Introduction to developmental biology Flashcards
1
Q
What is developmental biology?
A
- the process by which animals grow and develop
- the transient stages between egg and birth
2
Q
How do we study developmental biology?
A
- model organisms
- easy to breed
- easy to maintain in lab
- have some similarity to humans
3
Q
What models can be used?
A
- invertebrate models
- anamniotes
- amniotes
4
Q
Why are invertebrate models used?
A
- short lifespan
- easy to handle large numbers
- easily mutated
- genome sequenced
- ideal genetic model
- however not vertebrate
5
Q
Why are anamniotes used?
A
- develop external to mother
- large eggs
- transparent, good for anatomical development
- easy to mutate
- sequenced genomes
6
Q
Why are amniotes used?
A
- some develop external to mother (reptiles)
- mammalian transgenics (knockouts)
- easily experimentally manipulated
- closer to humans than anamniotes
- sequenced genomes
7
Q
Describe fertilisation:
A
- where the journey of life begins
- it required that 2 germ cells meet and fuse to from a zygote
- primordial germ cells form in the ovary or testis
- when they form, they are diploid (2n) - cells that contain two copies of each chromosome
- they undergo meiosis to form germ cells - sperm and egg
- these are haploid (1n) - cells that contain a single set of chromosomes
8
Q
What happens at fertilization?
A
- entry of sperm into oocyte leads to formation of the zygote
- oocyte becomes impenetrable to prevent multiple sperm entering (polyspermy)
- the two haploid cells fuse to make a diploid zygote
- mitotic cell division is initiated
9
Q
Describe the cleavage stage?
A
- cells divide and become smaller
- these cells are called blastomeres
- each cell touched the zona pellucida
10
Q
What is the morula?
A
- at 16 cell stage the embryo becomes the morula, a spherical solid cell mass of blastomeres
- cells re-organise so there is an inner core of cells and a superficial layer of cells
- the inner core cells will become the embryo proper
- the superficial layer will become extra-embryonic membranes
11
Q
What is the blastocyst stage?
A
- cells on the outside pump fluid into the embryo and forms the blastocyst cavity
- inner cells become the inner cell mass (embryonic stem cells)
- superficial layer of cells become trophoblasts
12
Q
What is blastocyst hatching?
A
- blastocytes hatches - breaks out of zona pellucida - starts to grow
- growth is species dependent
13
Q
Describe implantation in mammals
A
- hatched blastocysts implants into uterine wall - needs nutrition and to excrete waste
- trophoblast cells in contact with uterus induced to divide and start to invade endometrium.
- They differentiate 2 layers
- cytotrophoblast - inner, mononucleated cells
- syncytiotrophoblasts - outer, multinucleated syncytium
14
Q
The Inner cell mass forms what layers?
A
- epiblast - columnar cells adjacent to syncytiotrophoblasts
- hypoblast - cuboidal cells facing blastocyst cavity
15
Q
Why do we study developmental biology?
A
- to understand how the body plan is formed and why
- to understand why birth defects arise
- to understand embryonic stem cells and how these ca be used in the future
- to understand how some cancers may have arisen
