Regulation genetic Flashcards

Question

Variegated eyes in Drosophila

Answer 1

Herman Muller(1946 Nobel prize) Wild type red eye w+/w+ white eye w-/w- X-ray mutagenesis lead to mosaic white eye w+/w+ The position of the white locus, but not the genotype, has changed

Answer 2

Eukaryotic DNA is packaged into chromatin 150 bp DNA per nucleosome around 8 subunit 4 type Different regions of the chromosome have different chromatin structure Least condensed euchromatins to heterochrome most condense

Answer 3

-Histonine have many tails which can be modified Post-translational modification of lysines in histone tails by: • Histone deactylases (HDACs) condense • Histone acetyltransferases (HATs) relax • And others...

Answer 4

Mig1 is a DNA-binding protein (repressor of GAL1) bind to mig1 binding site Tup1 is a co-repressor, which recruits an HDAC > Histone deactylation condenses chromatin around GAL1

Answer 5

Nucleosomes are not fixed in position so DNA can slide back and forth -when the promoter is hidden by the nucleosome, it is inactive Shifting of nucleosomes can expose regulatory elements

Answer 6

-The post-translational modifications of histones defines the histone code -the state of chromatin are preserved after replication àChromatin state can be inherited (epigenetic inheritance)

Answer 7

-Mating requires the fusion of two haploid yeast cells Two mating types: ‘a’ and ‘⍺' which can be express to determine the gender of the spore -Haploid cells are able to switch mating type This is controlled by the MAT locus (can switch around)

Answer 8

MATa and MAT⍺encode transcriptional regulators of mating-type genes eg, pheromones production, pheromone receptors etc. MAT locus is flanked by transcriptionally silenced copies of MATa(HMRa) and MAT⍺ (HML⍺) During mating-type switching, the silent copies are transferred into the MAT locus by recombination silent information regulator (sir) mutants (affect the chromosomal structure) express both a and ⍺genes, mutants are sterile Sir2 is a HDAC histone deacetylation condenses chromatin

Answer 9

Two genetic screens in yeast identified mutants in the same locus switch (swi) – unable to switch mating type sucrose non-fermenting (snf) – cannot grow well on sucrose-media swi2/snf2 mutants • could not grow on sucrose, could not switch mating type • Swi2/Snf2 protein is part of the SWI-SNF complex > Required for gene activation by chromatin remodelling

Answer 10

TATA sequences is wrapped around nucleosome > RNA polymerase cannot access promoter SWI-SNF complex associates with promoter, Shifts nucleosomes, using ATP TATA sequence now accessible,RNA polymerase can initiate transcription

Answer 11

Inversion positions white locus near heterochromatin (centromere) àHeterochromatin spreads over to silence the white+ geneThis is called position-effect variegation (PEV)

Answer 12

Barrier insulators prevent spreading of heterochromatin. it is at the edge of heterochromatin and recruit HAT maintain euchromatin by localised histone acetylation

Answer 13

-another way of controlling gene expression | ~ 80% cellular energy is dedicated to protein synthesis

Answer 14

1. 5’-cap recognition -Cap-dependent initiation of translation in eukaryotes, eIF4E bind to the G7m 5' and recruit other IF, turn into eIF4F -eIF4F complex recruits small ribosomal subunit 2. Met-tRNAi eIF2 is required to place the Met-tRNAiin the P Site

Answer 15

- extract from Streptomyces hygroscopicus in easter island -have anti fungal property useful in • Immunosuppressant • Cancer treatment • Ageing

Answer 16

WT is unable to grow on Rapamycine, tor1 mutant able to | tor1 is a mutant of mTOR, a kinase protein (involve in modification of other protein)

Answer 17

-4E-Binding Protein prevents formation of eIF4F complex, -Blocks initiation of translation on nutrient rich situation: -mTOR is activated, 4EBP is phosphorylase Phosphorylation of 4E-BP by mTOR prevents binding to eIF4E ->cap-dependent initiation of translation proceeds In lo nutrition condition, mTOR is inactive, 4eBP is not phosphorilised and bind to eIF4E, prevent translation mTOR is a global regulator of translation

Answer 18

-DURING STRAVATION OF AMINO ACID, GCN4( increase in amino acid generation) and GCN2 (inhibition of translation ) is recruited Phosphorylation of eIF2 by GCN2 inhibits the formation of Met-tRNAi Reduced availability of Met-tRNAiinhibits initiation of translation

Answer 19

- transcription regulator must be transport in or out of the nucleus to assume their function -nuclear localisation sequence (NLS) is regconise by importins which trnasport it pass the nuclear pore complex, into the nucleus (found in the internal of the protein) nuclear export sequence (NES) is regconised by exportin which transport it out

Answer 20

GR is a enhancer which need to bind to the active binding site for gene expression In the absence of steroid, glucocorticoid receptor (GR) is bound to HSP90 in the cytoplasmIn the presence of steroid, HSP90 is displaced to reveal NLS, recognised by importin In the nucleus, GR binds to glucocorticoid response elements (GRE) to activate transcription

Answer 21

Ubiquitination is a eukaryote-specific post-translational modification - when a protein need to be removed, ubiqitine bind to it forming a ubiqutine chain. Ubiquitin is added to proteins by a ubiquitin ligase - the ubiquinated protein is then degrade by 26s proteasome

Answer 22

Levels of cyclin proteins are regulated through cell cycle progression Anaphase-promoting complex (APC/C) is a ubiquitin ligase which add Uq to cyclin

Answer 23

Some animal have direct development from their juvenile form into adult form ( growth) other have drastic change from their juvenile form to adult form metamorphosis

Answer 24

- egg is fertilized by the sperm into a blastocyte - Series of rapid cell divisions into blastula (Cleavage) - Cells move inwards to generate a multilayered embryo know as Gastrula (Gastrulation() - Formation of the tissues, organs and structures of the body (organogesesis)

Answer 25

Four distinct but overlapping processes occurring during embryogenesis Determination, Morphogenesis, Differentiation and Growth

Answer 26

Determination – establishment of the fate of a cell before specialised characteristics have developed

Answer 27

Cellular activities during embryogenesis: cells divide, move around, change shape and come together to form functional units (organs) Collectively these cellular activities are called morphogenesis Process that generates the structures of an organism (tissues and organs) – controls the spatial distribution of cells in the developing organism

Answer 28

Differentiation – process by which cells acquire their distinct characteristics and functions Associated with differences in gene expression House-keeping Expressed in all cells Cell specific Expressed in some cells

Answer 29

Homeotic mutants display homeosis – replacementof one body part by another （ultrabithorax antennapedia -occur in determination

Answer 30

Oraganisers is a cell that establish the idendity of nearby cell transplatn of organiser can have drastic effect on the embryo -transplant of organiser from the endoderm to ectoderm result in conjoined zebra fish -transplat of ZPA from anterior to posterior lead to extra digit in chicken

Answer 31

* Small gene size * Short generation time and large amount of offspring * Developmental mutants easy to observe

Answer 32

- flower first from different layer of swril and each swril develop into different organ/structure - mutant develop all swril into one structure

Answer 33

Zebrafish embryogenesis is fast and visualised in vitro - use to infer for vertabrate - see through embryo and newvborn

Answer 34

It is possible to follow the fate of every cells in nematode embryogenesis >generate a lineage map Cells become progressively more restricted in cell fate as development proceeds Position 1 = Zygote gives rise to 7 different cell types Position 2 = EMS cell gives rise to 5 different cell types Position 3 = C cell gives rise to 3 different cell types Establishment of cell fate involves changes in gene expression that allow a cell to proceed down one of a series of alternative pathways

Answer 35

Early embryogenesis is highly similar in vertebrates (and invertebrates) This ‘modularity’ facilitates evolution of body parts/organs

Answer 36

Homeotic genes are expressed in specific spatial domains and determine identity of body parts

Answer 37

Regulatory genes genes that control expression of other genes (e.g. transcription factors, signalling proteins) These genes play a major role in determination Effector genes genes that determine properties of the cell (e.g. cytoskeletal proteins, trafficking proteins, adhesion molecules etc.) These genes play a major role in morphogenesis and differentiation

Answer 38

Spatial domains express distinct sets of genes in an organised manner Groups of cells (called organisers) influence gene expression in other groups of cells Without cell communication, organisation is lost

Answer 39

Cells separated by plasma membranes must communicate through extracellular molecules –ligands Ligands bind to and activate receptors on another cell . Active the receptor leading to phosporilasation of TF leading to active or inactive. cis regulation

Answer 40

from head to tail is anterior - posterior from front to back is dorsal ventral z axis is mediolateral

Answer 41

Cells along the dorsoventral axis express genes depending on their relative spatial positions within the embryo from dorsal to ventral: ZEN,DPP, THISBE, TWIST

Answer 42

Twist is expressed in ventral cells and promotes furrow formation

Answer 43

1. Establish a morphogen concentration gradient 2. Cells perceive morphogen conveys positional information via concentration 3. Cell fate established according to positionpattern formation in response to morphogen concentration

Answer 44

Different genes expressed in response to specific concentrations of the morphogen Threshold concentrations mark the transition from one pattern of gene expression to another

Answer 45

Positional information along the dorsoventral axis is generated by a gradient of nuclear-localised Dorsal morphogen – determined by an external signal

Answer 46

Transcriptional activity of genes respond to different concentrations of Dorsal twist has an upstream cis-acting regulatory element (enhancer)with two low-affinity Dorsal binding sites >twist expression is activated in the ventral region of the embryo where there is a high conc. of Dorsal -thisbe has upstream cis-acting regulatory elements (enhancer)with three high-affinity Dorsal binding sites àthisbe expression is activated in the lateral region of the embryo where there is an intermediate conc. of Dorsal

Answer 47

Twist is a transcription factor àRegulates 100s genes ONE OF THEM IS FOG promotes apical constriction àVentral furrow formation

Answer 48

Fog is secreted from the apical side of cells àmyosin contraction and apical constriction

Answer 49

Maternal effect genes > Establish anteroposterior axis Gap genes > Formation of block of segments Pair-rule genes > Segment periodicity (marking of segment) Segmentation-polarity genes > Patterning within segments Homeotic genes > Fate determination

Answer 50

mutation of gap gene lead to kruppel, lack large segment of embryo (posterior region) Pair-rule genes have either evenskip or odd skip mutation ( lack segment at odd/even) mutation in segment polarity lead to goosberry mutant, iregualr polarity all are lethal

Answer 51

bicoid mRNA is produced in the nurse cells of the egg chamber and is deposited into the oocyte bicoid mRNA is anchored at the anterior end of the egg. Bicoid marks the anterior end of the developing egg

Answer 52

Early stages of embryogenesis – all nuclei contained within one cytoplasm – a syncitium When bicoid mRNA is translated, Bicoid protein diffuses to form a concentration gradient zygote post fetalization is immunolocalization (many nuclei in one cell) Maternal-acting gene bicoid encodes a transcription factor

Answer 53

Gap genes are expressed in specific regions along the anteroposterior axis Gap genes are regulated by the maternal-effect genes present in the anterior and posterior regions of the embryo (e.g. Bicoid) Gap genes also regulate each other (e.g. Hunchback)

Answer 54

The Gap gene hunchback is activated by Bicoid The hunchback promoter has three Bicoid binding sites Hunchback active in anterior region where there are high levels of Bicoid Sharp posterior boundary might arise from a threshold -when a reporter gene is added to measure the effect of mutant, the less bicoid binding site, the smaller affected area

Answer 55

Hunchback is an activator of Krüppel But high levels of Hunchback are associated with a lack of Krüppel expression Gap genes can also restrict each others expression domains through repression Giant and Knirps repress Krüppel High Hunchback concentration activates Giant Giant represses Krüppel.

Answer 56

there are 14 segement , the dorsal are fushi tarazu(ftz) while the anterior is even-skipped (eve) Expressed in a periodic pattern: 7 alternating transverse stripes - every second segment

Answer 57

-it is regulated by both maternal gene and gap gene

Answer 58

cis-acting regulatory elements of eve, different stripe are coded separately Stripes turned on one by one – independently regulated on the stripe 2 enhancer sequence, there is 5 acitivator sequnece for bicoid and 1 for hunch back. ontop of that there is 3 krippple and giant binding site (repressor)

Answer 59

``` Homeotic genes in Drosophila Conserved homeobox (Hox) transcription factors, 8 in drosophilla with distinct pattern of expression along to anterior - posterior but not segment related ```

Answer 60

Ubx regulate Distal-less (Dll) is a Hox target gene > promotes the formation of appendages (eg. limbs). each segment is mark by enrail (segement polarity) - mutation in Ubx lead to Dll express in A1 - mutation in both Ubx and abd-A lead to mutation in most of the abdomen => both gene work to control dll - mutation in engrail sequence prevent the binding of regulatory gene can also lead to mutation

Answer 61

``` In dipteran (fly) wg and DSRF gene is bind by Ubx > one pair of wing in lepidopteran (buterfly) Ubx cis-elements in target genes are absent ```

Answer 62

Hox genes are present throughout the animal kingdom Many have almost identical AA in the homeodomain These animals last shared a common ancestor over 500 mya Chicken Hox genes can perform the function of fly Hox genes

Answer 63

- expasion in number of copies (4) and gene loss lead to 39 hox gene - retain the arrangement of gene in the chromosome - genome order of hox gene still similar eventhough does not develop segmently - hox 1,3,4 in anteior while hox 8-13 in posterior

Answer 64

hox10 mutant Lumbar >thoracic (thorax should end at t13) hox11 mutant Sacral >lumbar Hox10 and Hox11 act in posterior segments to repress (more) anterior identity

Answer 65

-during the 4 cell stage :anterior ABa, ABp, P2, EMS posterior -glp-1 mRNA is present in all cells at four-cell stage BUT GLP-1 protein is only present in ABa/ABp cells Spatial Control Region (SCR) in glp-1 3’UTR is required for repression of GLP-1 in EMS and P2 (posterior) cells Translational repression of GLP-1 in EMS and P2 also requires Gld-1 GLD-1 expression is high in posterior cells, and associates with glp-1 3’UTR

Regulation genetic Flashcards

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