Chromosomes and Life Cycles
Chromosome Structure
All cells contain a nucleus that has a membrane around it. Inside the
nucleus are chromosomes. The chromosomes are made from a molecule
called deoxyribonucleic acid - which is commonly known as DNA. DNA is
a very long molecule, so long in fact that the DNA from just one
person is long enough to stretch all the way to the moon. Reading this
it would be hard to understand how DNA could fit into our cells, but
this problem is overcome due to it being highly coiled to make it much
shorter, and is also divided into lengths called chromosomes.
DNA has two jobs to do - 1) It must store information, this would
account for why the DNA molecule has to be so long, as it has to store
a phenomenal amount, and 2) It must be able to copy itself so that
this information can be passed on to the next generation. It is
important that the DNA can make an exact copy of itself with as few
mistakes as possible so that problems will not occur due to faulty
genes in the next generation.
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A simplified picture of DNA is shown above.
The DNA is divided into sections called genes. Each gene contains all
the information for a single instruction. This instruction is how to
make a single protein, which is produced in the cells cytoplasm. The
body uses the different proteins produced by the genes in many
different ways. Every cell in your body contains about 40,000
different genes. All this may be more easily understood by reading the
next statement,
'If all the chromosomes in a nucleus are represented by a book, and
each chromosome is represented by a chapter, then each gene would
represent a single letter.'
From species to species the number of chromosomes varies. In humans
there are normally 46 chromosomes. However on rare occasions there can
be more than this, but it always leads to health problems. An extra
DNA is the genetic material found in cells of all living organisms. Human beings contain approximately one trillion cells (Aronson 9). DNA is a long strand in the shape of a double helix made up of small building blocks (Riley). The repeat segments are cut out of the DNA strand by a restrictive enzyme that acts like scissors and the resulting fragments are sorted out by electrophoresis (Saferstein 391).
DNA (Deoxyribonucleic acid) is a molecule found in in the nucleus of all cells in the body which carries our genetic information. DNA is found in the form of chromosomes, with a total of 23 pairs in the human body1. DNA holds the genetic coding for all our characteristics, i.e. our eye colour, body shape, and how we interact with others on a daily basis.
The study of nucleic acids has now become a fruitful and dynamic scientific enterprise. Nucleic acids are of unique importance in biological systems. Genes are made up of deoxyribonucleic acid or DNA, and each gene is a linear segment, or polymer, of a long DNA molecule. A DNA polymer, or DNA oligonucleotide, contains a linear arrangement of subunits called nucleotides. There are four types of nucleotides. Each nucleotide has three components; a phosphate group, a sugar and a base that contains nitrogen within its structure. The sugar moiety in DNA oligonucleotides is always dexoyribose, and there are four alternative bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The phosphate groups and the deoxyribose sugars form the backbone of each DNA stand. The bases are joined to the deoxyribose sugar and stick out to the side. Both oligomers, DNA and RNA, consist of 5’->3’ phosphodiester-linked nucleotide units that are composed of a 2’-deoxy-D-ribose (DNA) or D-ribose (RNA) in their furanose forms and a heteroaromatic nucleobase (A, T, G, and C; A, U, G, C), and the resulting oligonucleotide chain is composed of a polar, negatively charged sugar-phosphate backbone and an array of hydrophobic nucleobases. The amphiphilic nature of these polymers dictates the assembly and maintenance of secondary and tertiary structures the oligonucleotides can form. In the DNA duplex structure, genetic information is stored as a linear nucleotide code. This code can be accessed and replicated. RNA, or ribonucleic acid, is another structurally related essential biopolymer. RNA differs from DNA in having the sugar ribose in place of the deoxyribos...
Trisomy 13 or Patau Syndrome” Trisomy 13 is a genetic disorder found in babies. It is also called Patau syndrome in honor of the physician who first described it, Krause Palau. Trisomy 13 is a genetic disorder in which there is three copies of chromosomes on Chromosome 13. Patau first described the syndrome and its involvement with trisomy in 1960. It is sometimes called Bartholin-Patau syndrome, named in part for Thomas Bartholin, a French physician who described an infant with the syndrome in 1656.
Compare and Contrast Mitosis and Meiosis. Meiosis and mitosis describes the process by which cells divide. either by asexual or sexual reproduction to produce a new organism. Meiosis is a form of cell division that produces gametes in humans.
As part of the cell cycle, mitosis is the nuclear division of replicated chromosomes by the disconnection of the replicated chromosomes to form two genetically identical daughter nuclei. Escorted by mitosis is commonly the process of cytokinesis. The cytokinesis process entails a dividing cell splitting into two, resulting in the subdivision of the cytoplasm into two cellular suites.
Deoxyribo Nucleic Acid (DNA) is a chromosome found in the nucleus of a cell, which is a double-stranded helix (similar to a twisted ladder). DNA is made up of four bases called adenine (A), thymine (T), guanine (G), and cytosine (C), that is always based in pairs of A with T and G with C. The four bases of A, C, G, and T were discovered by Phoebus Levene in 1929, which linked it to the string of nucleotide units through phosphate-sugar-base (groups). As mention in Ananya Mandal research paper, Levene thought the chain connection with the bases is repeated in a fix order that make up the DNA molecu...
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.
Cell division is extremely important; cells must divide in order to maintain an efficient volume to surface area ratio, allow organisms to grow and develop, and repair any damaged tissue. Cells are able to do all this through two processes: meiosis and mitosis. Without these processes, humans would not be able to do many of the basic functions we are so accustomed to, including growing, healing even the smallest cuts, and even reproducing! However, meiosis and mitosis, although both procedures for cell division, are very different.
Precise chromosomal DNA replication during S phase of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current “once-per-cell-cycle” model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters are sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within each replicon is initiated at periodic AT-rich origins along each chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix may be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by “lic...
“The effect of protein synthesis inhibition on the entry of messenger RNA into the cytoplasm of sea urchin embryos”, Hogan and Gross. J. Cell Biol. 49(3):692-701.
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
Meiosis is a specialized form of nuclear division in which there two successive nuclear divisions (meiosis I and II) without any chromosome replication between them. Each division can be divided into 4 phases similar to those of mitosis (pro-, meta-, ana- and telophase). Meiosis occurs during the formation of gametes in animals.
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. Simply put, DNA contains the instructions needed for an organism to develop, survive and reproduce. The discovery and use of DNA has seen many changes and made great progress over many years. James Watson was a pioneer molecular biologist who is credited, along with Francis Crick and Maurice Wilkins, with discovering the double helix structure of the DNA molecule. The three won the Nobel Prize in Medicine in 1962 for their work (Bagley, 2013). Scientist use the term “double helix” to describe DNA’s winding, two-stranded chemical structure. This shape looks much like a twisted ladder and gives the DNA the power to pass along biological instructions with great precision.
What is the cell cycle? It’s the way we reproduce. A series of events lead up from the beginning that which gives them life to the splitting of cells, The separate steps make up this very important process. Without the division of cells, we simply would not be here today.