BIO207 Developmental Genetics

development

when a single celled zygote develops into various different differentiated cell types of an embryo

development takes place through what 3 events?

1) specification - identity of a cell is based on its genetic and positional information

2) determination - developmental state of the cell

3) differentiation - when the cell achieves full form and function

morphogens

important class of soluble molecules involved in tissue morphogenesis

autocrine

signal affects that same cell as the one producing it

paracrine

signal affects the cell in vicinity to the one producing it

morphogens are soluble signalling proteins secreted by cells that act in (blank) and (blank)

autocrine, paracrine

morphogens normally exhibit (blank), so these genes are encoded by (blank) and are deposited as mRNA or protein molecules into the oocyte cytoplasm

maternal effect, maternal genome

what are the 2 classes of genes that control embryonic development in drosophila?

1) maternal effect genes

2) zygotic genes

what are the factors of the maternal effect genes?

1) morphogens encoded by maternal genome

2) egg receives gene products from maternal nurse cells

3) helps establish the main body axis

4) codes for transcription factors

what are the factors of the zygotic genes?

1) expressed from the zygote’s own genome under the effect of transcription factors encoded by the maternal effect genes

what are the two types of zygotic genes?

a) segmentation genes - development of segmentation pattern

b) homeotic genes - determines identity of each segment

what do the maternal effect genes encode?

encodes proteins that produce the anteroposterior and dorsoventral axes

what does the maternal effect activate?

gap genes

what is the role of gap genes?

to define organs

what do gap genes produce?

produce broad bands of proteins that act as transcription factors ot activate pair-rule genes

how are pair-rules expressed?

in alternating stripes

proteins encoded by pair-rule genes regulate what?

regulates segment polarity genes

what happens at the stage of segment polarity genes?

all of the segments of the body are defined

what is a key factor for all zygotic genes?

they are required one after another since the first one acts as transcription factor for the next

why are maternal effect genes short-lived?

there is no DNA

can maternal affect have any affect on the zygotic genes?

it can only have an effect on the pair-rule genes but not beyond

what is the function of the bicoid gene?

development of the head and thorax

what is the function of the nanos gene?

development of the abdomen

the genotype of the female parent determines what in the offspring?

the phenotype

what does bicaudal mean?

two-tailed

what happens to embryos that are derived from mothers who are homozygous?

the embryos fail to develop anterior areas that normally give rise

what happens to embryos whose mothers contain at least one wild-type, regardless if the genotype embryo is homozygous?

it will still develop normally

what happens to embryos that are derived from bcd- mothers?

those embryos will fail to develop anterior structures

what will happen to the embryos derived from nanos- mothers?

those embryos will fail to develop posterior structures

what does the expression of gap genes help define?

head, thorax and abdomen

what are some examples of gap genes?

hunchback, krupper and knirps

what are hunchback genes under the influence of?

they are under the influence bicoid genes

where are bicoid genes expressed and what is the function?

expressed in the ovary and regulates the expression of genes responsible for anterior structures and stimulates the hunchback

where is the nanos genes expressed and what is the function?

expressed in the ovary and regulates the expression of genes responsible for posterior structures and inhibits translation of hunchback mRNA

where is the hunchback gene expressed and what is the function?

in the embryo and regulates transcription of genes responsible for anterior structures

(blank) arise first, while segments form later

parasegments

what are the 2 pair-rule genes?

fushi-tarazu and even-paired genes

how are fushi-tarazu and even-paired genes expressed?

expressed in an alternating stripes pattern and forms parasegments

what do segment polarity genes establish?

the anterior-posterior axis of each parasegment

what are segment-polarity genes responsible for?

the formation of segmental boundaries

how are anterior and posterior boundaries of parasegments defined?

defined by narrow stripes of cells expressing the segment polarity genes

why do ftz and eve genes act together for the posterior part?

to repress wingless gene expression and allows it to be expressed in narrow stripes

what do the stripes of cells expressing wingless genes define?

defines the posterior part of each segment

why do ftz and eve act together for the anterior part?

act as activators of engrailed gene expression

what do the stripes of cells expressing engrailed genes define?

defines the anterior part of each parasegment

what are homeotic genes?

genes that encode proteins that specify identity to each segment of structure of the body

what do homeotic genes direct?

direct cells to form various parts of the body

what happens to the antennapedia mutant fly?

the antennae are replaced by legs in the fly

what happens in the bithorax mutation?

the fly gets 2 thorax segments and has reduced abdominwhtal segments

what are arabidopopsis flowers composed of?

4 concentric whorls of floral organs

what does each whorl contain?

whorl 1- 4 septals

whorl 2 - 4 petals

whorl 3- 6 stamens

whorl 4 - one pistil generated by the fusion of 2 carpels

what happens between class a and class c?

they inhibit each other’s expression

what must be required for classes a,b, and c?

class e must be required or none of the classes can be expressed on their own