bio-.cell cycle/reproduction Flashcards
Chromatin
Loosely wound strands of DNA
What is a chromosomes
A single strand of DNA condensed and wrapped around many histone proteins
Chromatid (sister chromatids)
Half of a chromosome
Centromere
Where sister chromatids are held together
Chromosome
Duplicated chromatids (duplicated for cell division )
Telomeres
Ends of chromosome
Two types of chromosomes and how many of each
Autosomes - 44 (determine your traits)
Sex chromosomes - 2 (determine your sex)
Homologous chromosomes
Two copies (one from each parent)
Carry genes for the same traits
Same size and shape
Diploid cells
2n
Cells that have two sets of chromosomes
Somatic cells
Haploid cells
n
Cells that only have one set of Chromosomes
Sex cells (sperm and egg only have 23)
Why is mitosis/cell division necessary
Cell gets bigger, DNA doesn’t
Asexual reproduction
Binary fission-cell growth and replication -plasme amembrwne grows inward and splits into two
In prokaryotic cells
Steps of mitosis
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
Steps of interphase - describe each
G1 - growth and acquire nutrients
S - DNA synthesis occurs, replicate every chromosome
G2 - completion of growth and readying for division
What and when are the three checkpoints
G1->S is DNA intact?
G2->M have you completed DNA replication?
Metaphase -> anaphase Are chromosomes aligned on metaphase plate?
3 major events during prophase
- Chromosomes condense
- Spindle microtubules form
- Chromosomes captured by spindle fibers
Metaphase
Spindle fibers (attached to chromosomes) align chromosome On metaphase plate
Anaphase
Sister chromatids are pulled apart and gather towards one pole, as spindle fibers begin to push cell apart
4 events of Telophase
- Spindle microtubules disintegrate
- Nuclear membrane firms around group of chromosomes at poles
- Chromosomes unwind into normal state
- Nucleoli reappear
Cytokinesis
Animal cells: microfilaments attach to membrane and form ring at equator and starts to pinch together
Plant cells : cell plate (with cell wall material) forms along equator of cell
What can happen if growth isn’t controlled
Tumors, cancer
Purpose of meiosis
Create haploid gametes that are genetically unique
Meiosis I
Separates homologous chromosomes
Meiosis II
Separates sister chromatids
Phases of meiosis I and II
Same as mitosis but with I or II to distinguish
When does crossing over occur
Prophase I
What’s different between metaphase I and regular metaphase / metaphase II
The homologous chromosomes are “zipped together” by proteins to ensure that they stay together when aligning on the metaphase plate, so that they separate during t anaphase
