ch 21

Question 1

genetic equivalence

Answer 1

• all cells in an organism contain the same genes
• clones are evidence for this

Question 2

how was Dolly cloned?

Answer 2

somatic cell nuclear transfer (SCNT):
1) one sheep mother donates mammary cells the other donates egg cell
2) fuse these cells together
3) the mammary gland cell’s nucleus is now in the egg cell
4) grow in culture to form embryo
5) implant early embryo in uterus of another sheep
6) embryo develops identically genetically to mammary cell donor that is also fertile
most attempts fail for cloning

Question 3

adult stem cells

Answer 3

• can only produce a limited subset of cells
• the source of cells needed to replace cells that die or are lost
• found in stem cell niches which keep them from differentiating

Question 4

hierarchical differentiation

Answer 4

1) undifferentiated cell produces daughter cells
2) these daughter cells commit to follow different paths of differentiation
3) these daughter cells produce more specialized cells until terminally differentiated cells are created

Question 5

terminally differentiated

Answer 5

• all the defining characteristics of a specific type of muscle, nerve, or skin cell are in place
• all specialized properties acquired
• typically can’t divide anymore, thus necessitating adult stem cells

Question 6

what causes a cell to commit to a developmental pathway?

Answer 6

epigenetic changes:
once gene expression patterns that determine a cell type are in place, these patterns are difficult to reverse

Question 7

tumor cells and differentiation

Answer 7

some scientists hypothesize that tumor cells actually revert back to a less mature, more undifferentiated state because they migrate, divide rapidly, and lose some specialized properties

Question 8

myoblasts

Answer 8

embryonic cells committed to becoming muscular cells

Question 9

how do myoblasts know to become muscle cells?

Answer 9

1) isolate mRNAs from myoblasts
2) convert mRNAs to cDNAs using reverse transcriptase
3) attach general promoters to cDNAs
4) introduce these cDNAs into non-muscle cells
5) these cells begin to produce muscle-specific proteins

Question 10

master regulator

Answer 10

• a gene product that can unleash a series of events that produce a specialized cell type/tissue/body structure
• ex: MyoD in myoblasts
• less prevalent than combinatorial control
• specific to a cell type

Question 11

combinatorial control

Answer 11

• a unique combination of regulators like multiple transcription factors determine a biological outcome
• allows for a smaller amount of regulators to achieve many outcomes
• can create many different specialized cell types

Question 12

pluripotency

Answer 12

the potential for embryonic cells to form any type of cell in the body

Question 13

iPS cells (induced pluripotent stem cells)

Answer 13

• created with a combo of 4 transcription factors
• causes some differentiated adult cells to de-differentiate and return to embryonic stem cell state

Question 14

how is a cell’s fate specified?

Answer 14

cytoplasmic determinants and induction

Question 15

cytoplasmic determinants

Answer 15

gene regulatory molecules that are signals present in the cytoplasm of a dividing cell

Question 16

induction

Answer 16

• works through external signals
• a cell that receives a signal is prompted to follow a different pathway of differentiation
• may be diffusible signals secreted by other cells
• may be present on the surface of one cell that contacts and consequently signals another cell
• may be anchored in the extracellular matrix

Question 17

gastrulation

Answer 17

during development cells in different parts of the mass rearrange into three distinct layers which lead into the specific parts of the body like the skin or stomach

Question 18

anterior-posterior axis

Answer 18

head to tail

Question 19

dorsal-ventral axis

Answer 19

back to stomach

Question 20

left to right axis

Answer 20

literally just left to right man idk

Question 21

pattern formation

Answer 21

• events that determine the spatial organization of cells in an embryo
• if a molecule signals that a target cell is in the anterior or posterior, dorsal or ventral side, left or right, in an embryo then that molec is part of pattern formation
• many of these molecs involved exist in a concentration gradient

Question 22

morphogen

Answer 22

• a molec that exists in a concentration gradient and provides spatial info to embryonic cells
• embryonic cells detect different concentrations and use this to determine their location
• high concentrations are near the source of the molec and low concentrations are farther away
• set up the three axes of the body
• major axes set up first
• Genes activated by morphogens generate signals that
  provide more specific information about cell location

Question 23

maternal effect mutations

Answer 23

mutation in a female parent that changes phenotype of offspring but no phenotype change in mother

Question 24

segments

Answer 24

• well-defined body region that is repeated along the anterior-posterior axis
• built in set of repeating units that produce distinct body structures

Question 25

bicoid

Answer 25

- "two-tailed", head was missing from a fly larva - morphogen that tells what should be developed in anterior, abundant in anterior and low concentration in posterior

Question 26

genetic regulatory cascade

Answer 26

- a set of linked regulatory genes in which one initially activated gene turns on the expression of other regulatory genes which then triggers even MORE regulatory genes WHICH THEN TRIGGERS EVEN MO- - each level of the cascade provides more info abt where the cell is located and what it should become in the embryo

Question 27

genetic regulatory cascade order

Answer 27

1) maternal effect genes 2) gap genes 3) pair-rule genes 4) segment polarity genes 5) hox genes 6) effector genes

Question 28

maternal effect genes

Answer 28

- morphogens that define the anterior-posterior axis of early embryo - ex: bicoid

Question 29

gap genes

Answer 29

- expressed under the control of maternal effect morphogens - mark our large, coarse subdivisions along anterior-posterior axis

Question 30

pair-rule genes

Answer 30

- expressed in response to gap gene products - expressed in alternating bands - each band roughly corresponds to a body segment that is forming along the embryo

Question 31

segment polarity genes

Answer 31

- turned on by pair-rule genes - expressed in a portion of each segment - define front, middle, and rear subregions within segments

Question 32

hox genes

Answer 32

- activated by gene products at many different levels of the regulatory cascade - specify what type of adult structure will develop from each segment in the mature organism - code for transcription factors w a dna binding sequence called a homeobox - the order of hox genes along a chromosome correspond to the order of where the genes are expressed along the anterior-posterior axis - similar order in many organisms--hox clusters are homologous (from a common ancestor)

Question 33

effector genes

Answer 33

- activated by hox gene products and works w segment polarity and pair-rule products - genes upstream of effector genes=managers that are involved in regulation - execute processes like cell proliferation, cell movement, cell-cell interactions, programmed cell death, and differentiation

Question 34

homeobox

Answer 34

conserved dna sequence that codes for dna-binding domain of a Hox-encoded transcription factor

Question 35

homeotic mutations

Answer 35

a mutation that causes one part of the body to be substituted for another (homeosis)

Question 36

tool-kit genes

Answer 36

- conserved sets of genes that encode for signal proteins, signal-transduction pathway components, and transcription factors that direct related aspects of development in many different species - establishes body plan - includes Hox genes - Mutations allow tool-kit genes to be used in new ways in different species – ex: similar genes help form bat wings and whale flippers – ex: fish gills and mammal outer ears

Question 37

SHH (sonic hedgehog gene)

Answer 37

- important for limb development - stupid ass name are we kidding - knocking out this gene serpentized them (limbless) - how snakes lost limbs by losing this gene - tool-kit gene

Question 38

how do eukaryotic cells regulate gene expression?

Answer 38

– Chromatin condensation – Transcriptional control – Alternative splicing & selective destruction of mRNAs – Translation rate – Activation and deactivation of proteins - Chromatin condensation patterns are especially important for differentiation and are the basis of epigenetic inheritance

Question 39

apoptosis examples

Answer 39

- cells between fingers die to form digits - about half of all neurons go through cell death - harmful immune cells die - inappropriate activation of programmed cell death linked to diseases like ALS and cancer

Question 40

in situ hybridization

Answer 40

used to find out where a particular mRNA is located: 1) Obtain a single-stranded DNA or RNA that is complementary to the target mRNA 2) label it with fluorescent tag 3) Allow the probe to hybridize to its complementary sequence 4) Wash away any unbound probe 5) Fluorescence shows where the mRNA is located - helped identify function of bicoid morphogen

Question 41

in situ hybridization and bicoid morphogen

Answer 41

Fluorescent in situ hybridization (FISH) showed that: – Bicoid mRNA was distributed in a gradient in Drosophila embryos – Highest concentration was at the anterior end – Bicoid mRNA is made by cells of the mother & transferred into the egg – Bicoid protein is also found in a similar gradient

Question 42

what happens if you inject bicoid mRNA into an embryo's anterior end?

Answer 42

– Caused anterior structures to form more posteriorly – Supports the claim that bicoid is a morphogen

Question 43

how does bicoid work as a regulatory transcription factor?

Answer 43

– It binds to enhancers and activates genes needed to form anterior structures – High bicoid concentrations indicate a cell is in the anterior – Lower concentrations indicate a cell is more posterior

Question 44

heterometry

Answer 44

- altered quantity of gene expression of a developmental gene - ex: Beak shape in Darwin’s finches is affected by the amount of expression of BMP4 and CaM during early development

Question 45

heterochrony

Answer 45

- altered timing of gene expression of a developmental gene - ex: The giraffe’s neck is not longer because of the addition of cervical vertebrae, rather the period of growth is extended so that the vertebrae grow longer, this signaling process is delayed in the neck vertebrae, so they grow longer.

Question 46

heterotopy

Answer 46

- altered spatial pattern of gene expression of a developmental gene - ex: webbed feet of ducks-Duck and chicken embryos both have webbing, and both express BMP4, a protein that instructs cells in the webbing to undergo apoptosis (programmed cell death). In ducks, a gene called Gremlin, which encodes a BMP inhibitor protein, is expressed in webbing cells that don’t undergo apoptosis (if Gremlin is expressed there will be webbing).