Evol Disease Unit 2

Why can insertion/deletion mutations be especially damaging?

If the change shifts the reading frame, it alters many codons downstream and may create an early stop codon, often changing or disrupting the protein.

Can scientists predict a mutation's fitness effect from its type alone?

Usually not. Its effect depends on the gene, the exact location, the resulting protein or gene regulation, and the environment.

How can DNA mutations help scientists reconstruct evolutionary relationships?

Mutations accumulate in lineages over time. Comparing DNA sequences can reveal shared variants and differences, helping infer common ancestry and divergence, while accounting for factors such as recombination.

What is the significance of human chromosome 2 in evolutionary evidence?

Human chromosome 2 appears to be the result of a fusion of two chromosomes corresponding to separate chromosomes in other great apes. Similar gene order and telomere-related sequence at the fusion site support common ancestry.

What is the FOXP2 gene associated with in the notes?

The notes connect FOXP2 with speech and language abilities; certain mutations can be associated with speech/language disorders. This does not mean one gene alone explains human language.

How can a single mutation cause sickle-cell disease?

A point mutation in the gene for beta-globin changes an amino acid in hemoglobin. Under certain conditions, the altered hemoglobin can form long chains, deforming red blood cells into sickle shapes. The serious disease is associated with inheriting two disease-associated alleles.

What is hemophilia, as described in the notes?

A group of inherited disorders involving impaired blood clotting. The notes emphasize mutations affecting clotting factor VIII and an X-linked recessive inheritance pattern for classic hemophilia A.

Why is classic hemophilia A described as X-linked recessive?

The relevant gene is on the X chromosome. An XY individual has only one X chromosome, so a disease-associated allele on that X can cause the condition; an XX individual with one typical and one disease-associated allele is often an unaffected carrier.

What is maple syrup urine disease (MSUD)?

An inherited metabolic disorder in which the body cannot properly break down the branched-chain amino acids leucine, isoleucine, and valine. These can build up to toxic levels; untreated disease can cause serious neurological problems and may be fatal.

How is maple syrup urine disease inherited in the notes?

As an autosomal recessive disorder: a child generally must inherit a disease-associated allele from each parent to be affected. The notes link it to variants affecting the BCKDHA gene.

Why can recessive disorders be more common in small or endogamous populations?

Founder effects and genetic drift can raise the frequency of a rare allele by chance. If people tend to marry within the community, two carriers of the same recessive allele are more likely to have children together.

What is Huntington's disease?

An inherited neurodegenerative disorder associated with an expanded CAG repeat in the HTT gene. The repeat encodes glutamine; excessive repeats can alter the protein and lead to neurological disease, typically with adult onset.

How is Huntington's disease inherited?

It is autosomal dominant: one disease-associated allele can cause the condition. A parent who carries the allele has a 50% chance of passing it to each child, though onset and severity can vary.

What CAG repeat ranges are given in the notes for Huntington's disease?

The notes describe 10â€"35 repeats as the typical range, 36â€"39 as an intermediate range with increased risk but uncertain symptoms, and 40 or more as strongly associated with developing Huntington's disease. Use your instructor's exact thresholds for the exam.

What is phenylketonuria (PKU)?

An inherited metabolic disorder in which the body cannot properly process phenylalanine. Without treatment, phenylalanine can build up and cause developmental and neurological harm. Management includes limiting phenylalanine in the diet; newborn screening helps identify it early.

What is a heterozygote advantage?

When individuals with two different alleles at a locus have higher fitness than either type of homozygote in a particular environment. This can maintain a disease-associated allele in a population.

How can the sickle-cell allele show heterozygote advantage?

In malaria-endemic regions, people with one sickle-cell allele can have increased protection against severe malaria compared with people without it, while people with two copies can develop sickle-cell disease. The balance depends on the environment.

What is the founder effect example involving Ellisâ€"van Creveld syndrome in the notes?

The notes describe Ellisâ€"van Creveld syndrome, involving features such as polydactyly, nail abnormalities, heart defects, and short stature, as more common in some Pennsylvania Amish communities due in part to a founder effect. The notes do not identify a known heterozygote advantage.

What is meiotic drive?

A process in which an allele is transmitted to gametes more often than the expected Mendelian proportion. Such a 'selfish' genetic element can increase in frequency even if it does not benefit the organism overall.

How is PCOS discussed in the notes' section on meiotic drive?

The notes present polycystic ovary syndrome (PCOS) as a possible example linked to unusual inheritance patterns and discuss it in the context of meiotic drive. Treat this as the lecture's proposed connection rather than a universally settled explanation.

What is the key reason natural selection may not eliminate recessive disease alleles?

A recessive disease-associated allele can be hidden in heterozygous carriers who do not show the disease phenotype. Selection has less ability to remove alleles when their effects are masked.

Why can a disease-associated allele persist if it causes symptoms after reproduction?

Natural selection is generally less effective against effects that appear after most reproduction has occurred, because those effects may have little impact on the number of descendants.

What is antagonistic pleiotropy?

A single allele affects multiple traits, with at least one effect beneficial and another harmful. If the beneficial effect increases reproductive success earlier in life, selection can maintain the allele even if it contributes to problems later.

What is ApoA-I Milano in the notes?

A rare variant of apolipoprotein A-I described in the notes as associated with reduced cholesterol deposition in arteries and potentially lower atherosclerosis risk.

What is LRP5 mentioned as an example of?

A gene in which some variants can increase bone density, potentially affecting risk of osteoporosis.

What is the CCR5-Î"32 variant associated with in the notes?

A deletion variant in the CCR5 gene that can reduce susceptibility to HIV infection because HIV commonly uses the CCR5 receptor to enter certain human cells.

What is tetrachromatic vision?

The ability to distinguish color using four types of cone photoreceptors or functional cone classes, rather than the usual three. The notes mention variants in opsin genes that may allow some XX individuals to have tetrachromatic vision.

What is a genetic predisposition?

An inherited variant or combination of variants that changes a person's probability of developing a condition. A predisposition does not always mean the condition will occur.

What does the human eye illustrate about evolution?

Evolution modifies structures that already exist rather than designing from scratch. The notes describe features such as the vertebrate blind spot and retinal organization as examples of evolutionary constraints or imperfect outcomes.

Why do humans have a blind spot?

In the vertebrate eye, the optic nerve passes through the retina at a point with no light-sensing photoreceptors. The brain often fills in the missing information, so people usually do not notice the blind spot.

What is myopia?

Nearsightedness: light focuses in front of the retina rather than directly on it, making distant objects blurry. Lenses can adjust focus so the image falls on the retina.

Why does the existence of genetic disorders not disprove evolution?

Natural selection is not a process that guarantees perfection. Recessive alleles can be masked in carriers, mutations continually arise, traits involve trade-offs, and selection is limited by existing variation and environmental conditions.

What is the Anthropocene, according to the notes?

A proposed geological interval emphasizing the profound influence humans have had on Earth's systems. Its formal start date remains debated; the notes mention nuclear testing and its distinctive radioactive isotope signature as one candidate marker.

When did life first appear on Earth according to the notes?

Approximately 3.8 billion years ago (3.8 bya).

What happened during the Permian mass extinction, according to the notes?

Around 240 million years ago in the notes' timeline, a major extinction eliminated roughly 95% of marine species and 70% of terrestrial vertebrates. Verify the exact date and figures against your lecture slides.

What happened at the end-Cretaceous mass extinction?

An asteroid impact near the Yucatán Peninsula is associated with abrupt environmental and climate change. About 75% of species went extinct, including non-avian dinosaurs; one dinosaur lineage survived and eventually gave rise to modern birds.

What happened to mammals after major mass extinctions?

Mammal lineages that survived diversified as ecosystems recovered and ecological opportunities opened up.

In which geological period did humans evolve, according to the notes?

The Quaternary, the most recent geological period in the notes.

What is aging?

The process of growing older over time, beginning at birth.

What is senescence?

The age-associated deterioration of bodily function that increases vulnerability to disease and death.

Why has average human lifespan increased in the industrial era?

Cultural changes such as sanitation, clean water, medicine, and reduced infant and infectious-disease mortality have allowed more people to survive to older ages. This does not necessarily mean the maximum human lifespan has increased by the same amount.

What is the difference between average lifespan and maximum lifespan?

Average lifespan is the mean length of life in a population; maximum lifespan is the upper limit of how long humans can live. The notes emphasize that average lifespan has risen substantially while the maximum has changed much less.

Why is the idea that aging evolved 'for the good of the species' flawed?

Natural selection does not act to benefit a species as a whole. It favors heritable traits that affect reproductive success, so aging is better explained by limits and trade-offs in selection rather than a purposeful program to make individuals die.

What is the mutation accumulation theory of aging?

Harmful mutations that affect people mainly at older ages are weakly removed by natural selection because many carriers have already reproduced. Such mutations can persist and accumulate in populations.

What is antagonistic pleiotropy as an explanation for aging?

An allele may improve fitness early in life but have harmful effects later. Selection can favor the early benefit even though the allele contributes to senescence after reproduction.

How can cellular mutations relate to aging and cancer?

DNA damage and mutations can accumulate in body cells as they divide and encounter internal or environmental stresses. Cell-cycle checkpoints and p53 can stop damaged cells or trigger apoptosis, but if these safeguards fail, abnormal cells may persist and sometimes become cancerous.

What is apoptosis?

Programmed cell death: a controlled process by which a cell is eliminated. It can help prevent damaged or abnormal cells from surviving.

What is p53?

A tumor-suppressor protein that helps respond to DNA damage and other cellular stress. It can pause the cell cycle or trigger apoptosis; loss of its function can allow damaged cells to survive and proliferate.

What is evolutionary mismatch?

A situation in which traits shaped by past environments interact poorly with a newer environment. Mismatch can contribute to disease when modern conditions differ substantially from those in which a trait evolved.

What is dysevolution as used in the notes?

The notes use dysevolution in discussing worsening health trends and environments that make unhealthy outcomes easier to produce. Follow your instructor's specific definition if it was given in class.

How can modern food environments contribute to evolutionary mismatch?

Humans may have evolved preferences for energy-dense foods containing fat, sugar, and salt when such resources were harder to obtain. In modern settings where calorie-dense foods are inexpensive and abundant, those preferences can contribute to excess energy intake.

What is the thrifty genotype hypothesis?

The hypothesis proposes that past selection favored genetic variants that helped people store energy efficiently when food was abundant and use stored energy during scarcity. In modern environments with constant access to calorie-dense food, these tendencies could contribute to metabolic disease. The notes state that specific responsible genes have not been clearly identified.

What is the thrifty phenotype hypothesis?

The hypothesis proposes that conditions during fetal development, especially maternal nutrition, can influence how a child's physiology is programmed. A body adapted developmentally to scarcity may be at greater risk of metabolic problems if later life provides abundant calories.

What is epigenetics?

Changes in gene activity or regulation that do not alter the DNA sequence itself. Environmental conditions during development can influence which genes are more or less active.

How does the thrifty phenotype hypothesis connect prenatal environment with later disease?

Insufficient maternal nutrition may lead a fetus to develop in ways suited to a low-resource environment. If the child later grows up with abundant calories, that mismatch may increase risk of obesity, insulin resistance, type 2 diabetes, and cardiovascular disease.

What is insulin resistance?

A condition in which cells respond less effectively to insulin, making it harder to regulate blood glucose. It is an important contributor to type 2 diabetes.

What is type 2 diabetes in the notes' evolutionary framework?

A chronic condition involving insulin resistance and/or insufficient insulin action, producing elevated blood glucose. The notes connect its rising prevalence to modern diet, sedentary lifestyles, and developmental mismatch, while emphasizing that causes are complex.

What is sedentarism?

Prolonged periods of little or no physical activity. The notes associate modern sedentary lifestyles with increased risk of coronary heart disease, high blood pressure, diabetes, some cancers, bone-density loss, sarcopenia, and premature mortality.

How does obesity relate to type 2 diabetes and cardiovascular disease?

Excess body fat, especially visceral fat around organs, is associated with insulin resistance, higher blood glucose, high blood pressure, and cardiovascular risk. These relationships are multifactorial and are not explained by one gene or one evolutionary hypothesis alone.

What are visceral and subcutaneous fat?

Visceral fat accumulates around internal organs; subcutaneous fat lies beneath the skin. The notes emphasize visceral fat as particularly relevant to metabolic health.

What is the hygiene hypothesis?

A broad hypothesis that reduced exposure to certain microbes in cleaner or more industrialized environments may contribute to increases in some immune-related conditions. It does not mean hygiene is bad or that dangerous infections should be sought out.

What is the Old Friends hypothesis?

The idea that humans evolved alongside certain microorganisms and parasites that helped train or regulate immune function. Reduced contact with some of these organisms may affect immune regulation and contribute to certain chronic inflammatory or allergic conditions.

What does it mean for a microorganism to be immunomodulatory?

It can influence how the immune system develops or responds, potentially changing the strength or type of immune response.

How might altered microbial populations contribute to disease?

Changes in the communities of microorganisms associated with the body can affect immune regulation and other biological processes. Some alterations may contribute to dysfunction or disease, although effects depend on the organisms and context.

What is an allergen?

A substance that can trigger an allergic immune response in a sensitized person. Examples in the notes include pollen, dust mites, mold, pet dander, and some foods.

What is the relationship between industrialization and allergies in the notes?

The notes connect the industrial era with reduced exposure to some pathogens and parasites and discuss observations that people with greater microbial exposure during childhood may have lower rates of some allergies. This is a hypothesis about immune regulation, not a reason to expose oneself to dangerous infections.

What is IgE?

Immunoglobulin E, an antibody involved in allergic responses and in defense against certain parasites. The notes suggest that this system may have functions beyond reactions to common allergens.

Why are food allergies potentially dangerous?

Food-triggered reactions can cause swelling and other systemic responses; swelling in throat tissues can interfere with breathing. Suspected severe allergic reactions require urgent medical care.

How does an evolutionary perspective interpret emotions?

Emotions can alter attention, physiology, motivation, and behavior in ways that may have helped ancestors respond to challenges. Their usefulness depends on context; an adaptive response can become harmful when too intense, persistent, or mismatched to circumstances.

How can fear, anger, and disgust be understood in an evolutionary framework?

They can motivate responses to threats, conflict, or possible contamination. These responses may be protective in some contexts but can become disruptive when they occur excessively or inappropriately.

What is the distinction between an adaptive emotion and an anxiety disorder?

Anxiety can help prepare a person for danger, but persistent or disproportionate anxiety can interfere with everyday activities and cause distress. An evolutionary explanation does not replace clinical assessment or treatment.

What are mania and depression in the notes?

The notes compare mood states using symptom examples. Mania may involve elation/euphoria, increased activity, rapid or multiple ideas, and reduced need for rest; depression may involve low mood, withdrawal, tiredness, slowed thought, and difficulty making decisions. These are educational descriptions, not a way to diagnose oneself.

How do the notes discuss schizophrenia?

They describe schizophrenia as a chronic and severe mental illness with distinct physiological effects in the brain and mention possible links between immune-system overactivation/inflammation and disease. These are complex topics and should not be reduced to one cause.

What is cancer?

A group of diseases in which cells acquire changes that allow them to grow and divide abnormally, evade normal controls, and sometimes invade other tissues. Cancer often develops through the accumulation of multiple genetic changes.

What is a carcinogen?

An environmental agent that can cause cancer, such as certain chemicals, radiation, or other exposures that increase the chance of damaging DNA or disrupting cellular regulation.

What proportion of cancers do the notes attribute to inherited predisposition?

The notes estimate that about 5â€"10% of cancers are due to inherited predisposition, while most are not directly inherited. Use the precise figure taught by your instructor.

How can cancer arise without a family history?

Cancer can result from spontaneous mutations during cell division, exposure to carcinogens, some viral infections, and other factors. A family history is not required for cancer to occur.

Why does cancer often involve multiple mutations?

One mutation usually is not enough to transform a normal cell. As mutations accumulate, they can disrupt cell-cycle control, DNA repair, programmed cell death, and other safeguards, allowing abnormal cells to survive and proliferate.

What is a tumor-suppressor gene?

A gene whose normal product helps restrain cell growth, repair DNA, or eliminate damaged cells. Loss of tumor-suppressor function can remove safeguards against cancer.

What is a proto-oncogene?

A normal gene involved in cell growth or division. If altered or excessively activated, it can become an oncogene that promotes uncontrolled cell growth.

How do loss-of-function and gain-of-function mutations contribute to cancer?

Loss-of-function mutations can disable tumor suppressors or DNA-repair functions. Gain-of-function mutations can activate proto-oncogenes, increasing growth signals or producing abnormal protein activity.

What is loss of heterozygosity in cancer?

A process in which a cell loses the remaining functional copy of a tumor-suppressor gene after one copy has already been inactivated. This can eliminate the gene's protective effect.

What are common characteristics of cancer cells in the notes?

Uncontrolled division, accumulation of mutations, evasion of normal cell death, and stimulation of blood-vessel formation to supply oxygen and nutrients. Cancer cells can outcompete nearby normal cells for resources.

How can cancer cells evolve resistance to chemotherapy?

Tumors contain genetic variation. A rare cell may already carry a mutation that makes it resistant to a drug; treatment kills susceptible cells while resistant cells survive and reproduce, making resistance more common through natural selection.

How does natural selection operate within a tumor?

Cancer cell lineages vary in traits such as growth rate and drug resistance. Cells that reproduce more successfully in the tumor environment leave more descendant cells, so selection can change the tumor's cellular composition.

How can viruses cause cancer?

Some viruses can alter host gene expression, disrupt tumor-suppressor functions, or activate growth-promoting pathways. The notes use HPV as an example of a virus associated with cervical cancer.

How does HPV E6 affect p53, according to the notes?

The notes state that HPV's E6 protein binds to p53 and promotes its degradation. With less active p53, damaged cells may evade apoptosis and normal growth control, increasing cancer risk.

How can viral integration affect host genes?

When viral DNA inserts into a host genome, it can disrupt a gene and cause loss of function, or it can alter nearby gene regulation. If a proto-oncogene becomes abnormally activated, this can contribute to cancer.

Why can chemotherapy change which cancer cells are common in a tumor?

Chemotherapy creates a selective environment: susceptible cells are removed more readily, while resistant variants may survive and become more frequent. This is an example of evolution occurring on a short timescale.

What environmental and biological factors do the notes list as cancer risks?

The notes list smoking, alcohol, sunlight/UV exposure, radiation, pollution and toxic chemicals, some viruses, hormonal factors, obesity, age, and genetic predisposition. Risk varies by cancer type and exposure.

Why does cancer risk generally increase with age?

Over time, cells undergo more divisions and accumulate more opportunities for DNA damage and mutations. Longer exposure to carcinogens can also increase the chance that multiple changes will arise.

What are G1 and G2 cell-cycle checkpoints?

Checkpoints that help assess whether a cell is ready to continue division. G1 checks conditions and DNA damage before DNA replication; G2 checks after replication for problems before division. Failed checkpoints can allow mutations to accumulate.

How is cultural evolution relevant to cancer prevention?

Changes in behavior, public health policy, technology, and the environment can reduce exposure to carcinogens. The notes mention smoke reduction and clean-air legislation as examples of cultural changes that can improve population health

Pea plant cross (WW × ww)

Crossing a homozygous purple-flowered pea plant (WW) with a white-flowered plant (ww) yields 0% white-flowered offspring on average in the first generation.

Fitness effect of most mutations

Most mutations that occur in lineages tend to be deleterious rather than beneficial.

Inclusive fitness and altruism

Inclusive fitness helps explain why altruism is typically directed at related individuals who share genetic alleles.

Type II diabetes risk factors

Type II diabetes is linked to obesity, diets high in simple carbohydrates, and the thrifty phenotype theory, but NOT to low BMI.

IgE antibodies and immune response

IgE antibodies react with allergens, animal venoms, and plant toxins as part of immune system responses.

What are the core requirements for natural selection to operate?

Heritable variation, differential reproduction, and a correlation between variation and descendant numbers.

What is genetic drift?

Random changes in allele frequencies in populations, such as through bottlenecking events from disasters.