-
Telomeres
- a protective cap at the end of the DNA
- every time a cell divides the telomere gets a bit shorter
- when the telomere becomes too short, the cell dies
-
Cancer
- cells that rebuild the telomere with each division can become cancerious
- cells that have forgotten how to die
- unrestrained cell growth and division
- can lead to tumors
- second leading cause of death in US
-
Prokaryotic Chromosomes
- genetic info is carried in a single circular chromosome
- this strand of DNA is attached at one site to the cell membrane
-
Eukaryotic Chromosomes
- genetic info is organized into linear chromosomes
- eukaryotic chromosomes float freely in the nucleus
-
Binary Fission
- prokaryotes divide by binary fission
- bacteria divide by binary fission
- circular chromosome duplicates itself and the cell splits into two indentical new cells
- asexual reproduction (daughter cells inherit their DNA from single parental cell)
-
Cell Division
- occurs in the mitotic phase
- the rest of the cycle is called interphase (two gap phases for growth, synthesis phase for replication of DNA)
-
Eukaryotic Cell Cycle
- Gap 1: cell's primary growth phase. Normal cellular functions (making proteins, getting rid of waste, etc) take place
- DNA Synthesis: cell begins preparations for division. Every chromosome creates an exact duplicate of itself in a process called replication
- Gap 2: Second period of growth and preparation for cell division.
- ALL ABOVE ARE INTERPHASE
- Mitosis: cell's nucleus duplicates, then divides
- Cytokinesis: cell then duplicates, forming two separate cells
-
Replication
- the process of DNA duplication
- cell division is preceded by replication
- unwinding then rebuilding (enzyme connects appropriate complementray base to the exposed base)
-
Complementarity
characteristic that in the double-stranded DNA molecule the base on one strand always has the same pairing-partner (called complementary base) on the other strand
-
Pairs
- Adenine to Thymine
- Guanine to Cytosine
-
Mutation
- errors in replication can lead to changes in the DNA sequence called mutations
- several DNA repair processes occur after replication
- if error remains, the sequences in a replicated DNA molecule can be different from those in the parent molecule
-
Mitosis
- most cells are not immortal: mitosis generates replacements
- two reasons for mitosis: growth and replacement
-
Apoptosis
A form of cell death in which a programmed sequence of events leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells. PROGRAMMED DEATH
-
Mitosis
- cells duplicate themselves, occurs in four steps then followed by the replication of chromosomes
- 1. chromosomes condense
- 2. all of the duplicated and condensed pairs of chromosomes move to the center of the cell
- 3. each chromosome is pulled apart from its duplicate
- 4. new cell membranes form around each complete set of chromosomes and the cytoplasm duplicates as well
- one parent cell becomes two daughter cells
-
Interphase
- first step in mitosis (preparation)
- chromosomes replicate in preparation for mitosis
- long, linear chromosomes that have replicated condense
-
Centromere
joint between two sister chromatids
-
Prophase
- FIRST STEP IN MITOSIS
- nuclear membrane breaks down
- sister chromatids (replicated chromosomes) condense
- spindle forms
-
Metaphase
- SECOND STEP IN MITOSIS
- sister chromatids line up at the center of the cell
-
Anaphase
- THIRD STEP IN MITOSIS
- sister chromatid pairs are pulled apart by the spindle fibers
- One full set of chromosomes goes to one side of the cell and another identical set goes to the other
-
Telophase
- FOURTH STEP IN MITOSIS
- chromosomes begin to uncoil as the nuclear membrane is reassembled around them
-
Cytokinesis
- cytoplasm and organelles duplicate and are divided into approximately equal parts
- cell splits into two
-
Metastasis
cancer cells can separate from a tumor and spread throughout the body via the circulatory system
-
Sexual Reproduction
- requires special cells made by meiosis (generates sperms and eggs)
- diploid cells: two copies of each chromosome
- haploid cells: one copy of each chromosome
-
Meiosis
- starts with a diploid cell (from gonads)
- gametes: special reproductive cells (gametes are produced through meiosis)/ have only half as many chromosomes as the rest of the cells in the body
- you have two copies of every gene
- reduces amount of genetic material in gametes (gametes have half as much genetic material as the parent cell)
- produces gametes that all differ from each other with respect to the combinations of alleles they carry (gametes carry different combinations of alleles)
-
Homologues and Sister Chromatids
- Homologues are the maternal and paternal copies of a chromosome
- A sister chromatid is a chromosome and its identical duplicated version held together at a centromere
-
Meiosis (2)
- cells undergoing meiosis divide twice (4 total)
- interphase: each chromosome in a homologous pair replicates to form a sister chromatid
- meiosis I: homologous pairs seperate
- meiosis II: sister chromatids seperate. results in four haploid cells, two contain a single copy on one of the original chromosomes and the other two contain a single copy of the other chromosome
-
Prophase I
- most complex of all phases of meiosis
- replicated chromosomes condense
- spindle is formed
- nuclear membrane disintegrates
-
Metaphase I
each pair of homologous chromosomes moves to the equator of the cell
-
Anaphase I
- beginning of the first cell division that occurs during meiosis
- homologues are pulled apart toward opposite sides of the cell
- maternal and paternal sister chromatids are pulled to the ends of the cell in a random fashion
-
Telophase I
- marked by the chromosomes arriving at the two poles of the cell
- the cytoplasm divides and the cell membrane pinches the cell into two daughter cells
-
Meiosis Division
separating the sister chromatids
-
Prophase II
- genetic material once again coils tightly making the chromatids visible under the microscope
- in the brief interphase prior to prophase II there is no replication of any of the chromosomes
-
Metaphase II
sister chromatids (each appearing as an X) move to the center of the cell
-
Anaphase II
the fibers attached to the centromere begin pulling each chromatid in the sister chromatid pair toward opposite ends of each daughter cell
-
Telophase II
the cytoplasm then divides, the cell membrane pinches the cell into two new daughter cells, and the process ends
-
Crossing over
crossing over during meiosis produces a mixture of maternal and paternal genetic material on each chromatid
-
Reassortment of Homologues
the homologues and sister chromatids distributed to each daughter cell during meiosis are a random mix of maternal and paternal genetic material
-
Alleles come from two parents
each parent donates his or her own set of genetic material
-
Sexual reproduction (offspring genetically different )
- crossing over in the production of gametes
- shuffling and reassortment of homologues during meiosis
- combining alleles from two parents at fertilization
-
Sex of Offspring
- in humans, male if the Y chromosome is present
- in birds, female if W chromosome is present
- presence or absence of sex chromosomes
- number of chromosome sets
- environmental factors
-
Karyotype
- a display of an individuals complete set of chromosomes
- can be used to identify abnormalities in a fetus's chromosomes early in development
- Down Syndrome: Trisomy 21 (caused by having an extra copy of chromosome 21)
-
Amniocentesis, CVS
- amniotic fluid: contains many cells from the fets (four months into pregnancy)
- tissue is removed from the placenta
- because the fetus and placenta both develop from the same fertilized egg, their cells contain the same genetic composition
- can be done several weeks earlier in the pregnancy, usually between 10 and 12
-
Nondisjunction
- unequal distribution of chromosomes during meiosis
- error of cell division that creates a gamete with zero or two copies of a chromosome rather than a single copy
-
Too Many of Too Few Sex Chromosomes
- Turner Syndrome: X_, short height, web of skin between neck and shoulders, underdeveloped ovaries (sterile), learning difficulties
- Klinefelter Syndrome: XXY, underdeveloped, testes, lower testosterone, some female features, long limbs, slightly taller
- XYY Males: taller than average, acne, lower intelligence
- XXX Females: may be sterile, no obvious physical or mental problems
|
|