EVOLUTIONARY DEVELOPMENT BIOLOGY

Question 1

What underlies much of the morphological evolution between species?

Answer 1

Differences in gene regulation, especially changes in cis-regulatory elements, underlie much of morphological evolution.

Question 2

What is cis element evolution?

Answer 2

Changes in enhancer sequences through mutations can lead to new traits, such as darker pigmentation in wings, by altering transcription factor (TF) binding and increasing gene expression.

Question 3

What is co-option in evolution?

Answer 3

Co-option is the novel use of pre-existing genes for new functions. Entire genetic pathways, like HOX genes for limb differentiation, have been co-opted in evolution.

Question 4

Give an example of trait loss due to regulatory mutations.

Answer 4

Pelvic morphology loss in stickleback fish, where mutations in the pelvic enhancer prevent TF binding, leading to the loss of pelvic structures like spines.

Question 5

Why are changes in regulatory elements favored over coding sequence mutations?

Answer 5

Changes in regulatory elements have specific impacts, allowing one aspect of a gene’s expression to change while preserving other functions, making this a less constrained route for evolution.

Question 6

What is trans element evolution?

Answer 6

It involves changes in transcription factor (TF) expression or binding ability through modifications in amino acid sequences, adding new functions while retaining pre-existing ones.

Question 7

What is pleiotropy?

Answer 7

Pleiotropy occurs when a single gene influences multiple unrelated traits, which can limit the “evolvability” of certain phenotypes.

Question 8

What is evo-devo (evolutionary developmental biology)?

Answer 8

Evo-devo studies how genetic and environmental processes give rise to phenotypes in individuals and populations, and how the transition from genes to physical structures evolves.

Question 9

What are cis-acting regulatory elements?

Answer 9

Cis-acting elements are DNA sequences located on the same molecule as the gene they regulate, serving as binding sites for TFs, promoters, enhancers, or silencers.

Question 10

What are trans-acting regulatory elements?

Answer 10

Trans-acting elements are molecules like TFs that are produced by genes elsewhere in the genome and move to bind to target cis-regulatory elements.

Question 11

How do maternal effect genes influence development?

Answer 11

Maternal effect genes provide initial positional information, such as Bicoid in Drosophila, which establishes the anterior-posterior axis through protein gradients.

Question 12

What are gap genes?

Answer 12

Gap genes respond to maternal effect gene gradients and divide the embryo into broad regions, marking the first stage of the embryo’s own gene expression.

Question 13

What are pair-rule genes?

Answer 13

Pair-rule genes organize the embryo into alternating segments through a striped pattern and are regulated by gap genes and maternal effect gradients.

Question 14

What are segment polarity genes?

Answer 14

Segment polarity genes maintain the anterior-posterior orientation within each segment and ensure the integrity of segment boundaries.

Question 15

What are homeotic genes?

Answer 15

Homeotic genes are master regulators that control the development of structures and organs, like HOX genes that determine body plan and the identity of repeated body units.

Question 16

What is the significance of HOX genes in evolution?

Answer 16

HOX genes are highly conserved across species and control the body plan. Mutations in these genes can cause developmental defects, such as body parts developing in the wrong location.

Question 17

What are receptors in the context of development?

Answer 17

Receptors are proteins on the cell surface or inside cells that detect and bind to signaling molecules, triggering a cellular response.

Question 18

What are diffusible signals in development?

Answer 18

Diffusible signals are molecules released by cells that diffuse through tissues to signal neighboring cells, such as the Hedgehog signaling pathway.

Question 19

What are enhancers in development?

Answer 19

Enhancers are DNA sequences that increase the transcription of specific genes by binding to transcription factors (TFs).

Question 20

What is the Hedgehog signaling pathway?

Answer 20

Hedgehog is a signaling molecule released by certain cells, detected by neighboring cells with the appropriate receptors, playing a key role in tissue patterning.

Question 21

What is the effect of mutations in maternal effect genes like Bicoid?

Answer 21

Mutations in Bicoid can result in the loss of anterior or posterior structures, preventing normal embryonic development.

Question 22

What happens with mutations in segment polarity genes?

Answer 22

Mutations in segment polarity genes cause defects in individual segments, such as mirror image duplications or loss of segment boundaries.

Question 23

What happens with mutations in gap genes?

Answer 23

Mutations in gap genes result in the loss of entire body sections, where groups of segments are absent.

Question 24

What are the effects of mutations in HOX genes?

Answer 24

Mutations in HOX genes lead to misidentification of segment identity, such as legs forming in place of antennae (homeotic transformations).

Question 25

What happens with mutations in pair-rule genes?

Answer 25

Mutations in pair-rule genes cause the loss of every other segment in the developing embryo, disrupting the normal segmental pattern.

Question 26

: How does cis-regulation affect the yellow gene?

Answer 26

Changes in the enhancer sequence of the yellow gene affect the expression of the transcription factor, influencing pigmentation patterns.

Question 27

How does trans-regulation affect the elongation gene?

Answer 27

ans-regulation changes the expression of the elongation gene, causing the transcription factor to also be expressed in sepals, leading to abnormal growth of structures.

Question 28

What is the role of cis-regulation in pigmentation genes?

Answer 28

Changes in the cis enhancer sequence alter the regulation of pigmentation genes, affecting the color and pattern of the organism.

Question 29

How can the environment influence developmental expression of the genotype?

Answer 29

The environment can cause a genotype to produce different phenotypes, demonstrating phenotypic plasticity, where environmental stimuli shape development.