Meiosis And Genetic Variation, Mutations Flashcards
What is fertilisation
A random event where a haploid cell sperm fuses with a haploid egg to make a cell with normal amount of chromosomes
Where does meiosis take place
Reproductive organs
How many chromosomes does a human have
46 chromosomes - 23 pairs
What are homologous pairs
The chromosomes that make up a pair even thought they may have different alleles
What is crossing over in meiosis
Where the chromatids in homologous pairs swap over to form a different combination of alleles but still containing the same genes
Chromatids swap over, different combination of alleles, same genes
What are 2 events that lead to genetic variation
- crossing over of chromatids
- independent segregation of chromosomes
What is chromosome mutation
Where meiosis goes wrong and daughter cells have different numbers of chromosomes instead of equal numbers
What is non disjunction chromosome mutation
The failure of chromosomes to separate freely
What are mutations
Changes to the base sequence of DNA
What are two types of mutations
- substitution
- deletion
What are mutagenic agents
Occurences that can increase the rate of mutations
- ultraviolet radiation UV
- ionising radiation
- chemicals and viruses
What is substitution
Substitutes a DNA base, which causes the DNA and the amino acid sequence to change. The amino acid sequence may not change though
What is deletion
Where a DNA base is removed from a sequence, changing the DNA and amino acid sequence always
