3.4.3 Meiosis And Mutation Flashcards
What is a gene mutation?
A change in the base sequence of chromosomes due to replication errors
How is DNA polymerase responsible for errors?
Can make proof reading errors where they mistakenly add or remove bases.
What is a point mutation?
mutation in a single base of DNA
What are the 2 types of base mutations?
base deletion
base substitution
What is base deletion?
- When one or more bases is deleted from the base sequence
- causes a frame shift
- protein formed will be altered
What is base substitution?
- one or more bases are incorrectly replaced by another base.
- won’t always alter protein as some substitutions will still code for the same amino acid.
What are mutagenic agents?
Things that can cause an increase in rate of gene mutations
- UV radiation
- ionising radiation
- some chemicals
- some viruses
Does the changing of the last base in a triplet code change the amino acid?
As long as the first two bases are correct the codon will still code for the same amino acid. Due to the degenerate nature of codons
What is chromosome non-disjunction?
When chromosomes fail to separate
correctly in meiosis, resulting in gametes
with one more or less chromosome than
normal.
Why might a mutation not lead to change in the
amino acid sequence?
● Genetic code is degenerate so
mutation may end up coding for same
amino acid as the original triplet.
● Mutation may occur in intron.
What is meiosis?
A form of cell division that produces four
genetically different haploid cells (cells
with half the number of chromosomes
found in the parent cell) known as
gametes.
How does meiosis differ from mitosis?
● Meiosis produces four genetically different
cells with half the number of chromosomes
as the parent cells.
● Mitosis produces two genetically identical
cells with the same number of
chromosomes as the parent cells.
What happens during meiosis Ⅰ?
- Homologous chromosomes pair
- Crossing over (exchange of sections of genetic
material) - Cell divides into two. Homologous chromosomes
separate randomly. Each cell contains either
maternal or paternal copy.
What happens during meiosis Ⅱ?
- Independent segregation of sister
chromatids. - Each cell divides again, producing 4
haploid cells.
Give 2 ways meiosis produces genetic variation?
- Crossing over during meiosis Ⅰ
- Independent assortment (random
segregation) of homologous
chromosomes & sister chromatids
Result in new combinations of alleles.
