genetic diversity as a result of mutation or meiosis Flashcards
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 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 a substitution mutation
when a nucleotide in the DNA sequence is replaced by another. this is more likely to be a quiet mutation, meaning 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
what is a mutagenic agent
factors that increase rate of gene mutation
examples of mutagentic agents
x-rays
UV light
gamma rays
certain chemicals for example in alcohol and tobacco
what is a polyploidy chromosome mutation
where an individual has three or more sets of chromosomes instead of two
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
a form of cell division that produces four genetically different haploid cells known as gametes
how does meiosis differ from mitosis
- meiosis produced 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 to form bivalents
- crossing over (exchange of sections of genetic material) occurs as chiasmata
- 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
