Genetics in Medicine - Part 4
Reading Frame
Almost all organisms translate their genes into protein structures using an identical, universal codon dictionary in which each amino acid in the protein is represented by a combination of only three nucleotides. For example, the sequence AAA in a gene is transcribed into the sequence UUU in messenger RNA (mRNA) and is then translated as the amino acid phenylalanine. A group of several codons that…
Recombinant DNA - Overview Of Recombination Techniques, Applications
Recombinant DNA refers to a collection of techniques for creating (and analyzing) DNA molecules that contain DNA from two unrelated organisms. One of the DNA molecules is typically a bacterial or viral DNA that is capable of accepting another DNA molecule; this is called a vector DNA. The other DNA molecule is from an organism of interest, which could be anything from a bacterium to a whale, or a …
Reproductive Technology - Pregnancy And Infertility, In Vitro Fertilization, The Risks Of Ivf, Embryo Transfer Techniques, Gamete Intrafallopian Transfer
Successful pregnancy requires ovulation (when an ovary releases an egg into a fallopian tube), transport of the egg partway down the fallopian tube, movement of sperm from the vagina to the fallopian tube, penetration by the sperm of the egg's protective layer, and implantation of the fertilized egg in the uterus. In the United States, infertility is an issue of great concern to many couple…
Rodent Models
Rodents play an important role in biology and medicine. Since the mouse and rat share many biological characteristics with humans, they are commonly used as model organisms for understanding disease processes and testing treatments. Moreover, it is relatively easy to experimentally manipulate the genetic composition of mice and rats and, thereby, to model human genetic disorders in these animals. …
Fred Sanger
Molecular Biologist 1918- Born August 13, 1918, in Rendcombe, Gloucestershire, United Kingdom, Fred Sanger has been breaking new ground in chemistry for decades. In fact, he is the only person to have won a Nobel Prize in chemistry twice, and is only one of four people ever to have won a Nobel Prize more than once. While at Cambridge University in England he developed a new method for sequencing a…
Science Writer - The Growth Of Specialization, Breaking Into The Field, Opportunities In Science Journalism - Compensation
All good journalists are storytellers, and science writers are simply journalists who like to tell stories about science. Still, it has only been in the last few decades that science writing has become a profession in its own right, with journalists specifically trained to cover research ranging from genetics to particle physics. Beginning science writers may earn a starting salary of around $20,0…
Severe Combined Immune Deficiency - Types And Severity Of Immunodeficiency Diseases, Scid, Gene Therapy
The development of the immune system is a very complicated process. Stem cells in the bone marrow continually give rise to the white blood cells responsible for producing antibodies (B-lymphocytes), recognizing and destroying foreign cells (T-lymphocytes) and performing immune surveillance for cancer and foreign cells. Immunodeficiency results when the normal complex interactions of the immune sys…
Sex Determination - Mammalian Mechanisms, Nonmammalian Mechanisms
Sex determination refers to the mechanisms employed by organisms to produce offspring that are of two different sexes. First we present an overview of the sex determination mechanisms used by mammals. Then we discuss the great variety of mechanisms used by animals other than mammals. A developing mammalian embryo's gender is determined by two sequential processes known as primary and second…
Signal Transduction - Signals, Receptors, And Cascades, The Importance Of Phosphorylation And Dephosphorylation, Signal Transduction: The Rtk Pathway
To survive, an organism must constantly adjust its internal state to changes in the environment. To track environmental changes, the organism must receive signals. These may be in the form of chemicals, such as hormones or nutrients, or may take another form, such as light, heat, or sound. A signal itself rarely causes a simple, direct chemical change inside the cell. Instead, the signal sets off …
Statistical Geneticist
Statistical geneticists are highly trained scientific investigators who are specialists in both statistics and genetics. Training in both statistics and genetics is necessary, as the nature of the work is highly interdisciplinary. Statistical geneticists must be able to understand molecular and clinical genetics, as well as mathematics and statistics, to effectively communicate with scientists fro…
Statistics
Statistics is the set of mathematical tools and techniques that are used to analyze data. In genetics, statistical tests are crucial for determining if a particular chromosomal region is likely to contain a disease gene, for instance, or for expressing the certainty with which a treatment can be said to be effective. Statistics is a relatively new science, with most of the important developments o…
Transcription - Functions Of Rna Transcripts, Promoters, Rna Synthesis, Regulation Of Transcription
Transcription is the process in which genetic information stored in a strand of DNA is copied into a strand of RNA. The sequence of the four bases in DNA, which are adenine (A), cytosine (C), guanine (G), and thymine (T), is preserved in the sequence of the four bases in RNA, which are A, C, G, and uracil (U). The first phase of RNA synthesis is initiation (Figure 1B). Initiation starts when the f…
Transduction - Generalized Transduction, Specialized Transduction, Uses In Research
Transduction is one of three basic mechanisms for genetic exchange in bacteria. Like transformation and conjugation, transduction allows the movement of genetic information from a donor cell to a recipient. Unlike the other mechanisms, however, transduction requires the participation of a type of virus called a bacteriophage in order to accomplish this movement. While transduction has been studied…
Transgenic Animals - Targeted Gene Replacement And "knockouts", Selection Of Gene Targeted Cells, From Transgene To Transgenic Organism
The term "transgenics" refers to the science of inserting a foreign gene into an organism's genome. Scientists do this, creating a "transgenic" organism, to study the function of the introduced gene and to identify genetic elements that determine which tissue and at what stage of an organism's development a gene is normally turned on. Transgenic animals ha…
Transgenic Organisms: Ethical Issues
A transgenic organism is a type of genetically modified organism (GMO) that has genetic material from another species that provides a useful trait. For instance, a plant may be given genetic material that increases its resistance to frost. Another example would be an animal that has been modified with genes that give it the ability to secrete a human protein. Bioethics addresses the impact of tec…
Transgenic Plants - Genetic Engineering Techniques, Agricultural Applications
Transgenic plants are plants that have been genetically modified by inserting genes directly into a single plant cell. Transgenic crop plants modified for improved flavor, pest resistance, or some other useful property are being used increasingly. Transgenic plants are unique in that they develop from only one plant cell. In normal sexual reproduction, plant offspring are created when a pollen cel…
Triplet Repeat Disease - Implicated In Diseases, Classification Of Triplet Repeat Disorders, Noncoding Triplet Repeat Disorders, Polyglutamine Diseases
Trinucleotide, or triplet repeats, consist of three consecutive nucleotides that are repeated within a region of DNA (for example, CCG CCG CCG CCG CCG). Expansion of a triplet repeat gene segment leads to increased disease severity and decreased age of onset in proportion to the degree of expansion. Repeats that are translated into protein alter the structure of the protein, conferring new fu…
Twins - Developmental Mechanisms, Monozygotic Versus Dizygotic Twins, Similarities And Differences Between Monozygotic Twins, Amazing Twin Similarities - Conclusion
Twins are siblings carried together in the womb and born at the same time. Similarities and differences between twins can be used to answer questions about the role genes and the environment play in the development of traits such as personality, intelligence, and susceptibility to disease. While results from any single pair of twins cannot provide conclusive answers to such questions, the study of…
Virus - Physical Description And Classification, Infection Outcomes, Viral Cancers, Vaccines - Virus Replication Cycle
A virus is a parasite that must infect a living cell to reproduce. Although viruses share several features with living organisms, such as the presence of genetic material (DNA or RNA), they are not considered to be alive. Unlike cells, which contain all the structures needed for growth and reproduction, viruses are composed of only an outer coat (capsid), the genome, and, in some cases, a few enzy…