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What is genetics?
- The scientific study of the patterns and process of inheritance.
- Genetics is about understanding ourselves and our origin.
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The history of genetics: Mendel
- Gregor Mendel (1822) Czechoslovakia.
- After returning to the temple from the University of Vienna, he worked in the garden and tested over 28,000 pea plants between 1856 and 1863 (around the same time as Darwin’s “On the Origin of Species.”
- Mendel’s conclusions:
- Each organism has two copies of a gene
- The two genes may or may not be alleles
- Dominant alleles mask recessive alleles.
- Gametes have only one copy of gene
- Law of segregation (alleles separate randomly)
- Law of independent assortment (true for two or more genes)
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The history of genetics: DNA double helix
- X-ray diffraction of wet DNA, 1952 by Rosalind Franklin
- Published in Nature in 1953;
- in 1962 Watson, Crick and Wilkins received the Nobel Prize in physiology and medicine.
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The history of genetics: The Human Genome Project
- Began in 1990.
- 2001, Francis Collins with the NHS, Craig Venter (public effort) started his own company
- They eventually published in the same month
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What is molecular genetics?
The field of biology and genetics that studies the structure and function of genes at a molecular level.
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How is Mitochondrial DNA transmitted?
Mitochondrial DNA is mostly received maternally. However, a recent paper has shown that a low frequency of paternal mitochondrial DNA exists in certain people (mostly with genetic diseases) Mitochondrial DNA from one source is fine, but a mixture of mitochondrial DNA leads to metabolic diseases, and even cancer.
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Explain mitochondrial Eve
- “mitochondrial eve” (mt-mrca) is the name given by researchers to the woman who is defined as the matrilineal most recent common ancestor (mrca) via the mitochondrial DNA pathway for all living humans.
- Every mtDNA in every living person is derived from hers.
- However, she is not the most common ancestor for the nuclear genome.
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Why is it hard to determine the MRCA of the nuclear genome?
As the nuclear genome shuffles every generation, it’s hard to determine the most common ancestor of the nuclear genome.
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Explain Y chromosomal Adam
- Y-chromosomal Adam, the paternal lineage of MRCA.
- Y-chromosomal Adam and mitochondrial eve did not necessarily around the same time.
- The existence of mitochondrial eve and y-chromosomal adam does not imply the existence of a first couple. They each lived within a large human population at a different time.
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Intron:
A segment of a DNA or RNA molecule that does not code for a protein.
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Exon:
A segment of DNA that codes for a specific protein.
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Polygenetic:
A trait whose phenotype is influenced by more than one gene.
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pleiotropy:
When one gene influences two or more seemingly unrelated traits. (important for gene editing)
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Law of segregation
When any individual produces gametes, two alleles of a gene separate, so that each gamete receives only one allele.
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Law of Independent Assortment
- Alleles of different genes assort independently of one another during gamete formation.
- Linkage violates this law of independent assortment. (Genes that are situated very closely to each other physically)
- Linkage is broken by recombination.
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Haplotype
- Combination of alleles as different loci on single chromosome that are transmitted together (linked).
- Recombination breaks a haplotype. A haplotype may be one locus, several loci, or an entire chromosome depending on the number of recombination events that have occurred between a given set of loci.
- Two genes that are closer together are more likely to be linked.
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How many nucleotides do we have in our genome?
3 billion base pairs in our gametes. 6 billion base pairs in total.
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History of the Human Genome Project
- 1977 Sanger publishes first sequencing method
- 1980 Bolstein et al propose RFLP human genetic mapping
- 2001 Draft genome published: Celera (the company owned by Venter) and public
- 2014-2015: The Cancer Genome Atlas (sequencing tumor cells and surrounding cells to study the mutations that lead to cancer)
- 2014-2015: Precision Medicine
- Current: TOPMed collect data from one million or more people to study a range of health issues and diseases)
- HGP generated an economic output of $796 billion, which is impressive, considering that total federal spending amounted to $3.8 billion.
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Goals of the Human Genome Project
- Determine the entire sequence of human DNA
- Identify all genes in human dna
- Store this information in databases
- Improve tools for data analysis
- Transfer related technologies to the private sector
- Address the ethical, legal and social issues that may arise from the project
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