Lecture notes
Lecture Notes
- Institution
- Queen Mary, University Of London (QMUL)
Lecture notes of 10 pages for the course Cell Biology and developmental genetics at QMUL
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By: betulalm • 3 year ago
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Mechanism of developmentLearning objective:
1. Reminder of mechanisms for regulating gene expression- an essential component of development
2. To Review key concepts of developmental biology and approaches used to study development
LO2. REVIEW KEY CONCEPT IN DEVELOPMENTAL BIOLOGY
The principle of development
Main question in developmental biology: how can fertilised eggs generate a complex organism?
Detailed questions of developmental biology
Differentiation
- How can fertilised eggs generate so many different cell types?
Morphogenesis
- How do cells move and change shape to create ordered structures?
Growth
- How do cells know when to stop dividing?
Reproduction
- How are gametes set aside
Evolution
- How do evolutionary changes in development create new body forms?
Environmental integration (‘’extended phenotype’’)
- How is development of organism integrated into the larger context of its habitat (environmental factors)?
The question of how eggs can generate whole organism goes back to the 6 th century
2 theories Preformationism Epigenesis
Adult is performed in egg or sperm Organism progressively built anew in each
All organisms were generated at the same generation
time No premade man
‘humunculus’= v.small human curled up in Aristotle supported epigenesis
the head of each sperm
DNA gives the instruction
The nucleus of the zygote and every cell that is produced during ontogenesis contains the complete genome
- Ontogenesis = development of individual organism or behavioural features from the earliest stage of maturity
Every cell (somatic and germ line cells) can be used to make a new animal
- Example is dolly the sheep
- Somatic cell = any cell of living organism other than reproductive cells (egg and sperm cells)
- Germ line cells = sperm and egg cells (gametes)
1. REMINDER OF MECHANISMS FOR REGULATING GENE EXPRESSION- AN ESSENTIAL COMPONENT OF DEVELOPMENT
, Differentiation: making cells different by regulation of gene expression
How are different cells types established during development?
- All cells contain the same genes
- Not all genes are expressed in all cells
- Expression of different sets of genes in different cell types
Factors that control gene expression regulate:
1. Chromatin structure
2. Initiation of transcription
3. RNA processing
4. Initiation of translation
5. Post-translational modification
1. Regulation of chromatin structure
DNA associated with proteins called histones
There are 8 histones that form an octomer
DNA wraps around the octamer and are tightly packed
Therefore, DNA not easily accessible to enzymes (RNA polymerase ll)
Genes within highly packed heterochromatin are usually not expressed
Heterochromatin = tightly packed form of DNA, which comes in
multiple varieties
~1.5 % DNA of human genomes codes for proteins
What affects gene regulation:
Location of gene promoter relative to nucleosome (DNA segment
+ histone octamer) and site where DNA is attached to the
chromosome scaffold or nuclear laminar can affect whether a
gene is transcribed
Nuclear laminar
- Filamentous protein network that coats the inner nuclear
membrane.
- Consists of intermediate filaments and membrane-associated
protein.
- Provides mechanical support
- Regulate cellular events i.e. DNA replication and cell division
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