Preformationism contended that either the egg or the sperm contained a miniature person called a homunculus; development was a matter of growing once outside the womb (DNA Watson). ... Sutton saw that chromosomes were doubled-up, just like Mendel's paired factors, but he also identified a type of cell in which they were not paired (DNA Watson). These unpaired chromosomes came to be known as the sex cells and coincided with Mendel's observation that his pea plant sperm cells carried a single copy of factors (DNA Watson). ... Using the Drosophila melanogaster, or fruit fly, Morgan d...

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With recent advancements in the mapping of the human genome, it will soon be possible to identify particular strings of DNA which may cause diseases like cancer or amyotrophic lateral sclerosis. ... One of these sources is the embryonic stem cell, which is a cell harvested from a non-implanted, frozen, fertilized egg. ... The desires of researchers to utilize embryonic stem cells in their research has opened an ethical debate about whether harvesting stem cells from frozen embryos is tantamount to murder or abortion since the eggs were first fertilized with the intention of implanting them ...

• Word Count: 2597
• Approx Pages: 10
• Has Bibliography
• Grade Level: Undergraduate

These strands could be attached to other strands of DNA. Cohen had found a way to cross species boundaries, using cells of DNA called plasmids, and had also came up with a way of isolating and cloning genes. ... Boyer's enzyme would allow Cohen to introduce specific DNA segments to plasmids. ... The oldest of these techniques is called Recombinant DNA. ... Recombinant DNA techniques rely on biological vectors such as plasmids or viruses to carry foreign genes into cells. ...

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This feature can be a disease causing mutation or a marker DNA sequence used to detect presence of another gene. Obviously these procedures used for testing the status of DNA, RNA or chromosomes are included in genetic tests. ... Meiotic recombinations that always occur take place during gamete generation, may separate a disease-associated gene and a marker DNA sequence which is used to detect mutated genes. ... During prenatal tests, a sample from the embryo's cells should be taken out by a procedure known as amniocentesis. ...

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Important Facts the smallest unit of life is the cell instructions for development are contained in DNA collectively, all of the chemical processes in a cell are called metabolism producers often obtain energy from the sun homeostasis refers to the ability to maintain a constant internal environment cells in domains archaea and eubacteria lack nucleii plants are multicellular producers an educated guess might be called a hypothesis science is based on evidence philosophy is not a step in the scientific method an atom is the smallest unit of substance that retains the properties of the subst...

• Word Count: 10700
• Approx Pages: 43
• Grade Level: High School

Subclass Pelobiontae includes one genus, Pelomyxa, large cells which lack almost every characteristic of eukaryotic cells except the existence of a membrane-bound nucleus; these cells' nuclei divide like bacterial nucleoids. ... Many dinomastigotes have cells below the cell membrane that are capable of discharging a substance that stings prey. ... While the DNA of most other eukaryotes forms fibrils that are 10nm wide, the DNA of dinomastigotes is only 2.5 nm wide. Also, eukaryotic DNA usually only condenses during mitosis, but the DNA of organisms in this phylum is always condensed. ...

• Word Count: 3806
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• Grade Level: Undergraduate

Cellular proliferation occurs as a result of two events, duplication of DNA within the cells and mitosis. ... Division involves proteins; some tell the cell when to divide, known as proto-oncogenes and some are responsible for making sure DNA is copied accurately. During this cell cycle there are checkpoints that ensure all replication is done accurately and any damage to the DNA is repaired before division occurs. ... Damage to the DNA repair genes mean any damage will remain, and defects to the tumour suppressor genes means that any damaged cell will survive and continue to divide. ... This ...

• Word Count: 3220
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• Has Bibliography
• Grade Level: Undergraduate

What the researchers actually did: they took an unfertilized egg cell from a female sheep and removed the entire DNA (genetic information) from the nucleus that is needed to produce an embryo. ... But this was the first time anybody had made adult mammal genes behave like genes in a fertilized egg. ... The technique would involve taking an unfertilized egg from a human female, removing the nucleus that contains the genetic information, and replacing it with the nucleus from a cell " any cell " of the person to be cloned. This egg, with its new nucleus, is then "tricked" into bel...

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The DNA string can be manipulated in such a way as to give plants or animals characteristics not common to that particular species. ... Frogs were successfully cloned as early as 1953(Dixon, P., 2000) and identical twins have been made in the lab by mechanically splitting a fertilized egg, although these eggs were never allowed to grow and develop. ... There is the forced splitting of a fertilized egg as mentioned above, and the more talked about and controversial method of nuclear transfer. ... Stem cell cloning is the growing of specific cells in the lab such as liver or spinal ti...

• Word Count: 3124
• Approx Pages: 12
• Has Bibliography
• Grade Level: High School

Along with witness accounts and such, postmortem (after-death) changes are the most accurate because of the known fact that when we breathe, oxygen comes into lungs and is circulated through our system by passage of blood cells. ... A basic rule of thumb for entomology follows these time allotments: ten minutes - after death (if in open air) flies lay 1000's of eggs in the mouth, eyes, etc. twelve hours - the eggs hatch and maggots begin to eat tissues twenty-four to thirty-six hours - dry skin is consumed by beetles forty-eight hours later spiders and other insects begin to eat the...

• Word Count: 4736
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• Grade Level: High School

Basically the process is rearranging the plants DNA and certain genes through molecular biology taking specific beneficial traits from different species of the plant in the same family, and combining their strengths into one modified seed. ... The American Academy of Environmental Medicine conducted studies finding that "several animals indicate serious health risks associated with GMO food consumption including infertility, immune system regulation, insulin regulation, cell signaling, and harmful changes in the liver, kidney, spleen, and gastro intestinal system" (Rodale 34). ...

• Word Count: 3733
• Approx Pages: 15
• Has Bibliography
• Grade Level: Undergraduate

Extreme weather is defined as severe, usually unexpected hazards that are out of the ordinary. Floods, droughts heat waves and bush fires are examples of extreme weather. Too much or too little precipitation, change in temperature, or high pressure systems create hazards which affect people all over...

• Word Count: 4336
• Approx Pages: 17
• Has Bibliography