Section 4 - Genetic information, variation and relationships between organisms: 9. Genetic diversity Flashcards
What is a mutation
A change in the arrangement of the bases in an individual gene, or in the structure of the chromosome (leading to changes in the arrangement of genes)
What are gene mutations
Changes in the sequence of bases
What are the 3 types of gene mutations
- Substitution
- Deletion
- Insertion
What is a substitution
When one nucleotide is replaced by another, changing one base in the sequence
What is the potential impact of a base substitution
- May have no impact, due to the degenerate code (could code for the same amino acid)
- If the amino acid does change, minimal impact as only one is different
What is a deletion
When one nucleotide is lost, so one base is missing from the sequence
What is an insertion
When one nucleotide is added, giving an extra base in the sequence
What is the potential impact of a base deletion/insertion
Causes a frameshift, as the following triplet codes are all moved along by one, impacting each of the following amino acids
(can completely change the protein structure)
What are chromosome mutations
Changes in the structure or number of whole chromosomes
What are the 5 types of chromosome mutations
- Deletion
- Duplication
- Inversion
- Translocation
- Whole chromosome mutations
What is Gene deletion
When a section of a chromosome is removed
What is Gene duplication
When a section of chromosome is added from its homologous partner, giving one chromosome 2 copies of one gene
What is Gene inversion
When a section of a chromosome is reversed
What is Translocation
When sections of chromosomes are swapped between two chromosomes
What are whole chromosome mutations
When an entire chromosome is lost or replaced
What is Polyploidy
The process (Chromosome mutations) leading to becoming Polyploid (having more that two sets of chromosomes)
Mainly in plants
What is Non-disjunction
When pairs of chromosomes fail to separate in meiosis, leading to one more/less chromosome
Eg. Downs syndrome: Additional chromosome 21
What are the possible effects of mutations
- Production of new/superior proteins (Reproductive advantage)
- Neutral mutation (No change, due to degenerate code)
- Production of no/inferior proteins (potentially causing disease and fatality)
What is meiosis
Cell division producing 4 daughter cells, each with half the number of chromosomes as the parent
What happens during meiosis 1
Homologous chromosomes separate into different cells
What happens during meiosis 2
Chromatids from the homologous chromosomes are separated into 4 cells
(same as mitosis, but splits into 4, rather than 2)
What is the importance of meiosis
Allows for gametes to be produced with half the number of chromosomes (Haploid number), so when they fuse during fertilisation, the off-spring has the correct diploid number.
What is Independent segregation (random assortment)
During meiosis 1, each of the chromosomes in the homologous pair will randomly pass to each daughter cell
What is the effect of Independent segregation (random assortment)
As each chromosome will have a different allele of the same gene, the arrangement of the pair before separation in meiosis 1, and the following division of meiosis 2, will impact the allele of the daughter cell