Gene and Heritability, Phylogenetics, Evolution, and Natural Selection

A comprehensive set of flashcards covering key concepts, definitions, and examples from the topics of genetics, heritability, phylogenetics, evolution, and natural selection.

What are the different levels of genetic variation that contribute to heredity?

Alleles, recombination during meiosis, segregation of homologous chromosomes, random segregation of sister chromatids, and independent assortment of chromosomes.

What are alleles?

Different forms of the same gene.

What is recombination during meiosis?

The exchange of DNA between homologous chromosomes during crossing over, creating new allele combinations.

What occurs during segregation of homologous chromosomes?

Homologous chromosome pairs separate during meiosis I so that each gamete receives one chromosome from the pair.

What is random segregation of sister chromatids?

During meiosis II, sister chromatids separate randomly into different gametes.

What is independent assortment of chromosomes?

The random orientation and separation of different chromosome pairs during meiosis, producing many genetic combinations.

What is a genotype?

The genetic makeup or set of genes an organism carries.

What is a phenotype?

Any observable trait or characteristic of an organism.

What does phenotype include?

Anything observable in any way, including physical traits, biochemical traits, and behavior.

What is genetic polymorphism?

The presence of more than one discrete phenotype for a trait within a population.

What inheritance patterns can genetic polymorphisms follow?

Dominant/recessive, incomplete dominance, or co-dominance.

What is polyphenism?

Multiple phenotypes produced from the same genotype depending on environmental conditions.

What is another term describing polyphenism?

A form of phenotypic plasticity.

What determines which phenotype appears in polyphenism?

Environmental conditions.

What are quantitative traits?

Traits that can be measured and usually vary continuously (such as height or weight).

What are quantitative trait loci (QTLs)?

Genes that influence quantitative traits.

What is QTL analysis?

A method used to identify which genes affect quantitative traits.

What are some environmental factors that affect phenotype?

Nutrition, stress, and other environmental conditions.

What are morphogens?

Molecules that influence the development and pattern formation of tissues during development.

What is phenotypic plasticity?

A non-reversible change in phenotype caused by environmental influences.

What are phylogenies?

Visual representations of evolutionary relationships.

What kinds of biological units can phylogenies represent?

Populations, species, genes, or other taxonomic levels.

What is the root of a phylogeny?

The common ancestor of all organisms in the tree.

What is a branch in a phylogenetic tree?

A lineage evolving through time.

What is a node?

A point where a lineage splits into two or more lineages.

What is an internal node?

A node that represents a common ancestor within the tree.

What is a tip in a phylogenetic tree?

The end of a branch representing a present-day species or taxon.

What is a clade?

A group consisting of a common ancestor and all its descendants.

What is a cladogram?

A phylogeny showing evolutionary relationships but not timing.

What is taxonomy?

The field of study concerned with classification of organisms.

What are taxa?

Groups of organisms classified based on shared characteristics.

What does monophyly mean?

A group that includes a common ancestor and all of its descendants.

What is polyphyly?

A group that does not include the most recent common ancestor.

What is paraphyly?

A group that includes a common ancestor but not all descendants.

Why are phylogenies considered hypotheses?

Because new data can change the inferred evolutionary relationships.

What is a character in phylogenetics?

A heritable trait that can be compared among organisms.

What is a synapomorphy?

A derived trait shared by all descendants of a common ancestor.

What is an outgroup?

A distantly related group used to help determine ancestral traits.

What is homoplasy?

A similar trait that evolved independently in different lineages.

What is convergent evolution?

Independent evolution of similar traits in different lineages.

What is evolutionary reversal?

When a derived trait returns to the ancestral state.

What is parsimony in phylogenetics?

The principle that the simplest evolutionary explanation is most likely correct.

What is a consensus phylogeny?

A tree combining multiple equally parsimonious trees.

What is a polytomy?

A node with three or more unresolved branches.

How do fossils help phylogenies?

They add a timing component to evolutionary relationships.

Why are more fossils useful for phylogenetic studies?

They provide better estimates of when evolutionary events occurred.

How can fossils show evolutionary transitions?

By revealing intermediate forms between species.

What is horizontal gene transfer?

The movement of genetic material between unrelated organisms.

Why does horizontal gene transfer complicate phylogenies?

Because genes may come from distantly related species.

How are molecular phylogenies similar to morphological phylogenies?

Both use characters to infer evolutionary relationships.

What molecular features can be used as characters?

Alleles, genes, or individual nucleotide sites.

What is coalescent theory?

A method that traces gene variants backward in time to a common ancestor.

What can coalescent theory estimate?

When alleles originated and past population sizes.

How does coalescence behave over time?

Events become fewer and more distant as we go back in time.

What does a growing population show in coalescent patterns?

Most coalescent events occur far in the past.

What does a shrinking population show in coalescent patterns?

Many recent coalescent events.

What can coalescent theory reveal about natural selection?

Signs of positive selection or balancing selection.

What example is commonly used in humans for coalescent analysis?

Human mitochondrial DNA (mtDNA).

What is introgression?

The transfer of genes between species through hybridization.

What is incomplete lineage sorting?

When gene histories differ from species histories due to ancestral variation.

What is molecular phylogenetics?

Using DNA, RNA, or protein sequences to determine evolutionary relationships.

What is maximum parsimony?

Selecting the tree requiring the fewest evolutionary changes.

Why are exons useful for studying distant species?

They are highly conserved.

Why are introns useful for studying closely related species?

They evolve more rapidly.

What is bootstrapping?

A method that tests tree reliability by resampling data.

What is the distance-matrix method?

Comparing genetic sequences to measure similarity or difference.

What is neighbor joining?

A method that builds phylogenies by minimizing total branch length.

What is maximum likelihood?

A method that finds the tree most likely given mutation probabilities.

What are Bayesian methods?

Methods that repeatedly adjust trees to find the most likely evolutionary relationships.

What is a synonymous substitution?

A mutation that does not change the amino acid.

What is a non-synonymous substitution?

A mutation that changes the amino acid.

Which DNA regions evolve fastest?

Pseudogenes.

What is a molecular clock?

A method that estimates divergence time using mutation rates.

How do many adaptations occur?

Through changes in gene regulation rather than gene sequence.

What are gene regulatory networks?

Interacting genes that control gene expression.

What are Hox genes?

Developmental regulatory genes controlling body patterning.

What is gene recruitment?

When a gene gains a new function.

What is gene duplication?

The creation of two copies of a gene.

What are paralogs?

Duplicated genes with similar sequences.

What is neofunctionalization?

One duplicated gene evolves a new function.

What is subfunctionalization?

Duplicated genes divide the original function.

What are promiscuous proteins?

Proteins that can perform multiple functions.

How do snake venom genes evolve?

Through gene duplication, recruitment to venom glands, and neofunctionalization.

Why can developmental genes strongly affect evolution?

Small changes in regulatory genes can alter entire body structures.

What determines limb structure differences among vertebrates?

Timing and location of Hox gene expression.

How do fish fins differ from tetrapod limbs genetically?

Different Hox gene expression in mesoderm vs ectoderm.

What do all animal eyes use to detect light?

Photoreceptors with opsin proteins.

What are opsins?

Light-sensitive proteins that trigger neural signals.

What are crystallins?

Lens proteins that focus light.

What are evolutionary constraints?

Limits on evolution caused by physical, genetic, or developmental factors.

What is antagonistic pleiotropy?

When a gene benefits one trait but harms another.

What is an example of evolutionary imperfection?

The blind spot in the vertebrate eye.

What is convergent evolution?

Independent evolution of similar traits in unrelated lineages.

What is deep homology?

Similar traits arising from related genetic mechanisms.

What do Darwin’s finches demonstrate about evolution?

Natural selection can change traits like beak size based on environmental conditions.

What does the oldfield mouse example show?

Similar environmental pressures can produce convergent evolution in coat color.

What three conditions are required for natural selection?

Phenotypic variation, heritability, and differential reproduction.

What adaptation do snowshoe hares show?

Seasonal coat color changes.

How can climate change affect snowshoe hares?

It may favor brown winter coats in warmer areas.

What is an extended phenotype?

A trait expressed outside an organism’s body that affects survival.