Chapter 14: Mitosis and Meiosis Flashcards
What is a karyotype?
The chromosomes contained in a cell, usually listed in descending order of size
What are homologous chromosomes?
Chromosomes of the same length and shape, and have the same alleles (genes)
What is interphase?
An active period where protein synthesis, DNA replication and increase in number of mitochondria (and chloroplasts in plant cells) occur
What happens to the centrioles during interphase in animal cells?
They divide to form two pairs of centrioles
What is the centromere in a chromotid?
The region where two chromatids are most closely attached
What is mitosis?
A nuclear division where the daughter nuclei produced contains the same number of chromosomes as the parent nucleus (daughter cells are identical to the parent cell)
What are the four stages of mitosis?
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
What happens during prophase in mitosis?
Early prophase: Microtubules form around the centriole, and the two pairs of centrioles move to the opposite poles of the cell, connected by spindle fibres
Late prophase: The nuclear envolope disappears, and a spindle forms with the spindle fibres extending from one pole to another
What happens during metaphase in mitosis?
Chromosomes line up around the equator of the spindle. and the centromere of each chromosome is attached to a spindle fibre
What happens during anaphase in mitosis?
The centromeres split, and the sister chromotids are dragged to the opposite poles of the cell by the spindle fibres
What happens during telephase in mitosis?
The spindle fibre breaks down, and a nuclear envelope forms around the chromosomes at each pole of the cell. A nucleolus forms and the chromosomes uncoil and lengthen to become thin chromatin threads
What happens during cytokinesis?
The cytoplasm divides after mitosis
What are some differences in mitosis in plant cells comparred to animal cells?
1) There are no centrioles in plant cells
2) Cleavage of cytoplasm does not happen for plant cells
3) A cell plate is formed inbetween two daughter nuclei in plant cells
How does growth occur?
Cells undergo mitosis, and new cells are differentiated to form tissues and organs
What are cancerous tumor cells?
Undifferentiated cells that continue to divide uncontrollably
When does a cell undergo apoptosis?
When a genetic error occurs within a cell, it will undergo apoptosis, which is programmed cell death (suicide)
How are tumors generated?
When errors in DNA replication or mitosis cause the uncontrollable division of cells. This might cause a mass of abnormal cells within normal tissue
What is a benign tumor?
A tumor where the abonormal cells remain at their original site
What happens if a tumor is malignant?
It will multiply and spread to neighbouring cells and tissues where they form secondary tumors
What is meiosis?
A form of nuclear division that produces daughter nuclei containing half the number of chromosomes as the parent nucleus (reduction division
Where does meiosis often occur?
At the reporductive organs of organisms to form gamates
What is the difference between a diploid an haploid cell?
A diploid cell has both pairs of chromosomes, while a haploid cell has one set of each homologous pair of chromosomes
What is the difference between meiosis 1 and 2?
Meiosis 1 is the seperation of homologous chromosomes, while meiosis 2 is the seperation of two sister chromatids
Why is meiosis required prior to fertillisation in sexual reproduction?
Since sexual reproduction involves the fusion of two gamates, the zygote will have double the normal number of chromosomes. Therefore meiosis is required to bring the number of chromosomes back to the normal amount
What happens during prophase 1 in meiosis?
Chromatin threads condense to form chromosomes, and asters form around the centrioles which move apart to opposite poles of the cell. The spindle fibres form, and the nuclear envolope and nucleolus disappears.
Additionally, in meiosis, homologous chromosomes pair up with their sister chromatids along their whole length. The chromatids of homologous chromosomes may cross and twist around each other, causing them to break off and exchange parts (crossing over). This produces new combinations of alleles along the chromosomes
What happens during metaphase 1 in meiosis?
The pairs of homologous chromosomes arrange themselves along the equator of the cell, and the two chromosomes of each pair face opposite poles of the cell, and each chromosome is attached to a spindle fibre
What happens during anaphase 1 in meiosis
The homologous chromosomes seperate, and are pulled to opposite poles of the cell. In meiosis, the chromosomes are still made of two chromatids
What happens during telophase 1 in meiosis?
A nuclear membrane forms around the chromosomes at each pole
What happens during cytokinesis 1 in meiosis?
The cytoplsm cleaves producing two daughter cells, each with the haploid number of chromomes, and the centrioles replicate
What happens during prophase 2 in meiosis?
The centrioles move to opposite poles, the nuclear envolope breaks down, and the spindle fibres appear
What happens during metaphase 2 in meiosis?
The chromosomes arrange themelves along the equator of the spindle
What happens during anaphase 2 in meiosis?
The centromeres divide, and the sister chromatids seperate. The daughter chromatids are pulled to opposite poles of the cell
What happens during telophase 2 in meiosis?
The spindle fibres disappear, and the nuclear envelope forms around the two daughter chromosomes at each pole. A nucleolus reforms
What happens during cytokinesis in meiosis?
The cytoplasm cleaves into two, and two daughter cells are produced. The daughter cells have a haploid number of chromosomes as the parent cell
What is the difference between metaphase 1 and 2?
In metaphase 1, the chromosomes arrange themselves along the equator of the cell (vertically). In metaphase 2, the chromosomes arrange themselves along the equator of the spindle (horizontally)
