Chapter 6: Cell Division till (6.2) Flashcards
What is cell division?
- a process in which a parent cell divides to form new daughter cells which occur in two main stages
What are the two stages of cell division?
- karyokinesis
- cytokinesis
Explain karyokinesis and cytokinesis.
- karyokinesis is the division of the nucleus to form two nuclei
- cytokinesis is the division of the cytoplasm to form two daughter cells
Cell division involves the passing of _______ _______ from parent cells to daughter cells.
- genetic information
Inside the nucleus, ____ and ____ together form structure called ______.
- DNA
- protein
- chromosome
What are the two types of body cells?
- somatic cells
- gametes
What are somatic cells?
- diploid cells with two sets of chromosomes in the nucleus of a cell
- one set is the paternal chromosomes and another set is the maternal chromosomes
Each paternal and maternal chromosome of the same characteristic pair up to form _________ _________.
- homologous chromosomes
What are diploid cells and haploid cells?
- diploid cells are cells that have two complete sets of chromosomes
- haploid cells are cells that have one complete set of chromosomes
What are gametes?
- haploid cells with one set of chromosomes in the nucleus
The chromosomes are not ____ and appear like long threads called _____.
- visible
- chromatin
At the same time cell division begins, each chromosome is seen to consist of two ____ ____.
- identical chromatids
What is a cell cycle?
- sequence of events that a new cell undergoes as it grows and develops and then divides to form two daughter cells
The cell cycle consists of ____ and _____ which are two main phases.
- Interphase
- Mitosis phase ( M phase )
Explain Interphase and mitosis.
Interphase
- no cell division
- cell grows and prepares to divide
- consists of three subphases ( G1, S, and G2 )
mitosis
- cell division occurs
- two subphases ( mitosis and cytokinesis )
Explain the G1 phase.
- cell grows rapidly
- synthesizes organelles
- chromosomes in the form of chromatin
Explain the S phase.
- synthesis of DNA
- replication of DNA occurs ( one strand of a chromosome is replicated to form two identical strands called sister chromatids )
- each chromosome is made up of two strands of sister chromatids
- in animal cells, centrioles duplicated
Explain the G2 phase.
- cell continues to grow and remains metabolically active
- cell stores energy and prepares for cell division
What is Mitosis?
- a nuclear division which is followed by cytokinesis to form two genetically identical daughter cells
What occurs in the prophase?
- chromatin condense become visible
- each chromosome is made up of two sister chromatids joined at the centromere
- centrioles move to opposite poles of the cell and spindle fiber begin to form
- in plant cells, spindle fibres are formed without centrioles
- at the end, the nucleolus disappears and the nuclear membrane disintegrates
Explain metaphase.
- chromosomes line up along the equator of the cell
- spindle fibres formed completely and attaches to the centromere
- centromere divides
What happens in anaphase?
- centromere splits
- spindle fibres pull the sister chromatids apart
- now knows as daughter chromosomes
- at the end, each pole has a set of complete and identical chromosome
Explain telophase.
- spindle fibers disappear
- new nuclear membrane is formed around the chromosomes at each pole
- nucleolus reform in each nucleus
- chromosomes uncoil and become thin chromatin threads
Microfilament is formed around the center of the plasma membrane. The centre of the cell ________ ______, forming a ______ _____. The cleavage furrow deepens until the cell separates into two ______ cells.
- constricts inwards
- cleavage furrow
- daughter
A cell ____ is formed between the two daughter nuclei. The cell plate grows _____ from the centre of the cell dividing the cytoplasm into two halves.
- plate
- outwards
Comparison between mitosis in animal cells and plants cells.
Mitosis in animal cells - centrioles found - mitosis occurs in stem cells Mitosis in plant cells - centrioles are absent - occurs in meristematic tissues
What is the necessity of mitosis?
- development of an embryo
- healing of wounds on the skin ( replace dead and damaged cells )
- regeneration ( lizards are able to grow a new tail to replace the tail that is lost )
- asexual reproduction ( aids organisms such as hydra to produce new individuals through formation of new buds )
