✅9 - Genetic Diversity Flashcards
What is a mutation?
A change to the base sequence of DNA
What is substitution?
When one nucleotide is exchanged for another
What does the significance of a substitution mutation depend on?
The importance of the original amino acid
How can a substitution affect the amino acid sequence?
If the codon is altered to code for a different amino acid, then the sequence will be altered and the polypeptide changed
What is a deletion mutation?
When a nucleotide is lost from the normal DNA sequence
What can deletion cause?
Frame shift
What are chromosome mutations?
Changes in the structure or number of whole chromosomes
What are the two forms of chromosome mutation?
Changes in whole sets of chromosomes
Changes in the number of individual chromosomes
When do changes in whole sets of chromosomes occur?
When organisms have three or more sets of chromosomes rather than the usual two, called polyploidy
When do changes in the number of individual chromosomes occur?
When chromosomes fail to separate in meiosis, and organisms get one more or one less chromsome
What is mitosis?
Produces two daughter cells with the same number of chromosomes as the parent cell and as each other
What is meiosis?
Usually produces four daughter cells. each with half the number of chromosomes as the parent cell
Why is meiosis important?
Otherwise the number of chromosomes would double each time the gametes fused
What happens in the first division of mitosis?
The homologus chromosomes pair up and their chromatids wrap around each other - crossing over may occur
What happens in the second division of meiosis?
The chromatids move apart and four cells form
