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https://notebooklm.google.com/notebook/dae913a8-c6b8-4dc6-b183-3946459a6658/audio
I've taken the liberty of making flashcards from this summary.
Here you can find the detailed flashcard deck with most of what you may need to know (73 card deck):
Here you can find the condensed flashcard deck focusing only on information that I don't feel is intuitive and needs more memorization. I also have a strong genetic background so I removed more basic terms that are entry level (ex: gene, allele, locus) condensing the above deck to 39 cards:
Key Definitions:
Locus: Position on a chromosome where a gene or genetic marker is located.
Gene: A segment of DNA that encodes a functional molecule (e.g., a protein).
Allele: A variant form of a gene at a particular locus.
Homozygous/Heterozygous: Describes individuals with two identical or different alleles at a locus, respectively.
Hemizygous: only one copy of a gene is present in a diploid organism, rather than the typical two copies. Ex: sex chromosomes
Genotype vs. Phenotype: Genotype refers to the genetic makeup, while phenotype is the observable characteristics.
Types of DNA Mutations:
Substitution (SNPs): A nucleotide is replaced by another, which can be:
Missense mutation: Changes the amino acid in the sequence.
Nonsense mutation: Converts an amino acid into a stop codon, terminating protein synthesis.
Synonymous (silent) mutation: A change that does not affect the amino acid sequence.
Insertion/Deletion (Indels): Addition or removal of nucleotides, potentially causing frameshift mutations.
Frameshift Mutation: Alters the gene's reading frame, significantly impacting protein function.
Mutations can arrise through wobble (due to the flexibility in the DNA molecule) or Slippage (looping out of a newly synthesized strand)
Examples of Mendelian Disorders:
Citrullinaemia in Cattle:
Description: Caused by a single base substitution in the urea cycle. Calves appear normal at birth but quickly deteriorate due to ammonia poisoning, leading to death within days.
Cause: Single base substitution leading to a stop codon.
Inheritance: A recessive disorder (dd = diseased; DD or Dd = healthy).
Clinical Signs: Depression, aimless wandering, unsteady gait, and eventual death.
Myostatin Deficiency ("Double Muscling"):
Caused by: Mutations in the myostatin (GDF8) gene, leading to the suppression of myostatin, which normally inhibits muscle growth.
Examples:
Belgian Blue: 11bp deletion causes frameshift
Piedmontese: Missense mutation makes protein non functional
Both exhibit a 40% increase in muscle mass. Homozygous animals (mm) are affected.
Challenges: Increased muscle mass comes with health issues like dystocia, reduced feed intake, and susceptibility to diseases.
Ehlers-Danlos Syndrome (EDS):
Description: A connective tissue disorder leading to fragile skin due to defective collagen.
Cause: Mutations affecting collagen production, either recessive or dominant depending on the species.
Impact: Similar clinical signs in different species, resulting from various genetic mutations (genetic heterogeneity).
Types of Gene Action:
Dominant Allele: Phenotype is expressed in both homozygous and heterozygous individuals (e.g., Black coat color in horses due to MC1R gene).
Recessive Allele: Phenotype is only expressed in homozygous individuals (e.g., Citrullinaemia).
Incomplete Dominance: Heterozygotes exhibit an intermediate phenotype between the two homozygotes (e.g., cream dilution gene in horses).
Co-Dominance: Both alleles in a heterozygote express their phenotypes (e.g., certain fur color patterns).
Genetic Testing and Disease Diagnosis:
Challenges: Diseases can be caused by different mutations, making diagnosis more complex. While some disorders are linked to specific mutations, others may involve multiple genes (polygenic traits).
Role in Veterinary Medicine: Genetic markers and tests help identify carriers of recessive disorders or diagnose single-gene mutations, aiding breeders and veterinarians in managing hereditary diseases.
Summary of Lecture 2: Genome Technologies
Genome: The complete set of genetic material in an organism, including coding (genes) and non-coding regions. It contains the information required for the organism's structure, function, and inheritance. The epigenome, which refers to chemical modifications like DNA methylation, also plays a critical role in regulating gene expression without altering the DNA sequence itself.
Sequenced Animal Genomes: Genomes of species important to veterinary science, including chickens, dogs, horses, cows, and pigs, have been sequenced. Genome sequencing is rapidly evolving with projects like the Earth BioGenome Project aiming to sequence over 1.5 million eukaryotic species.
Genome Sequencing Technologies:
First-generation sequencing (Sanger sequencing): dNTP's build a growing strand from fragmented DNA, then chain-terminating ddNTPs selectively stop DNA strand synthesis at specific bases (A, T, C, G). The resulting fragments are separated by size using gel or capillary electrophoresis. The sequence of nucleotides is determined by detecting the labeled ddNTPs.
Known for high accuracy but slow and costly. It reads small DNA fragments and is still used for detecting single nucleotide variations.
Second-generation sequencing (Illumina): Involves fragmenting the DNA, attaching adapters, and amplifying the fragments using a process called bridge amplification on a flow cell. Fluorescently labeled nucleotides are incorporated into the growing DNA strands during sequencing by synthesis, and a camera records the emitted light as each base is added
Also called massively parallel sequencing, it is faster and cheaper than Sanger. It reads short DNA fragments and is widely used today.
Third-generation sequencing (Oxford Nanopore Technology): Individual DNA strands pass through tiny nanopores embedded in a membrane. As the DNA moves through the nanopore, changes in electrical current are measured, which correspond to specific nucleotide sequences.
Can sequence longer DNA fragments in real-time but has higher error rates. Useful for on-site environmental analysis and pathogen monitoring.
Genome Assembly and Annotation:
Genome assembly involves reconstructing the genome from overlapping DNA fragments (contigs). Repetitive DNA segments pose challenges during assembly, often requiring third-generation sequencing to resolve.
Genome annotation identifies genes and functional elements within the genome. Software tools help automate this process.
Applications in Veterinary Medicine: Genomics helps in understanding diseases, developing vaccines, breeding programs, and conservation. Genomic data also assists in identifying pathogens and understanding drug resistance mechanisms.
Summary of Lecture 3: Animal Breeding
Polygenic Inheritance: Traits influenced by multiple genes, where alleles have an additive effect, often referred to as complex or quantitative traits. Examples include human height and livestock disease resistance.
Example: In cattle, traits like milk production and growth rate are polygenic. These traits do not follow simple Mendelian inheritance but are influenced by many genes, each contributing a small effect. For instance, milk yield in dairy cattle is influenced by hundreds of genes, making it a classic polygenic trait.
Quantitative Genetics: This branch of genetics deals with phenotypes that vary continuously (like weight or disease susceptibility). It employs statistical methods to link genotypes to phenotypes, using metrics like heritability (h²), which measures the proportion of phenotypic variation due to genetic differences.
Example: In pig breeding, quantitative genetics is used to understand and improve traits such as feed efficiency and carcass quality. These traits show continuous variation and are measured across populations to determine how much is influenced by genetics versus the environment.
Heritability (h²): Indicates how much of a trait's variation is due to genetics. For example, the heritability of human height is around 0.80, meaning 80% of the variation is genetic. In contrast, resistance to parasites in livestock has a heritability of around 0.40.
Example: In sheep, resistance to gastrointestinal parasites (measured by fecal egg count) has a heritability of around 0.30-0.40. This means 30-40% of the variation in parasite resistance is genetic, making it possible to improve this trait through selective breeding.
The Breeder’s Equation:
R = (h² )(S),
Where R is the response to selection, h² is heritability, and S is the selection differential. This equation predicts how much a trait will change in the next generation based on selective breeding.
Example: If the heritability of milk production in cows is 0.25, and farmers select cows whose milk production is 20% higher than the average (selection differential), the improvement in the next generation would be ( R = 0.25 x 20% = 5%), meaning milk production is expected to increase by 5% in the next generation.
Genome-Wide Association Studies (GWAS): GWAS identifies genetic variants (e.g., SNPs) associated with traits by comparing the genomes of individuals with different phenotypes (e.g., diseased vs. healthy). This method is crucial for identifying genes linked to complex traits like body weight or disease resistance.
Example: In dairy cattle, GWAS has been used to identify SNPs associated with increased milk yield and better udder health. By analyzing genetic differences between high- and low-producing cows, researchers have identified genetic markers that breeders can use to select for improved production traits.
Genomic Prediction: This method uses genome-wide SNP data to predict the estimated breeding values (EBV) of individuals, accelerating genetic improvement in livestock compared to traditional progeny testing.
Example: In beef cattle, genomic prediction can estimate the breeding value of calves shortly after birth by analyzing their DNA. This allows farmers to select the best animals for breeding long before they mature, significantly speeding up genetic improvement for traits like carcass weight or feed efficiency.
Summary of Lecture 4: Animal Breeding II, Companion Animals, Wildlife
Linkage Disequilibrium (LD):
LD refers to the non-random association of alleles at two or more loci on the same DNA strand. This impacts the way traits are inherited together, which is important for understanding patterns of inheritance.
Example: If two genes controlling coat color and size in dogs are in LD, selection for one may unintentionally affect the other.
Pleiotropy:
Occurs when one gene influences two or more seemingly unrelated traits.
Example: The gene responsible for fur pigmentation might also affect a dog's eye color.
Genetic Correlations:
Genetic correlation (rg) measures how the genetic influences on two traits relate, ranging from -1 to 1. A positive correlation suggests that selection for one trait could improve the other, while a negative correlation implies trade-offs.
Example: In cattle, selecting for high milk production might negatively correlate with fertility, meaning cows that produce more milk may have lower fertility rates.
Breeding Values and Multivariate Breeder’s Equation:
Breeding values predict an individual’s genetic contribution to future generations. The multivariate breeder's equation uses heritability and genetic correlations to predict how multiple traits will respond to selection.
Example: Breeding low-methane sheep based on easily measured traits like rumen microbial content could indirectly select for lower methane emissions due to positive genetic correlations.
Dog Breeds and Evolution:
Dogs were the first animals domesticated by humans. Modern breeds descend from a small group of founders, leading to high phenotypic homogeneity and genetic issues due to small population size and inbreeding.
Example:The Xoloitzcuintli is one of the oldest dog breeds, having migrated with humans across the Bering Strait.
Unintended Genetic Consequences of Breeding:
Intense selection for breed standards can lead to health problems due to inbreeding and genetic drift. Many breed-related health issues arise from recessive mutations becoming more common in inbred populations.
Example: Brachycephalic syndrome in bulldogs is linked to their short snouts, a trait emphasized by breed standards but contributing to respiratory problems.
Companion Animal Genomics:
Genomic data can enhance understanding of evolution, animal health, and disease modeling. Genetic testing is used for detecting inherited conditions, helping with selective breeding to minimize health issues.
Example: Single mutation tests can identify carriers of diseases like hip dysplasia or hereditary deafness in dogs.
Conservation Genetics:
Conservation genetics aims to maintain genetic diversity in wildlife populations to avoid inbreeding depression and loss of adaptive potential. Genetic tools also assist in translocation and reintroduction programs.
Example: In marmots at Calgary Zoo, studying genetic factors contributing to dilated cardiomyopathy can guide breeding programs to avoid this lethal condition.
Wildlife Genetics in Veterinary Science:
Genetic testing is also used in wildlife for diagnosing disease, understanding disease etiology, and preventing pathogen spread.
Example: In situ conservation uses genetic analysis to identify populations with low diversity, informing breeding programs to prevent inbreeding depression.
Summary of Lecture 5: Molecular Diagnosis
Molecular diagnostics is a powerful tool in veterinary medicine that allows the analysis of DNA, RNA, and proteins to diagnose diseases, identify genetic risks, and monitor responses to treatment.
Key Points:
In veterinary practice, molecular diagnostics help detect infectious agents, cancer markers, and genetic conditions.
Techniques include PCR, ELISA, and Next-Generation Sequencing (NGS).
Key Techniques:
PCR (Polymerase Chain Reaction): A technique used to amplify specific DNA sequences. PCR can detect the presence of pathogens or genetic mutations by amplifying targeted DNA regions.
PCR in Practice: PCR is widely used in veterinary clinics to detect infectious diseases like Bovine Viral Diarrhea. The veterinarian collects a sample (blood or tissue), and PCR amplifies the virus's DNA, confirming infection.
Commonly used to detect viral infections in animals, such as Canine Parvovirus or Avian Influenza.
Next-Generation Sequencing (NGS): A high-throughput technique that sequences entire genomes or specific regions. It is especially useful for identifying genetic variants associated with diseases.
NGS in Veterinary Genetics: NGS can identify genetic mutations in horses that cause diseases like HYPP (Hyperkalemic Periodic Paralysis), which affects muscle function.
PCR is a fundamental molecular diagnostic tool that revolutionized how diseases are detected by allowing scientists and clinicians to detect specific sequences of DNA or RNA in a sample.
The PCR Process:
Denaturation: The double-stranded DNA is heated to ~94°C to separate it into two single strands.
Annealing: The temperature is lowered to ~50-65°C so primers can bind to their complementary sequences.
Extension: The temperature is raised to ~72°C, allowing Taq polymerase to synthesize new DNA strands by adding nucleotides.
This cycle repeats ~30 times, exponentially increasing the amount of target DNA.
Primers are short DNA sequences that start the DNA replication process during PCR. Proper primer design is crucial for PCR success.
Key Considerations:
Length: Primers should be 18-25 nucleotides long.
Tm (Melting Temperature): Tm of primers should be within 5°C of each other to ensure efficient binding during the annealing step.
Avoid Secondary Structures: Such as hairpins and dimers, which can reduce the efficiency of PCR.
After the PCR reaction, the amplified DNA fragments must be visualized to confirm the success of the amplification.
Gel Electrophoresis:
Process: DNA fragments are loaded into a gel matrix and subjected to an electric current. Smaller fragments move faster, separating based on size.
Staining: DNA is stained with agents like ethidium bromide and visualized under UV light.
Diagnosis of Tick-Borne Diseases: In diagnosing Lyme Disease in dogs, PCR can amplify Borrelia DNA, and gel electrophoresis confirms the presence of the pathogen.
Though PCR is widely used, it has some limitations:
Prior Knowledge Required: You must know the target sequence to design primers.
Contamination Risk: PCR is very sensitive, and contamination can lead to false-positive results.
Errors in Amplification: Taq polymerase lacks proofreading ability, which can introduce errors, especially in longer sequences.
Sample Inhibitors: Some biological samples may contain substances that inhibit PCR.
Several modifications of PCR are widely used, depending on the diagnostic need:
Reverse Transcription PCR (RT-PCR): Converts RNA into DNA for amplification, allowing the detection of RNA viruses (e.g., Feline Leukemia Virus).
Quantitative PCR (qPCR): Measures the amount of DNA or RNA in real-time using fluorescence, providing quantitative data on gene expression or pathogen load.
qPCR in Veterinary Oncology: Measuring the expression levels of cancer-related genes in dogs with Mast Cell Tumors can help predict prognosis and treatment response.
DNA metabarcoding is a technique that allows the identification of multiple species within a single sample using specific marker genes. It is particularly useful in analyzing complex samples such as microbiomes or environmental samples.
Application in Veterinary Parasitology: DNA metabarcoding can identify various parasite species in a single fecal sample from livestock, helping monitor parasite burdens and control measures.
Unlike PCR, isothermal amplification does not require thermal cycling. It amplifies DNA at a constant temperature, making it faster and simpler for point-of-care diagnostics.
Loop-Mediated Isothermal Amplification (LAMP) for Avian Influenza: A field-based test for rapid detection of avian influenza in poultry farms without the need for sophisticated laboratory equipment.
ELISA (Enzyme-Linked Immunosorbent Assay) detects specific proteins or antigens in a sample by using antibodies. It is widely used in veterinary diagnostics to detect infections or measure antibody levels.
ELISA for Heartworm Detection in Dogs: Detects heartworm proteins in the blood, confirming the presence of an infection.