Chromosomes And Cellular Reproduction Flashcards
What is a prokaryote? (3 items)
Unicellular with no compartmentalized cell structure.
DNA is circular and not highly packed.
Made up of eubacteria and archaebacteria.
How do prokaryotes replicate? (3 items)
Simple division: separation of replicated circular chromosome
Single origin of replication
High rate of replication
What is a eukaryote? (3)
Both unicellular and multicellular with compartmentalized cell structure.
DNA resides in the nucleus.
DNA is wrapped around histones to form tightly packed chromosomes.
Number of human chromosomes (1)
23 pairs = 46 chromosomes.
Chromosome structure (3)
Centromere - attachment point for spindle microtubules
Telomeres - tip of a linear chromosome
Origins of replication - where DNA synthesis begins
Chromatid (1)
One half of a paired chromosome (can also be called a chromosome)
Interphase (1)
Cell growth
Stages of interphase (3)
G1, S, G2
G1 (1)
Cell growth
G0 (3)
Non-dividing phase
Occurs when errors are present
Often leads to apoptosis
G1/S checkpoint (2)
DNA error checking point before entering S phase
Cancer blows through this checkpoint
S Phase (1)
DNA synthesis phase
G2 (1)
Mitosis preparation
G2/M checkpoint (1)
Last checkpoint before mitosis
M phase (1)
Mitosis and cytokinesis
Genetic consequences of the cell cycle (3)
Produces two cells that are genetically identical to each other
New cells contain a full complement of chromosomes
Each new cell contains approximately half (but not necessarily identical) the cytoplasm and organelle content of the original parental cell
Stages of Mitosis (5)
Prophase Prometaphase Metaphase Anaphase Telophase
Interphase (2)
Nuclear membrane is present
Chromosomes are relaxed
Prophase (3)
Chromosomes condense
Each chromosome possesses two chromatids
Centrosomes and mitotic spindles forms
Prometaphase (2)
Nuclear membrane disintegrates
Spindle microtubules attach to chromatids
Metaphase (1)
Chromsomes line up on the metaphase plate
Anaphase (1)
Sister chromatids separate and move toward opposite poles
Telophase (3)
Chromosomes arrive at the spindle poles
Nuclear membrane reforms
Chromosomes relax
Cytokinesis (2)
Cytoplasm divides
Cell membranes close
Cohesin (1)
Controls the separation of chromatids in mitosis and meiosis
Shugoshin (1)
Protects the breakdown of cohesin near the centromere
Stages of Prophase I (5)
Leptotene Zygotene Pachytene Diplotene Diakinesis
Leptotene (1)
Chromosomes contract and become visible
Zygotene (4)
Chromosomes continue to condense
Homologous chromosomes pair up
Homologous chromosomes begin synapsis - a very close pairing association
Each pair of chromosomes has four sister chromatids called a bivalent or tetrad.
Pachytene (2)
Continued condensation
Formation of synaptonemal complex
Crossing over (2)
Crossing over of chromosome segments from the sister chromatid of one chromosome to the sister chromatid of the other synapsed chromsome
Can occur in zygotene, pachytene, or diplotene phases, but mostly pachytene
Diplotene (2)
Centromeres move apart
Chromosome still attached at each chiasma
Diakinesis (4)
Continued chromosome condensation
Chiasmata move to tips of chromosomes
Nuclear membrane breaks down
Meiotic spindle forms
Metaphase I (1)
Homologous pairs of chromosomes line up along the metaphase plate
Anaphase I (2)
separation of homologous chromosome pairs
Random distribution of chromosomes into two newly divided cells
Telophase I (3)
Chromosomes arrive at opposite poles
The cytoplasm divides.
Chromosomes relax.
Prophase II (1)
Chromsomes recondense
Stages of Meiosis (3)
Interphase - DNA synthesis and chromosome replication
Meiosis I - separation of homologous pairs and reduction of chromosome number by half
Meiosis II separation of sister chromatids
Metaphase II
Individual chromosomes line up along equatorial plate.
Anaphase II (1)
Sister chromatids separate and move toward the opposite poles.
Telophase II (2)
Chrosomes arrive at spindle poles
Cytoplasm divides
Consequences of Meiosis and Genetic Variation (3)
Four cells are produced from the original cell
Chromosome number in each new cell is reduced by half - new cells are all haploid.
New cells are genetically different from one another and from the parental cell.
