5.2 Flashcards
Gametes
meiosis yields one oocyte and 3 polar bodies (XX) or 4 sperm cells (XY)
Meiosis
Interphase: replication of chromosomes (46 X, one diploid set)
Meiosis I: first meiotic division (23 X, one haploid set) 2 cells
Meiosis II: second meiotic division (23 I, one haploid set) 4 gametes
Meiosis I (reductional division)
Prophase I: homologous chromosomes condense and undergo synapsis (pairing homologous X) and crossing over (recombinant chromatids) (2S, 2C) also spindle formation and nuclear envelope break down
Metaphase I: tetrads (2X) line up, each homologous X is attached at centromere
Anaphase I: homologous chromosomes separate but not sister chromatids
Telophase 1: 2 daughter cells, slightly uncondense, slight nuclear envelope reform (1S, 2C)
Meiosis II (equational division)
Prophase II: condense, nuclear envelope break down, spindle formation
Metaphase II: chromosomes align, microtubules attach
Anaphase II: sister chromatids seperate
Telophase II: cytokinesis, nuclear envelope reforms
chromosome number variation
- first division nondisjuction: 2 gametes missing X, 2 gametes extra X
- second division nondisjunction: 1 gamete missing X, 1 gamete extra X, 2 gamete ‘normal’
medel studied which traits of which plants
Pea plants, 7 traits:
- color of seed
- shape of seed
- color of pod
- shape of pod
- color of flower
- position of flower
- plant height
names of generations
P: parental
F: filial
punnet square
we love punnet squares, know how to draw them, capital is dominant gene (A) lower case is recessive (a)
- monohybrid cross: one trait
- dihybrid cross: 2 traits
Mendels laws of inheritance
- Law of dominance: hybrid offspring only inherit dominant trait
- Law of segregation: offspring aquire one factor from each parent
- Law of independant assortment: pairs of traits assort independently (only applies to genes located on different chromosomes)
wrinkled vs smooth seed
found in SBE1 gene, in wrinkled peas it’s interrupted, cannot convert sugar to starch, young seed swells then adult seed deflates looking wrinkled