Building a Fruit-fly. Flashcards
The scientists who studied the development of fruit flies were particularly interested in what aspect?
In mutant fruit flies that led to a change in body axis.
What did the scientists do to make mutant fruit flies?
They treated male fruit flies with a mutagen called EMU which created random point mutations.
These would be breed to female flies and the offspring would be analysed to see if the body axis was disrupted.
How many independent mutations in the fruit fly were essential for life?
30,000.
How many independent mutations in the fruit fly were essential for embryonic development?
8000.
How many independent mutations in the fruit fly were essential for anterior/posterior or dorsal/ventral axis development?
750.
How many genes in the fruit fly were essential for anterior/posterior or dorsal/ventral axis development?
150.
What are maternal effect mutations?
Maternal effect mutations are caused by mutations in the mother where the offspring shows the phenotype.
Do maternal mutations damage the mother or the offspring?
They damage the offspring.
How do maternal affects damage the offspring?
Because the gene products that are deposited in the egg during oogenesis are faulty.
Can maternal affects be rescued by paternal genes?
No.
As the father makes no genetic contribution to the cytoplasmic determinants.
What are the genes of interest in fruit fly development?
Those that pattern the embryo.
How does a fruit fly develop.
It goes from a fertilised egg to a larvae which then pupates into a fly.
What is the first thing that happens to divide the fly egg up?
It is divided into its anterior and posterior sections.
What happens after the anterior posterior axis is determined?
The middle is determined.
Then smaller segments are determined.
The smaller segments are defined.
HOX genes tell the smaller segments what to form.
What happens if UV light is shone on the front of the embryo?
A larvae develops that lacks anterior structures.
What happens if cytoplasm is removed from the front half of the embryo?
A larvae develops that lacks anterior structures.
What happens if cytoplasm is removed from the front half of the embryo and placed in the middle another embryo?
The other embryo will develop 2 heads, one in a normal place and one in the middle.
What does the front of the embryo determine?
The head.
Anterior region.
What happens if a mother has a homozygous mutation for the BICOID gene?
The offspring will lack a head and a thorax.
If BICOID mRNA is synthesised and injected into eggs that lack BICOID, what happens?
A normal embryo will develop.
BICOID is an example of what?
A morphogen.
What is a morphogen?
They have the ability to direct and alter the fate of cells so that produce certain structures.
If BICOID is implanted in the middle of an organism, what will happen?
A 2nd head will grow at the site of implantation.
What happens if the gene NANOS is mis-expressed?
A mutation in this gene lead to a lack of posterior structures in the embryo.
If an embryo lacks NANOS and it is artificially inserted, what will happen?
A normal embryo will develop.
Where is BICOID and NANOS expressed in the embryo?
Bicoid in the anterior.
NANOS in the posterior.
How does the fruit fly embryo develop?
When the blastula is produced in fruit flies, nuclear division occurs.
Each of these nuclei will migrate to the periphery of the egg and end up sharing a common cytoplasm.
Membranes begin to form around these nuclei and we get small cells.
How is BICOID translated in the sinsisual blastula of a fruit fly?
BICOID mRNA can be translated in the anterior portion and then diffuse across the embryo until cells are formed.
The formation of cells traps BICOID proteins into the cells.
