The word meiosis originates from the Greek language. It means to lessen; this refers to the lessening of the number of chromosomes within the cell. Meiosis is the process of chromosomal reduction in eukaryotic cells (plants, animals, and fungi), which leads to the production of germ cells (gametes/sex cells) needed for sexual reproduction.
Purines and pyrimidines are the two families of nitrogenous bases that make up nucleic acids – in other words, they are the building blocks of DNA and RNA. While they are similar in many respects, there are a number of key differences between them that you will be expected to know for the AP® exam. Before we get into those, however, let’s make sure you understand what purines and pyrimidines are so you can recognize questions about them even if the wording is tricky.
Heredity is the passing on of characters from parents onto their progeny. In some organisms, like humans, a parent passes on one copy per gene to their offspring and as a result, the progeny gets two copies in total from its parents. These organisms are called diploids (2n).
Meiosis is how eukaryotic cells (plants, animals, and fungi) reproduce sexually. It is a process of chromosomal reduction, which means that a diploid cell (this means a cell with two complete and identical chromosome sets) is reduced to form haploid cells (these are cells with only one chromosome set). The haploid cells produced by meiosis are germ cells, also known as gametes, sex cells or spores in plants and fungi.
Mitosis is the process whereby a cell reproduces asexually to produce two identical daughter cells. This occurs via nuclear division. Before mitosis, the number of chromosomes in the cell is doubled via chromosome replication, transforming the cell from a diploid (2n) cell to a tetraploid (4n) cell.
In 1887, the German anatomy biologist, Water Fleming, coined the term mitosis which comes from the Greek language which translates to “warp thread” from mitos and “act or process” from the osis part of mitosis. This term was based on the warped thread appearance of the chromatin of the cell nucleus in the first stages of mitosis.
Transcription generally refers to the written form of something. In biology, transcription is the process whereby DNA is usedas a template to form a complementary RNA strand – RNA is the “written” form of DNA. This is the first stage of protein production or the flow of information within a cell. DNA stores genetic information, which is then transferred to RNA in transcription, before directing the synthesis of proteins in translation. Three types of RNA can be formed: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).
Deoxyribonucleic acid, fondly known as DNA, is a molecule in the shape of a double helix, which is responsible for storing genetic information in the cells of all living organisms. Most people know or should know this. But what is DNA made of exactly?
In this post, we will discuss what happens in the G1 and G2 Phases of the Cell Cycle. Cell division entails making more cells through duplication of the one cell’s contents and then splitting this cell into two equal and identical cells. These cells are identical to the parent cell. This is how we grow and replace injured cells.
The cell cycle encompasses the whole life of a cell from birth through to its death. It is the time from the formation of a cell from its parent cell until its division into its daughter cells. An important part of the cell cycle is cell division, the process whereby a cell is replicated to form either two daughter cells, through the process of mitosis, or asexual reproduction; or four daughter cells, through the process of meiosis, or sexual reproduction. However, this division forms only a small part of the cell cycle.