Lecture 15 - Evo-Devo

Question 1

What does “Evo-Devo” stand for?

Answer 1

Evolutionary developmental biology, studying how genetic and environmental processes drive phenotype development and how these influence evolution.

Question 2

How does Evo-Devo connect development and evolution?

Answer 2

It links development (genotype to phenotype) and evolution (selection acting on phenotypes to alter genotypes over time).

Question 3

Define “cis-acting elements” in gene regulation.

Answer 3

DNA regions close to a gene, such as enhancers and promoters, that regulate the gene’s expression.

Question 4

What are “trans-acting elements” in gene regulation?

Answer 4

Proteins, such as transcription factors, that bind to DNA at distant locations to regulate gene expression.

Question 5

Proteins, such as transcription factors, that bind to DNA at distant locations to regulate gene expression.

Answer 5

Enhances transcription factor binding stability, creating sharp boundaries of gene expression, crucial for development.

Question 6

What is the importance of signalling pathways in development?

Answer 6

They enable communication between cells, influencing gene expression and guiding tissue and organ formation.

Question 7

What are maternal-effect genes?

Answer 7

Genes whose mRNA or proteins are deposited in the egg by the mother, influencing early embryonic development.

Question 8

Describe the anterior-posterior axis development in Drosophila.

Answer 8

Maternal-effect genes set gradients (e.g., bicoid protein) that guide the spatial expression of segmentation genes.

Question 9

What are “pair rule genes” and “segment polarity genes”?

Answer 9

Pair rule genes: Define repeated embryonic stripes.

Segment polarity genes: Refine boundaries and pattern within each segment.

Question 10

How do homeotic (Hox) genes influence body development?

Answer 10

They assign identity to body segments, with their spatial arrangement corresponding to their chromosomal order.

Question 11

What is the “genetic toolkit” of development?

Answer 11

A set of conserved genes that regulate body patterning, formation, and primary axes in various organisms.

Question 12

Why are regulatory mutations key for evolution?

Answer 12

They can alter gene expression in specific tissues or times without disrupting overall protein function, offering adaptability.

Question 13

What is the evolutionary significance of “cis-element evolution”?

Answer 13

It allows tissue-specific or time-specific gene expression changes, influencing traits without altering the protein.

Question 14

What developmental adaptation is seen in Stickleback fish?

Answer 14

Loss of pelvic spines in shallow water populations due to mutations suppressing pelvic enhancer activity.

Question 15

How does trans-regulation evolve?

Answer 15

By adding new binding motifs to transcription factors, enabling them to interact with new DNA targets or proteins.

Question 16

What are developmental constraints?

Answer 16

Limits to evolution caused by genetic correlations or essential developmental pathways.

Question 17

Give an example of developmental plasticity.

Answer 17

Aquatic plants producing aerial and submerged leaf types in response to environmental conditions.

Question 18

What role do enhancers play in gene regulation during development?

Answer 18

Enhancers act as binding sites for transcription factors, influencing where, when, and how much a gene is expressed.

Question 19

How are multiple cis-elements used for cooperative gene regulation?

Answer 19

Multiple identical cis-elements can bind transcription factors, and cooperative binding ensures rapid and robust activation of gene expression.

Question 20

What is the difference between maternal-effect genes and zygotic genes in development?

Answer 20

Maternal-effect genes are deposited in the egg by the mother and guide early development, while zygotic genes are expressed by the embryo itself.

Question 21

Why are chiasmata essential in meiosis?

Answer 21

Chiasmata, resulting from crossovers, ensure proper segregation of homologous chromosomes by holding them together until separation.

Question 22

Chiasmata, resulting from crossovers, ensure proper segregation of homologous chromosomes by holding them together until separation.

Answer 22

The bicoid gradient provides positional information along the anterior-posterior axis, guiding the expression of gap and pair-rule genes.

Question 23

How do gap genes contribute to development?

Answer 23

Gap genes are expressed in broad regions of the embryo and establish the primary body plan by regulating pair-rule and segment polarity genes.

Question 24

What is the role of Hox genes in segment identity?

Answer 24

Hox genes specify the identity of segments by controlling the expression of downstream genes that shape morphology.

Question 25

Explain the concept of "positional information" in development.

Answer 25

Positional information refers to spatial cues, like morphogen gradients, that determine the location-specific activation of genes during development.

Question 26

How do mutations in cis-regulatory elements drive evolution?

Answer 26

Cis-element mutations can change gene expression patterns without affecting protein function, enabling morphological diversification.

Question 27

How does trans-element evolution differ from cis-element evolution?

Answer 27

Trans-element evolution involves changes in transcription factors, such as their binding abilities or interaction with other proteins, leading to novel functions.

Question 28

What is the significance of conservation in the genetic toolkit?

Answer 28

Conserved genes like Hox clusters indicate their critical roles in development and evolution, as their functions have been maintained across diverse species.

Question 29

What is the role of signalling components like Hedgehog in development?

Answer 29

Hedgehog acts as a morphogen, creating gradients that regulate tissue patterning and segment formation.

Question 30

How do enhancer mutations affect pigmentation in Drosophila species?

Answer 30

Mutations in wing enhancers of the yellow gene increase transcription factor binding, leading to higher expression and darker pigmentation.

Question 31

How do segment polarity genes refine the body plan?

Answer 31

Segment polarity genes define and stabilize segment boundaries, ensuring proper organization of the body.

Question 32

What is the evolutionary importance of gene duplication?

Answer 32

Gene duplication provides raw material for evolution, allowing one copy to maintain its function while the other can acquire new roles.

Question 33

How does environmental plasticity impact development?

Answer 33

Environmental cues can alter phenotypic expression, enabling organisms to adapt to varying conditions without genetic changes.

Question 34

What is the connection between gene dosage and chromosomal segregation?

Answer 34

Imbalances in gene dosage due to incorrect segregation can disrupt cellular function and lead to developmental disorders.

Question 35

What developmental constraints limit "evolvability"?

Answer 35

Limited genetic variation, strong correlations between traits, and pleiotropic effects restrict the potential for evolutionary changes.

Question 36

What is the "context dependency" of the genetic toolkit?

Answer 36

Genes in the toolkit are reused in different developmental processes, with their function depending on the specific tissue or time of expression.

Question 37

What is the significance of "modular" changes in cis-elements?

Answer 37

Modular changes allow gene expression to be altered in specific tissues or times, minimizing negative impacts on overall fitness.