Bio ch 8 Flashcards
what is meant by “like begets like”
only maple trees produce more maple trees, only dogs produce more dogs, etc
what is it called when a cell undergoes reproduction
cell division
describe the genetics of the two daughter cells that result from a parent cell that undergoes cell division
the 2 daughter cells are genetically identical to each other and the original parent cell
what happens to the chromosomes in a cell before the cell divides
they are duplicated by the cell
what happens to the duplicated chromosomes in a cell during the division process
one set is distributed to each daughter cell; each receives identical sets of chromosomes from the parent cell, making each offspring cell genetically identical to the other and to the parent cell
what is asexual reproduction
the creation of genetically identical offspring by a single parent without the participation of sperm and egg
what is the main principle of asexual reproduction
the lone parent and each of its offspring have identical genes
what is sexual reproduction
requires fertilization of an egg by a sperm; can produce great variation among offspring
describe the offspring of sexual reproduction
not genetically identical to their parents or to each other
compare asexual and sexual reproduction
asexual: single parent, genetically identical offspring
sexual: requires fertilization of sperm and egg, genetically unique offspring
how do prokaryotes reproduce
binary fission
describe the process of binary fission
- as the chromosome inside the prokaryote is duplicating, the copies move towards opposite ends of the cell
- the cell elongates
- when the chromosome duplication is complete and the cell has almost doubled in size, the plasma membrane grows inward and more cell wall is made, dividing the parent cell into genetically identical 2 daughter cells.
what is chromatin
DNA in the form of a diffuse mass of long, thin fibers composed of roughly equal amounts of DNA and protein molecules; not visible under a light microscope
what happens to a cell’s chromatin as it prepares to divide
its chromatin coils up, forming tight, distinct chromosomes that are visible under a light microscope
what is budding
a form of asexual reproduction in which a new organism develops from an outgrowth or bud (polyp) due to cell division at one particular site. The new organism remains attached as it grows, separating from the parent organism only when it is mature, leaving behind scar tissue.
what is fragmentation
a form of asexual reproduction or cloning in which an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are clones of the original organism.
what is parthenogenesis
a type of asexual reproduction in which a cell fertilized the egg but it wasn’t a cell from a male; may be clones of the mother, haploid, or diploid
what is vegetative propagation
a form of asexual reproduction of a plant. plant tissues and organs are regenerated from another part of the plant and a new organism can be produced
how is chromatin different from chromosomes
less condensed, cant be seen with a light microscope, composed of roughly equal amounts of DNA and protein molecules (chromosomes have more proteins to to help maintain structure and control activity of its genes
explain the process of cell reproduction in eukaryotes
- chromosomes are duplicated before they condense and the cell divides
- the DNA molecule of each chromosome is replicated and new protein molecules attach as needed. each chromosome now consists of two copies called sister chromatids, which contain identical copies of the DNA molecule
- the 2 sister chromatids are joined together especially tightly at a narrow waist called the centromere
- when the cell divides, the nucleus and the cytoplasm also divide, and the sister chromatids of a duplicated chromosome separate from each other. Once separated it is called a chromosome and it is identical to the parent chromosome
- each of the new chromosomes goes to one of the daughter cells. Each daughter cell receives a complete and identical set of chromosomes
why is cell division important
it is the basis of reproduction for every organism
enables multicellular organisms to grow to adult size
replaces worn-out or damaged cells
what are the 2 main stages of the cell cycle
interphase
mitotic phase
what is the cell cycle
an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells
what happens during interphase
the cell roughly doubles everything in its cytoplasm and precisely replicates its chromosomal DNA; increases its supply of nutrients; nuclear envelope exists; 2 centrosomes have formed, each with two centrioles
what happens during the mitotic phase
the actual cell division
what are the three subphases of interphase
G1 (first gap), S phase, and G2 (second gap)
what happens in the G1 stage of interphase
the cell grows
what happens in the S phase of interphase
Cell continues to grow
Chromosomes are duplicated; S stands for synthesis of DNA (DNA replication
what happens in the G2 stage of interphase
cell grows more as it completes preparations for cell divisions
what are the two phases of the mitotic phase
mitosis
cytokinesis
what happens during mitosis
Nucleus and its contents (most importantly the duplicated chromosomes) divide and are evenly distributed, forming two daughter nuclei
what happens during cytokinesis
Cytoplasm is divided into two
what are the phases of mitosis
prophase prometaphase metaphase anaphase telophase and cytokinesis
what happens during prophase
nucleoli disappears
chromatin forms sister chromatids with centromeres
mitotic spindle forms
centromeres move away from each other
what happens during prometaphase
nuclear membrane breaks down
spindle microtubules connect to kinetochores on the chromatids
chromosomes move towards the middle
what happens during metaphase
chromosomes lie in the metaphase plate
mitotic spindle is fully formed
what happens during anaphase
centromeres come apart and chromatids are separated and pulled toward opposite ends of the cell
daughter chromosomes have formed
cell is elongated
what happens during telophase
cell continues to elongate daughter nuclei and nucleoli appear chromosomes uncoil mitotic spindle disappears division is complete
what happens during cytokinesis
Division of cytoplasm
separation into two daughter cells
animal cells - cleave furrow (cel pinches in two)
plant cells - cell plate (vesicles containing cell wall material join to form a cell plate which grows outward to join the parent cell wall)
why is cytokinesis different for plant and animal cells
bc plant cells have a cell wall and animal cells don’t
what controls cell division
anchorage dependence
density dependence
growth factors
what is a growth factor
a protein secreted by certain body cells that stimulates other cells to divide
what is an example of a growth factor
VEGF
what is a density dependent inhibition
a phenomenon in which crowded cells stop dividing
ex: animal cells on the surface of a dish multiply to form a single layer and usually stop dividing when they fill the space and touch one another; the physical contact of cell surface proteins between adjacent cells is responsible for inhibiting cell division
what is one difference between cancer cells and normal cells
cancer cells don’t exhibit density-dependent inhibition
what is anchorage dependence
they must be in contact with a sold surface, such as the inside of a culture dish or the extracellular matrix of a tissue, to divide
what is the cell cycle control system
a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
explain how the cell cycle control system is not like a row of falling dominoes
for example, in the M phase, metaphase does not automatically lead to anaphase. Instead, proteins of the cell cycle control system must trigger the separation of sister chromatids that marks the start of anaphase
what is a checkpoint in the cell cycle
a critical control point where stop and go-ahead signals can regulate the cycle
where are the 3 major checkpoints in the cell cycle
in the G1 and G2 sub phases of interphase and in the M phase
what is the Gzero phase
a permanently non-dividing state; mature nerve cells and muscle cells are in the Gzero phase
explain how a growth factor might affect the cell cycle control system
A cell that responds to a growth factor has molecules of a specific receptor protein in its plasma membrane. Binding of the growth factor to the receptor triggers a signal transduction pathway in the cell. This conveys a message to the cell that leads to cell division. The “signals” are changes that each protein molecule induces in the next molecule in the pathway. Via a series of relay proteins, a signal finally reaches the cell cycle control system and overrides the breaks that otherwise prevent progress of the cell cycle.
what is a signal transduction pathway
a series of protein molecules that conveys a message
what is apoptosis
programmed cell death; the cell goes through a series of steps to shut down; The cytoskeleton collapses, the nuclear envelope disassembles, and the nuclear DNA breaks up into fragments; a way to keep the amount of cells constant
what is cancer
cells that do not respond to the cell control system and divide excessively; an individual with a malignant tumor is said the have cancer
what is a tumor
an abnormally growing mass of body cells
what is a benign tumor
generally harmless; the lump that results if the abnormal cells remain at the original site; often can be completely removed by surgery
what is a malignant tumor
harmful; can spread into neighboring tissues and other parts of the body, displacing normal tissue and interrupting organ function as it goes
what is metastasis
the spread of cancer cells beyond their original site
what are 2 ways cancer can metastasize
cancer cells may separate from the original tumor or secret signal molecules that cause blood vessels to grow towards the tumor
what are carcinomas
cancers that originate in the external or internal coverings of the body; ex: skin or lining of intestine
what are sarcomas
cancers that arise in tissues that support the body; ex: muscle or bone
what are leukemias and lymphomas
cancers of blood-forming tissues; ex: bone marrow, spleen, and lymph nodes
what are some things that differentiate cancer cells from normal cells
- do not heed normal signals that regulate the cell cycle
- come cancer cells make growth signals and divide continuously
- if they do stop dividing, they do so at random points in the cell cycle
- cancer cells are immortal and can go on dividing indefinitely
what are some treatments for cancer
surgery (used for localized tumors)
radiation (but this is high energy and damages normal body cells as well)
chemotherapy (used to treat widespread or metastatic tumors)
what are homologous chromosomes
a pair of chromosomes (one from each parent); both carry genes controlling the same inherited characteristics in the same places (they may still have different versions of the same gene)
what is a diploid cell
any cell with 2 homologous sets of chromosomes (2n); somatic cell
what is a haploid cell
any cell with one set of chromosomes (n); sex cells
what are sex chromosomes
determine sex; XX or XY
what are gametes
egg and sperm cells
what happens in fertilization
a haploid sperm cell from the father fuses with a haploid egg cell from the mother
what is a zygote
a fertilized egg
why are our gametes haploid
to prevent the number of chromosomes from doubling in every generation
what is meiosis
a type of cell division that produces haploid gametes in diploid organisms
what are the phases of meiosis
Interphase Prophase I Metaphase I Anaphase I Telophase I/Cytokinesis Prophase II Metaphase II Anaphase II Telophase II/Cytokinesis
what happens during interphase of meiosis
the chromosomes and centrosomes duplicate
what happens during Prophase I
Chromatin coils up and individual chromosomes become visible
homologous chromosomes (each composed of 2 sister chromatids) come together as pairs (process called synapsis); the resulting structure of 4 chromatids is called a tetrad
crossing over occurs; exchange of genetic info
mitotic spindle begins to form
nuclear envelope breaks into fragments
chromosome tetrads move toward center of cell
what happens during metaphase I
tetrads line up at metaphase plate
spindle fibers attach to centromere of each homologous chromosome
what happens during anaphase I
homologous chromosomes separate but sister chromatids remain attached
what happens during telophase I/cytokinesis
chromosomes arrive at the poles of the cells; each chromosome still consists of two sister chromatids
2 haploid daughter cells have formed
what happens during prophase II
a spindle forms and moves the chromosomes towards the middle of the cell
what happens during metaphase II
chromosomes are aligned on metaphase plate
what happens during anaphase II
sister chromatids separate and move toward opposite ends of the cell
what happens in telophase II
nuclei form at cell poles and cytokinesis occurs at the same time
there are now 4 daughter haploid cells
how are meiosis and mitosis different
mitosis:
- provides for growth, tissue repair, and asexual reproduction
- produces 2 genetically identical diploid daughter cells
- involves one division of the nucleus
Meiosis:
- needed for sexual reproduction
- produces 4 genetically unique haploid daughter cells
- involves 2 nuclear and cytoplasmic divisions
how are meiosis and mitosis the same
chromosomes duplicate only once, during the S phase of interphase
what leads to genetic variations in offspring
- the alignment of the tetrads at metaphase one; they orient independently and there are many possible arrangements
- random nature of fertilization
- the fact that homologous chromosomes can bear 2 different kinds of genetic information for the same characteristic
- crossing over
what is the total number of combinations of chromosomes that meiosis can package into gametes
2^n where n is the haploid number
how many combinations of chromosomes are there when a gamete from one person unites with a gamete from another person in fertilization
64 trillion
how many possible chromosome combinations are there that meiosis can create in humans
8 million
what is crossing over
an exchange of corresponding segments between non-sister chromatids of homologous chromosomes
what does crossing over do
produces hybrid chromosomes with new combinations of maternal and paternal genes
what is a karyotype
an ordered display of magnified images of an individual’s chromosomes arranged in pairs
how do you prepare a karyotype from a blood sample
A blood sample is treated with a chemical that stimulates mitosis
Grown in culture for several days
Treated with another chemical to stop mitosis at metaphase
what is it called when there are 3 number 21 chromosomes
trisomy 21, or Down Syndrome
how do the chances of having a child with down syndrome relate to the age of the mom
directly proportional
what is nondisjunction
when a pair of homologous chromosomes fails to separate in meiosis I or a pair of sister chromatids fails to separate in meiosis II, which creates an abnormal amount of chromosomes in some or all of the gametes
what causes down syndrome
nondisjunction
what is it called when males have an extra X chromosome (XXY)
kleinfelter syndrome
symptoms: Have male sex organs, normal intelligence, abnormally small testes, are sterile, and has female body characteristics
what is it called when females only have one X chromosome (XO)
turner syndrome
symptoms: Short, have web of skin extending between the neck and shoulders, are sterile, poor development of breasts, normal intelligence
what happens when males have an extra Y chromosome (XY)
No well defined symptoms, tend to be taller than avg
what happens when women have an extra x chromosome (XXX)
Cannot be distinguished from XX females except by karyotype
how could a diploid plant become a polyploid plant
if the gametes are accidentally produced by mitosis, it will produce a tetraploid (4n) plant
what are some polyploid plants
wheat, potatoes, apples, and corn
what are the 4 alterations of chromosome structure
deletion
duplication
inversion
translocation
what is a deletion
if a fragment of a chromosome is lost, the remaining chromosome will have a deletion (ex: cri du chat syndrome is the result of a deletion)
what is a duplication
if a fragment from one chromosome joins to a sister chromatid or homologous chromosome
what is an inversion
if a fragment reattaches to the original chromosome but in the reverse orientation
why are inversions less likely than duplications or deletions to produce harmful effects
bc in inversions all genes are present in their normal number
what is a translocation
attachment of a chromosomal fragment to a nonhomologous chromosome; may be reciprocal - 2 homologous chromosomes may switch segments; translocation in somatic cells may cause cancer
