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Genetics > Week 8 > Flashcards

Week 8 Flashcards

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Biology 101 flashcards
1
Q

Epistasis

A

Epistatic interactions are assyed by comparing the phenotype of a double mutant organism with that of the singly mutant organism

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2
Q

Epistasis criteria for the two mutations

A

Have related phenotypes

  • growth control
  • sex determination
  • dorsal ventral axis determination

Work on a pathway that makes a distinct decision

  • growth/non-growth
  • male/female
  • expression/non-expression

The two mutation have distinct/opposite phenotypes

  • all males versus all females
  • expression always ON versus always OFF
  • Ventrilized versus dorsalized
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3
Q

Reproduction and cell phenotypes

A

Sperm fertilizes an egg forming the zygote and zygotic genome. The cells divide, during early division the maternal information coming form the maternal genome is important.

zygote starts out as totipotent but as the cells divide they become differentiated into specific cell types

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4
Q

Order of differentiation

A

Pluripotent cell undergoes determination to become a determined cell the determined cell will differentiate into a differentiated cell with a distinct identity (has an identity now we can excute to give rise to a cell with the identity)

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5
Q

Body plan

A

Anterior posterior axis
the body plan is where cells will end up in the fully developed organisms

the cells are being assigned identities

this nucleus divides

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6
Q

The nucleus divides

A

This gives rise to a single layer of cells called the blastoderm (5,000 cells) monolayer of periphery cells.

at this stage the cells know exactly what they are going to become

the anterior posterior axis has already been determined

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7
Q

Number of genes involved in the body plan

A

120 genes associated with the determination of the anterior posterior axis is the segmentation of the body plan

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8
Q

Genetic hierarchy regulating determination of the A-P

A

Maternal coordinate genes (bicoid and nanos)

Zygotic Gap genes (hunchback)

Pair rule genes (fushi tarazu)

Segment polarity genes

Homeotic selector genes antennapedia

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9
Q

Maternal coordinate genes

A

determines the development of the axis

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10
Q

Zygotic gap genes

A

regulates the expression of pair ruled genes

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11
Q

Pair rule genes

A

determine the number of segments that will form

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12
Q

Segment polarity genes

A

patterns the axis within each segment

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13
Q

Homeotic selector gene

A

determine what the segments will become

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14
Q

Maternal to zygotic genome (humans)

A

transition form a developmental program being run off of information provided by the maternal genome and placed in the egg to the information that’s going to be expressed from the zygotic genome

transition occurs at the first cleavage cycles

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15
Q

Maternal to zygotic genome (drosophila)

A

transition occurs at the blastoderm stage

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16
Q

Maternal effect screens

A

Create larvae that are homozygous for a DNA seuqence change and ask whether the DNA seuqence change affects the development of the zygote.

in a maternal screen establish a homozygous mother who cannot pass down info to her progeny

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17
Q

Generation timing of maternal effect screen vs zygotic screen

A

Maternal screen: F4 embryo/ F3 homozygous mother

Zygotic screen: F3 dead embryo

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18
Q

bcd/bcd mother vs bcd/bcd (lf)

A

bcd/bcd mother normal egg

bcd/bcd (lf) larva missing a head

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19
Q

Body plan and the anterior posterior axis

A

coordinate genes determine the basis axis of the head.

bicoid mRNA is located at the future anterior end of the egg, nanos is at the posterior end

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20
Q

Nanos located in the posterior end

A

Nanos is required to surpress HB protein expression.

HB is present in the anterior end

nanos (lf) results in HB being expressed in both axis: development of larvae lacking abdominal segments

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20
Q

Nanos located in the posterior end

A

Nanos is required to surpress HB protein expression.

HB is present in the anterior end

nanos (lf) results in HB being expressed in both axis: development of larvae lacking abdominal segments

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21
Q

Bicoid transcription factor activates zygotic HB expression

A

Encodes a transcription factor that binds to DNA binding sites of the hunchback protein

22
Q

Dual regulation

A

Bicoid increases HB expression in the anterior portion of the cell by activating zygotic expression.

Nanos surpresses the expression of hunchback form a messenger RNA deposited by the mother.

23
Q

Gap genes

A

first genes zygotically expressed

maternal affect gene determine the axis. They interact with gap genes that are expressed in broad domains of the cell

they determine other large developmental domains of the body plan, they tell the cells to become a specific segment

24
Q

Gap genes (mutation)

A

Lf mutations in gap genes results in deletion of segments

In gap lf mutants, contiguous set of segments

25
Q

Gap genes….

A

Encode transcription factors defining broad regions of the body plan, this expression pattern defines large domains along the anterior-posterior axis.

Gap TFs regulates the expression of other gap genes and the expression of pair rule genes

26
Q

Kruppel and Knirps

A

Knirps regulates expression of Kruppel

26
Q

Kruppel and Knirps

A

Knirps regulates expression of Kruppel

27
Q

Pair-rule genes

A 
segment the body plan
expressed from the zygotic genome
encode transcription factors
pair-rule proteins define the segments of the body plan
very specific pattern of expression
28
Q

Pair rule gene (lf)

A

portion of every other segment is missing.
alternative deletion of segments. the segments deleted are the segments the pair-rule gene is expressed

regulate pair rule genes and segment polarity genes

29
Q

Segment Polarity genes

A

pattern the segments

expressed from the zygotic genome

expressed in every segment

segment polarity proteins pattern the structure of every segment

30
Q

segment polarity genes (lf)

A

every segment is present and every segment is defective. anterioir posterior polarity within a segmnet is often affected

parts of the segment are deleted and duplicated

31
Q

Why do the segments look different from one another

A

homeosis: the transformation of one body part into the likeness of another

homeotic selector gene

32
Q

Antennapedia

A

a switch for antenna versus leg development

WT: antennapedia is expressed in leg primordia

Antp(lf): no antennapedia resulting in legs becoming antenna

Antp(gf): antenna results in antenna becoming legs

This tells us that the atennapedia gene encodes a factor important for leg development but is not important to tell other cells to become a leg.

33
Q

Proboscipedia

A

homeotic selector genes are switch genes, Pb lf results in the transformation of the feeding tube into a pair of tarci, no proboscic and no supression of development of tarsus

34
Q

The origin of animals and relationship between animal groups

A

look for evidence in the fossil record

porifera: sponges

sponge genome is the second closest to the most recent common ancestor

spongest are the base group of animals

35
Q

Hypothesis

A

what the most recent common ancestor looked like and what machinery did this ancient animal have that allowed the diversification into all these animal gorups

36
Q

Animal phylogeny

A

Placozoa (two layers of cells)

difficult to group organism based on morphology

bilaterians: symmetric; head and tail; axis of symmetry

more related to starfish

37
Q

Common ancestor of bilaterians

A

Urbilateria

had all the genetic machinery we consider in terms of the body plan; axis and organs

38
Q

a complex organism existed at the proteosome deutorostome split

A

complex machinery of developmental pathways back 650,000,000 years ago. it had the complex machinery to set up a central nerovus system, segmentation, regionlized gut, primitive heart and eyes, as well as body out growths

39
Q

Experimental/Observational approach of evo/devo

A

conservation of structure: similar amino acid sequence
conservation of expression: genes of different organisms expressed similarly
conservation of requirement: are the different genes required for similar things
conservation of function (functional equivalence): can i take one gene in one organism and replace it in another and have that work

40
Q

Conservation of sequence (eyeless and pax6)

A

eyeless proteins in drosophila are very similar in sequence to the Pax6 protein in vertebrates

41
Q

Conservation of expression (eyeless and Pax6)

A

expression of eyeless and pax6 occurs in group of cells that give rise to the eye

42
Q

phyogenetic comparison of expression

A

expressed in the tissues that give rise to an array of photoreceptors

43
Q

Conservation of requirement

A

Eyeless is required for drosophila eye development

800 facet with photoreceptor

compund eye is reduced in drosophila with no eyeless gene

Pax6 is required for mouse eye development; homozygous knockout leads to no eye development

44
Q

Aniridia

A

Mutantions in human Pax6 result it aniridia; lack of an iris when heterozygous

the functional allele shows haploinsufficiency resulting in a missing iris.

45
Q

Conservation of function (functional equivalence)

A

take the eyeless gene and place it in a vertebrate to see if there is the formation of the vertebrat eye; express eyeless gene in other parts of the body

46
Q

UAS GAL4 ectopic expression system

A

Take a yeast transcription factor and placed it in drosophila, seperate gal4 expression from the uasgal4 which is this cis element upon which gal4 will bind to activate transcription of galactose gene.

we get extopic expression only when when we bring them together

47
Q

Binary or two component system

A

Fly stock A: UAS line; GAL4 bindging sites UASGAL4 next to YFG

Fly stock B: Driver line; enhancer and GAL4 gene that expresses the GAL4 activation/DNA binding domain proteins

mate the flies togehter in cells of the progeny where both genes are expressed you get ectopic expression of your gene

48
Q

Why a 2 component system

A

The ectopic expression of the gene may be lethal so are able to establish the UAS stock first with no expression

Expression occurs only after we have crossed the UAS line with GAL4 driver line

49
Q

Ectopic expression of eyeless

A

Induces ectopic eye formation
expression of eyeless in cells other than the eye
wherever gal4 is expressed we see the formation of eye tissue

50
Q

Expressing Pax6

A

Create a UAS that contains the UAS dused to mouse Pax6

induction of ectopic eyes

Pax6 from mice and eyeless can both induce ectopic eye formation in drosophila indicating the mouse pax6 is functionally equivalent to drosophila eyeless function

51
Q

Urbiletaria

A

experiments conclude that urbilaterian had a complicated set of geentic pathways that controlled the development of the primitive eye, heart structures, cns, segmentation, body wall out growth, body plan and throughoutput cut

this common ancestor radiated through divergence to create all of the biletarian organism

Genetics (16 decks)

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