Genetic Diversity - mutation / meiosis Flashcards
(12 cards)
What is a mutation?
An alteration to the DNA base sequence
Often arise spontaneously during DNA replication
Why might a mutation NOT lead to change in amino acid sequence?
Genetic code is degenerate so mutation may code for same amino acid as the original triplet
Mutation may occur in intron
What is a substitution mutation?
When a nucleotide in the DNA sequence is replaced by another
This is likely to be a quiet mutation - no change occurs in the amino acid sequence
What is a deletion mutation?
When a nucleotide in the DNA sequence is lost. This is more likely to be harmful and significant, as it leads to a frame shift which means the entire amino acid sequence will be different
What is a mutagenic agent?
Give an example
Factor that increase rate of gene mutation
For example, UV light, gamma rays, certain chemicals like alcohol and tobacco
What is a polyploidy chromosome mutation?
Where an individual has 3 or more sets of chromosomes instead of 2
What is chromosome non-disjunction?
When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal
What is meiosis?
Form of cell division that produces 4 genetically different haploid cells (cells with half the number of chromosomes found in the parent cell), known as gametes
What is the difference between meiosis and mitosis?
Meiosis produces 4 genetically different cells with half the number of chromosomes as the parent cells
Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cells
What happens during meiosis 1?
Homologous chromosomes pair to form bivalents
Crossing over (exchange of sections of genetic material) occurs at chiasmata
Cell divides into two. Homologous chromosomes seperate randomly. Each cell contains either maternal or paternal copy
What happens during meiosis 2?
Independent segregation of sister chromatids
Each cell divides again, producing 4 haploid cells
Give 2 ways meiosis produces genetic variation
Crossing over during meiosis 1
Independent assortment (random segregation) or homologous chromosomes and sister chromatids
Results on new combination of alleles
