T3

Question 1

why do offspring resemble parents?

Answer 1

because parents transfer there genes that contain the genetic material that produce traits

because gametes are produced by meiosis rather than mitosis, the child and parents are not genetically identical because only half of one parents gametes are involved

Question 2

meiosis

Answer 2

allows for sexual reproduction because it produces gametes
- 4 haploid daughter cells are produced
- 2 cell divisions
- genetically varied

this is useful as it introduces variation and genetic diversity to a population - more stable

Question 3

independent assortment of chromosomes

Answer 3

this allows genetic variation to be introduced
- the homologous chromosomes are separated randomly during meiosis 1 - anaphase

Question 4

crossing over of non sister chromatids

Answer 4

this introduces genetic variation
- during prophase 1 the HC pair, the non sister chromatids twist and exchange lefts of chromatids to form recombinant alleles

Question 5

random fertilisatio

Answer 5

this introduces genetic variation as the two gametes that fuse to form a zygote is completely random and there are endless combinations

Question 6

why is it important that the number of chromosomes are maintained?

Answer 6

important to maintain the diploid number from generation to generation so that members in the same species can sucessfully reproduce

Question 7

what is the evolutionary link of genetic variation?

Answer 7

variation and diversity in a population drives natural selection and therefore the evolution of a species

having more alleles ensures a higher chance of survival for a species in the even of a catastrophic change or change of environment

Question 8

why does asexual reproduction produce offspring that are genetically identical to parent?

Answer 8

because asexual reproduction involves mitosis which produces genetically identical diploid cells
and only involves one parent so the genetic material in the offspring is the same as the parent
- no genetic variation

Question 9

meiosis 1 in detail

Answer 9

PROPHASE 1
- the nuclear envelope breaks down, the chromosomes condenser and are visible
- the duplicated HC pair-up and crossing over occurs between the non-sister chromatids this forms a chiasmata

METAPHASE 1
- pair of HC line up along the equator with each HC lined up independently of other pairs
- the microtubules from the poles attach to the kinetochores at the centromeres

ANAPHASE 1
- the two HC separate as the spindle fibres contract to opposite poles

TELOPHASE 1 AND CYTOKINESIS
- two diploid cells form each chromosome consisting of 2 sister chromatids

Question 10

meiosis 2 in detail

Answer 10

similar process to mitosis expect no DNA replication