Topic 3.3 Meiosis Flashcards
What is meiosis?
the process of producing 4 haploid nuclei from a single diploid cell
The halving of chromosomes allows what?
a sexual life cycle with fusion of gametes
What happens before meiosis?
DNA is replicated so that all chromosomes consist of 2 sister chromatids
How is DNA in each sister chromatid?
identical and condensed (after meiosis, becomes unique separate chromosomes)
What is the process of meiosis?
made up of 2 cell divisions, which produce haploids
What is crossing over?
In Prophase I, sections of the DNA that can be exchanged between homologous chromosomes (new alleles combination) (sections are swapped)
What is Random Oreintation?
(Metaphase I; II) results in nearly infinite combinations of chromosomes (2^23 possible without crossing)
What is non-disjunction?
occurs in meiosis when chromosomes fail to separate correctly
(results to daughter cells with too many or few chromosomes)
What are the chances of having Down Syndrome?
As parents age, the higher the chance of having a child with Down Syndrome
What is amniocentesis?
a needle passed through the abdomen into the amniotic sac
(Amniotic fluid taken contains fetal cells)
(late pregnancy–low miscarriages)
What is chorionic Villas Sampling?
a tube inserted through the cervix and used to remove the placenta called chorionic Villa (contains fetal cells)
(early pregnancy–higher miscarriages
Where do genetic variations take place?
in prophase I, Metaphase I and II
