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Universidad Autónoma de Nuevo León Preparatoria no. 9

Mendelian Genetics Fundaments of genetic & biotechnology STAGE 2 – INTEGRATIVE ACTIVITY

Natalia Daenna González Viera Karina Lizeth Limas Macías Miranda Inaara Flores Abrego Jorge Alberto Cantú Reyes

Modern genetics began with the work of the Augustinian friar Gregor Johann Mendel. His work on pea plants, published in 1866, described what came to be known as Mendelian inheritance. Many theories of heredity proliferated in the centuries before and for several decades after Mendel's work.

Historical context of genetics

johann Gregor Mendel (1822-1884) Father of Genetics

Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.

He recognized the mathematical patterns of inheritance from one generation to the next. Mendel's Laws of Heredity are usually stated as:

2) The Law of Independent Assortment: Genes

1) The Law of Segregation: Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.

for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another.

3) The Law of Dominance: An organism with alternate forms of a gene will express the form that is dominant.

Genetics Timeline 5000 BC – 2003 AC

Demonstrating some understanding of inheritance, humans worldwide begin to selectively breed more useful varieties of livestock and crops, including wheat, maize, rice and dates

5000 BC

400 BC Greek philosophers contemplate the mechanisms of human inheritance. Aristotle believes that traits acquired during life, such as injuries, can be passed to offspring. He also develops the theory of “pangenesis”, which attempts to explain how these traits are transmitted via particles called “gemules” to the reproductive cells

Discovery: Natural Selection Charles Darwin wrote “On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life.”


1865 Discovery: Heredity Transmitted in Units Gregor Mendel’s experiments on peas demonstrate that heredity is transmitted in discrete units. The understanding that genes remain distinct entities even if the characteristics of parents appear to blend in their children explains how natural selection could work and provides support for Darwin’s proposal.

Discovery: Rediscovery of Mendel’s work 1902 Botanists DeVries, Correns, and von Tschermak independently rediscover Mendel’s work while doing their own work on the laws of inheritance. The increased understanding of cells and chromosomes at this time allowed the placement of Mendel’s abstract ideas into a physical context.


1902 Discovery: Orderly Inheritance of Disease A British physician, Archibald Garrod, observes that the disease alkaptonuria is inherited according to Mendelian rules. This disease involves a recessive mutation, and was among the first conditions ascribed to a genetic cause.

Discovery: The Word Gene is Coined Wilhelm Johannsen coins the word “gene” to describe the Mendelian unit of heredity. He also uses the terms genotype and phenotype to differentiate between the genetic traits of an individual and its outward appearance.


1941 Discovery: One Gene, One Enzyme Hypothesis George Beadle and Edward Tatum’s experiments on the red bread mold, Neurospora crassa, show that genes act by regulating distinct chemical events. They propose that each gene directs the formation of one enzyme

Discovery: Jumping Genes Barbara McClintock, using corn as the model organism, discovers that genes can move around on chromosomes. This shows that the genome is more dynamic than previously thought. These mobile gene units are called transposons and are found in many species.


1959 Discovery: Chromosome Abnormalities Identified Jerome Lejeune and his colleagues discover that Down Syndrome is caused by trisomy 21. There are three copies, rather than two, of chromosome 21, and this extra chromosomal material interferes with normal development.

Discovery: First Restriction Enzyme Described 1972 Discovery: First recombinant DNA Scientists describe restriction nucleases, enzymes that recognize and cut specific short sequences of DNA. The resulting fragments can be used to analyze DNA, and these enzymes later became an important tool for mapping genomes.


1973 Discovery: First animal gene cloned Researchers fuse a segment of DNA containing a gene from the African clawed frog Xenopus with DNA from the bacterium E. coli and placed the resulting DNA back into an E. coli cell. There, the frog DNA was copied and the gene it contained directed the production of a specific frog protein.

Discovery: First Time a Disease Gene is Positionally Cloned A method for finding a gene without the knowledge of the protein it encodes is developed. So called, positional cloning can help in understanding inherited disease, such as muscular dystrophy.


1987 Discovery: Yeast Artificial Chromosomes Scientists discover that artificial chromosomes made from yeast can reliably carry large fragments of human DNA containing millions of base-pair pieces. Earlier methods used plasmids and viruses, which can carry only a few thousand base-pair pieces. The ability to deal with much larger pieces of DNA makes mapping the human genome easier.

Discovery: Microsatellites Are New Genetic Markers Repetitive DNA sequences called microsatellites are used as genetic landmarks to distinguish between people. Another type of marker, sequence–tagged sites, are unique stretches of DNA that can be used to make physical maps of human chromosomes.


1992 Discovery: SecondGeneration Genetic Map of Human Genome A French team builds a low-resolution, microsatellite genetic map of the entire human genome. Each generation of the map helps geneticists more quickly locate disease genes on chromosomes.

Discovery: Mouse Genetic Map Completed 1997 The lab mouse is valuable for genetics research because humans and mice share almost all of their genes, and the genes on average are 85% identical. The mouse genetic increases the utility of mice as animal models for genetic disease in humans.


1999 Discovery: Chromosome 22 Sequenced The first finished, full-length sequence of a human chromosome is produced. Chromosome 22 was chosen to be first because it is relatively small and had a highly detailed map already available. Such a map is necessary for the clone by clone sequencing approach.

Discovery: Human Genome Working Draft Completed By the end of Spring 2000, HGP researchers sequence 90 percent of the human genome with 4-fold redundancy. This working draft sequence is estimated to be 99.9% accurate.


2002 Discovery: Mouse Genome Working Draft Assembled and Analyzed The Mouse Genome Sequencing Consortium publishes an assembled draft and comparative analysis of the mouse genome. This milestone was originally planned for 2003.

Discovery: Completion of the Human Genome Sequencing The finished human genome sequence will be at least 99.99% accurate.


FUTURE It will take decades of research for scientists to understand all of the information that is contained within the human genome. In time, more human diseases will be understood at the level of the molecules that are involved, which could dramatically change the practice of medicine by leading to the development of new drugs, as well as to genetic testing to improve and individualize treatments.

ยง Albinism ยง Hemophilia ยง Cystic Fibrosis ยง Tay-Sachs ยง Huntington

Genetic disorders

GENOTYPE § Ocular albinism type 1 results from mutations in the GPR143 gene. § Most mutations in the GPR143 gene alter the size or shape of the GPR143 protein.

§ OCA gene mutation usually has an autosomal recessive inheritance pattern.


§ OA gene mutation has an x-linked recessive inheritance pattern. It affects only boys.

PHENOTYPE § There are two types of albinism: § When the skin, hair, and eyes are involved, it is called oculocutaneous,

It is a group of inherited disorders that results in albinism (OCA). little or no production of the pigment melanin, which determines the color of the skin, hair and § When the eyes are involved, but skin and hair colouring are normal, it is eyes. called ocular albinism (OA).

GENOTYPE ยง They are caused by mutations in different genes. Changes in the F8 gene are responsible for hemophilia A, while mutations in the F9 gene cause hemophilia B.


Hemophilia It is a bleeding disorder that slows the blood clotting process.

ยง Mutations in the F8 or F9 gene lead to the production of an abnormal version of coagulation factor VIII or coagulation factor IX, or reduce the amount of one of these proteins. The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury. These problems with blood clotting lead to continuous bleeding that can be difficult to control.

ยง The mutations that cause severe hemophilia almost completely eliminate the activity of coagulation factor VIII or coagulation factor IX. The mutations responsible for mild and moderate hemophilia reduce but do not eliminate the activity of one of these proteins.

GENOTYPE ยง Mutations in the CFTR gene cause cystic fibrosis. The CFTR gene provides instructions for making a channel that transports negatively charged particles called chloride ions into and out of cells.


Cystic Fibrosis

ยง The disorder's most common signs and symptoms include progressive damage to the respiratory system and chronic digestive system problems. The features of the disorder and their severity varies among affected individuals.

ยง Mutations in the CFTR gene disrupt the function of the chloride channels, It is an inherited disease characterized by the buildup of thick, sticky mucus that can damage many of the body's organs.

preventing them from regulating the flow of chloride ions and water across cell membranes. As a result, cells that line the passageways of the lungs, pancreas, and other organs produce mucus that is unusually thick and sticky. This mucus clogs the airways and various ducts, causing the characteristic signs and symptoms of cystic fibrosis.

GENOTYPE ยง Mutations in the HEXA gene cause Tay-Sachs disease. The HEXA gene provides instructions for making part of an enzyme called betahexosaminidase A, which plays a critical role in the brain and spinal cord.


PHENOTYPE ยง Affected infants lose motor skills such as turning over, sitting, and

It is a rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord.

crawling. They also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with Tay-Sachs disease experience seizures, vision and hearing loss, intellectual disability, and paralysis. An eye abnormality called a cherry-red spot, which can be identified with an eye examination, is characteristic of this disorder. Children with this severe infantile form of Tay-Sachs disease usually live only into early childhood.

GENOTYPE ยง Mutations in the HTT gene cause Huntington disease. The HTT gene


provides instructions for making a protein called huntingtin. Although the function of this protein is unknown, it appears to play an important role in nerve cells (neurons) in the brain.The HTT mutation that causes Huntington disease involves a DNA segment known as a CAG trinucleotide repeat.

PHENOTYPE ยง Early signs and symptoms can include irritability, depression, small

It is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability (cognition).

involuntary movements, poor coordination, and trouble learning new information or making decisions. Many people with Huntington disease develop involuntary jerking or twitching movements known as chorea. As the disease progresses, these movements become more pronounced. Affected individuals may have trouble walking, speaking, and swallowing.

CONCLUSION As a conclusión, we think that genetics are very inportant in us. We are conformed of it, and if we check ourselves, we can think that all it´s n ormal, and it is, but we must understand that our genetics are in pefect state. Because, as we have seen in class and by this investigation, we now that there are so many deffects in genetics in people, as consecuence, people can have serious diseases and problems with their body, as we have seen with the albinism or the Tay- Sachs, that is about how the genes were organized. Tis can be considered the risks, of genetics, when they didn´t have a good organization, the people can have diseases. And tje benefits, is that we discovered by this investigation about the inheritance of genes, about how the gene of the passed generation can come to our generation. And we now that all the information is in us about our passed generation.

REFERENCES Albinism. Mayo Clinic. March 20, 2018; Haldeman-Englert C, Zieve D. Albinism. MedlinePlus. March 20, 2018; /article/001479.htm.

430 genetics int2 gonzálezviera  

Mendelian Genetics

430 genetics int2 gonzálezviera  

Mendelian Genetics