stem cells and development

Question 1

define cell differentiation

Answer 1

the process by which cells acquire different fates, through changes in gene expression

Question 2

define pattern formation

Answer 2

how cells, organs and limbs are positioned; determined by genes

Question 3

define polarity

Answer 3

localisation of specific proteins and mRNA to specific areas of the cell

Question 4

name 4 types of polarity

Answer 4

• apical / basal
• ventral / dorsal
• bilateral symmetry / zygomorphic
• actinomorphic (flowers)

Question 5

define stem cells

Answer 5

• found in all multicellular organisms
• gives rise to all cell types

Question 6

what is the Shh gene?

Answer 6

the sonic hedgehog gene; governs limb, digit and CNS formation

Question 7

what is asymmetric division?

Answer 7

• cell division whereby the two daughter cells are of different fates
• stem cells divide in this way to maintain their population

Question 8

define multipotent cells

Answer 8

stem cells that can develop into a various but limited amount of cell types within a lineage

Question 9

define pluripotent cells

Answer 9

stem cells that can develop into almost every cell type, except extra-embryonic tissues

Question 10

define totipotent cells

Answer 10

stem cells that can develop into every cell type and can generate a new organism

Question 11

what cells make up the blastocyst in mammals?

Answer 11

pluripotent cells

Question 12

what is the process of making embryonic stem cells?

Answer 12

• inner cell mass cells are taken from the blastocyst
• cells are put in tissue culture
• and become embryonic stem cells

Question 13

what 3 things can embryonic stem cells be used for?

Answer 13

• introducing genes
• gene knockout
• chromosomal rearrangements/deletions

Question 14

define transgenesis

Answer 14

the process of introducing exogenous or modified genes into an organism

Question 15

out of the ESCs and the blastocyst, which is the wild-type and which is the mutant in the formation of transgenic mice?

Answer 15

• ESCs are wild-type (AACC)
• blastocyst is mutant (aacc)

Question 16

what is the genotype of the F1 generation of transgenic mice?

Answer 16

both AACC and aacc
phenotype is chimeric

Question 17

what is the genotype of the F2 generation of chimeric mice?

Answer 17

• grey: AaCc
• white: aacc

Question 18

how can homozygous mice be made

Answer 18

through breeding siblings

Question 19

how can somatic nuclei be transformed into totipotent cells?

Answer 19

• by being injected into an enucleated stem cell
• this can regenerate an adult organism

Question 20

how are induced pluripotent stem cells be generated?

Answer 20

introducing transcription factors to fibroblast cells (fully differentiated)

Question 21

what is the size of the drosophila genome?
14..

Answer 21

140 Mb, 16,000 genes

Question 22

how many pairs of chromosomes does drosophila have?

Answer 22

4: X, Y, 2, 3, 4

Question 23

what is axis formation determined by in fruit flies?

Answer 23

maternal effect genes: the position of mRNA in the oocyte

Question 24

what keeps mRNA is specific places in a fruit fly oocyte?

Answer 24

anchor proteins

Question 25

what is the role of bicoid mRNA?

Answer 25

- tethered to the anterior portion of the oocyte - suppresses caudal protein once translated, which establishes the lower part of the body

Question 26

what is the role of nanos mRNA?

Answer 26

- tethered at the posterior end of the cell - suppresses the hunchback protein once translated - establishes segmentation

Question 27

what type of genes do the bicoid and nanos gradients dictate?

Answer 27

zygotic genes: GAP, homeotic and segment polarity

Question 28

what is the result of bicoid mutations?

Answer 28

loss of the head and thorax - lethal

Question 29

what do nanos regions result in?

Answer 29

loss of abdominal regions

Question 30

define homeotic genes

Answer 30

genes which regulate the development of anatomical structures, repressing extra limb formation - known as hox genes in vertebrates

Question 31

how are homeotic genes organised in fruit flies?

Answer 31

into complexes - the order of genes corresponds to the order of limbs of the body

Question 32

what do homeotic mutations result in?

Answer 32

anatomical conversions

Question 33

define the ultrabithorax mutation

Answer 33

a homeotic mutation in which the 2nd thoracic segment is doubled, resulting in two pairs of wings

Question 34

define the antennapedia mutation

Answer 34

a homeotic mutation in which instead of the antenna, a fruit fly has another pair of legs

Question 35

what is the evolutionary basis for homeotic genes?

Answer 35

- at some point in evolution, an early ancestor had a millipede structure - homeotic genes exist to repress extra limb formation

Question 36

what are homeobox genes (translated)?

Answer 36

- homeodomain transcription factors - most have a homeobox (180 bp) - have a 60 aa binding domain

Question 37

why don't we see conversions in mammals?

Answer 37

because of redundancy of genes; there are several copies of the same gene

Question 38

what does the HOX-D13 mutation result in?

Answer 38

syndactly; where two or more digits are fused together

Question 39

what do Shh mutations result in?

Answer 39

holoprosencephaly; the failure of the division of the two hemispheres of the brain

Question 40

what are the four organs of a wild-type flower?

Answer 40

sepal, petal, carpel, stamen

Question 41

describe the apetala-1 mutation

Answer 41

has two carpel and 2 stamen the sepal and petal is converted into the other two organs