Independent Assortment/Abnormal Meiosis (genetics) Flashcards
variability? meaning?
“chance”
-> things are never genetically identical
What is indepedent random assortment? and How does it work?
random Independent Assortment refers to the random orientation of homologous chromosome pairs (tetrads) along the metaphase plate during metaphase I of meiosis.
–> homologus chromosoems can line up in any way, therefore its “random”
The way these pairs align is completely random, and this randomness directly influences how chromosomes are separated during anaphase I.
how do you find the possible combinations of chromosome pairs? How likely is it for each arrangement?
Diploid organisms (2n)→ number of combinations is 2^n
3 pairs of chromosomes → 2^3 = 8
Ex. 23 pairs of chromosomes (like in humans)
2^23 = ?
2^23 = 8,388,608 possible combinations
N= refers to the NUMBER of PAIRS (2)
each arrangement is equally likely!
what is gametogenisis?
the production of gamates (sex cells)
-> contains the haploid number of chromosomes and is produced by meiosis
what is spermatogenisis
the production of mature sperm cells
what is oogenesis?
the production of mature egg cells
what happens in oogenesis?
cytoplasm does not divide equally, 1 cell receives most/all the cytoplasm (and all other cells become polar bodies and die)
–> creation of a ovum
–> 1 egg cell get all the cytoplasm/nutrients because it holds the baby, therefore needing optimal enviroment
what happens in spermatogenesis?
-> cytoplasm divides equally, producing 4 sperm cells (all small insize, made for mobility)
-> does not need a lot of nutrients because it does not hold the baby, therefore only needed to pass DNA down
what is sex determination + examples?
what determines the reproductive organs/sex of an organism, for humans it is the XY chromosomes (x indicating females, y indicating males, passed down by our parents)
other sex determinations include:
temperature
age
social structure
infection
errors in meiosis + what is it influenced by?
Factors that interfere with meiosis and/or fertilization can contribute to genetic disorders and infertility
Can be caused by:
Random meiotic errors
disease
environmental factors
what is NONDISFUNCTION
failure of homologous chromosomes to move to opposite poles of the cell during meiosis; (fail to separate correctly)
results in an abnormal number of chromosomes in the daughter cells (cells with an extra chromosome, or missing a chromosome)
Not able to function normally
can happen during Anaphase I or during Anaphase II of the meiosis
what is (n+1)
trisomy, a extra chromosome (extra genetic information) (3 chromosomes)
what is (n-1)
monosomy, missing chromosome, (missing genetic information) (1 chromosome)
risk factors of nondisjunction increase with?
age, (despite being healthy)
downsyndrome chromosome error where?
3 x #21 chromosome
Trisomy of chromosome 21
