Genetics & Inheritance: Probability, Exceptions & Misinterpretations (Deck 25)

Question 1

Why is Mendelian inheritance an oversimplification?

Answer 1

Most traits are influenced by multiple genes and environmental factors.

Question 2

Why do dominant traits not always appear in every generation?

Answer 2

Incomplete penetrance can prevent expression.

Question 3

What is penetrance?

Answer 3

The proportion of individuals with a genotype who express the phenotype.

Question 4

What is expressivity?

Answer 4

The degree to which a trait is expressed among individuals with the same genotype.

Question 5

Why are penetrance and expressivity often confused?

Answer 5

Both affect phenotype visibility but describe different phenomena.

Question 6

Why are most human traits polygenic?

Answer 6

Multiple genes contribute small effects.

Question 7

Why do polygenic traits show continuous variation?

Answer 7

Effects add together across many loci.

Question 8

Why does environment matter more for polygenic traits?

Answer 8

Small genetic effects are easily modified by conditions.

Question 9

Why is height not inherited like eye color?

Answer 9

Height is polygenic and environmentally influenced.

Question 10

Why are genetic probabilities not certainties?

Answer 10

Inheritance involves random assortment and environmental interaction.

Question 11

Why does linkage violate independent assortment?

Answer 11

Genes close together on chromosomes are inherited together.

Question 12

Why does recombination reduce but not eliminate linkage?

Answer 12

Crossing over is probabilistic, not guaranteed.

Question 13

Why is genetic distance measured in centimorgans?

Answer 13

It reflects recombination frequency, not physical distance.

Question 14

Why can sex-linked traits appear to skip generations?

Answer 14

Expression depends on sex-specific inheritance patterns.

Question 15

Why are X-linked disorders more common in males?

Answer 15

Males have only one X chromosome.

Question 16

Why is mitochondrial inheritance exclusively maternal?

Answer 16

Mitochondria are inherited from the egg cytoplasm.

Question 17

Why do mitochondrial diseases affect high-energy tissues?

Answer 17

Those tissues have the highest ATP demand.

Question 18

Why does heteroplasmy complicate mitochondrial inheritance?

Answer 18

Different cells contain different proportions of mutant mitochondria.

Question 19

Why do lethal alleles persist in populations?

Answer 19

They may be recessive or confer heterozygote advantage.

Question 20

Why is sickle cell disease common in malaria regions?

Answer 20

Heterozygote advantage protects against malaria.

Question 21

Why is pleiotropy common?

Answer 21

Single genes often affect multiple traits.

Question 22

Why does pleiotropy complicate prediction?

Answer 22

Changing one gene has multiple downstream effects.

Question 23

Why is epistasis common in genetics?

Answer 23

Genes interact within pathways.

Question 24

Why does epistasis break simple ratio predictions?

Answer 24

One gene can mask or modify another.

Question 25

Why are most mutations neutral?

Answer 25

They do not significantly affect fitness.

Question 26

Why are harmful mutations more visible than beneficial ones?

Answer 26

Damage is easier than improvement.

Question 27

Why does genetic background matter?

Answer 27

Effects depend on other alleles present.

Question 28

Why do the same mutations cause different outcomes in different people?

Answer 28

Genetic and environmental context differs.

Question 29

Why does inbreeding increase genetic disease risk?

Answer 29

It increases homozygosity of recessive alleles.

Question 30

Why is outbreeding generally beneficial?

Answer 30

It increases genetic diversity.

Question 31

Why does heritability not equal genetic determinism?

Answer 31

Heritability is population-specific and environment-dependent.

Question 32

Why are heritability estimates often misused?

Answer 32

They are incorrectly applied to individuals.

Question 33

Why can high heritability still allow environmental intervention?

Answer 33

Genes influence risk, not destiny.

Question 34

Why do GWAS studies find many small-effect loci?

Answer 34

Complex traits arise from many contributors.

Question 35

Why does missing heritability exist?

Answer 35

Effects are spread across many rare variants and interactions.

Question 36

Why is prediction from genetics still limited?

Answer 36

Complex interactions reduce accuracy.

Question 37

Why do identical twins differ phenotypically?

Answer 37

Epigenetics and environment diverge over time.

Question 38

Why is epigenetic inheritance controversial?

Answer 38

Most marks reset between generations.

Question 39

Why does meiosis introduce randomness?

Answer 39

Independent assortment and recombination shuffle alleles.

Question 40

Why is genetic counseling probabilistic?

Answer 40

Exact outcomes cannot be guaranteed.

Question 41

Why do people overestimate genetic explanations?

Answer 41

Genes are simpler narratives than interactions.

Question 42

Why is genetics often misused in social debates?

Answer 42

Statistical results are oversimplified.

Question 43

Why is population genetics different from individual genetics?

Answer 43

It describes trends, not predictions.

Question 44

Why is natural selection blind to individual suffering?

Answer 44

Selection operates on reproductive success only.

Question 45

Why is understanding exceptions more important than rules?

Answer 45

Most real traits violate simple models.

Question 46

Why is genetic mastery crucial for teaching biology?

Answer 46

It prevents deterministic misunderstandings.

Question 47

If teaching genetics mastery in one sentence, what’s the key idea?

Answer 47

Genes shape probabilities through complex interactions, not fixed outcomes.