Chapter 20 - Gene expression Flashcards
What is a mutation?
Change to the structure of quantity of DNA
What is a substitution mutation?
A base is switched for another
What are the three possibilities that can occur as the result of a substitution mutation?
A stop codon can be formed - the production of the polypeptide would be stopped
A non-functional protein is formed
No change
Why can deletion mutations be bad?
If they occur near the start of a polypeptide chain, all following codons will experience a frame shift = non-functional protein produced
What is an addition mutation?
Base randomly added to sequence
Why can addition mutations be bad?
If they occur near the start of a polypeptide chain, all following codons will experience a frame shift = non-functional protein produced
What is a base duplication?
One of the bases is repeated
What effect does a duplication mutation have?
Frame shift to the right
What is an inversion mutation?
A group of base sequences becomes separated and rejoins in the inverse order
What is a translocation mutation?
A group of bases becomes separated from the DNA sequence on one chromosome and is inserted into another
What are mutagenic agents?
Increase the frequency and likelihood of mutations
Examples of mutagenic agents
Ionising radiation
Chemicals
Why is ionising radiation a mutagenic agent?
Disrupts DNA structure
Why are chemicals mutagenic agents?
Alters DNA structure and interferes with transcription
What is cell differentiation?
Cell develops into a structure suited to the role it will carry out
How do cells specialise?
Only certain genes are expressed (turned on)
What are totipotent cells?
Can mature into any body cell
How are only some of the genes in a cell expressed?
Only part of the DNA in a cell is made into proteins needed to carry out a specialised function
In which ways does the cell prevent genes from being expressed?
Preventing transcription and translation
What are stem cells?
Can differentiate into other cells
What are embryonic stem cells?
Come from early embryos
Initially, they can differentiate into any type of cell
What are umbilical cord blood stem cells?
Similar to adult stem cells
What are placental stem cells?
Can develop into a limited number of cells
What are adult stem cells?
Specific to tissue or organ
Produce cells to repair and maintain tissues
What are totipotent stem cells?
Found in early embryo, can differentiate into any cell
What are pluripotent stem cells?
Found in embryos, can differentiate into ALMOST any cell
Example of totipotent cells
Zygote
Example of pluripotent cells
Embryonic/fetal stem cells
What are multipotent stem cells?
Found in adults, can develop into limited number of cells
Examples of multipoint stem cells
Adult stem cells
What are unipotent stem cells?
Only differentiate into one cell, derived from multipotent stem cells
Examples of unipotent stem cells
Cardiomyocytes