Genetic Information Storage and Transfer Flashcards
How is genetic information stored
In units called genes
What is the genotype
the sets of genes inherited
What is the phenotype
Individual characteristics and appearance
What mostly determines the phenotype
Why is this not always so simple
Genotype determines phenotype
There are other influences which can alter the observed effect
What phrase could one use to describe the genotype in eukaryotes
Fuzzy instructions
What are the key factors affecting phenotype, other than genotype
Epigenetics
Environment
Randomness
How does Epigenetics affect phenotype
Chemical modification to genes that turn them on/off
Heritable and passes on as cells divide
How does the environment affect phenotype
Classic example height: malnutrition stunts growth and lowers final height
In plants: day length and temperature cycles can affect flowering time
Complex examples in human health: heart disease, Crohns disease
How does randomness affect the phenotype
During cell development some processes do not repeat exactly
Cell-cell interactions may be subtly different
How would you study the effect of genetics
- Take organisms from very similar genetic backgrounds
- Use very similar environments
- Doing both at once is common to reduce the effect of phenotypic variation in animal studies
Inbred mice (highly similar genetics)
Kept in identical environments, fed identical food etc - Use knockout or gene-edited animals to examine the role of genetic change
Animals are very similar apart from a known change (congenic)
Common to use siblings/littermates
How could u study the influence of the environment on phenotype
If you had clones (genetically identical individuals) you could study influence of environment
This is done widely with bacteria, yeast and human cell lines
What is the problem with using animal clones to study the effect of the environment with
Many animal clones have been created but not always identical
How would you create a cat clone (or other mammals)
- Take an egg cell and remove the genetic material
- Fuse the enucleated egg with a cell from the animal to be cloned, or transfer the nucleus from the donor cell
- Zap with an electrical pulse to activate the new hybrid cell
- Implant into surrogate mother and wait for delivery
How do the genetics of coat colour work in cats
- Orange or black depends on a gene on the X chromosome, allele O=orange, o=black
In female mammals, one random copy of X is inactivated in each cell - known as X inactivation
So a female with a mixed genotype will have some cells expressing orange allele and some expressing black - which results in mixed colours of orange and black fur - tortoiseshell
White patches of a calico are random and a result from the action of another gene on one of the autosomes
Is human cloning allowed
Human cloning is considered unethical and is explicitly banned in most countries
Similarly, human gene editing is also prohibited in most countries
However in the UK, nuclear transfer can be used to avoid mitochondrial diseases (3 parent babies)
Why are we all not clones of our parents or siblings
Each individual has a unique genotype - a complete set of inherited
This is because their genome is a randomised mixture of their parents
Sexual reproduction results in individuals, with unique genotypes
Briefly, how do genes influence phenotypes
- Genes code for proteins
- Proteins act inside cells
- Cell interact with other cells
- Organs and tissues are established
- Organism is assembled and grows
