BMS1021 - Lectures 1 to 11
BMS1021 - Lectures 1 to 11
A. Chromatin; the complex containing DNA, histones, and other proteins that combine to form a chromosome.
B. Chromosome; a single large DNA molecule and its genetic information.
C. Chromatid; a duplicate of a chromosome.
A continuous production process with millions of sperm produced each day.
and before that
Spermatogonial stem cell
Primary Spermatocytes (Diploid Cell)
somatic cells that supply key signals to support and "nurse' the germ cells
any cell expect a sperm or an egg or their precursors
A long process where eggs form in embryo but complete their development years later.
Primary Oocytes (Diploid Cell) present at birth
arrested in prophase of meiosis I until follicles mature (one each month)
arrested at metaphase of meiosis II until ovulation, sperm entry
; a haploid reproductive cell such as an egg or sperm
second polar body
first polar body
A. Specialised Diploid cell
Any cell with two chromosome sets and has a diploid number of chromosomes; 2n.
Homologs pair up and separate. This forms pairs of duplicated homologous chromosomes containing sister chromtids.
C. Meiosis I
Prophase I (crossing over occurs)
Homologous chromosomes separate and create two haploid cells with duplicated chromosomes.
D. Meiosis II
Sister chromatids separate and create four haploid cells with unduplicated chromosomes.
the period in the cell cycle when the cell is not dividing. Chromosomes and organelles are duplicated.
Cell division phases: Mitosis
E. Cytokinesis (splitting of cell)
binding and fusion of sperm and egg
enzyme digestion of the jelly coat.
slow block to polyspermy.
the diploid cell produced by the union of haploid gametes during fertilisation
Intracytoplasmic Sperm Injection (ICSI) i
s a specialised form of In Vitro Fertilisation (IVF) and involves the injection of a single sperm directly into a mature egg.
C. Embryonic Development
Day 1: Cleavage :red_flag:
rapid cell division following fertilisation (no increase in size) generates a blastocyst
Day 4: Blastocyst :red_flag: and contains a wall of cells the
trophoblast and the inner cell mass
becomes part of uterus
the source of embryonic stem cells
Day 8: Implantation and inner cell mass resolves into epiblast and hypoblast (bilaminar disc)
blastocyst undergoes "hatching" from the zona pellucida ready for implantation into the uterus
Day 10: Formation of the;
yolk sac from the extra-embryonic endoderm
Day 15: Further development of;
bilaminar germ disc (epiblast and hypoblast)
will develop into the embryo proper.
the process of generating the three germ layers of the embryo which give rise to all tissues and organs through rapid cell movement and proliferation from the
through the primitive streak :red_flag:
9 more items...
4 more items...
(displace the hypoblast as hypoblast doesn't contribute to adult structures)
2 more items...
Stem cells ; :red_flag:
undifferentiated cells that can self renew via mitosis and differentiate into one or more specialised cell types
Embryonic Stem Cells (ES cells)
Adult stem Cells (e.g. bone marrow)
iPS cells (induced pluripotent stem cells) :red_flag:
iPS cells avoid th ethical concerns regarding the use of human embryos
ability to differentiate
Pluripotent e.g. Embryonic stem cells derived from the inner cell mass of a blastocycst :red_flag: these are not totipotent because they dont form the trophoblast cells
Multipotent; give rise to multiple cell types but does not normally generate cell types from all germ layers :red_flag:
Totipotent e.g. Zygote :red_flag:
D. Disorders of development
Universal mechanisms of animal development
Morphogens; diffusible molecules that influence cell fate in a concentration dependent manner
Morphogenesis is the development of the form of an organism and its structures.
The activities of a cell depend on the genes it expresses and the proteins it produces. Almost all cells in an organism have the same genome therefore differential gene expression results from the genes being regulated differently in each cell type.
e.g. Sonic Hedgehog a diffusible molecule along a concentration gradient regulates digit formation
Basic stages of development
Pattern Formation :red_flag:
The process by which spatial and temporal patterns of cell activities within the embryo so that well-ordered structure develops
genes pattern the body axis
:red_flag: and are clusters of
are developmental control genes found in all animals. Homeotic genes all have the Homeobox DNA sequence.
In mammals the four HOX clusters are;
HOXA, HOXB, HOXC, HOXD.
Master regulatory genes
act as genetic switches :red_flag:
Cell Differentiation :red_flag:
Cleavage Divisions :red_flag:
Two major approaches to the study of Developmental Biology
Descriptive Approaches (anatomical)
Asking questions like where is that gene expressed? What are the changes in tissue in birth defects?
Asking questions like how do molecules cause viable changes in embryos? How do genes control development?
:red_flag: Birth Defects are congenital defects
E.G. enzyme deficiency, hypospadias
E.G. Down Syndrome
Single Gene Disorder
E.G. huntingtons disease
Syndrome often due to several genes on the chromosome being affected
E.G. Down syndrome is an example of aneuploidy (error in number of chromosomes)
Endocrine disruptions tend to be seen in adult structures
E.G. Folic acid in diet greatly reduces risk of neural tube defects
Tetrogen-induced (environmental agents that come from outside the body and cross the placenta)
E.G. Drugs (Thalidomide) and Alcohol (FAS) :red_flag:
Genetic background can influence severity of a teratogen :red_flag:
E.G. Scoliosis - low oxygen
Developmental Origins of adult Health and Disease
E.G. Hongerwinter malnutrition
What is a living cell?
A cell is the lowest level of structure capable of performing all the activities of life (growth, division, energy transduction etc)*
Lower and upper limit of a living cell size
limit of the cell is defined by the surface area to volume ratio. Cells cant be too big as the volume exceeds the surface area and surface area is important for transport of nutrients and waste into and out of the cell respectively.
limit of the cell is defined by the minimum space required to fit all necessary components to sustain cell operation.
Minimum requirements for a cell :red_flag:
Evolution of a cell requires
B. Polymerisation of simple organic molecules (most difficult step)
C. Aggregation of polymers and other molecules into areas separates from the environment
(formation of a membrane)
A. Abiotic synthesis of small organic molecules from inorganic matter
D. The capacity for heredity / self replication
eukaryotes differ from prokaryotes in that they have
linear DNA localised within a membranebound organelle the nucleus
possess a complex endomembrane system and a range of membrane bound organelles each with specialised functions
Not in the endomembrane system
are oxidative organelles that transfer hydrogen from various compounds to oxygen
Glyoxysomes; specialised peroxisomes in plant tissue
Compartmentalisation of the cell
Endomembranes - a system of internal, membrane bound compartments within the cell that can form physical links to exchange components
The nuclear envelope is connected to the rough ER which is also continuous with the smooth ER.
proteins passed into the lumen
carbohydrates can be added
Receiving, sorting, shipping and some manufacturing
Nuclear envelope (nucleus)
Nucleolus produces ribosomal RNA and assembles ribosomes
Nuclear pore complexes in the envelope regulate entry and exit
Nuclear envelope is continuous with the Endoplasmic Reticulum (ER)
Lysosome (recycling centres), vacuoles (water filled and provide support for plants), vesicles
Membranes and proteins produced by the ER move via transport vesicles to the Golgi
Getting from prokaryotic to eukaryotic
membrane infoldings to form endomembrane system
endosymbiotic events (i.e. mitochondria or chloroplasts)
cell; single cells
small bacterium-like organisms that usually have parasitic existence in plant or animal cells
free living in soil or water
in bogs, ocean depths and hot springs
Features and essential functional requirements that reflect the minimum requirements of a cell ( :red_flag:)
Internal foldings of the membrane
DNA - single circular strand not enclosed by a membrane in a region called the nucleoid
Cell wall (and capsule)
Flagella; locomotion organelles of some bacteria
Ribosomes; protein making complexes
The fluid mosaic model of membranes
Not all the same
Proteins are an essential component of all biological membranes
Intercellular joining and attachment to extracellular matrix
Glycolipids - for signal perception and cell-cell recognition
Cholesterol - reduces fluidity and prevents membrane freezing
A phospholipid bilayer forms the semi-fluid framework of all membranes
Transport across the membrane
Movement of water molecules
Movements of solutes
The mechanism by which many cells are joined into a coherent organism
Communication and connection
Plasmodemata - so water and small solutes can pass through from cell to cell
Simple properties of cells and staining methods
Different types of microscope including light and electron density
Relationship between view size and magnification
Assisted Reproductive Treatment (ART)
Intracytoplasmic sperm injection
Preimplantation genetic diagnosis
Histology of the seminiferous tubules
Spermatogonium (diploid germ stem cell)
Round spermatid (haploid)
Primary spermatocyte (diploid)
Sertoli cell (diploid)
Major Macro molecules
Water in biological systems
Water structure and polarity
The role of hydrogen bonding
The ionisation of water
Protonation and charge of amino acids at varied pH
The concept of dynamic equilibrium and why amino acids don't separate in an electric field