chapter 13-genetic control of development

Genetics 380 with Sinha at Rutgers University - New Brunswick/Piscataway

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By: Bhumika Patel
Textbook:

Genetics: Analysis of Genes and Genomes
Created: 2011-05-02
Size: 36 flashcards
Views: 89

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fertilized egg is totipotent?

capable of making all possible organs and tissues
**divides into 2, 4, 8
**descendent cells become less and less capable

pattern formation

emergence of spatially organized and specialized cells that form the embryo form cell division and differentiation of the fertilized egg

development

a program that results in the specific expression of some genes in one cell and not in another
**cell progressively appear that differ qualitatively in the genes that are expressed

positional information

fates that a cell can take is determined partly by its location in the developing embryo

polar or nonpolar egg prior to fertilization?

polar
**cytoplasm in the front end is different from that in the rear end

blastula stage

after fertilization, zygote undergoes a series of rapid division creating a ball of cells with a hollow space inside

gastrula

after the blastula stage, the surface undergoes invagination (folding) creating multiple layers and some cells move into the space inside creating this

nurse cells

helper cells connected to the oocyte by cytoplasmic channels

why is development in Drosophilas studied?

many of the genes involved in fly development have homologs in humans that play similar roles

genetic control of development in Drsophila

**3 larval + a pupa stage = adult fly = 10 days

**(1) 9 rapid nuclear divisions = syncytium
(2) 10 germ line precursor cells cut off at posterior end = becomes somatic cells
(3) 3 nuclear division = 2000 nuclei created
(4) membranes formed creating blastoderm

syncytium

multinucleate bag
* 9 rapid nuclear division without septa formation forms this

blastoderm

membranes are formed creating a monolayer of cells at the surface

maternal effect genes

the genes that are active in the mother during the creation of the egg (oocyte)
**establishes polarity of the egg before fertilization takes place
** determines the basic body plan of the embryo

zygotic genes

genes that function in the embryo
**these interpret and respond to positional information laid out in the egg by maternal effect genes

what is meant by polarity established by maternal effect genes?

**m/m females x +/+ males -> +/m progeny (abnormal embryo development due to defective maternal products in the egg)

**+/+ females x m/m males -> +/m progeny (normal embryo development due to normal maternal products in the egg)

** even thought genotypes are the same in the zygotes, developmental outcomes = diff b/c of nature of mRNA stored in the egg by the mothers

segmentation genes

genes that control the correct development of the segments; further subclassified into: (1) co-ordinate genes, (2) gap genes (3) pair-rule genes (4) segment polarity genes

co-ordinate genes

these genes set up the polarity of the embryo (anterior vs. posterior and dorsal vs. ventral)
** 3 kinds of mutants: anterior, posterior, and terminal for anterior-posterior axis determination and 4th set of genes -> dorsal-ventral axis

**mutants in anterior genes affect head+thorax
**mutants in bicoid gene are lacking head + thorax

bicoid

codes for transcription factor (helix-turn-helix; similar to lac repressor and CAP proteins of the lac operon in its DNA-binding domain)
**activates genes needed for the development of the anterior structures

posterior

mutations in these genes affect abdominal segments (may/may not affect pole cells destined to become germ cells)
*EX: gene nanos

terminal

mutants in these genes affect both the front and rear end
*EX: gene torso

dorsal-ventral axis determination

products of these gens are distributed in dorsal-ventral gradient
*key gene = dorsal

gap-genes

*mutations in them result in loss of segments in the adult body plan
**they are zygotic genes (mRNA is not prestored in the egg)
**EX: hunchback and kruppel code for transcription factors of the zinc-finger type

pair-rule genes

mutants in these are missing alternating segments of the body
**EX: hairy expressed in 7 striped in the early embryo

segment-polarity gene

**these determine polarity of a segment (14 such genes known)
** mutants have reversal of polarity in segments (anterior becomes posterior and posterior becomes anterior in segment after segment)
**EX: engrailed

imaginal disks

20 group of cells

** these are the ones that ultimate organs develop from and set aside in early development

homeotic genes

*control the specification of the fate of a segment/parasegment
*control rates of cell division, planes of cell division and capacity to differentiate into legs, bristles, wings etc

**mutations in them transform one body segment to another

homeobox

DNA sequence found within genes that are involved in the regulation of development (morphogenesis) of animals, fungi and plants
**genes with homeobox = homeobox genes and form homeobox gene family

**discovered by Walter Gehring + colleagues

Hox genes

particular subgroup of homeobox genes
**found in a special gene cluster, the Hox cluster
**function in patterning the body axis
**by providing the ID of particular body regions, Hox genes determine where limbs and other body segments will grow in a developing fetus or larva

mutation in hox genes =?

growth of extra, typically non functional body parts in invertebrates
**MISCARRIAGES usually occur

linear regulatory pathway

**genes are either activators or repressors wchih control other regulatory genes and many structural genes

if 2 mutants are combined to make 1-b- double mutant

a = having to low expression
b=having a too high expression phenotype
**one of the genes will be epistatic (the one that acts later in the pathway)
**the other one hypostatic (the one that acts earlier)
**so total expression = too low expression...b first then a later

lactose operon: i-, z-polar double mutant

**uninducible
**the step affected z-polar occurs later than the step affected in i-
**repressor is either produced earlier or not produced

o^c, z-polar

uninducible
**structural protein synthesis occurs later than the repressor-operator interaction step

vulva in caenorhabditis elegans

either vulvaless (too little activity) or multivulva (too much activity)

About this deck

By: Bhumika Patel
Textbook:

Genetics: Analysis of Genes and Genomes
Created: 2011-05-02
Size: 36 flashcards
Views: 89

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis