Reproduction Flashcards
What is cell division?
the process by which a cell doubles its organelles and cytoplasm, replicates its DNA, and then divides in two.
When does Unicellular organisms use cell division
as a means of reproduction
When does multicellular organisms use cell division?
its a method of growth, development, and replacement of worn out cells.
What are the two types of cell division
mitosis and meiosis
Mitosis
the division and distribution of the somatic cells DNA to its two daughter cells in that both receives a complete copy of the original genome.
Karyokinesis
nuclear division
Cytokinesis
cell division
Karyo and Cyto kinesis in mitosis
Nuclear division is followed by cellular division.
How long does a cell spend in interphase?
90 percent of its life
what occurs in interphase
each chromosome is replicated so that during division, a complete copy of the genome can be distributed to both Daughter cells.
What happens to chromosomes after replication in interphase
they consist of sister chromatids held together at a central region called the centromere
Chromatin
uncoiled DNA
Chromosome
a single chromatid or the pair of chromatids attached at the centromere.
ploidy
the number of chromosome within the cells.
Diploid
2N This number in a single cell is due to the presence of homologous pairs of chromosomes made up of haploids
Haploid
N chromosomes that originate from the gamete cells of each parent.
Mitosis phases
prophase: chromosomes condense spindles form
metaphase: chromosomes align
anaphase: sister chromatids separate
telophase: new nuclear membranes form
Prophase
the initiation phase of mitosis the chromosomes condense and the centriole pairs (in animals) separate and move toward opposite sides poles of the cell.
spindle apparatus forms between them and the nuclear membrane dissolves, allowing spindle fibers to interact with the chromosome
Metaphase
during this phase of mitosis the centriole pairs are now at opposite poles of the cell
the fibers of the spindle apparatus attach to each chromatid at the centromere to align the chromosomes a the center of the cell forming the metaphase plate
Anaphase
The centromeres split so that each chromatid has its own distinct centromere allowing the chromatids to separate. the sister chromatids are pulled to opposite ends of the of the cell by the shortening of spindle fibers which consist of microtubules
Telophase
last phase of mitosis the spindle apparatus disappears and a nuclear membrane forms around the newly formed chromosomes. thus each contains the same number of chromosomes as the original parent. the chromosomes uncoil and resume their interphase form
Cytokinesis (phase)
near the end of telophase the cytoplasm divides into two daughter cells, each with a complete nucleus and its own set of organelles.
Cleavage furrow
in cytokinesis in animals when the cell membrane indents along the equator of the cell and finally pinches thorugh the cell separating the two nuclei
Cell plate
in plants it is an expanding partition that grows outward from the interior of the cell until it reaches the cell membrane during cytokinesis
Gametes
specialized sex cells produced by each parent
Meiosis
the process by which sex cells are produced for sexual reproduction. similar to mitosis other than it produces haploid cells halving the number of chromosomes and two divisions. resulting in 4 cells (gametes)
First meiotic division
preceded by interphase, first division produces two intermediate daughter cells with 2N chromosomes with sister chromatids.
Prophase I, Metaphase I Anaphase I, Telephase I
Prophase I
The chromatin condenses into chromosomes, spindle apparatus forms, the nucleoli and nuclear membrane disappear. Homologous chromosomes come together and initiate synapsis leading to recombination.
synapsis
Each chromosome consists of two sister chromatids, where the synaptic pair of homologus chromosomes contain for chromatids forming a tetrad.
Homologous chromosomes
chromosomes that code for the same traits, one inhereted from each parent.
chiasmata
when chromatids of homologous chromosomes connect and then break at corresponding points
crossing over
where homologous chromosomes exchange equivalent species of DNA at chiasmata during synapsis
Recombination
leads to increased genetic diversity within a species. Sister chromatids are no longer identical after recombination
Metaphase I
homologus pairs (tetrads) align at the equatorial plate and each pair attaches to a separate spindle fiber by its kinetochore.
Anaphase I
Homologous pairs separate and are pulled to opposite poles of the cell. called disjunctions. separated to the poles at random.
Disjunction
each chromosome of paternal origin separates form its homologue of maternal origin and either chromosome can end up in either daughter cell.
Telophase I
a nuclear membrane forms around each new nucleus. At this point each chromosome still consists of sister chromatids joined at the centromere. then they perform cytokenesis
Second meiotic division
Similar to miosis except that it is not preceded by chromosmal replication. the sister chromatids are split, move to opposite poles and are surronded by reformed nuclear membrane.
Gonads
specialized organs where gametes are produced, male- testes form sperm, female -ovaries form oocytes
Hermaphrodites
species that have both functional male and female gonads. includes the hydra and earthworm
Spermatogenesis
sperm production, begins at puberty that occurs in the seminiferous tubules. Dipliod cells called spermatogonia undergo mitosis to produce primary spermatocytes n undergo meiosis to produce four hapliod spermatids of equal size.
Sperm
(male gamete) mature sperm is an elongated cell with a head, tail, neck, and body. The head consists almost entirely of nucleus which contains the paternal genome. The tail is flagellum that propels the sperm and the neck has mitochondria to provide energy
Oogenesis
the production of female gametes, occurs in ovaries during embryonic development. One diploid oogonia divides by mitosis to produce primary oocyte cell that undergoes meiosis in the ovaries to produce a single mature egg.
polar body
which is a small cell that contains a little more than a nucleus. they rapidly degenerate after being produced by meiosis in oogeneis.
the mature ovum
is a large cell containing most of the cytoplasm, RNA organelles and nutrients needed by a developing embryo.
Fertilization
the union of the egg and sperm to form a zygote with a diploid number of chromosomes
External fertilization
occurs in vertebrates that reproduce in water (fish and amphibians). The female lays eggs in the water and the male deposits sperm in the vicinity. The lack of direct passage reduces chances
Internal fertilization
practiced by terrestrial vertebrates and provides a direct route for sperm to reach the egg cell. This increases the chances for fertilization and females produce fewer eggs.