science-genetics

• Genetics is the study of heredity and the variation of inherited characteristics.
• The trait is also carried by the autosomes and not the sex chromosomes.
• Genetics is a branch of biology that deals with the heredity and variation of organisms.
• Genetics involves the genetic makeup and phenomena of an organism, type, group, or condition.
• Heredity refers to the genetic heritage passed down by our biological parents.
• Heredity is the transmission of traits from one generation to the next.
• These traits can be physical, such as eye color, blood type or a disease, or behavioral.
• Inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents.
• Genetic variation refers to differences among the genomes of members of the same species.
• Genetic variation within a species can result from a few different sources.
• Mutations, the changes in the sequences of genes in DNA, are one source of genetic variation.
• The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop.
• During meiosis, the pairs of homologous chromosomes are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.
• Mitosis is a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells.
• Mitosis is the step in the cell cycle that the newly duplicated DNA is separated, and two new cells are formed.
• Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
• Meiosis is the process in eukaryotic, sexually-reproducing animals that reduces the number of chromosomes in a cell before reproduction.
• There are four main concepts related to the Principle of Independent Assortment: A gene can exist in more than one form or allele.
• Organisms inherit two alleles for each trait.
• When sex cells are produced (by meiosis), allele pairs separate leaving each cell with a single allele for each trait.
• When the two alleles of a pair are different, one is dominant and the other is recessive.
• The gene for seed color in pea plants exists in two forms: one form or allele for yellow seed color (Y) and another for green seed color (y).
• In this example, the allele for yellow seed color is dominant, and the allele for green seed color is recessive.
• When the alleles of a pair are different (heterozygous), the dominant allele trait is expressed, and the recessive allele trait is masked.
• Seeds with the genotype of (YY) or (Yy) are yellow, while seeds that are (yy) are green.
• Punnett square is a chart that allows you to easily determine the expected percentage of different genotypes in the offspring of two parents.
• An example of a Punnett square for pea plants is shown in the Figure below.
• Both parents in this example are heterozygous for flower color (Bb).
• In 1902, Theodor Boveri observed that proper embryonic development of sea urchins does not occur unless chromosomes are present.
• Walter Sutton observed the separation of chromosomes into daughter cells during meiosis in 1902.
• The Chromosomal Theory of Inheritance, which identified chromosomes as the genetic material responsible for Mendelian inheritance, was developed based on these observations.
• Centrioles are organelles involved in cell division and their function is to help organize the chromosomes before cell division occurs so that each daughter cell has the correct number of chromosomes after the cell divides.
• The typical behavior of chromosomes in meiosis is that homologous pairs synapse, recombine, and then separate at anaphase I.
• At anaphase II, sister chromatids separate.
• In contrast to mitosis, the sister chromatids of each homolog remain attached to each other at meiosis II.
• The chromosomes occur in pairs in the cell, so do the Mendelian factors.
• Homologous chromosomes pair during meiosis and only one member of each pair finds its way into given germ cell.
• Mendelian factors segregate from one cell to another in similar fashion.
• By the process of fertilization the original number of chromosomes is restored in the zygote, similarly Mendelian factors (pairs of contrasting characters) reduced to one half their original number during germ cells formation are restored by fertilization.
• Mendel’s first law, known as the law of segregation of factors, is due to the segregation of the two factors of a hereditary trait from each other during the formation of gametes.