Lecture 12

Question 1

How does studying the phenotype of a mutant tell you what a gene does?

Answer 1

can tell the function of the gene that has been mutated

Question 2

Define genetic screen

Answer 2

identifies specific phenotypic abnormalities in a pop. of organisms that have been mutagenized

Question 3

Define saturation mutagenesis.

Answer 3

mutagenesis aimed at identifying mutant alleles within a genome by introducing mutations to every gene

Question 4

mutagenesis

Answer 4

the purposeful mutation of a gene

Question 5

What properties make an organism a good model for genetic screen?

Answer 5

-laboratory life span
-short time for sexual maturity
-lots of progeny

Question 6

What is a mutagen?

Answer 6

A chemical, physical, or biological agent capable of damaging DNA and creating a mutation.

Question 7

Is it easier to find dominant or recessive mutations? Which are more common? Why?

Answer 7

-D more easy to display because they are haplosufficient
-R mutations are more common because they are concealed in the heterozygous so are less targeted by natural selection

Question 8

How has genetics helped developmental biologists understand development?

Answer 8

B/c development is a genetically programmed process across species (helps to identify abnormalities mutations and mechanisms of development)

Question 9

Define totipotent.

Answer 9

cells that have the potential to differentiate into any tissue or cell type
eg. embryonic stem cells

Question 10

Define pluripotent.

Answer 10

cells that retain the potential to give rise to many but NOT all cell types
eg. later embryonic stem cells

Question 11

Define differentiated.

Answer 11

cells that take on different morphologies and undertake different physiological activities
eg. neurons, osteocytes, etc.

Question 12

Define induction.

Answer 12

The process by which one cell or tissue PROMOTES a particular developmental fate in neighboring cells or tissues.

Question 13

Define inhibition.

Answer 13

The process by one cell or tissue PREVENTS a particular developmental fate in neighboring cells or tissue.

Question 14

What is the basic segmental pattern of an adult fly?

Answer 14

Head, thorax abdomen?

Question 15

What tool did Drs. Nüsslein-Vollhard and Wieschaus use to identify genes needed for pattern
formation in the fly?

Answer 15

large-scale genetic screens

Question 16

What were the five classes of genes expressed in the Drosophila embryo?

Answer 16

1. Coordinate genes (affect pole of larvae)
2. Gap genes (mutants are missing large groups of segments)
3. Pair-rule genes (mutants are missing parts of adjacent segment pairs in alternating patterns)
4. Segment polarity genes (patterning)
5. Homoeotic genes (identify of segment)

Question 17

What is a Hox gene?

Answer 17

the genes that often pattern the anterior-posterior axis and are homeotic genes

Question 18

What are homeotic genes?

Answer 18

Genes that determine the developmental region of the body of an organism

Question 19

What is an example of a Hox gene mutation?

Answer 19

The Antennapedia Complex: legs instead of antennae

Question 20

When Antp is expressed correctly, it is located in a segment
(T2/yellow) that gives rise to a leg. If you express Antp in the head segment, what does it do?
What does this tell you about Antp’s function?

Answer 20

Results in legs coming out of the head–> Ant responsible for leg growth

Question 21

What other animals have Hox genes? Do they have the same function as in flies? What does this
imply?

Answer 21

All other animals have Hox genes. They generally perform the same function (conserved). This implies that they are all evolutionarily linked.