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
characteristics of down syndrome?
Excess genetic information and an unpaired chromosome in every cell
Experience physical and mental challenges
a round, full face
short height, larger forehead
Maintain a wide range of abilities and are able to carry out rich fulfilling lives
Turner Syndrome chromosome malfunctionaility?
XO-one X chromosome and no Y chromosome (missing sex chromosome)
turner syndrome characteristic?
Female in appearance but do not mature sexually.
Most fetuses are miscarried before 20th week of pregnancy
Klinefelter’s Syndrome chromosome
extra chromosome (x) (trisomy)
klinefelter syndrome characteristics
Males usually sterile
Exhibit some feminine body characteristics but severity varies
patau syndrome chromosome
extra chromosome on the 13th pair (trisomy)
patau syndrome characteristics
Large triangular nose, cleft lip
Weak muscle tone
Skeletal abnormalities
Serious developmental problems (brain, kidney, heart defects)
Rarely live past birth
Children rarely live more than a few months
Edwards syndrome chromosome
Extra chromosome on the 18th pair (trisomy)
edward syndrome characteristics
Many organ system defects
Very low survival rate
Most fetuses die before birth
Or live less than one month
how do you figure out a non-disfunction?
Nondisjunction disorders are usually confirmed by preparing a karyotype.
Small sample of white blood cells and stimulate them to divide
Solution added that stops division at metaphase when chromosomes are most condensed
Examined and disorders can be diagnosed
