20.1 - 20.6 Gene expression Flashcards
List some mutagenic agents
- X-rays
- Alpha particles
- Mustard gas
- Tobacco tar
What is a mutation?
Any change to the quantity or structure of DNA
What is a gene mutation?
Any change to one or more nucleotide bases or a change in the sequence of DNA bases
Describe how a change of one or more bases can produce sudden and distinct differences between individuals
- Change in nucleotide so different base
- Different DNA triplet, different mRNA codon
- May code for a different amino acid
- Different primary structure
- Hydrogen, ionic and disulphide bonds form in different places so different secondary structure
- Different tertiary structure
- Protein behaves differently, different phenotypes
Give the types of mutation
Gene mutation
Non-disjunction:
Failure of homologous chromosomes to separate
Polyploidy:
An extra set of chromosomes
List the 6 types of gene mutation
- Substitution
- Addition
- Deletion
- Duplication
- Inversion
- Translocation
Describe a base substitution
A nucleotide in a DNA molecule is replaced by another nucleotide that has a different base
Give the possible consequences of a base substitution
- Production of a stop codon
- Formation of a codon for a different amino acid
- Formation of a different codon but for the same amino acid
Describe the deletion of a base
A nucleotide is lost from the normal sequence of DNA. One deleted nucleotide causes all the triplets after the mutation to be different (frame shift).
Describe duplication
One or more bases repeated (frame shift)
Describe inversion
Group of bases separate and then rejoin in reverse order
Describe translocation
Group of bases from one chromosome insert into another
What causes mutations?
- Spontaneous
- However, rate of mutation can be increase by mutagenic agents
Define differentiation
The process by which each cell develops into a specialised cell
Define stem cell
An undifferentiated dividing cell that requires constant replacement and can differentiate to produce specialised cells
List the types of mammal stem cells
- Embryonic
- Umbilical cord blood stem cells
- Placental stem cells
- Adult stem cells
Describe embryonic stem cells
Differentiate into any type of cell in the initial cells
Define totipotent
Differentiate into any/all specialised cells and are only found in early embryos