Heredity and Evolution Test - 8

Karyotype is the number and appearance of chromosomes in a nucleus of somatic cell. Somatic cells are diploid cells which make up the body. They have two sets of chromosomes. So, if an egg cell (gamete cell) which is a haploid cell (with single set of chromosomes)has 10 chromosome, then number of chromosomes present in a somatic cell will be 20 chromosomes . As egg cells are produced by female body, then among 20 chromosomes, two X chromosomes will be sex chromosome. So, karyotpe of that animals will be showing 18 autosomes.

Charles Darwin was a British naturalist who proposed the theory of biological evolution by natural selection. Darwin defined evolution as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor. The mechanism that Darwin proposed for evolution is natural selection. Because resources are limited in nature, organisms with heritable traits that favor survival and reproduction will tend to leave more offspring than their peers, causing the traits to increase in frequency over generations.

An egg or sperm only has half of the parent's sex chromosome pair. An egg will always have an X chromosome, since the woman's sex chromosome pair only has Xs. Sperm can have either an X chromosome or a Y chromosome.

If a sperm with an X chromosome fertilizes the egg, the new cell will have two X chromosomes. One came from the father's sperm and one came from the mother's egg. Since the sex chromosome that is made is XX, the cell will grow into a girl baby.

A retrovirus is any virus belonging to the viral family Retroviridae. All The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell.

The X0 sex-determination system is a system that determines the sex of offspring among grasshoppers, crickets, cockroaches, and some other insects. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (X0), while females have two (XX).

The zero (sometimes, the letter O) signifies the lack of a second X. Maternal gametes always contain an X chromosome, so the sex of the animals' offspring depends on whether a sex chromosome is present in the male gamete. Its sperm normally contain either one X chromosome or no sex chromosomes at all

Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly.

Each DNA molecule consists of two twisted strands of bases that form a shape called a double helix. The two strands are held together by hydrogen bonds between pairs of bases.

A nitrogenous base is simply a nitrogen containing molecule that has the same chemical properties as a base. They are particularly important since they make up the building blocks of DNA and RNA: adenine, guanine, cytosine, thymine and uracil.

Lamarckism – Theory of Inheritance of Acquired Characters is the first theory of evolution, which was proposed by Jean Baptiste de Lamarck (1744-1829), a French biologist. Although the outline of the theory was brought to notice in 1801, his famous book “Philosophic Zoologique” was published in 1809, in which he discussed his theory in detail.