Chromosome Segregation Flashcards
Are germ cells haploid or diploid?
Haploid, 23 chromosomes
Are somatic cells haploid or diploid?
Diploid, 46 chromosomes
Basic phases in cell cycle
- Interphase
- M phase (mitosis)
What happens in interphase?
Replication, where homologous chromosomes that are very similar to one another, replicate
Main processes of prophase?
- chromosomes condense
- nucleolus disappears
- centrioles move to poles
- spindles begin to form
-nuclear membrane breaks down
Late prophase/ prometaphase
Movement of chromosomes to center of cell
During which phase of the cell cycle does chromosomal DNA replicate?
Interphase
Main processes of metaphase?
chromosomes align at equatorial plane of the cell, mitotic spindle formation
Main processes of anaphase?
Sister chromatids split.
- chromosomes move to poles of cell
- cell begins to elongate
- cleavage furious starts
Main processes of telophase?
Chromosomes reach poles.
- nuclear membrane reforms
-chromosomes de condense
-nucleoli reform
-spindle fibers disappear
-cleavage furrow continues
Main processes of cytokinesis?
Completion of cleavage furrow and production of 2 cells
During which phase do chromosomes condense as part of the cell cycle?
Prophase
Chromosomes align at equatorial plane of the cell during telophase T/F?
False
Difference between mitosis and meiosis?
Meiosis only occurs in germ cells, produces gametes, involves two sequential cells divisions without DNA replication
Meiosis I
Reduction division, segregation of homologous chromosomes. 2n –> n
Meiosis II
Equational division. Same as mitosis EXCEPT going to 1N
Meiosis Prophase I Stages
- leptotene
- zygotene
- pachytene
- diplotene
diakinesis
Leptotene
- Chromosomes begin to condense and become visible
- Thickened regions (chromosomes) appear
Zygotene
- Chromosomes continue to condense and there is active pairing of chromosome threads between non-sister chromatids
Pachytene
-Chromosomes become fully aligned
Diplotene
- Aligned homologous pairs become less tightly aligned
- Chiasmata become apparent
Chiasmata
point in chromosomes that cross over and share genetic info
Diakinesis
- Compaction is completed and chromosomes are ready to be segregated
Bivalent chromosomes
pair of connected homologous chromosomes
What is the importance of meiosis?
- Production of haploid cells by meiosis is critical for sexual reproduction.
- Independent assortment of chromosomes during meiosis I produces diversity in offspring.
- Recombination increases diversity by shuffling genetic information between chromosomes
How many possible combinations can occur from 23 pairs of chromosomes?
8,324,608
At the end of meiosis, the daughter cells contain diploid genome T/F?
False
Meiosis can occur in sperm cells T/F?
True
