8.1 Mutations Flashcards
What is a point/gene mutation?
change in DNA base sequence
changes the amino acid sequence
changes primary structure
changes tertiary structure
changes the function
When does a point mutation occur?
during DNA replication in interphase
What increases the chance of mutations?
mutagens
Why are mutations a good thing?
important for an organism to live through natural selection
the population can evolve
What is a chromosome mutation?
a change in the number of chromosomes - extra/less
When does a chromosome mutation occur?
during meiosis in anaphase 1 or 2
What are all the different types of point mutations?
substitution
insertion
deletion
duplication
inversion
transloaction
What is substitution mutation?
only 1 amino acid is changed in the sequence
Why does a substitution reaction have little effect?
degenerate code - can code for the same amino acid so its a silent mutation
What is insertion mutation?
adding an extra base to the sequence
What is a frameshift?
every codon downstream of the mutation will change so potentially every amino acid downstream of the mutation will change
What is deletion mutation?
removal of a base
What is duplication mutation?
the base that came before is copied and inserted
What is inversion mutation?
a group of bases becomes separated from the DNA and rejoin in reverse order
What is translocation mutation?
bases are separated from DNA sequence and one chromosome is inserted in a different chromosome
What 3 types of mutation cause a frameshift?
insertion
deletion
duplication
What does polysomy mean?
there is an extra chromosome in the gamete
What does polyploidy mean?
changes in the whole set of chromosomes as all homo pairs have failed to seperate and end up in the gametes so there is more than 2 sets of chromosomes
What does non-disjunction result in?
the gamete has one more or one less chromosome
When does a whole change in a set of chromosomes occur?
when an organism has 3 or more sets of chromosomes rather than 2
What is hybridisation?
the combining of genes of different varieties or species of organism to produce a hybrid
What is triploid?
3 sets of chromosomes
What causes down-syndrome?
a tripsomy 21 gamete
What is monosomy?
1 set of chromosomes
What type of female gamete is most likely to experience non-disjunction?
older gametes
What are mutagens?
any outside factor that increases the rate of mutation
What are carcinogens?
mutagens that cause cancer
What are examples of physical mutagens?
ionisinf radiation
x-rays
alpha and beta particles
How do physical mutagens work?
breaks the polypeptide chain in DNA
What are examples of biological mutagens?
viruses
benzopyrene in tobacco smoke
How does a virus work as a mutagen?
injects viral material and disrupts DNA bases
When does non-dysjunction occur in meiosis?
meiosis 1 = chromosomes fail to serparate during anaphase 1
meiosis 2 = chromatids fail to seperate during anaphase 2
What happens to a monosomy zygote?
dies
Describe the process in how polyploidy occurs by non-disjunction in meosis 1
- each homo pair is doubled due to DNA replication in interphase
- non-disjunction in meiosis 1 = all chromosomes fail to serparate
- all chromosomes are in 1 cell, the other cell is empty and has no chromosomes
- normal division in meiosis 2 so chromatids separate equally
- produces 2x 2n gametes (diploid)
What would happen if a diploid gamete fused with is normal haploid gamete?
produce a triploid zygote = 3 copies of every chromosome
Describe the process of how polyploidy occurs by non-dysjunction in meiosis 2
- each homo pair is doubled due to DNA replication in interphase
- normal dividion in meiosis 1 = chromosomes separate equally
- non-disjunction in meiosis 2 = all chromatids fail to separate equally in 1 of the cells produced from meiosis 1
- produces a 2n gamete and a gamete with no chromatids
What are the 2 types of chromosome mutations?
polyploidy and aneuploidy
What is aneuploidy?
changes in the number of individual chromosomes
individual homo pairs fail to separate during meiosis
What is the result of aneuploidy?
the gamete will have 1 more or 1 less chromosomes
What is an example of aneuploidy mutation?
down syndrome
Describe the process of aneuploidy in meiosis 1
- each homo pair is doubled due to DNA replication in interphase
- Non-disjunction in meiosis 1 = one chromosome does not separate equally
- both homo pairs are therefore present in 1 cell
- meosis 2 occurs = chromatids separate equally
- results in x2 n+1 gametes and x2 n-1 gametes
What does aneuploidy result in in terms of gametes made from non-disjunction in meiosis 1?
x2 n+1 gametes = with an extra chromosome
x2 n-1 gametes = with one less chromosome
they are all still haploid gametes
In terms of number of chromosomes, what is formed when you fuse a n+1 gamete with a normal n gamete?
2n + 1 zygote
diploid zygote with an extra chromosome
In terms of number of chromosomes, what is formed when you fuse a n-1 gamete with a normal n gamete?
2n - 1 zygote
a diploid zygote with one less chromosome
Describe the process of aneuploidy in meiosis 2
- each homo pair doubles due to DNA replication in interphase
- normal division in meiosis 1 = chromosomes separate
- non-disjunction in meiosis 2 = one chromatid fails to separate equally
- resulting in x1 n-1 gamete, x1 n+1 gamete, x2 n gametes (normal)
What does aneuploidy result in in terms of gametes made from non-disjunction in meiosis 2?
x1 n-1 haploid gamete
x1 n+1 haploid gamete
x2 n (normal) haploid gametes
