meiosis

Question 1

explain importance of meiosis in life cycle of a sexually reproducing organism

Answer 1

meiosis halves the number of chromosomes (formation of haploid gametes)
restoration of diploid number at fertilisation
introduces genetic variation

Question 2

what happens to chromosomes in meiosis

Answer 2

chromosomes condense
chromosomes associate in homologous pairs
crossing over
join to spindle fibres at centromere at equator of cell
independent assortment-chromosomes move to opposite poles
chromatids separated in 2nd division

Question 3

describe how meiosis causes variation and explain the advantage of variation to the species

Answer 3

crossing over
independent segregation of homologous chromosomes in meiosis 1
random assortment of chromatids in meiosis 2
advantages:
different adaptations- some better adapted to environment
some survive through natural selection to reproduce and pass on gene which increases frequency in the gene pool
allows for changing environment

Question 4

explain how crossing over can contribute to genetic variation

Answer 4

sections of chromatids exchanged
sections have different alleles
new combinations of linked alleles

Question 5

other process that result in genetic variation

Answer 5

mutation- new allele formed as sequence of genes changed
random fusion of gametes in fertilisation- new combination of alleles
independent assortment of chromosomes- shuffling of maternal and paternal chromosomes and new combination of alleles

Question 6

basic overview of meiosis

Answer 6

meiosis 1 is like mitosis. meiosis 1 results in the production of two diploid daughter cells. each of the phases of meiosis are the same as normal mitosis
crossing over occurs in meiosis 1, this is where genetic material is exchanged between homologous chromosomes. resulting in the formation of new combinations of genetic material, creating genetic diversity in the daughter cells
two diploid daughter cells are produced. homologous chromosomes are separated from each other and assorted into two diploid daughter cells

meiosis 2
two diploid daughter cells divide in order to produce 4 haploid daughter cells, each with a single copy of every chromosome