Life is defined as the condition that distinguishes animals and plants from inorganic matter. All living things are called organisms. Organisms have multiple abilities which only living things have including the capacity for growth, reproduction, functional activity, and continual change. These processes are preceded by death. Living things are re-created by the process of cellular reproduction. Through cellular reproduction identical cells to pre-existing cells, as well as cells with a new genetic make-up are created. Reproduction is responsible for the continuity of life.
Reproduction is the ability of an organism to create new individuals. There are two modes of reproduction. These modes include sexual and asexual. In asexual reproduction a new offspring is produced from a single parent. The parent and offspring have the same genes and thus have the same traits. On the contrary, sexual reproduction involves two parents. Each parent produces special cells called gametes which fuse in a process called fertilization to form a zygote. (3) These cells are genetically different to each parent cell. Cellular reproduction consists of two processes: meiosis and mitosis will be discussed in detail later in the essay.
Cells consist of many organelles, each of which plays a vital role in its function. The nucleus, however, is the most vital component of the cell. It is the membrane enclosed area of the cell which contains most of the cell's genetic material, organized as multiple long linear DNA molecules. (1) It is therefore also known as the "control center" of the cell.
DNA is the hereditary material in humans and almost all other organisms. It's full name is deoxyribonucleic acid. It consists of nitrogenous bases, which include ...
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...elope reforms around each chromosome set, the spindle fibres disappear, and the nucleolus reforms as it was in the parent cell. (6) Finally, in telophase a cleavage furrow becomes evident and the cytoplasm of the cell divides in a process called cytokinesis, resulting in two separate and independent but identical diploid daughter cells.
Meiosis occurs in two successive nuclear divisions: meiosis I and meiosis II. Meiosis I reduces the ploidy level from 2n to n (reduction) while Meiosis II divides the remaining set of chromosomes in a mitosis-like process (division). (8)
The continuity of life is based on heritable information in the form of DNA and its transmission from one generation to the next. Without the processes of DNA replication and the division of cells by meiosis and mitosis, life would not continue. There would also be no diversity of life on earth.
11.2) Asexual reproduction involves a single individual / parent who pass duplicates of all its genes to its offspring without the fusion of gametes. Sexual reproduction involves two parents who give rise to offspring that have unique combination of genes inherited from the two parents.
In telophase, these separate chromatids uncoil to become chromosomes. This division produces two identical cells.
The process of mitosis can take place in either a haploid (23 chromosomes) or a diploid (46 chromosomes) cell. Before a cell can be ready for a mitotic division it must primarily undergo its interphase stage. Following the interphase stage several other stages come into play. These stages are prophase, prometaphase, metaphase, anaphase, and telophase. During each specific stage certain sequences of events take place that assist to the completion of the division.
Sexual reproduction is that the union of male and feminine gametes to create a fertilised egg or zygote. The ensuing offspring inherit one-half their traits from every parent. Consequently, they 're not genetically similar to either parent or siblings, except within the case of identical twins. As theorised by Mendel, adults are diploid, meaning as 2N, having 2 alleles offered to code for one attribute. The gametes should be haploid, signified by N, containing just one allele in order that once 2 haploid gametes mix, they manufacture a traditional diploid individual. The method where haploid sex cells are created from diploid parents is known as meiosis, and it happens solely within the reproductive organs.
This means that all the sperm in males and eggs in females are produced from meiosis. Sperm and egg cells are haploid cells-they contain only one of each type of chromosome. Meiosis actually starts with a diploid cell that undergoes two divisions; the end products are four gametes, all genetically different. Meiosis is known as a reduction division because the daughter cells always contain half the amount of chromosomes as the diploid beginner cell. Chromosomes come in pairs and these pairs are called homologous pairs. Homologous chromosomes mean that both of the chromosomes in the pair have the same gene sequence. Human somatic cells(diploid) contain 46 chromosomes consisting of 23 homologous pairs; therefore, human gametes, which are haploid, have 23 total chromosomes-one from each homologous pair. Just like in mitosis, meiosis undergoes all of the same phases. However, because meiosis involves two divisions, the cell goes through all the phases twice. When referring to the first time the cell undergoes a phase, we say 1, and when referring to the second time, we say 2. For example, when a cell starts prophase the first time in meiosis, we say it is going through prophase 1(P1). Also, there are some differences in the process itself. During P1, homologous chromosomes exchange a section of themselves in what is known as crossing over. This provides a source of genetic variation since part of each chromosome switched places with each other, thus making both chromosomes distinct from the original. Another important difference to know is that in anaphase 1, the doubled chromosomes are not separated into sister chromatids. This doesn’t happen until A2 to ensure that each of the four gametes receives one of each kind of chromosome. There are many key points to understand about meiosis. The first being that cells in meiosis do not go through interphase twice. Interphase is a “one-time” thing; DNA
The nucleus is the CEO of the cell. It controls all cell activity, It regulates movement, reproduction, and eating in the cell. The nucleus contains the of the cell's genetic information. This information is organized as deoxyribonucleic acid molecules, in conjunction with a spread of proteins, to create chromosomes.
A chromosome is made up of two identical structures called chromatids. The process of nuclear division is called interphase; each DNA molecule in a nucleus makes an identical copy of itself. Each copy is contained in the chromatid and a characteristic narrow region called the centromere holds the two chromatids together. The centromere can be found anywhere along a chromosome but the position is the characteristic for a particular chromosome. Each Chromatid contains one DNA molecule. DNA is the molecule of inheritance and is made up of a series of genes. The fact that the two DNA molecules in the sister chromatids, and hence their genes, are identical is the key to precise nuclear division.
The process of cell division plays a very important role in the everyday life of human beings as well as all living organisms. If we did not have cell division, all living organisms would cease to reproduce and eventually perish because of it. Within cell division, there are some key roles that are known as nuclear division and cytokinesis. There are two types within nuclear division. Those two types being mitosis and meiosis. Mitosis and meiosis play a very important role in the everyday life as well. Mitosis is the asexual reproduction in which two cells divide in two in order to make duplicate cells. The cells have an equal number of chromosomes which will result in diploid cells. Mitosis is genetically identical and occurs in all living
III. Conclusions All organisms in life are made of at least one or more cells. Cells are the basic units to life. Without cells life cannot exist.
The nucleus contains genetic material that controls all the activities within a cell. A nucleus is made up of D...
Inside the cells that produce sperm and eggs, chromosomes become paired. While they are pressed together, the chromosomes may break, and each may swap a portion of its genetic material for the matching portion from its mate. This form of recombination is called crossing-over. When the chromosomes glue themselves back together and separate, each has picked up new genetic material from the other. The constellation of physical characteristics it determines is now different than before crossing-over.
Discoveries in DNA, cell biology, evolution, and biotechnology have been among the major achievements in biology over the past 200 years, with accelerated discoveries and insight’s over the last 50 years. Consider the progress we have made in these areas of human knowledge. Present at least three of the discoveries you find to be the most important and describe their significance to society, health, and the culture of modern life. DNA (deoxyribonucleic acid) is a self-replicating molecule or material present in nearly all living organisms as the main constituent in chromosomes. It encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses.
Once the sperm fuses with the ovum both chromosomes will pair up and begin the first stages of cell division.
Life according to scientists is “the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death, also the way of life of a human being or animal.”("Life,”) In order for one to have life, one must have the nine characteristics to be considered a living thing. These nine characteristics are; all living things are made up of cells, living things are able to reproduce, living thing use energy, maintain homeostasis, respond and adapt to the environment, grow and develop, have a life span, evolve over time, and are interdependence. All of the nine characteristics have one thing in common, something that is needed for all living things to use, even if they do not know it. This beautiful thing that all living things should value is photosynthesis. Without photosynthesis there wouldn’t consist humans, animals, insects, and most importantly life!
There are certain things that must happen first before the cell can actually split. There is a six step process required during Mitosis. The first five steps of mitosis are called prophase, prometaphase, metaphase, anaphase, and telophase. This is where all the training and preparation is done for cell division. The sixth step is Cytokinesis, and that is when the cell literally splits into two. Like I said, there are certain things in order to happen before it can enter the M phase. first, it must meet the requirements of the certain size and environment. Since in the S phase the cell duplicated it’s amount of chromosomes it be represented as 2N, where N equals the number of chromosomes in the cell. Cells about to enter M phase, which have passed through S phase and replicated their DNA, have 4N chromosomes. Because of this they are now allowed to enter within the M phase to prophase. Here is where the cell thickens up its chromosomes and begin to sprout microtubules from clone centrosomes. Microtubules tub-like are protein filaments and where the chromosomes migrate but are still within the nuclear envelope in the nucleus. There are centromeres, that are inside the chromosomes and during the later process of this phase, specialized microtubules called kinetochores, assemble on the centromere then later attach to these sites. They act like magnets and go