4.3 Genetic Diversity can arise as a result of Mutation or during Meiosis Flashcards
What is mutation?
An alternation to the DNA base sequence. Often arise spontaneously during DNA replication
Why might a mutation not lead to a change in the amino acid sequence?
. Genetic code is degenerate so mutation may end up coding for the 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 sequence?
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 examples of this
Factors that increase the rate of gene mutation.
For example, x-rays, UV light, gamma rays
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 fails to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal.
What is meiosis?
A from of cell division that produces four genetically different haploid cells known as gametes.
How does meiosis differ from mitosis?
. Meiosis produces four genetically different cells with half of 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 occurs at 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 cells divides again, producing 4 haploid cells.
Give two ways meiosis produces genetic variation?
- Crossing over during meiosis I
- Independent assortment of homologous chromosomes & sister chromatids
Results in new combinations of alleles.
