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Mitosis is a type of cell division which produces two new cells genetically identical to its mother cell. In terms of the cell cycle, mitosis is the part of the division process where DNA in the cell’s nucleus is divided into two equal sets of chromosomes. Mitosis is broken down into four phases: prophase (sometimes separated again into early & late prophase), metaphase, anaphase, and telophase.
Mitosis is a process used for most of our bodys cell division requirements. Mitosis generates fresh cells during development and replaces our timeworn cells till death. Mitosis creates daughter cells that are genetically identical to their mothers, with not a single chromosome more or less.
Meiosis
Whilst mitosis is used to generate identical cells for growth and repair, meiosis is used to for only one process. The production of gametes (sex cells, sperm, egg cells). Mitosis creates daughter cells with the exact same number of chromosomes as the mother cell, meiosis creates daughter cells with exactly half the number of chromosomes. Meiosis goes though similar stages to Mitosis and implements similar strategies to complete and organise the separation of chromosomes. However, meiosis has a much more complicated task: separating sister chromatids (two halves of duplicated chromosome) these are homologous chromosomes, the similar but not identical chromosome pairs an organism obtains from its parent cells. Meiosis uses a two-step division process. Homologue pairs divide during the first round of cell division, this is Meiosis 1. Then, Sister chromatids separate during the second round, Meiosis 2. During both rounds of division, the cells go through the same four stages as Mitosis: prophase, metaphase, anaphase, and telophase.
Meiosis is the division process that transforms a diploid cell (with two sets of chromosomes) into haploid cells (a single set of chromosomes). In humans, the haploid cells which are made in meiosis are the sperm and egg cells. The reason the diploid cell is halved is so that when the sperm and an egg combine in fertilization, the two haploid sets of chromosomes can form a complete diploid set (a new genome).
Formation of Gametes
Gametes are the reproductive cells which join during sexual reproduction. These form a new cell called a zygote. Gametes are formed through the cell division process called meiosis. Meiosis forms 4 haploid daughter cells. As mentioned before haploid cells contain one pair of chromosomes, when these haploid cells unite in fertilisation, they form a zygote which is a diploid cell (containing 2 sets of chromosomes)
Variation
Variation by definition is a different or distinct form or version of something. Genetic variation is used to describe the variation in the DNA. Genetic variation is a significant force in evolution, Genetic variation can be caused by mutation (which creates entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reorganises alleles in an organisms offspring). Genetic variation is beneficial to a population, as it allows for individuals to adapt to the changing environment whilst also sustaining the survival of the population.
Mutations/ Errors in crossing over
Chromosome mutations or block mutations occur as a result of errors in crossing over during meiosis. Chromosome mutations affect significant segments of DNA which contain many genes. Mutations can be separated into four different types of: Deletions, Translocations, Duplications, missense, nonsense and Inversion.
Certain mutagens such as radiation or a chemical substance, which induces genetic mutation can also encourage Chromosomal mutations.
DNA Replication
DNA replication is the process by which DNA copies itself during cell division. DNA replication occurs before a cell is duplicated and divided into daughter cells during either mitosis or meiosis, Replication of DNA is necessary to ensure that each new cell receives the correct number of chromosomes. DNA Replication follows several steps that involve various proteins called replication enzymes and RNA. In eukaryotic cells, this process occurs in the S phase of interphase during the cell cycle. This process of DNA replication is a necessity for cell growth, repair, and reproduction in organisms.
Protein synthesis
Protein synthesis is the process in which cells (DNA specifically) make proteins. This occurs in two steps: Translation and Transcription.
Transcription: Transcription is the first step in gene expression. Transcription starts by copying a gene’s DNA sequence in order to create an RNA molecule. Transcription is performed by specific enzymes called RNA polymerases; their job is to join nucleotides to form an RNA strand using the DNA strand as a template. Transcription can be broken into three parts; Initiation, Elongation and Termination.
- Transcription is the first step of transcription. It occurs as the enzyme RNA polymerase attaches to the area of a gene known as the promoter. This then signals the DNA to unravel in order for the enzyme to read the bases on one side of the DNA strands. The enzyme is prepared to make a strand of mRNA (messenger RNA) with a matching sequence of bases.
- Elongation is the process of adding of nucleotides to the mRNA strand.
- Termination is the end of transcription. The mRNA strand is finalised, and it detaches itself from the DNA.
- Translation: Translation is the second part of gene expression. It is the method where ribosomes found in the cytoplasm or ER synthesize proteins after the process of transcription of DNA to RNA in the cell’s nucleus. In simple form translation is the decoding of mRNA in order to develop a polypeptide (a chain of amino acids). The mRNA contains the blueprints for the construction of polypeptides. These instructions come in the form of groups of three nucleotides called codons. In translation, the codons of an mRNA are read by molecules called tRNAs (transfer RNAs). Each tRNA has an anticodon, an anticodon is a set of three nucleotides that binds to a complementary mRNA codon through a process called base pairing. The other end of the tRNA transports the specified amino acid. Much like Transcription, Translation can also be broken into three parts. Initiation, Elongation and Termination.
- Initiation: During this stage, ribosomes get together with the mRNA and the first tRNA so the process can begin.
- Elongation: in this stage, the amino acids are carried to the ribosome by tRNAs and fixed together to create a chain.
- Termination: this is the last stage; the finalised polypeptide is freed to go and complete its various jobs in the cell.
How Population Genetic Patterns Change
Natural Selection
Pioneered by Charles Darwin, Natural selection, along with mutation, migration and genetic drift, is one of the basic mechanisms of evolution and changes population genetics. variation, differential reproduction, and inheritance, natural selection impact evolution. Natural selection by definition is a process by which organisms & species which are best adapted to their environment survive and in turn reproduce with the genotypes that are best suited. Natural selection means that the species organism with best suited adaptations survive to transfer their genes to the next generation.
Asexual Reproduction
Asexual Reproduction is a process of reproduction which only requires one parent. There are four main types of asexual reproduction, these include: Budding, binary fission, fragmentation and Parthenogenesis.
- Binary Fission: Single parent cell doubles its DNA, then splits into two identical cells. commonly occurs in bacteria.
- Budding: A small growth on surface of the parent breaks off, subsequently forming two genetically identical individuals. Occurs in yeast and some animals.
- Fragmentation: Organisms split into multiple fragments which then develop into a new organism. This process Occurs in many plants, as well as some animals (such as coral and starfish).
- Parthenogenesis: An embryo forms from an unfertilized cell. This occurs in invertebrates, as well as some fish, amphibians, and reptiles.
Sexual Reproduction
Sexual reproduction requires two parents, both contribute a gamete, when these combine in fertilisation they result in the creation of a zygote. The Zygote will develop into an embryo.
Techniques in Predicting Change
Examples of different techniques
There are multiple ways to predict change. These various techniques include: Pedigree chart, Polymerase chain reaction (PCR), Gel Electrophoresis and a punnet square. These techniques can all be used to predict Phenotypes transferred to offspring, create a DNA fingerprint, Separation of DNA fragments, genotypes, test for genes associated with a particular disease, evolutionary relationships among organisms, make copies of DNA, DNA cloning, medical diagnostics, and forensic analysis of DNA, heredity patterns and inheritance patterns.
Differences in outcome of Sexual and Asexual reproduction
Asexual reproduction results in genetically identical offspring. Whereas, Sexual reproduction results in unique offspring due to two parents contributing genetic information in the form of gametes which meet in fertilisation.
Influence of the environment
the environment, including the ecosystem the organism is located or develops in, as well as the organism’s internal world, which includes such factors as its hormones and metabolism, can have radical influences on the expression of genes in an organism. A major internal environmental influence that has major effects on gene expression is gender. Specifically, with sex-influenced and sex-limited traits. Drugs, chemicals, temperature, and light are the various external environmental factors that can control which genes are used and unneeded, thereby influencing the way an organism develops and functions.
Conclusion
A summary of findings
The genetics behind population change boil down to two main points; Mitosis and Meiosis. With those two terms in mind, they explain how cells replicate themselves for growth and repair through mitosis. Meiosis the more complicated of the two, which is the division process that transforms a diploid cell (with two sets of chromosomes) into haploid cells (a single set of chromosomes). Meiosis does this because they are tasked with the singular process of producing of gametes (sex cells, sperm, egg cells). When the two gametes meet in fertilisation, the chromosomes cross over which sometimes result in mutations due to errors in crossing over or some mutagens. Variation occurs when the genetic information carried in the two gametes combine. Genetic variation is a significant and beneficial force in evolution, as it allows for individuals to adapt to the changing environment whilst also sustaining the survival of the population.
Natural selection by definition is a process by which organisms & species which are best adapted to their environment survive and in turn reproduce with the genotypes that are best suited. Natural selection, as well as mutation, migration and genetic drift, contribute to evolution and changes population genetics. Asexual reproduction is the process by which a parent reproduces and births genetically identical offspring, the energy and time used in this method is unquestionably superior to sexual reproduction however the offspring produced are far less resistant to environmental Changes in environmental conditions due to the limited genetic variation. Sexual reproduction on the other hand involves the combination of two gametes which combine resulting in a genetically different offspring, with half the genetic input coming from one gamete and the other half from the other one. Sexual reproduction make take longer to fertilise the offspring however the offspring will be more resistant to changes in the environmental conditions.
There are multiple ways to predict and monitor genetic change. These various techniques include: Pedigree chart, Polymerase chain reaction (PCR), Gel Electrophoresis and a punnet square. These techniques can all be used to predict Phenotypes transferred to offspring, create a DNA fingerprint, Separate DNA fragments, identify genotypes, test for genes associated with a particular disease, evolutionary relationships among organisms, make copies of DNA, DNA cloning, medical diagnostics, and forensic analysis of DNA, heredity patterns and inheritance patterns.
Evaluation of answering question
Through the analysis of the genetics behind population change, as well as how population genetics may change and finally a look into some of the techniques which could be employed to predict changes in population genetics, one could gather an understanding of how population genetics change, how they may change and how scientists could possibly predict this change. However, the answer of whether population genetics patterns could be predicted? The answer is no. With radical changes constantly going on inside and outside our bodies including the extreme environmental change which regulate which genes are used and which are not, influencing the way a population develops and functions over time as well natural selection being the driving force for variation and change making it impossible to track the mutations and genetic variation which occurs. Punnet Squares, Pedigree charts, Gel electrophoresis and polymerase chain reaction are effective methods which can measure, monitor and predict genetic changes in short term and on a smaller scale. However, determining population genetics on a large scale and long term, for the time being at least. Is impossible or at least with some level of accuracy. Possibly as technology advances we will be able to predict these changes with high levels of accuracy.
References
- https://www.nature.com/scitable/topicpage/environmental-influences-on-gene-expression-536/
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