Genetics Primer - Weebly

Genetics Primer - Weebly

Genetics Primer Its All in the Genes! How many times have you heard one of your relatives say something like this to you? You look just like your mom did when she was your age! Youve got your dads curly hair.

Youre so smart, just like my side of the family. People have known for centuries that certain characteristics are passed from parents to their offspring and that selective breeding can bring out desirable traits in plants and domesticated animals. However, it was an Austrian monk named Gregor Mendel who, in 1865,

first studied inheritance patterns in a scientific way using garden pea plants. Mendel described the patterns of inheritance in his plants and observed that traits were inherited as separate units. These units are now known as genesthe basic units of heredity. Mendels Work formed the foundation for later scientific achievements that

heralded the era of modern genetics- the study of the function and behavior of genes. DNA Every living organism, from the smallest bacteria to the largest animal on Earth, carries a set of genes inside its cells. Genes are bits of biochemical information, and the information they carry is transmitted

from generation to generation by coiled molecules called DNA (deoxyribonucleic acid). DNA is one of several types of nucleic acid thats found in cells. DNA DNA usually exist in a double-stranded form that naturally winds together to form a double helix. The genes exist as segments along the

length of a DNA molecule. Chromosomes The DNA that carries genetic information in cells is usually packaged in the form of one or more large molecules (macromolecules) called chromosomes. A chromosome is a very long, continuous piece of DNA, which contains many genes interspersed among so-called junk

segments. Our genes are the blueprints that direct the synthesis of proteins the molecular laborers that carry out all life-supporting activities in the cell. Although all humans share the same set of genes, individuals can inherit different forms of a given gene from their parents, making each person genetically unique (except for identical

twins, whose genes are exactly the same!) This inheritance process is responsible for the great variation in traits that we see in nature, such as the color of a flower, your pets coat pattern and human behavioral traits such as musical talent. Genetic Engineering Geneticists are scientists who study genes and their variations.

Genetic engineering is a technique used by geneticists to manipulate genes. Genetic engineering has produced many advances in medicine and industry, but the potential for abuse with this technique also has raised many ethical and legal controversies. Why is Genetics Important? Genetic Maps are used to chart the position of

known genes and other markers relative to each other. Using genetic engineering techniques, researchers are mapping the genomes (the whole hereditary information of an organism that is encoded in the DNA) of numerous species! The Human Genome detailed maps that identify the chromosomal locations of the estimated 20,000 to 25,000 human genes. The blueprint for humans!

Mendels Rules: A Pattern of Inheritance Mendel found that each trait had two forms: a dominant trait and a recessive trait. Allele any one of a number of viable DNA codings of the same gene occupying a given locus (position) on a chromosome. Genotype the combination of genes that code for a trait. Phenotype the physical manifestation of

that trait. Mendels Rules Dominant and Recessive Genes Mendels Rules Dominant and Recessive Genes Punnett Square a diagrammatic representation of a particular cross used to predict the probability of possible

genotypes of offspring. Mendels Rules Dominant and Recessive Genes Exceptions to Mendels Rules 1. Incomplete Dominance The dominant and recessive alleles blend to produce an intermediate characteristic.

Exceptions to Mendels Rules Some traits are determined by more than just one pair of genes 2. Quantitative inheritance each pair of genes has only a slight effect on the trait, while the cumulative effect of all the genes determines the physical characteristics of the trait. Example: skin color

Exceptions to Mendels Rules 3. Multiple alleles traits controlled by multiple alleles have complex rules of dominance. For example: blood type (three alleles: A, B, and O) 6 possible genotypes, only 3 possible phenotypes.

Exceptions to Mendels Rules 4. Gene linkage Independent assortment occurs when the genes affecting the phenotypes are found on different chromosomes, and may not be inherited together. When genes occur close together on the same chromosome, they are inherited as a single unit

said to be linked. Sometimes chromosomes exchange pieces of their DNA during meiosis, this is called crossing over. Exceptions to Mendels Rules 5. Sex-linked traits

XX = female XY = male Sex-linked traits are traits that are carried on the X allele. Males have a higher chance of being affected by sex-liked traits. The Genetic Code

The biochemical instructions found within most genes, known as the genetic code, specify the chemical structure of a particular protein. Proteins are composed of long chains of amino acids, and the specific sequence of these amino acids dictates the function of each protein. The Genetic Code

DNA molecules form from chains of building blocks called nucleotides, which consist of a sugar molecule (deoxyribose), a phosphate group, and one of four bases: 1. 2. 3. 4. Adenine (A)

Cytosine (C) Guanine (G) Thymine (T) The Genetic Code The order of the bases in a DNA molecule the genetic code determines the amino acid sequence of a protein. Reading the Code

To produce the proteins involved in every activity of a cell, the DNA goes through a process known as transcription to produce an intermediary molecule called ribonucleic aced (RNA). Transcription involves the production of a special kind of RNA known as messenger RNA (mRNA). Reading the Code

Once transcription is complete and the genetic code has been copied onto mRNA, the genetic code must be converted into the language of proteins. This is done by the process of translation. Reading the Code Translation takes place in cellular organelles called ribosomes.

The ribosomes act like a clamp on a workbench, holding the mRNA strand and coordinating the activity of enzymes and other molecules essential to translation. Reading the Code

Reading the Code Ribosome Mutations Genes may undergo mutations mistakes that occur during DNA replication and protein synthesis. While most mutations occur spontaneously, some can be caused by exposure to

physical or chemical agents in the environment, called mutagens. Ultraviolet rays from the sun Medical X-rays Cigarette smoke Mutations Some mutations can have serious effects on the chromosomes, resulting in breakage or merges.

These can cause serious genetic diseases or death of the developing organism. Other mutations are silent, meaning they do not affect the function of the protein, and occasionally, might even be beneficial. Gene Regulation The processes that enable information to be copied from genes and then used to

synthesize proteins must be regulated if an organism is to survive. Gene regulation A variety of mechanisms that regulate gene activity in cells during the transcription and translation processes. The Human Genome

Project The Human Genome Project (HGP) was an international research effort to sequence and map all of the genes (the genome) of humans. This accomplishment has been likened to the Apollo space program in the 1960s and 1970s that sent Americans to the Moon, in terms of the years spent and the labor involved. Was completed in April 2003 provided a complete genetic blueprint for building a human

being. The Human Genome Project It took scientist years to find the many mistakes that cause disorders and diseases. The completed human genome contains far fewer genes than originally predicted 30,000 to 35,000 genes compared to the expected 100,000.

Humans only have about twice the number of genes as a fruit fly! HGP and New Fields In a new science called Proteomics, researchers are identifying the structure and function of all the proteins in the human body. The gene map created by the Human Genome Project also provides important

information to support the promising field of Gene Therapy the insertion of one or more genes into an individual to treat a disease, especially inherited (genetic) diseases. Genes and Society The tools of modern genetics allow us to learn much about individuals and their genes. This information can save lives, assist

couples trying to decide whether to have children, and even help law enforcement officials solve crimes. However, this opportunity has also raised troubling social concerns about privacy and discrimination. Genes and Society If an individuals genetic information becomes widely available

Could health insurers deny coverage to people with certain risk factors? Could employers reject certain high-risk job applicants? Furthermore, many genetically linked problems are more common among certain racial and ethnic groups many minority groups fear the expansion of genetic testing could create whole new avenues of discrimination.

Genes and Society New technologies that allow the manipulation of genes have raised even more disturbing possibilities. Gene therapy advances, which allow scientists to replace defective genes with normal genes, offer people with typically fatal diseases new hope for healthy lives.

Genes and Society However, the application of gene therapy techniques to gametes (the egg and sperm cells involved in reproduction) seems inevitable. Such manipulation might help prevent the transmission of disease from on generation to another, but it could also produce unforeseen problems with long-lasting consequences. Genes and Society

Many people worry that new genetic techniques could be used to alter or encourage traits now viewed as part of normal human variability such as shortness or baldness. At various times in the past century, people have advocated efforts to improve the human condition by promoting the perpetuation of certain genes. This is known as eugenics the study of hereditary improvement of the human race by controlled selective breeding. Eugenics typically involves encouraging people with positive genes to reproduce, and discouraging

those with inferior genes from having offspring. Genes and Society Many people fear new genetic technologies used to manipulate the human genome could give people previously unattainable methods to take extreme forms of eugenics.

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