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Cell division and reproductiona are gundamental biological processes to life, used by all living beings to grow in number. Multicellualar organisms use cell divions growth and repair, whereas unicellular organism use it as a means of reproruction. A key feature of cell division and reproduction is the passing of chromosomes from parents to the daughter cells. Chromosomes carry data for traits, which are passed to offsprings by parents in a process called heredity.
Genetic is the scientific study of heredity and variation. Living things inherit traits from their parents but what causes traits to be passed on from parent to offspring?:
Genetic material refers to all material of an being storing genetic data. In a chromosome, genetic data is contained in a molecule of deoxyribonucleic acid/DNA. All this knowledge has stemmed from the basic understanding of the organization of genetic material within cells and the mechanism of heredity from one generation to the next. Each DNA molecule is made of countless of chemical subunits acting as a cell's set of chemical instructions.
Each distinct sequence of genetic info is called a gene, which is a portion of a DNA molecule carrying info helping to create an organism's specific trait, each occupying a location or locus (loci), of a chromosome (Figure 2.)
Usual chromosomes have information for countless of different genes. By inheriting traits from parents, whats inherited is genetic data, which is present in segments of DNA called genes, located at specific parts with chromosomes, which with all the genetic data they have, areduplicated during cell division.
Chromosomes are present in all eukaryotic cells' chromosomes and vary widely between organisms of various species in numbers and appearances.
Some organisms have few chromosomes in their body cells while others have many in each body cell. Most multicellular organisms have less than 100 chromosomes in the nucleus of each body cell (right table). I most multicellular organisms, chromosomes ccurs in sets. Diploid cells have 2 chromosome sets. Haploid sets have half the normal number of chromosomes. Some cells have 3+ of chromosome, called. polyploid.
Though much of a cell's genetic material is made of DNA molecules in its nucleus both mitochondria and chloroplasts have small amounts of genetic material.
Figure 3 Called the "mother of thousands" plant,Kalanchoe daigramontiana create asexual "baby" plants with its leaves' edges.
Copy or Combine?
Copy or Combine?
Organisms inherit genetic data parents. Some have only one (asexual reproduction), others have 2 (sexual reproduction). Here's how these reproduction forms influence heredity, their prom and con.
Asexual reproduction is a form of reproduction in which a new being is produced from 1 parent by cell division (without sex cells). While asexual reproduction vary from species, it almost always involves cell division. Recall that , cell division is a cellular process in which the chromosomes of the parent cells are duplicated and then divided like that each of 2 daughter cells receive a copy of a chromosome. The result is 2 new cells genetically same to the one another and the parent. If 1+ of these develop into a new, independent being, the result is asexual reproduction. The production of genetically identical offspring is a key distinguishing feature of asexual reproduction. There are many biological benefits to asexual reproduction. The parent doesn't have need a mate. Asexual reproduction results in heredity that's direct and invariable. Through generation, offspring remain genetically identical to their parents.
Modes of asexual reproduction
Modes of asexual reproduction
Asexual reproduction are useful. Recall that plants produce asexually by putting roots developing into new plants. That small plant seed, from a strawberry, is blown onto a large patch of bare ground. The seed germinates and starts growing and the plant is ready to reproduce. Instead of blooming, it starts sending out runners. These above-ground stems, produced by cell division, quickly extend and develop into new plants.
Figure 1
They grow and start sending out own runners. In a short time, many new plants spread out and occupy new areas. Budding is a type of asexual reproduction when oe develops from an outgrowth on an organism' body. The hydra is a siple multicellular animal related to jelly fish, can reproduce asexualy by budding (Figure 1). When growing conditions are favourable, hydra grow 1+ extension on their side. When big enough, the buds detach and start living as a same copies.
Not all asexual reproduction has the direct outward growth of new child from the parent's body. A cool examplpe are aphids, with more than 4k species of small bugs. Females give birth tto female childrens (Figure 2). They're can give birth when a few days old. Since all females, their numbers can grow exponentially. One species has produced 41 generations in a year. In the spring, they can produce a population of 1 trillion.
All fungi species are said to do asexual reproduction, which often results from fragmentation, a process when parts of the growing mass of fungi are simply break off and continue to grow alone. While the frequency and patterns of asexual reproduction are highly avariable form species, at cellular level, they share all mitosis process.
Cell division
Cell division
Mitosis is the stage of cell cycle when the nucleus's genetic material of a eukaryotic cell is split equally into 2 new nuclei. The rest divides i cytokinesis. Mitosis is sometime used for both nuclear division and cytokinesis. The 3rd stage of cell cycle. during which cells are between cell division called interphase, which is when the cell grows and carries out its normal functions. The chromosomes in the nucleus the form a mass of threat-like things caled chromatin, made of DNA and protains. In form of chromatin, chromosomes are long, thing strands disperesed throughout the nucleus Chromosomes replication in interphase results in pairs of sister chromatids, each with the same exactly genes as the loci. Each attached by a structure are centromere. While attacked, they're sister chromatids.
Figure 3. A double chromsome is made of 2 identical sister chromatids together at the centromere. Each have exact copies of same genes.
In the wild, Many reproduce asexually by mitotic cell division. Cloning is the process of forming same offsprings from one single cell or tissue. Those create by mitotic cell divsion are natural clones. But cloning isn't limited to natural processes. Biotechnology is a fied of biology for the use of livings in engineering, industry, and medicine, such as cloning plants in agriculture (e.g. plants with predictable traits can be cloned to produce bigger crop yields). It has many benefit for society.
Figure 5. Plant cloning from a cell allows growers to produce big amout of new plants from just one.
Plant cloning
Plant cloning
Plant biologist in 1958 Fredreick Steward announced his sucess to clone a plant from a carrot cell (Figure 5). It was remarkable as he could clone plant from mature, specialized cells fom another carrot. By growing individual root cells in a nutrient-rich medium with some plants hormones, he could get the cells to return to an undifferentiated state (lacking ressemblances to carrot tissues). The cels then restarted the growth process, and develop into new plants.
This technique is used today to produce strains of plants with same traits. Plant tissues cloning methods are widely used commerically. Valuable ornament plants like orchids and petunias can be cloned. as well as soe valuable agricultural plants, like bananas and graps. Other plant families, like important grasses and legumes, don't respond well to the same effort, hard to clone.
Animal cloning
Animal cloning
Dolly the sheep, born in 1996, is the first mammal cloned an adult body cell. The challenge to overcome was that animal body cells couldn't be stimulated into restarting the process of growth and differatiation starting with fertilized egg cell.
I was at Dr. Ian Wilmut of the Roslin Institute
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