meiosis and mutations Flashcards
what occurs before Meiosis I
DNA unravels and replicates so 2 copies of chromosomes called chromatids
DNA condense to form double arm chromosomes formed from sister chromatids joined by a centromere in the middle
what occurs in meiosis I
chromosomes arrange themselves into homologous pairs
pairs separated halving chromosome number
what occurs in Meiosis II
pairs of sister chromatids that make up each chromosome are seperated
four genetically unique haploid daughter cells
what are the two processes that increase genetic diversity during meiosis
independent segregation of chromosomes
crossing over
outline the process of crossing over
when homologus chromosomes pair up in meiosis I
they twist around each other and bits of chromosomes swap over
they now contain different alleles of the same genes
what is the consequence of crossing over
each cell has a different set of alleles and therefore a larger genetic diversity in the offspring
outline independent segregation of chromosomes
when chromosomes seperated in meiosis I it is completely random which chromosome from each pair ends up in each daughter cell
what is a gene mutation
a change to the DNA base sequence of chromosomes
name two types of mutation
deletion
substituion
what is a substituion mutation
one where base is substitued with another
what is a deletion mutation
where one base is deleted
what is the effect of mutations
some substituions will code for same amino acids
deletions will always change the amino acid coded for
what are the two types of chromosome mutation
changes in whole sets of chromosomes
change in individual number of chromosomes
outline changes in whole sets of chromosomes
they occur when organisms have three or more sets of chromosomes
the condition is called polyploidy
outline changes in the number of individual chromosomes
sometimes individual homolgus pairs of chromosomes fail to seperate during meiosis
this is known as non-disjunction
results in a gamete having one or more fewer chromosomes
