L3 Drosophila (Imported from Quizlet)

Who established drosophila as a genetic model?

Thomas Hunt Morgan

What is drosophila used for as a genetic model?

To understand the basis of hereditary and genetics

The genes residing on chromosomes are the basis of what?

Hereditary

Many genes that control development of the fly were discovered and they are very similar to genes that control the development of ...?

Vertebrates (including humans)

Evolution reuses and adapts _____ and _____ rather than inventing new ways

Genes, principles

Genetic distance is measured in a unit named after Thomas Hunt Morgan, what is the name of this unit?

The Centi Morgan

What does one centi Morgan distance mean?

That two genes that are linked on a chromosome have a 1% chance of being separated in the progeny of an animal

What did Christiane Nusslein-Volhard and Eric Weischaus realise?

That drosophila genetics could be applied to find genes controlling development

What is meant by forward genetics?

If they are mutated they should lead to developmental defects that illustrate their function

A mutation in a gene required for head development should lead to what?

Headless embryos

Forward genetics starts with a _______, what is known and what must be determined?

Mutant, function known, gene sequence needs to be determined

What is forward genetics used for?

Positional identification/cloning

Reverse genetics starts with a _______, what is known and what must be determined?

Gene, gene sequence known, gene function needs to be determined

What is reverse genetics used for?

Gene knockout

Forward genetics is a technique that does what?

Identifies gene function fist, once you have identified an interesting gene function the responsible gene sequence needs to be identified

Researches often work backwards, if you have an interesting looking gene and want to know the function this is often done using what technologies?

Gene knockout

What does saturate screening rely on?

Statistics

What was known about saturation screening?

That treatment with DNA damaging chemicals could destroy an "average" gene with a decent frequency, for example 1 in 500

These frequencies in saturation screening can be estimated by using genes that influence what?

Eye colour

In order to make a mutation a chemical (____) was used which acts at ______, this treatment was adjusting such that an average gene would be destroyed with a chance of 1 in 500

EMS, random

So if there is one gene that is specifically required to form a head and you search 1 line = ___% of finding it, 10 lines = ____%, 100 lines = ___%, 500 lines = ____%, 1000 lines = ____%, 2000 lines = _____%

If there are 5 genes required for making a head you will find them all

0.2, 2, 19, 64, 87.5, 98

An important part of the innovation was developing methods for ______ and ______ eggs from 1000s of lines very efficiently

Keeping, screening

Flies are ____ploid

Di

What did mutant screens lead to?

Basic understanding of how genes are controlling the elaboration of a body plan

Molecular identification of many new genes and biological signalling pathways

Confirmed "genetics" as an extremely powerful way to dissect biological processes

These genes are not just important during development but often remain important throughout life during _____, ______, ______ and ______

Homeostasis, cancer, regeneration, ageing

Principles and genes identified and also the methods employed drove a lot of progress in the understanding of ...?

Human disease

The screen led to a basic understanding of the logic of how genes do what?

Pattern the developing embryo, a complex hierarchy of signalling molecules

The fly has a conveniently short life cycle of about __ days, to go from a _________ ___ of a zygote to a ________ mature adult

9, fertilised egg, sexually

Dependent on ________, flies have a maximal lifespan of around ____ days at ____

Temperature, 140, 18°C

The fly embryo develops into a larvae that hatches around ____hpf then the hatched larvae starts feeding and grows, it needs to malt __ times in order to grow because of what?

24, 2, its cuticle is rigid

The stages of a fly's life cycle are called ____, _____ and _____ instar larva, it then _____ and undergoes _______ before hatching out of the pupa as an adult fly

1st, 2nd, 3rd, pupates, metamorphosis

What is a micropyle?

A small hole in the insect egg for sperm entry

Drosophila embryos initially develop as a ______ this is very important later when what is set up?

Syncytium, A/P axis

3 hours post fertilisation the embryos consists of a single layer of cells enclosing the yolk (containing a few nuclei) at the posterior of the embryo, what is separated off and what do they form?

Pole cells are separated off which will form the germ line

The egg is fertilised through the ______, which consists of two flaps (dorsal appendages)

Micropyle

The sperm and egg nucleus fuse and then the zygotic nucleus undergoes very rapid ______, no membrane is _______ between the nuclei so the embryo is a _______

Division, formed, syncytium

After 90 minutes most of the nuclei migrate to the ______, a few cells at the end of the embryo are _______, what are these called?

Periphery, segregated, pole cells

What do pole cells do?

Form the germ line which will make the next generation

What will the membrane of the syncytial blastoderm do?

Invaginate and become enclose peripheral nuclei, thereby creating a cellular blastoderm

Once a cell has been specified to one of these fates (______, ______, _____) all dependents will ________ that fate

Mesoderm, endoderm, ectoderm, adopt

What is meant by anterior?

Head

What is meant by posterior?

Tail

What is meant by dorsal?

Back

What is meant by ventral?

Belly

What is the endoderm?

Gut

What is the mesoderm?

Muscle

What is the ectoderm?

Epidermis and nervous system

At the ______ _____ several regions can be identified

Cellular blastoderm

What is the axis nomenclature?

A/P axis, antero/posterior axis

What does the ventral region contain?

Mesoderm

What does the anterior and posterior regions contain?

Endoderm

What is the aminoserosa?

Extra embryonic tissue and will not really contribute to structures in the embryo

The embryo undergoes a complex set of cell/tissue movements, what do these movements act to do?

Bring the mesoderm and endoderm on the inside of the animal

Where does gastrulation start?

On the ventral side

Gastrulation starts with the formation of a _____ where ______ cells invaginate moving _____

Furrow, mesodermal, internally

At almost the same time as gastrulation, at the ____ and _____ end, the ______ invaginate thus the embryo is transformed from a simple single cell sheet enclosing the yolk to a ______ _____-______ structure

Anterior, posterior, endoderm, complex multi-layered

During gastrulation the ventral part of the embryo _____ pushing aside the ______, this is called ___ _____ ______, later it will _____ again and enclose the ________

Extends, aminoserosa, germ band extension, retract, aminoserosa

What becomes obvious during germ band extension?

Segmentation of the embryo

At 24h the larvae hatches and is ready to do what?

Start feeding

The correct or abnormal patterning of the embryo can be scored precisely by making ____ ____

Cuticle preps

After hatching, the larvae start _____ but as they have a ______ cuticle they need to ____ in order to ____

Feeding, rigid, malt, grow

The larval stages are named 1 instar after ______, 2nd and 3rd instar after ____ ______ _____

Hatching, each consecutive malt

At one point the 3rd instar larva forms ...?

A pupa

During pupation the larvae will do what?

Strongly change their appearance and metamorphose into the adult fly

What causes these strong changes in appearance during pupation?

Groups of cells that are set aside during early development

Where can these groups of cells that are set aside be found, what are they called?

In feeding larvae, these groups of cells are called imaginal disc and each disc will form a particular part of the fly

Which disc is most important to us and why?

The wing disc because is is often used as a very convenient tool in genetic and molecular studies to understand functions of particular cell-to-cell signalling pathways and pattering processes

Where are sperm cells formed?

In males

What do sperm cells contain and what do they do?

Germline stem cells at their tips that divide and generate progenitor cell which will divide further and over time differentiate into mature sperm

The females have ...?

Ovaries

What do ovaries consist of?

A collection of ovarioles, these overrules similarly have a gremlin stem cell located at the tip of each overiole

The gremlin stem cells are descendants of what?

Pole cells that were set aside early during development

Each end of the larva has unique structures, each segment has a characteristic pattern of ______

Denticles

Denticles have a particular ______, this allows ______ of ________ polarity in each segment

Orientation, recognition, anteroposterior

What is the screening stage?

Where embryos are analysed for patterning defects

What does this image show?

2 examples of mutant phenotypes that were found

The first is a gap gene mutant here 2 segments are missing and thoracic segment T1 is fused directly to abdominal segment 1 (A1) thus the gene mutated is required for forming segments T2 and T3

In the second mutation every other segment is missing thus this gene is required for formation of alternating segments