Lecture 20

Question 1

Why was Haekel’s work important in terms of providing evidence for Darwin’s ideas of common
ancestry and evolution?

Question 2

Define a homeotic mutation and provide an example

Answer 2

refers to a mutation leading to body part developing in wrong place

Question 3

3. Explain the concept of Waddington’s landscape in the context of cell differentiation.

Answer 3

as differentiation proceeds it does not go from embryonic straight to differentiated cell. differentiation progressively limits which genes can be expressed and what type of cells can be produced by that lineage

differentiation is almost always irreversible

Question 4

How can concentration gradients of give rise to discreet boundaries of gene expression?

Answer 4

There are thresholds concentrations allow gradients to produce discrete boundaries of gene expression. Over that threshold you will get certain level of expression in one zone and beanth the threshold you will get another a lower level of express in that zone

Question 5

Suppose you injected bicoid mRNA into the center of a Drosophila embryo, what might be the
expected phenotype?

Question 6

Suppose you transplant cells from one frog embryo to a different relative position in another and do
not observe any abnormal changes in the body plan of the eventual adult. What can you infer about
the transplanted cells?

Question 7

Define syncytium

Question 8

Prove the broad roles for each of the five main types of genes involved in Drosophila development.

Question 9

Define a maternal effect gene

Question 10

Explain hunchback’s pattern of protein expression in the early embryo and how this pattern is
established.

Question 11

Explain how even-skipped demonstrates the principle that enhancers can integrate spatial
information via the presence or absence of several transcription factors.

Question 12

Suppose a mutation caused kruppel to not be expressed in parasegement 4. Based on the figure

Question 13

Use runt as an example to explain why studying fruit fly development can be important and
relevant to the study of mammalian development

Question 14

. Describe the typical pattern of hox gene placement within animal genomes.

Question 15

Explain how hox genes may provide strong evidence for Ohno’s ideas concerning gene
duplication and evolutionary innovation.

Question 16

Provide two reasons why regulatory mutations often have milder phenotypes than structural
mutations.

Question 17

How does hox10 demonstrate that hox genes play a role in specifying “segments” in mammals

Question 18

Why does anchor cell ablation lead to a vulva-less phenotype?

Question 19

Suppose you analyzed a triple mutant: lin-3 LOF + let-23 LOF + let-60 GOF. What is the expected
phenotype and why?

Question 20

Explain the roles of lag-2 and lin-12 in lateral inhibition

Question 21

Why do extra digits always have an identity that is identical to an adjacent digit in individuals with
polydactyly?