Ferdig Module Personalized Medicine Review

NotebookLM analyzed all the quizzes, concept checks, and discussion questions/slides

What feature best characterizes a genetically simple, Mendelian trait?

One genomic locus has a major effect that produces distinct, discrete phenotypic classes.

Why are protein-coding variants a useful starting point when investigating genetically simple traits?

A change in a protein's coding sequence can directly alter its structure or function, leading to a clear change in phenotype.

Why were Gregor Mendel's pea plant traits especially useful for uncovering the basic rules of inheritance?

They displayed clear, discrete phenotypic categories and unusually simple (monogenic) inheritance patterns.

In a phenotype-first (forward genetics) approach, what is the initial starting point for researchers?

Researchers begin with individuals that show observable differences in phenotype.

Why is forward genetics described as an 'unbiased' genetic approach?

researchers do not need to choose a specific candidate gene in advance.

What are the core sequential steps involved in a forward genetics approach?

1. Identify phenotypic variation.

2. Use inheritance and recombination mapping to locate a genomic region.

3. Narrow the region to pinpoint the causal gene and variant.

Why is malaria considered an excellent model system ('teacher') for genetics concepts?

It directly connects observable phenotypes, genetic inheritance/recombination, chromosomal locus mapping, and alterations in protein function.

Which specific gene variant confers chloroquine resistance in the malaria parasite Plasmodium falciparum?

Variants in the PfCRT (Plasmodium falciparum chloroquine resistance transporter) gene.

What phenotype is caused by mutations in the HBB (beta-globin) gene discussed in class?

Sickle cell disease (and sickle cell trait/malaria resistance).

What enzyme variant causes the wrinkled pea phenotype studied by Gregor Mendel?

A mutation in the starch-branching enzyme gene (SBE1).

What general principle is illustrated by the examples of PfCRT, HBB, and the starch-branching enzyme?

A genetic variant alters protein structure/function, which directly produces a distinct, observable phenotypic change.

Which non-genetic and genetic factors can make inheritance more complex than simple Mendelian inheritance?

Multiple contributing genes, environmental effects, incomplete dominance, multiple alleles in a population, and genetic linkage.

Does the mere presence of chromosomes make genetic inheritance complex?

No. Mendel's classic simple traits are also carried on chromosomes; chromosome presence alone does not imply complex inheritance.

Why did the early 20th-century Biometricians disagree with the Mendelians regarding human traits?

Biometricians observed continuous variation in traits like human height, whereas Mendelians proposed discrete binary inheritance.

How did R.A. Fisher resolve the disagreement between Mendelian inheritance and continuously varying traits?

Fisher demonstrated that many Mendelian loci, each with small additive effects, act together (polygenic inheritance) to produce continuous variation.

What is the key difference between a polygenic trait and a monogenic trait?

A monogenic trait is controlled by a single genomic locus, while a polygenic trait is influenced by multiple genomic loci.

Which statement best defines genetic heritability?

Heritability measures the proportion of total observed phenotypic variation within a population that is attributable to genetic factors.

Why is it incorrect to say that a heritability score of 0.80 means 80% of an individual's trait is caused by genes?

Heritability applies strictly to population-level variance, not to the proportion of a trait within a single individual.

Does a high heritability score imply that environmental factors cannot influence the phenotype?

No. High heritability indicates genetic variance explains population differences in a given environment, but changing the environment can still alter phenotypes.

What critical foundational resource did the Human Genome Project provide to geneticists?

A high-quality reference sequence for the human genome, enabling identification of specific genetic differences among individuals.

Why is having a complete DNA sequence insufficient by itself to predict human disease or phenotype?

Sequence alone does not reveal gene expression patterns or the precise functional consequences of individual sequence variants.

Why is gene expression described as the 'bridge' between genotype and phenotype?

Gene expression controls when, where (tissue specificity), and how strongly (abundance) genetic information is used to produce proteins/traits.

Humans and mice share approximately 90\% of the same protein-coding genes. How do they develop such distinct phenotypes?

Differences in non-coding regulatory elements (like enhancers and promoters) create distinct expression patterns for similar proteins.

What is the primary function of regulatory elements such as promoters and enhancers?

They bind transcription factors and RNA polymerase to control the rate, timing, and tissue specificity of gene transcription.

On what biological entity does natural selection directly operate during evolution?

Natural selection operates directly on the phenotype (which determines relative fitness in an environment), not directly on the genotype.

How does a neutral DNA variant differ functionally from a phenotype-altering genetic variant?

A neutral variant does not change gene expression, protein structure, or phenotype, and thus has no effect on organismal fitness.

What adaptive phenotypic response is observed in native Tibetan populations at high altitudes?

A 'blunted hypoxia response,' where red blood cell levels do not surge excessively despite low atmospheric oxygen concentrations.

Why is a blunted hypoxia response advantageous for high-altitude adaptation in Tibetans?

It prevents blood hyperviscosity (thickening), reducing complications like stroke or heart strain while maintaining efficient oxygen delivery.

What molecular mechanism underlies the Tibetan high-altitude adaptation phenotype?

A genetic variant (near EPAS1) causes reduced activity/expression of a key hypoxia-responsive transcription factor.

What are Human Accelerated Regions (HARs) in evolutionary genomics?

Genomic sequences highly conserved across non-human species that underwent rapid, accelerated nucleotide changes specifically in the human lineage.

Why does strong sequence conservation across non-human species indicate evolutionary importance?

High conservation across millions of years indicates purifying selection, meaning the sequence performs a crucial biological function.

What does a sudden increase in sequence changes specifically in the human lineage suggest about a HAR?

It suggests positive selection driving functional evolution that may contribute to human-specific physical or cognitive traits.

Are most Human Accelerated Regions (HARs) found within protein-coding genes or non-coding regions?

Most HARs are located in non-coding regulatory regions, influencing gene expression rather than protein structure.

Why are laboratory experiments required after computational analysis identifies candidate HARs?

Computational tools only detect statistical sequence divergence; functional experiments are needed to determine the exact biological mechanism and phenotype.

Which statement best distinguishes Cystic Fibrosis (CF) from Huntington's disease?

CF is an autosomal recessive disorder caused by many distinct variants in CFTR, whereas Huntington's is dominant caused by CAG repeats in HTT.

What is allelic heterogeneity, as exemplified by Cystic Fibrosis?

When many different mutations or variants within the same gene (CFTR) can all lead to the same disease phenotype.

Why did identifying the CFTR gene not immediately yield a universal cure for Cystic Fibrosis?

Because hundreds of distinct variants cause CF, requiring different therapeutic strategies to fix different mutant protein defects.

What specific type of mutation causes Huntington's disease within the HTT gene?

An expansion of CAG trinucleotide repeats encoding an unstable polyglutamine tract in the huntingtin protein.

What is the primary objective of a Genome-Wide Association Study (GWAS)?

To scan millions of genetic variants across many individuals to find statistical associations between specific loci and a phenotype.

Does a statistically significant association in a GWAS prove that the identified SNP directly causes the trait?

No. GWAS identifies associations; the lead SNP may simply be in linkage disequilibrium with the true causal variant.

What is population stratification in the context of GWAS, and why is it problematic?

Systematic allele frequency differences due to differing ancestry between groups, which can create false-positive gene-phenotype associations.

Why is precise and consistent phenotypic measurement essential for a successful GWAS?

Inconsistent or noisy phenotype data reduces statistical power and obscures true genetic associations across large study populations.

How does GWAS differ from candidate gene studies?

GWAS is hypothesis-free and surveys the entire genome, whereas candidate gene studies preselect specific genes based on prior assumptions.

What is the defining characteristic of epigenetic modifications?

They alter gene expression and chromatin structure without altering the underlying nucleotide sequence of DNA.

Name the two types of epigenetic markers/modifications talked about in class

DNA methylation, Histone modification

How does DNA methylation regulate gene expression?

Adding methyl groups to DNA (typically cytosines) blocks transcription factor binding or recruits repressors, leading to gene silencing.

How do histone modifications influence transcriptional activity?

Chemical tags on histone tails alter chromatin accessibility (e.g., loosening chromatin to euchromatin), allowing transcription machinery access.

Are transcription factors and promoters classified as epigenetic modifications?

No. Promoters are DNA sequences and transcription factors are regulatory proteins; epigenetic modifications are molecular tags (e.g., methylation, histone marks).

What do phenotypic differences between identical (monozygotic) twins demonstrate about human traits?

They show that environmental factors and epigenetic modifications can produce distinct phenotypes despite identical DNA sequences.

In a genetic mapping study, what does 'genetic linkage' refer to?

The tendency of DNA sequences located close together on the same chromosome to be inherited together during meiosis.

How does genetic recombination affect linkage analysis?

Recombination breaks up linkage between distant loci on a chromosome, allowing geneticists to map the boundaries of a locus.

What is incomplete dominance in Mendelian genetics?

A scenario where heterozgyotes express an intermediate phenotype between the two homozygous phenotypes rather than a completely dominant trait.

What is the difference between a functional non-coding variant and a protein-coding variant?

A coding variant alters amino acid sequence/protein structure, whereas a non-coding variant alters transcription timing, level, or tissue localization.

Why is determining the functional effect of a genetic variant necessary after genomic sequencing?

To prove whether a sequence difference directly impacts biological function (protein activity or expression) rather than being a benign bystander mutation.

How can a non-coding variant in an enhancer affect expression of a distant gene?

Enhancers loop through 3D chromatin space to interact with promoters, so sequence changes in enhancers alter transcription factor recruitment.

What is an allele?

One of two or more alternative functional sequence versions of a gene or genetic locus present in a population.

In polygenic architecture, what is meant by 'small effect size'?

An individual genetic variant contributes only a tiny fraction toward increasing or decreasing the trait value.

Why is human height considered a classic complex trait?

It is controlled by thousands of genetic loci with small additive effects combined with environmental inputs like nutrition.

How did comparative genomics enable the identification of Human Accelerated Regions (HARs)?

By aligning genomes across multiple species (e.g., chimp, mouse, chicken) to find conserved loci, then highlighting human sequence divergence.

What biological process converts genetic information from DNA into functional RNA/protein?

Gene expression (transcription followed by translation).

Why do monogenic traits produce distinct phenotypic classes, whereas polygenic traits show continuous distributions?

Single major-effect genes create discrete genotype-phenotype tiers; multiple small-effect loci sum together to create a smooth bell-curve continuum.

Is sleeping under a bed net considered an effective measure to reduce malaria transmission?

Yes. Bed nets prevent mosquito bites, blocking the vector-borne transmission cycle of malaria parasites.

Does a gene always encode a protein?

No. Many genes encode functional non-coding RNAs (such as rRNA, tRNA, and microRNAs) rather than proteins.

How can a genetic variant alter cellular function without changing a protein's amino acid sequence?

It can modify gene expression levels by altering regulatory regions like promoters or enhancers.

What mechanism generates genetic diversity during sexual reproduction in malaria parasites?

Genetic recombination between male and female gametes during the sexual cycle inside the mosquito.

An _____ is defined as a specific variant or version of a gene or DNA sequence that can be inherited from a parent.

Allele

What is another name for the phenotype-first approach in genetic research?

Forward genetics

Why can forward genetics be initiated without prior knowledge of the underlying genotype?

Because it begins by observing physical or physiological phenotype variations, then works backward to find the locus.

Why is forward genetics described as an 'unbiased' approach?

It scans the genome without pre-selecting a specific candidate gene suspected of causing the trait.

What population structure is required to perform traditional forward genetic mapping?

A segregating population, such as siblings or offspring from a controlled genetic cross.

Must the causal variant identified in a forward genetics study be located in a protein-coding region?

No. Causal variants can also reside in noncoding regulatory elements such as enhancers or promoters.

How does reverse genetics differ fundamentally from forward genetics?

Reverse genetics starts with a specific gene or sequence to determine its function, whereas forward genetics starts with a phenotype.

What phenotype distribution pattern within a family is characteristic of a genetically simple trait?

A bimodal (+/- or present/absent) discrete phenotypic distribution.

Which classical framework best models the inheritance patterns of genetically simple traits?

Mendel's laws of inheritance

How many genome loci primarily determine a genetically simple trait?

A single genome locus

Although not strictly limited to coding regions, simple Mendelian traits are most likely caused by variants in _____ genes.

Protein-coding

_____ measures the proportion of phenotypic variation within a population attributable to genetic differences among individuals.

Heritability

Does a trait's heritability estimate apply to a single individual or to a specific population?

It applies exclusively to a population under specific environmental conditions, not to an individual.

In twin studies, what shared genetic percentage distinguishes monozygotic (MZ) twins from dizygotic (DZ) twins?

MZ twins share 100% of their genetic sequence, whereas DZ twins share approximately 50% on average.

If monozygotic twins show significantly higher trait concordance than dizygotic twins raised together, what does this indicate?

High heritability, indicating genetic differences strongly influence trait variation.

Who led the publicly funded Human Genome Project (HGP)?

Francis Collins

Who led the private venture Celera Genomics in the race to sequence the human genome?

Craig Venter

Did sequencing the human genome take only 5 years and 100 million?

No. It took over 10 years (1990-2003) and cost approximately 2.7 billion.

Which innovative sequencing methodology was heavily championed and scaled by Celera?

Whole-genome shotgun sequencing

Could Celera have easily assembled the human genome without relying on data from the public Human Genome Project?

No. Celera relied on the public project's physical mapping data to correctly align and assemble its shotgun reads.

What surprising finding regarding gene count emerged at the completion of the Human Genome Project?

Humans possess far fewer protein-coding genes (~20,000) than expected, making up less than 2% of the genome.

Are all genetic differences found between members of the same species considered adaptations?

No. Differences represent genetic variation; an adaptation is specifically a heritable trait that enhances relative fitness.

Do all genetic variations in an organism have either a positive or negative functional effect?

No. Many genetic variations are neutral, having no measurable impact on fitness or phenotype.

How do environmental changes influence evolutionary adaptation?

Environmental shifts alter selective pressures, changing which traits provide a survival or reproductive advantage.

Does natural selection act directly on an organism's genotype or its phenotype?

Directly on phenotype. Survival and reproduction depend on expressed physical and behavioral traits.

Define natural selection based on evolutionary principles.

The process where organisms with traits better suited to their environment survive and reproduce more successfully.

Is natural selection restricted to traits controlled by a single gene?

No. Natural selection acts on both monogenic traits and polygenic traits controlled by multiple loci.

Why does strong sequence conservation across distant species suggest noncoding DNA is functionally important?

Purifying selection eliminates deleterious mutations in functional regions, maintaining sequences across evolutionary time.

What are Human Accelerated Regions (HARs)?

Genomic regions conserved throughout vertebrate evolution that accumulated substitution changes rapidly in the human lineage.

How is comparative genomics utilized to study noncoding regulatory elements?

By aligning genomes of multiple species to locate conserved or rapidly evolving noncoding sequences under selection.

Is identifying an accelerated noncoding region computationally sufficient to determine its biological function?

No. Laboratory experimental validation (e.g., reporter assays, gene editing) is essential to determine precise molecular function.

Was inaccurate genetic testing technology a primary driver of 23andMe's financial difficulties?

No. High drug discovery costs, privacy breach concerns, and a one-time purchase business model were the major causes.

Why does the potential sale of consumer genetic databases during bankruptcy pose unique privacy risks?

Genetic data is immutable and remains reveals sensitive information about tested individuals and their biological relatives indefinitely.

How can genetic variation impact an individual's response to prescribed pharmaceuticals?

It can alter the rate of drug metabolism or modify drug targets, leading to therapeutic failure or severe toxicity.

What field of biomedical science studies how genetic variation influences individual drug responses?

Pharmacogenomics