Chapter 3 - Cell Division/ Chromosomes Flashcards
meiosis I
homologous chromosomes separate from one another, reducing the diploid number of chromosomes (2n) to the haploid number (n)
meiosis II
sister chromatids separate to produce haploid gametes, each with one chromosome of the diploid pair
purpose of mitosis
to produce genetically identical cells for growth and maintenance
product of mitosis
2 genetically identical diploid daughter cells that continue to divide by mitosis
purpose of meiosis
to produce gametes for sexual reproduction that are genetically different
product of meiosis
4 genetically different haploid cells that mature to form gametes and unite to form diploid zygotes
3 important events in meiosis I
- homologous chromosome pairing
- crossing over between homologous chromosomes
- segregation of homologous chromosomes that reduce chromosome to the haploid number
4 stages of meiosis I
- prophase I
- metaphase I
- anaphase I
- telophase I
stages of prophase I of meiosis I
- leptotene
- zygotene
- pachytene
- diplotene
happenings of prophase I of meiosis
homologous chromosome pairing and recombination (crossing over) takes place during pachytene stage
happenings of metaphase I of meiosis I
tetrads align along metaphase plate
this is where independent assortment occurs
happenings of anaphase I or meiosis I
homologous chromosomes separate and sister chromatids remain attached
happenings of telophase I and cytokinesis (end of meiosis I)
nuclear membrane reforms to create 2 new cells each with a haploid set of chromosomes
happenings of prophase II of meiosis II
nuclear envelope breaks down and centrosomes appear
happenings of metaphase II of meiosis II
chromosomes align along the metaphase plate
happenings of anaphase II of meiosis II
sister chromatids separate
happenings of telophase II and cytokinesis (end of meiosis II)
nuclear envelope reforms to create 4 new genetically different haploid cells
synapsis
alignment of homologous chromosomes pairs in zygotene of prophase I
3 stages of interphase of mitosis
- G1 - cell expresses its genetic info
- S - replicates its chromosomes; results in double the amount of DNA and the creation of 2 sister chromatids for each chromosome
- G2 - prepares for entry into M phase
5 stages of M phase
- prophase
- prometaphase
- metaphse
- anaphase
- telophase
major difference between meiosis and mitosis
in meiosis, the sister chromatids stay attached
hemizygous
referring to the genotype of males that carry a single copy of each x-linked gene
barr body
a condensed and mostly inactivated X chromosome
lyon hypothesis
an X is randomly chosen in each cell for inactivation early in development
nondisjunction
the failure of homolog or sister chromatid separation during cell divisions; results in nuclei with the wrong number of chromosomes
