fertilisation and early embryonic development Flashcards
What is fertilisation?
Fertilisation is the fusion of a male gamete (sperm) and a female gamete (egg) to form a zygote.
What happens to the zygote after fertilisation in multicellular organisms?
After fertilisation, the zygote divides by mitosis, producing an embryo made up of genetically identical cells.
How do the cells in an early-stage embryo behave?
In an early-stage embryo, the cells are unspecialised and can develop into any type of cell in the organism.
What is differentiation?
Differentiation is the process by which unspecialised cells in the embryo develop into specialised cells with specific functions.
Why is differentiation important in multicellular organisms?
Differentiation allows cells to develop the ideal structure and enzymes needed to efficiently perform specific functions, leading to more efficient processes in the organism.
How many different cell types are there in humans?
In humans, there are 220 distinct cell types, each highly specialised for specific functions.
What happens when a gene is expressed?
When a gene is expressed, it is “switched on,” and the information in the gene is used to make proteins or other gene products
How does gene expression relate to cell differentiation?
Different sequences of genes are expressed in different cell types, causing cells to differentiate into specialised cells with distinct functions.
What determines how a cell differentiates in an embryo?
A cell’s position in the embryo determines how it differentiates, with gradients of signalling chemicals guiding the differentiation process.
What role do signalling chemicals play in differentiation?
Signalling chemicals act as regulators of gene expression, creating gradients that help cells know their position and guide them along specific differentiation pathways.
What is retinoic acid and how does it influence differentiation?
Retinoic acid is a signalling chemical that forms gradients in the embryo, helping to guide the differentiation of cells involved in the development of organs like the forelimbs, pancreas, lungs, and kidneys.
How does the expression of genes vary between different types of cells?
In different cell types, certain genes are switched off while others are switched on, leading to the development of different cell functions. For example, some genes are switched off in salivary gland cells and others in hair cells
Why is it important for there to be enough cells of each type in multicellular organisms?
In multicellular organisms, it is essential to have enough cells of each type in the correct positions to perform specific functions and maintain the organism’s structure and function.
How does the position of a cell in an embryo influence its differentiation?
The position of a cell in an embryo influences its differentiation by determining which gradients of signalling chemicals it is exposed to, which in turn directs which genes are expressed and what cell type it becomes.
