Cell and Developmental Biology

Question 1

Describe the principle of gene constancy

Answer 1

Almost all cells in the body contain the same genetic information.

Question 2

Name 3 possible functions of general transcription factors

Answer 2

1. ) Recognizing the TATA box sequence in the promoter region
2. ) Recruitment of RNA Polymerase II to the initiation complex
3. ) Unwinds the DNA helix

Question 3

Describe the MAP Kinase pathway

Answer 3

1. ) FGF - fibroblast growth factor binds to it’s receptor, resulting in dimerisation
2. ) The intracellular tyrosine kinase domains are activated and phosphorylate each other
3. ) Proteins bind to the domain at ‘docking’ sites, forming a complex
4. ) The Grb2 adaptor protein recruits GEF to the complex, this stimulates Ras to cycle to it’s active GTP bound form
5. ) Ras then recruits Raf (MAP kinase kinase kinase), this recruits MEK (MAP kinase kinase) which in turn recruits Erk (MAP kinase)
6. ) Activation of MAP kinase + phosphorylation of transcription factors in the nucleus leads to changes in gene expression.

Question 4

How do we know the order of Intracellular Compartmentalization?

Answer 4

Experiments by Palade used autoradiography to show movement of proteins within a cell every 10 minutes. This shows the order in which proteins move through a cell.

Question 5

Summarize the SNARE hypothesis

Answer 5

The SNARE hypothesis is used to explain the specificity of protein transport

• There are 2 types of snares: V-SNARES (found on vesicles) and T-SNARES (found on target membranes)
• Each vesicle with a V-SNARE recognizes it’s partner T-SNARE on the appropriate membrane
• V/T - SNARE binding recruits cell machinery that mediates membrane fusion

Question 6

Advantages of Multicellularity

Answer 6

1. ) Better protection from predation
2. ) Buffered and more protected from environment
3. ) Allows development of cell types with specialized functions

Question 7

What is the Flagellar Synthesis Constraint Hypothesis?

Answer 7

The microtubule organizing machinery needed for the flagella is also needed for the formation of the spindle fibres. This means that cells with functional flagella do not divide

Question 8

Name the requirements of multicellularity

Answer 8

1. ) Cells must stick together
2. ) Cells must communicate
3. ) Cells must participate in a network of genetic interactions that regulates cell division

Question 9

Give 5 examples of where the activity of a protein coding gene can be regulated

Answer 9

1. ) Gene transcription
2. ) Processing of pre-mRNA to produce mature mRNA
3. ) Transport of mRNA from nucleus
4. ) Translation of mRNA to produce protein
5. ) Post-translational modification of activity and stability

Question 10

Describe the Organizer Graft experiment

Answer 10

The experiment involved transplanting the Dorsal Blastopore Lip of a frog embryo onto another, resulting in an embryo with two dorsal blastopore lips. This produced a twinned embryo.
The experiment was then repeated with a stained donor lip. This showed that the majority of the tissue in the second axis was host derived so the graft must be producing signals to recruit the host tissue to form the secondary axis

Question 11

Name the functions of a signal transduction pathway

Answer 11

1. ) Amplification of the signal
2. ) Integration of multiple signalling pathways
3. ) Allows multiple levels of regulation

Question 12

How do Hydrophilic molecules enter a cell vs Hydrophobic ones

Answer 12

Hydrophilic
Unable to get across the hydrophobic cell membrane
Must bind to cell surface receptors

Hydrophobic
Insoluble in water
Bound to carrier proteins for transport to cell
Once at cell can just diffuse in

Question 13

Name + describe the three types of signalling

Answer 13

1.) Contact dependent/juxtacrine
- Requires direct contact between cells
2.) Endocrine signalling
- Signal is produced locally and is transported to
responding cells
3.) Paracrine
- A paracrine signal acts on the cells neighboring
the signalling cell
4.) Autocrine
- An autocrine signal acts back on the cell that
secreted it

Question 14

How are pulripotent cells grown in vitro?

Answer 14

1. ) Pulripotent cells from the inner cell mass of a blastocyst are separated from the surrounding tachyoderm
2. ) ICM is plated into a culture dish + grown in nutrient medium supplemented with serum, supported by irradiated Fibroblast feeder layers
3. ) Cells divide to form colonies
4. ) Colonies removed, dissociated and re-plated, to allow further expansion
5. ) Cells allowed to divide for several months without differentiating.

Question 15

Stages of differentiation in Multipotent cells

Answer 15

1. ) Multipotent stem cell
2. ) Multipotent progenitor cells
3. ) Lineage Committed Progenitor Cells
4. ) Mature Cells

Question 16

Signs of a necrotic cell

Answer 16

• Disruption of an apoptotic cell
• Nucleus intact
• Lesions on outside of the cell
• Even nuclear pores

Question 17

Signs of an apoptotic cell

Answer 17

• Condensed nucleus
• Blebbing on outside of cell
• Clustered Nuclear Pores