Historical development of genetics final

Historical Development in Genetics

Ariane Ruby B. Sogo-anMST Biology

Recall:

What is Genetics?- One of the discipline of Biology, is the science of

genes, heredity, and provides scientific explanation on the concept of variation in living organisms.

- Genetics concerns the process of inheritance from parents to offspring, including the molecular structure and function of genes, gene behavior in the context of a cell or organism (e.g. dominance), gene distribution, variation and change in populations.

Note:

• Given that genes are universal to living organisms, genetics can be applied to the study of all living systems; including bacteria, plants, animals, and humans.

Terms and Definition

• Genes – Unit of information about specific traits and they

are passed by from parents to offspring.

Gametes- sexual reproductive cell that fuses with another sexual cell in the process of fertilization.

Terms and Definition

Allele – molecular form of a gene. (ex. AA, Aa or aa)- Homozygous – pair of alleles are identical- Heterozygous – having unidentical pair of

alleles

Terms and Definition

• True Breeding lineage- when offspring of the genetic crosses inherit a pair of identical alleles for a trait.

• Hybrid offspring – having unidentical alleles • Genotype – refers to a particular an individual

carries• Phenotype – refers to individual observable

trait.

Old Concept

• Blending of traits from parent to offspring – Father’s blob of information is blended with the

mother’s blob of information.

Charles Darwin – Natural Selection

- through the generations, the variation that improve that chance of surviving and reproducing will occur with greater frequency than those that do not.

Gregor Mendel

• Published “Experiments in Plant Hybridization”

Why Peas? (Pisum sativum)1. It is self Fertilizing2. Easy to breed3. Fast growth and development

1866

• First established the basic laws of inheritance– Theory of Segregation– Theory of Independent Assortment– Incomplete Dominance

Mendel’s Protocol

1. Stamen are cut out from the plant leaving the female reproductive part2. Pollen from a plant is brushed onto another floral bud. (to ensure cross breeding)3. Cross fertilized seeds and each seeds are allowed to grow onto new plant. 4. Observe traits.

Theory of Segregation

• Mendel’s hypothesis: – In every generation, a plant inherits two (2)

“units” of information about a trait, one from each parent.

Monohybrid crosses: - insert picture of monohybrid cross

F1 – All heterozygousF2 – 3:1

Independent Assortment

• Mendel attempted to explain HOW two pairs of genes might be assorted into gametes

Dihybrid Crosses:

Incomplete Dominance

• One allele isnt completely dominant over its partner, a heterozygous phenotype somewhere in between the two homozygous phenotypes emerges.

• Cross-Breeding of White and Red Snapdragon.– All F1 came out as Pink. (still referred as

genotipically heterozygous )

Johann Friedrich Miescher• Extraction of DNA.• - At first, Miescher focused on the various

types of proteins that make up the leucocytes.

• Miescher noticed that a substance precipitated from the solution when acid was added and dissolved again when alkali was added

• He had, for the first time, obtained a crude precipitate of DNA. Miescher stated that

“According to known histochemical facts, I had to ascribe such material to the nuclei and he decided to examine the cells’ nuclei more closely.”

1869

Walther Flemming

• Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread.

• However, he did not see the splitting into identical halves, the daughter chromatids.

• He studied mitosis both in vivo and in stained preparations, using as the source of biological material the fins and gills of salamanders.

1882

Boveri-Sutton

• The Boveri–Sutton chromosome theory

(also known as the chromosome theory of inheritance or the Sutton–Boveri theory) is a fundamental unifying theory of genetics which identifies chromosomes as the carriers of genetic material.

1902

Boveri-Sutton

• It correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. It also states that chromosomes are linear structures with genes located at specific sites called loci along them.

• It states simply that chromosomes, which are seen in all dividing cells and pass from one generation to the next, are the basis for all genetic inheritance.

• The demonstration of the chromosomal basis of inheritance gave rise to the modern science of genetics.

William Bateson

• Described gene linkage• Used Mendel’s work as his

basis for inheritance principle.

• First suggest the term Genetics 1905

1902

• Bateson had close contacts with clinicians interested in inherited disorders, notably Archibald Garrod, to whom he suggested the recessive inheritance of alkaptonuria.

• . Bateson's views on human inheritance were far sighted and cautious. Not only should he be regarded as one of the founders of human genetics, but human genetics itself should be seen as a key element of the foundations of mendelian inheritance, not simply a later development from knowledge gained by study of other species.

Archibald Garrod

• Discovered alkaptonuria, understanding its inheritance.

• Discovery of genetically inherited diseases. He was one of the first scientists to apply Mendelian genetics to the study of human disease.

1908

• Garrod treated a three-month-old boy with alkaptonuria.

• Over the next several years Garrod compiled data on this disease, much of it gathered from interviews with the families of 39 alkaptonuria patients.

• None of the parents of children with the disease were affected; however, every set of parents turned out to be first cousins.

Pedigree

Conclusion: - alkaptonuria was not caused by a bacterial

infection error triggered by the pairing of two rare recessive genes. Individuals with both recessive genes lack the enzyme needed to break

Inborn Errors of MetabolismRevised edition included: albinism and porphyria

Herman Muller

• Best known for his successful induction of mutations of genes in the fruit fly by the use of X rays.

• He is known also for his dire warnings concerning the effects of nuclear radiation on human genes.

1927

• Muller frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing, helping to raise public awareness in this area.

• When he started working with Thomas Hunt Morgan in the early 1900s, they would occasionally find mutant flies (includes white eyed flies).

• They already suspected that phenotypic expression of the flies is caused by mutation.

• He based from a literature that X-Ray destroys Chromosomes (however, it was not yet established by that time that it can also cause mutation).

• To test his theory, he made an experiment to look for mutation induced by X-Rays.

• He used a special strain to female flies carrying lethal recessive gene.

• In the first cross, female fly carrying a recessive lethal gene was crossed with male whose sperm had been bombarded with X-Ray. He found that male flies that inherited the lethal gene died.

• He also found that male in the 2nd cross that inherited mutation induced by X-Ray gene also died. Therefore, X-ray causes mutation.

Erwin Chagaff

• Regularity in proportion of DNA in each Species.

• He began with the belief that if DNA from different species exhibited different biological activities, there should also be chemically demonstrable differences between the DNA.

1950

Recall:

Chemical Structure of the DNA

1. The first was the separation of the DNA mixture into individual components by paper chromatography.

2. The separated compounds were converted into mercury salts.

3. The purines and pyrimidines were identified via their ultraviolet absorption spectra.

Chargaff tested the method on several mixtures of purines and pyrimidines and reported his encouraging results in the Classic.

• Insights of the composition of DNA with the scientific community:

• - Amount of Adenine relative to Guanine differs from one species to the next.

• - The Amount of Adenine in DNA always equals that of Thymine and the amount of guanine always equals to Cytosine.

• Thus, • A = T and G = C

Maurice Wilkins/Rosalind Franklin

• Found that DNA was at least a helix shape

• They took x-ray crystallographic photographs (x-ray diffraction) of protein structures and found that DNA was a helix.

1952

Process: beam of x-rays is directed at a molecule. The molecule scatters the beam in patterns that can be captured of film. The pattern itself consist only in dots and streaks.

Francis CrickJames Watson

• Crick determined that DNA was a double helix made of two polynucleotide strands

• They looked at the photo taken by Rosalind Franklin closer and found that DNA was a double helix and that it was made of two polynucleotide strands.

1953

Chagaff Rule:

Marshall Nirenberg

• The Genetic code was discovered; scientists are now able to predict characteristics by studying DNA. This leads to genetic engineering, genetic counseling.

1961

The Genetic Code

Paul Berg

• Creates first recombinant DNA molecules.

• He was the first to combine deoxyribonucleic acid (DNA) molecules from different organisms, creating a hybrid known as recombinant DNA.

1972

• He selected the genes of simian virus 40 (SV40), a monkey virus known to cause cancer in human cells and in laboratory cultures. First, he combined the DNA molecule of SV40 with the DNA of a bacterial virus called lambda.

• He then planned to insert this hybrid molecule into the bacterium Escherichia coli, where the lambda virus would then attack the bacteria.

• Berg surmised that when the virus entered the baterial cell, it would inject its own DNA—the recombined SV40-lambda molecule. The bacteria would then multiply, causing the alien gene to replicate itself in large quantities.

• His genetic-engineering technique is used to manufacture specific human proteins like interferon, and has created the potential for curing genetic defects.

Human Genome Project

• Human Genome Project (headed by Charles DeLisi), international scientific collaboration that seeks to understand the entire genetic blueprint of a human being.

• James D. Watson 1988-1992 replaced by Francis Collins in April 1993.

• Project completed in 2003

2000

Goal of HGP

• Through a process known as sequencing, the Human Genome Project has identified nearly all of the estimated 20,000 to 25,000 genes (the basic units of heredity) in the nucleus of a human cell. The project has also mapped the location of these genes on the 23 pairs of human chromosomes, the structures containing the genes in the cell’s nucleus.

1. The genome was broken into smaller pieces; approximately 150,000 base pairs in length.

2. These pieces were then ligated into a type of vector known as "bacterial artificial chromosomes", or BACs, which are derived from bacterial chromosomes which have been genetically engineered.

3. The vectors containing the genes can be inserted into bacteria where they are copied by the bacterial DNA replication machinery.

4. Each of these pieces was then sequenced separately as a small "shotgun" project and then assembled. The larger, 150,000 base pairs go together to create chromosomes.

This is known as the "hierarchical shotgun" approach, because the genome is first broken into relatively large chunks, which are then mapped to chromosomes before being selected for sequencing.

Key findings of the draft (2001) and complete (2004) genome sequences include:

• 1. There are approximately 20,500 genes in human beings, the same range as in mice.

• Understanding how these genes express themselves will provide clues to how diseases are caused.

• 2. The human genome has significantly more segmental duplications (nearly identical, repeated sections of DNA) than other mammalian genomes. These sections may underline the creation of new primate-specific genes.

Field ContributionHorticulture, Animal Breeding

Scientists to alter a plant or animal to make it more useful.- GMO Fruits, Vegetables- Livestock breeding - Improve milk production

Economy Address food shortage - Rice

Forensic Science Helped convict criminals via DNA test on semen, torn out skin, blood, hair etc.

Medicine - Genetically alter bacteria so that they mass-produce specific proteins, such as insulin used by people with diabetes mellitus

- Human growth hormone (Chlorella) used by children who suffer from growth disorders.

Contribution Controversies OutcomeThe production of medicines through the use of genetically altered organisms

Critics of recombinant DNA fear that the pathogenic, or disease-producing, organisms used in some recombinant DNA experiments might develop extremely infectious forms that could cause worldwide epidemics.

National Institutes of Health (NIH) in the United States has established regulations restricting the types of recombinant DNA experiments that can be performed using such pathogens.

Production of transgenic animals to improve yield and quality (ex. fish)

Some experts fear that this process may change the characteristics of wild fish in unpredictable and possibly undesirable ways.

Currently under study

Contribution Controversies OutcomeUse of genetically engineered bovine somatotropin (BST) to increase the milk yield of dairy cows

Some critics question the safety of BST for both the cows that are injected with it and the humans who drink the resulting milk.

Canadian Scientist found out that:BST caused mastitis, lameness and infertility to cow but still safe for human consumption.

Transgenic plants to improve crops and yield (soybeans)

Allergens can be transferred from one food crop to another through genetic engineering.

Found out that it causes allergic reaction to humans - Project was

canceled.

References:1. BIOLOGY Concepts and Application 4th Edition Cecie Starr 20092. www. Wikipedia.com3. American Society for Biochemistry and Molecular Biology 2013

(Online ISSN 1083-351X)4. www.lucasbrouwers.nl5. "The Discovery of the Molecular Structure of DNA - The

Double Helix". Nobelprize.org. Nobel Media AB 2013. Web. 30 Jun 2013.

6. 2002 - 2011, DNA Learning Center, Cold Spring Harbor Laboratory

7. Department of Biology, Davidson College, Davidson NC 280358. National Center for Biotechnology Information, U.S. National

Library of Medicine

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