo without fertilisation.

Gamete Transfer

1. In Algae, Bryophytes and Pteridophytes : The male and female gametes are flagellated and motile, need a medium (water) to reach the egg.

2. In seed Plants : Pollen grains are transferred to stigma of flower of same species by various agents.

3. In animals :

(a) By Copulation . e.g., Reptiles, Birds and Mammals.

(b) By External medium . e.g., Fishes and Amphibians.

Sporulation :- During unfavorable conditions organisms like Amoeba surrounded by resistant coat (three layered - hard covering ) or cyst. This is called encystation . Within cyst a number of spores are formed . On returning favourable conditions, the cyst burt and spores are liberated and gradually grows into adults. This process is known as sporulation.

Fragmentation : It is a type of asexual reproduction where an organism splits into fragments. There fragments develops into fully grown individual. eg. spirogyra, fungi and some annelids.

Regeneration: It is a process of renewal, restoration and growth. It can occur at the level of the cell tissue and organ . It is common in Hydra , Planaria and echinoderms .ŸIn human, liver has power of regeneration, if it is partially damaged.ŸDuring danger a lizard discard a part of tail which can regenerate latter.

CHAPTER 2

SEXUAL REPRODUCTION IN FLOWERING PLANTS

Autogamy : When pollen grains of a flower are transferred from anther to stigma of the same flower.

Coleorhiza : Aprotective sheath of radicle in monocot seed.

Endothecium : A fibrous layer in the anther next to epidermis.

Geitonogamy : Self pollination between flowers of the same plant.

Micropyle : Asmall pore in the ovule through which the pollen tube enters.

Nucellus : Multicellular tissue in the centre of ovule where embryo sac is present.

Tapetum : Inner most layer of cells in pollen sac which provide nutrition to developing pollen grains

Viability of Seed : Ability of seed to retain the power of germination.

1. Microsporangium (Pollen sac) : Outermost layer = Epidermis

Second layer = Endothecium

Middle layer = 2 - 4 layers of cells

Innermost layer = Tapetum [Nourishes the developing pollen grains(Microspores)]

2. Microsporogenesis : Process of formation of microspores from a pollen mother cell.

Megasporangium (Ovule) :

ŸThe ovule is a small structure attached to the placenta by means of a stalk called funicle.

ŸThe point of attachment of the body of the ovule to the funicle is known as hilum. The main body of the ovule is composed of paranchymatous cells known as nucellus.

ŸEach ovule has one or two protective integument, which encircle the ovule except at the tip having small opening called micropyle.

ŸOpposite to micropylar end, is chalaza. Generally a single embryosac or female gametophyte located in

nucellus.

ŸCells of nucellus have abundant reserve food material and provide nourishment to the developing embryo.

 Female gametophyte (Embryo sac) : In a majority of flowering plant one of the megaspore is functional while other three degenerate.

The functional megaspore develops in embryo sac.

The nucleus of the functional megaspore (n) undergoes three successive mitotic cell division which results the formation of eight nucleate stage of embryo sac (free nuclear division).The cell wall formation starts at eight nuclear stages. Three cells are grouped together at micropylar end to form the egg apparatus.(2 synergids + 1 egg cell).

Dicot Embryo : A typical dicot embryo consist of an embryonal axis and two cotyledons.The portion of embryonal axis above the level of cotyledons is the epicotyle which terminates with the plumule or stem tip.

The portion below the level of cotyledons is hypocotyl that terminates at its lower end in the radicle or root tip.

Monocot Embryo : Monocot (Rice, Maize etc.) has one cotyledon called Scutellum.The embryonal axis has the radicle and root cap enclosed by a sheath called Coleorrhiza.

The upper end (epicotyle) has plumule which is covered by hollow folder sturcture, the coleoptile.

Apomixis : Apomixis is a form of asexual reproduction that mimics sexual reproduction where seed are formed without fertilisation.

Polyembryony : Occurance of more than one embryo in a seed. e.g. Orange, lemon, onion, mango, ground nut.

Reasons of polyembryony : More than one egg may be formed in the embryo sac.More than one embryo sac may be formed in an ovule.

Ramsar Sites Notes

RAMSAR SITES

Ramsar sites are wetlands considered to be of international importance. The international convention which forms the basis for their identification is commonly referred to as the "Ramsar Convention" after the city in Iran where the convention was signed in 1971. The Convention is an international treaty for the conservation and wise use of wetlands. All joining Parties of the Ramsar Convention commit themselves to work towards the “three pillars” of the Convention.

Ensuring the conservation and wise use of wetlands it has designated as Wetlands of International Importance,

Including as far as possible the wise use of all wetlands in national environmental planning, and

Consulting with other Parties about implementation of the Convention, especially in regard to transboundary wetlands, shared water systems, and shared species.

Sites are selected by the Contracting Parties for designation under the Convention by reference to the Criteria for the Identification of Wetlands of International Importance. Sites must meet one or more of the following nine criteria:

·         Contains a representative, rare or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region.

·         Supports vulnerable, endangered, or critically endangered species or threatened ecological communities.

·         Supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region.

·         Supports plant and/or animal species at a critical stage in their life cycles, or provides refuge during adverse conditions.

·         Regularly supports 20,000 or more waterbirds.

·         Regularly supports 1% of the individuals in a population of one species or subspecies of water birds.

·         Supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions and/or populations that are representative of wetland benefits and/or values and thereby contributes to global biological diversity.

·         Is an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depend.

·         Regularly supports 1% of the individuals in a population of one species or subspecies of wetland-dependent non-avian animal species.

v

IMPORTANT DIAGRAMS