Contributors to Genetic Variation and Cell Division Check Points Flashcards
Contributors to genetic variation
- independent assortment of homologous chromosomes at the metaphase plate in meiosis I
- random fertilization
- crossing over
Independent assortment of homologous chromosomes means that
there is a 50% chance of 1 arrangement of chromosomes and a 50% chance for the other one
Orientation of homologous chromosomes is random like “ “
a flip of a coin
The number of possible combinations for the gametes is calculated by
2^n, where n = the number of chromosomes in the genome
ex 4 chromosomes = 2^4 or 16 possibilities
in independent assortment, the amount of possible assortments is
1 of 8 million
in random fertilization, the number of possible assortments jumps to
1/64 trillion diploid combinations (zygote)
Crossing over increases variability: true or false
true
How many cell cycle check points are there?
3
Check point 1
after G1
- are there enough nucleotides to make the strand
- checks for DNA replication enzymes
- checks for sufficient nutrients and O2 present for S-phase
Check point 2
After S
- is all the DNA replicated ?
Check point 3
after G2
- are enough organelles present for 2 cells identical to the parental cell or 4 gametes
- are all structural proteins needed present? (tubulin)
- are critical proteins needed for mitosis and meiosis present
Two types of cell cycle control molecules
kinases and cyclins
kinases
enzymes that activate or inactivate proteins by phosphorylating them
cyclins
cycle in concentration throughout the cell cycle
MPF
maturation promoting factor/mitosis promoting factor
