Chapter 7 Flashcards
Asexual Reproduction
making new individuals, common in nature
clones
the results of asexual reproduction
mutations
the only reason that there would be a change in genetic information in DNA replication
Sexual Reproduction
the fusion of two specialized cells called gametes
how do gametes form?
by meiosis
meiosis
a process of cell division, everything is randomly separated and reorganized so that the daughter cells differ from one another
chromosomes
daughter cells consist of chromosomes, they are made up of DNA and proteins
somatic cells
cells that are not specialized for reproduction, each contains two sets of chromosomes
homologous pairs
the pairs of chromosome sets in somatic cells
haploid
haploid gametes only have one homolog
zygote
two fused gametes in the process of fertilization
fertilization
the fusing of two gametes in meiosis.
diploid
after the gametes have fused, they have two sets of chromosomes, a homologous pair,
haplontic organisms
most protists, fungi, some green algae, they usually just spread their spores
alternation of generations
most plants and fungi go through this. form a haploid lifestage called a gametophyte
diplontic organisms
animals, plants, fungi, brown algae, the gametes are the only haploid cells in the life cycle. the mature organism is diploid
random selection of half of the diploid chromosome set
to make a haploid genome
reproductive signal
initiates cell division
replication of DNA
two new cells will have a full complement of genes
segregation
the cell must distribute the replicated DNA to each of the new cells
cytokinesis
the division of the cytoplasm to make two daughter cells. for this to happen, enzymes must be synthesized, new material must be added to the cell membrane
binary fission
this is how prokaryotes divide, the cell grows then it replicates its DNA, then it separates from the cytoplasm, and makes the DNA into two cells
replication of DNA
many times chromosomes are cicular, they are joined at the ends.
ori
the site where replication of the circular chromosome starts (the origin of replication)
ter
the site where replication ends (the terminus of replication)
replication complex
chromosome replication takes place as the DNA is threaded through a replication complex of proteins near the center of the cell, it begins at the ori and moves toward the ter. once they are done replicating, they can segregate
segregation
so replication begins near the center of the cell, then the ori moves toward the outside of the cell and the DNA binds to proteins adjacent to the ori.
cytokinesis
the division of a single cell into two cells begins in the cytoplasm. the fibers of the microtubules actually work to break the cells apart.
replication of DNA in eukaryotes
similar to replication in prokaryotes, occurs only at specific stages of lifecycle
segregation of DNA in eukaryotes
a copy of each chromosome must end up in each of the two new cells. they are super close to each other in eukaryotes, they become highly condensed, mitosis segregates them into two new nuclei.
mitosis
the proces that separates the chromosomes into two new nuclei in eukaryotic segregation, the cytoskeleton is involved
cytokinesis
follows mitosis, the literal breaking up of the two cells, always starts in the cytoplasm, different in plant and animal cells because animal cells have no cell walls
cell cycle
the period of one division to the next, in eukaryotes this is mitosis and cytokinesis, referred to as the M phase, and a much longer interphase
interphase of eukaryotes
the cell nucleus is visible and typical cell functions occur, including DNA replication in cells that are dividing
the three subphases of interphase
G1, S, and G2, the G stands for Gap
G1
quite variable, cell may spend a long time in this phase carrying out specialized functions
S phase
the cells DNA is replicated during this
G2
the cell makes preparations for mitosis, EX. like synthesizing components of the microtubules that will move teh segregating chromosomes to opposite ends of dividing cell
prophase
the appearance of the nucleus changes as the cell enters this stage, the beginning of mitosis
condensed chromosomes
each chromosome contains a very long double stranded DNA molecule
sister chromatids
after DNA each chromosome has two DNA molecules, they are held together at the centromere until separation during mitosis
centromere
where the two DNA molecules are held together until separation during mitosis
kinetochores
special proteins that assemble on the centromeres, one on each chromatid. important for chromosome movement
karyotype
constituted by size and number of chromosomes
centrosome
the central body
centrioles
the centrosome consists of a pair of these
spindle
Microtobules in the spindle apparatus that control chromosome movement
polar microtubules
Microtobules extending from the centrioles that overlap to form the spindle apparatus,
kinetochore microtubules
Microtubules extending from the centrioles to the chromosome kinetechores.
daughter chromosomes
the sister chromatids become after separation
prometaphase
the nuclear envelope breaks down and the compacted chromosomes, each consisting of two chromatids, attatch to kinetochore microtubules
metaphase
the chromosomes line up at the middle of the cell, the equatorial position
anaphase
the chromatids separate, the daughter chromosomes move away from each other toward the poles
telophase
occurs after the chromosomes have separated and is in the last phase of mitosis
animal cell cytokinesis
begins with furrowing of plasma membrane, it like threads through it, this is called the contractile ring
the contractile ring
composed of microfilaments of actin and myosin, form a ring on the cytoplasmic surface of the plasma membrane
plant cell cytokinesis
the cytoplasm divides differently because plants have cell walls
growth factors
mammals produce a variety of these, they stimulate cell division and differentiation, like when you cut yourself
G1-S transition
it marks a key decision point for the cell, if it passes the restriction point, it usually means that the cell will proceed with the rest of the cycle
the restriction point
the cell must pass this point or it is unlikely that it will finish the cycle
cell fusion
the merging of two or more cells into a single cell
cyclin dependant kinases
cell cycles that are dependant on protein kinases, they have to go through cdk checkpoints
cell cycle checkpoints
each cdk checkpoint has its own cyclin to activate it, it can only be made at the right time
what two things happen in meiosis?
crossing over and independant assortment
chiasma
the point where genetic material is exchanged between non sister chromatids on homologous chromosomes
crossing over
when genetic material is exchanged between nonsister chromatids on homologous chromosomes
recombination
what crossing over results in, its the recombination of chromatids, each increases in genetic variation among products of meiosis by reshuffling genetic information among homologous pairs
independant assortment
(genetics) The process of random segregation and assortment of chromosomes during anaphase I of meiosis resulting in the production of genetically unique gametes.
