Mitosis & Meiosis Flashcards
What is mitosis?
Typical cell growth
Results in daughter cells having the same number and kind of cells as the parent cell
Occurs in somatic cells
What is meiosis?
Division and duplication of reproductive cells
There are two nuclear divisions that occur and four haploid cells are produced
What is the cell cycle?
2 stages: interphase and actual cell division (mitosis)
Cells spend most of their life in interphase (growing and DNA replication)
What are the stages of interphase?
G1: rapid cell growth
S: Synthesis - duplication of chromosomes
G2: more growth, getting ready for another cell division
What are the four phases of mitosis?
Prophase (prepare)
Metaphase (middle)
Anaphase (apart)
Telophase (two)
What happens in prophase?
Chromosomes become visible under a microscope as they shorten and thicken
Nuclear membrane breaks down
Centrioles move to opposite pole creating spindle fibres between them
What are centrioles?
Small protein body found in the cytoplasm that migrate to opposite poles
What are spindle fibres?
Protein structure that attaches to centrioles and guides chromosomes during cell division
What happens in metaphase?
Chromosomes composed of sister chromatids move to the center of cell (equatorial plate)
Chromosomes appear as dark, thick, filamentous structures and become intertwined
What happens in anaphase?
The centromere splits apart and the chromatids move to opposite poles along the spindle fibres
If mitosis proceeds correctly, the same number and type of chromosomes will be found at each pole
What happens in telophase?
The chromosomes reach the poles
A new nuclear envelope forms around each ear of separated chromosomes
Mitosis is complete, but cell division is not yet complete
What is cytokinesis?
Divides the cytoplasm and its organelles roughly equally into two daughter cells in somatic cells
What two cells can reproduce endlessly?
Sperm cells
Cancer cells
What is the diploid number?
The diploid chromosome number is 46 in humans
Refers to the entire amount of chromosomes present in a human cell
Can be represented as 2n
What is the haploid number?
The haploid chromosome number is 23 in humans
Humans have 23 pairs of chromosomes
Can be represented by n
What happens in prophase 1 in meiosis 1?
Chromosomes condense and become visible, centrioles move toward the poles, and nuclear membrane begins to dissolve
Homologous chromosomes pair up, forming tetrads
Each tetras is comprised of four chromatids
What is the process of crossing over?
Occurs in prophase 1 and metaphase 1 of meiosis 1
Homologous pairs will swap genetic material
Crossing over serves to increase genetic diversity by creating four unique chromatids
What happens in metaphase 1 in meiosis 1?
Homologous chromosomes attach to spindle fibres and line up in the middle (equatorial plate)
What happens in anaphase 1 in meiosis 1?
The homologous chromosomes separate
What happens in telophase 1 in meiosis 1?
Nucleus completes division, the chromosomes are still composed of sister chromatids
What happens in meiosis 2?
Prophase 2, metaphase 2, anaphase 2, and telophase 2, repeats the same steps but with half as much genetic material
There is no replication of chromosomes prior to meiosis 2
What happens in cytokinesis 2 in meiosis 2?
The final step of meiosis where each cell splits into two daughter cells
A total of four gametes, each with half the number of chromosomes is formed
What is nondisjunction?
When two homologous chromosomes fail to separate
One of the daughter cells will have too many chromosomes, the other too few
What is a trisomy?
If the gamete with 24 joins a normal gamete with 23, the resulting individual will have 47 rather than 46 chromosomes
What is a monosomy?
If the gamete with 22 joins a normal gamete with 23, the resulting individual will have 45 chromosomes rather than 46
What causes Down syndrome?
Trisomy 21
Three copies of chromosome 21
What causes Turner syndrome?
Produces females with a single X chromosome
What causes Klinefelter Syndrome?
Inherits two X chromosomes and one Y
