Chapter 20 & 21 Flashcards
What two steps occur when a cell with a distinct nucleus divides?
- Mitosis
2. Cytokinesis
What is mitosis?
When the nucleus divides to form two nuclei
Hereditary material in parent cell duplicates and then divides into two identical sets
2n -> 2n 2n
What is cytokinesis?
When the cytoplasm divides into two parts, each contains one of the newly formed nuclei
How does DNA exist in the nucleus in a cell that is not dividing?
It exists in a mass of thin twisted threads called chromatin
What does DNA do when a cell is about to split?
They like into chromosomes then make duplicates to make double chromosomes (or a chromatid)
How many different chromosomes do humans have?
23 pairs
46 chromosomes
What does a centromere do?
The double chromosome attaches to the centromere in the middle and the spindles reach out and connect to the centromere
What are the centrioles?
The ends of the cell during cell division that the spindles spring out of
When does cytokinesis take place?
Inbetween anaphase and telophase
What causes cell division to stop and start?
It is not known yet
What is it called when a group of cells begin to divide in an uncontrolled fashion?
Cancer
What causes cancer?
Genetic changes (mutations) in the DNA of somatic cells
What is asexual reproduction in multicellular organisms?
The offspring develop from undifferentiated, unspecialized cells of the parent organism
Has exactly same hereditary information as parents
Examples of asexual reproduction?
Binary fission
Budding
Regeneration
Spore formation
What is Vegetative reproduction?
When undifferentiated cells divide miotically and then differentiate to produce an independent plant
Has same hereditary characteristic as parents
What are gametes?
Sex cells (male or female) Haploid cells
What is fertilization?
The fusion of the nuclei or the male and female gametes
What is a zygote?
The single cell formed from the fusion of fertilization
How are gametes formed?
Meiosis
What are somatic cells?
The cells of an organism except the cells that play a part in sexual reproduction
What are homologous chromosomes?
Pairs of chromosomes that carry genes for the same traits
One member of the pair comes from female while the other comes from male
What is meiosis?
A kind of cell division that results in gametes with half the number of chromosomes as the parent cell
Meiosis is the division of specialized cells to form sex cells called gametes
Results in haploid cells
What is the difference between haploid and diploid cells?
Diploid cells have all the homologous chromosomes paired together while haploid only has one chromosome from each pair
(Diagram page 419)
Diploid - 2n
Haploid- n
Difference between mitosis and meiosis?
Mitosis is the division of a diploid cell into two diploid cells that have the same amount of chromosomes as parent
Meiosis is the division of a diploid cell into four haploid cells that have half the amount of chromosomes as parent
Meiosis is the splitting of homologous chromosomes leading to non identical daughter cells while mitosis has daughter cells that are identical to eachother and the parent
The fundamental sequence of event in meiosis and mitosis is the same except in meiosis the division happens twice
Both undergo cytokinesis and both result in daughter cells as a result of parent cells
Mitosis produces somatic cells while meiosis produces gamete cells
