Unit 6: Mitosis Flashcards
Sexual reproduction
Offspring that generally resembles parents more closely than to other individuals of the same species. Each offspring inherits a unique characteristic of genes from each parent
Asexual reproduction
Creation of genetically identical offspring by a single parent
Chromosomes
Structures that contain most of an organisim’s DNA
Cell dividion
Reproduction of cells
Binary fission
How prokaryotes reproduce, the cell divides in half
Proteins exist of long thin fibers called…, which are a combination of…
Chromatin
Proteins and DNA molecules
When are compact , distinct chromosomes formed?
As a cell prepares to divide
The chromosome becomes visible under a light microscope
Each eukaryotic chromosome contains…
one long DNA molecule, which has hundreds or thousands of proteins
What happens before a cell begins to divide?
It duplicates all its chromosomes. As each chromosome is copied, new proteins molecules attach, each chromosome has two copies, called sister chromatids, which have identical copies of DNA
When sister chromatids are joined together, the narrow “waist” is called…
the centromere
Cell cycle
process of cell division
Interphase vs miotic phase steps
INTERPHASE: growing phase (longest phase)
- G1 (first gap)
- S phase
- G2 phase (second gap)
MIOTIC PHASE: when the cell actually divides
- mitosis
- cytokinesis
What stage does the cell spend most of its life in? What happens to the cell during this time?
Most time is spent in interphase, when the cell grows and copies its chromosomes
Prophase/Prometaphase
Prophase: Chromatin fibers become more coiled and folded, chromosomes can be seen with a light microscope. Identical sister chromatids join together. Microtubules grow out of centrosomes
Prometaphase: Nuclear membrane breaks up and microtubules attach to centromeres. Centrosomes are moved towards the center of the cell
Metaphase
Chromosomes line up against the middle (the metaphase plate)
Anaphase
Centromeres of each chromosome come apart, separating the sister chromatids. Once they are separated, each chromatid is called a chromosome. Microtubules shorten
Telophase
Cell continues to elongate. Chromatin Tiber of each chromosome uncoils and the nucleoli reappear.
Cytokinesis
The division of the cytoplasm. Two daughter cell completely separate.
(In an animal cell, there is a cleavage furrow that pinches the cell in two)
Growth factor
Protein secreted by certain body cells that stimulates other cells to divide
Density dependent inhibition
Phenomenon where crowded cells stop dividing
Anchorage dependence
Cells (most animal cells) must be in contact with a solid surface in order to divide
How do growth factors signal the cell cycle control system?
The cell cycle control system operates a set of molecules in the cell that triggers and coordinates key events in the cell cycle. A checkpoint in the cell cycle is critical control point to regulate stop and go signals. There are three major checkpoints during the G1, G2 subphases of interphase and the M phase. A growth factor might affect the cell cycle control system at the G1 checkpoint. A cell that responds to a growth factor has molecules of the growth factor to the receptor triggers a signal transduction pathway in a cell, which leads to cell division.
3 subphases of interphase
G1, S phase, G2 phase
During these phases, the cell grows
G1 phase
Cell grows
S phase
Chromosomes are copied
G2 phase
Cell grows more and completes preparations for cell division
M phase
The mitotic phase, the part of the cell cycle where the cell actually divides
2 phases, mitosis and cytokinesis
Tumor
An abnormally growing mass of body cells
Benign tumor
If the abnormal cells remain at the original site. They can cause problems if they grow in and disrupt certain organs
Malignant tumor
Can spread into neighboring tissues and other parts of the Jory, displacing normal tissue and interrupting organ function as it goes
Metastasis
The spread of cancer cells via the circulatory system beyond their original site
Carcinomas
Cancers that originate in the external or internal coverings of the body such as the skin or lining of the intestine
Sarcomas
Arise in tissues that support the body such as bone or muscle
3 reasons for mitosis
- Growth
- Cell replacement
- Asexual reproduction
A typical human somatic cell contains ___ chromosomes, __ matched pairs, called ___
46 chromosomes
23 matched pairs, homologous pairs
Where is each gene located?
The locus, specific place on a chromosome
What are the sex chromosomes?
X and Y
What are autosomes?
The other 22 pairs of chromosomes
Diploid cells
Any cell with 2 homologues sets of chromosomes
Gametes
Sperm and egg cells
Haploid
Cells that have a single chromosome sets
Fertilization
When a haploid sperm cell reaches and fuses with a haploid egg cell
Zygote
The fertilized egg is zygote and diploid
Meiosis
A type of cell division that produces haploid gametes in diploid organisms
Meiosis I: interphase
Chromosomes duplicate. At the end of interphase, each chromosome consists of 2 genetically identical sister chromatids attached together
Meiosis I: Prophase 1
Homologous chromosomes pair up forming a tetrad
Crossing over occurs
Meiosis I: Metaphase 1
Chromosome tetrads align on metaphase plate. Sister chromatids are attached at centromeres. Spindle microtubules attach to kinetichores at centromeres. In each tetrad, homologus chromosomes are held together at sites of crossing over. Homologous chromosomes of each tetrad are lined up to move in opposite directions of the cell
Meiosis I: Anaphase 1
Chromosomes move towards the 2 poles of the cell. Sister chromatids are still attached at centromeres. Only the tetrads (pairs of homologous chromosomes) split. 3 doubled chromosomes move towards each spindle
Meiosis I: Telophase 1 and Cytokinesis
Chromosomes arrive at the poles of the cell. Each pole of cell has a haploid chromosome set once the chromosomes reach their spot. Each chromosome still has 2 sister chromatids. In cytokinesis, 2 haploid daughter cells are formed
Meiosis II: Prophase II
Spindle forms and moves chromosomes tpwards the middle of the cell
Meiosis II: Metaphase II
Chromosomes are aligned on metaphase plate, NOT in homologous pairs, with the kinetichores of sister chromatids of each chromosomes pointing toward opposite poles.
Meiosis II: Anaphase II
Centromeres of sister chromatids separate and sister chromatids of each pair (now individual daighter chromosomes) move toward opposite poles of the cell
Meisos II: Telophase II and Cytokinesis
Nuclei forms at cell poles and cytokinesis also occurs. 4 daughter cells form
What is the end result of meiosis?
4 daughter cells with haploid number of chromosomes
What is crossing over? What phase of meiosis does it occur in?
The exchange of corresponding segments between 2 homologus chromosomes
Occurs during prophase 1
What is a karyotype?
An ordered display of magnified images of an individual’s chromosomes arranged in pairs. They show the chromosomes condensed and doubled as they appear in metaphase of mitosis
What is nondisjunction?
When members of a chromosome pair fail to separarte
Deletion
A fragment of a chromosome is lost
Duplication
A fragment from 1 chromosome joins to a sister chromatid or homologus chromosome
Inversion
A fragment reattaches to the original chromosome but in the reverse direction
Translocation
Attachment on a chromosomal fragment to a nonhomologus chromosome
Oncogene
a gene that can cause cancer when present in a single copy of the cell
Proto-oncogene
A normal gene with the potential to become an oncogene
Tumor-suppressor gene
cells with genes whose normal products inhibit cell divisions
The proteins they encode help prevent uncontrolled cell growth
At least how many mutations must be acquired for cancer to develop?
At least 4
What is a carcinogen?
Cancer causing agent, factors that alter DNA and make cell cancerous. Promote cell division (X-rays, UV rays, tobacco)
