Molecular Patterning During Development

Question 1

Cell Differentiation

Answer 1

Process by which embryonic cells become different from one another, enabling cell specification and emergence of specialised cell types and the achievement of a stable terminal state

Question 2

Totipotent Stem Cells

Answer 2

Can turn into anything

Question 3

Pluripotent Stem Cells

Answer 3

Can turn into any cells but not embryonic

Question 4

Multipotent Stem Cells

Answer 4

More restricted options

Question 5

Potency (Cell Differentiation)

Answer 5

The entire repertoire of cell types a particular cell can give rise to in all possible environments

Question 6

Stages of Commitment (Cell Differentiation)

Answer 6

First Stage: Specification (Reversible) - capable of differentiating autonomously if placed in isolation but can be re-specified if exposed to certain chemicals/signals

Second Stage: Determination (irreversible) - cell will differentiate autonomously even when exposed to other factors or placed in a different part of the embryo

Question 7

Competence of a Cell

Answer 7

The ability of a cell to respond to the chemical stimuli, which is lost by changes in surface/intracellular receptors

Question 8

What is the progress of a cell during development?

Answer 8

Naive > Specified > Determined (loss of competence for alternative fates) > Differentiated

Question 9

Function of Bivalent Chromatins

Answer 9

Bivalent Chromatins are the mechanistic basis of cell fate decisions which occurs in a small number of “master regulator” genes that control particular differentiation routes

Chromatin will close/open: Type A cell may have it open, Type B may have it closed

Combinations of a few regulatory proteins can generate many cell types
and a lot of regulatory proteins (eg HOX) are actually proteins (transcription factors) that bind to DNA upstream of genes

Question 10

Describe the process of somatic cell reprogramming/therapeutic cloning?

Answer 10

1. Isolate cells from patient and remove the nucleus from an egg cell
2. Transfer the nucleus DNA content from the patient cell into the egg cell and allow the egg cell to reprogram the patient’s DNA to a base state
3. get cell to divide and get to blastocyst stage then get the inner mass cells and grow them in vitro

Question 11

How do you create induced pluripotent stem cells?

Answer 11

1. Isolate cells from patient and grow them in a dish
2. Treat cells with reprogramming factors
3. Wait a few weeks
4. Get pluripotent stem cells! Profit
5. Change culture conditions to stimulate cells to differentiate into a variety of cell types

Question 12

Where does intramembranous ossification take place?

Answer 12

in fibrous connective tissue and flat bones (mandible, cranium) related to the embryonic germ layer from the mesoderm (mesenchyme derives from this)

Question 13

HOX genes

Answer 13

Related group of genes that are expressed along the long axis of the embryo from head to tail; ancient genes and are present in many animal groups

Question 14

What is the role of HOX genes in determining body axes?

Answer 14

During embryonic development HOX genes determine the body axis and the position of the limbs along the body axis using intrinsic factors

The products of HOX genes belong to a class of proteins known as transcription factors, which bind to DNA and thereby regulate the transcription of other genes

Question 15

When and where do upper/lower limb buds appear?

Answer 15

Upper Limb buds appear at day 24 between somites C5-T1

Lower limb buds appear on approx Day 28 between somites L1-S2

Question 16

At what stage of foetal development are all major components of the limbs present and medial rotation of the lower limb complete?

Answer 16

Week 8

Question 17

What happens to the rotation of foetal limbs in Week 7 of gestation?

Answer 17

The forelimbs rotate 90 degrees laterally and himb limbs do that medially resulting in flexor compartments being anterior in the upper limb and posterior in the lower limb