Ch 8 bio
haploid
(genetics) an organism or cell having only one complete set of chromosomes
diploid
(of a cell or nucleus) containing two complete sets of chromosomes, one from each parent.
human haploid number is
23
each mature gamete contains
23 chromosomes.
after telophase II
4 haploid cells are formed.
human diploid number is
46
humans have ____ chromosomes in all.
46
Tetrads
A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.
chromosome
A rod-shaped, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.
centromere
Area where the chromatids of a chromosome are attached
interphase
Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases. DNA replicates. organelles replicate.
prophase I
Chromatin coils into chromosomes, nuclear membrane and nucleolus disappear, spindle forms and attaches to centromere.
telophase I
Chromosomes uncoil into chromatin, nuclear membrane and nucleolus reappear, spindle fibers disappear, cytokinesis occurs.
cytokinesis
Division of the cytoplasm during cell division
interkinesis
Period of time between meiosis I and meiosis II during which no DNA replication takes place.
metaphase I
Phase of mitosis and meiosis in which the chromosomes line up across the center of the cell
anaphase I
Phase of mitosis in which chromatids of a chromosome separate at the centromere and more to opposite poles of the cell.
Crossing over
Portions of chromatids break off and attach to adjacent chromatids on the homologous chromosome. make stripy things
gamete
Sex cells
prophase II
The first phase of meiosis II. Prophase II is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis I.
telophase II
The fourth and final phase of meiosis II. identical to mitotic telophase, except that the number of chromosomes was reduced by half during meiosis. I.
metaphase II
The second phase of meiosis II. Metaphase II is identical to mitotic metaphase, except that the number of chromosomes was reduced by half during meiosis I.
anaphase II
The third phase of meiosis II. During it the sister chromatids are finally spearated at their centromeres and puled to opposite sides of teh cell. Note that it is identical to mitotic anaphase, excep the number of chromosmes was reduced by half during meiosis I.
mitosis
a cell division which preserves the same chromosome number as the parent. the cell's nucleus is divided in two.
DNA
a long, thick molecule that stores genetic information.
karyotype
a picture of all the chromosomes.
gene
a short segment of DNA that contains the instruction for a single trait.
the chromosomes of most prokaryotes consist of proteins and
a single circular DNA molecule.
centrioles
a small, cylindrical cell organelle, seen near the nucleus in the cytoplasm of most eukaryotic cells, that divides in perpendicular fashion during mitosis, the new pair of centrioles moving ahead of the spindle to opposite poles of the cell as the cell divides.
Meiosis
a type of cell division that results in FOUR daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
in mitosis and meiosis, chromosomes begin their migration to opposite poles of the cell during
anaphase
between cell divisions, the DNA in a eukaryotic cell is uncoiled and spread out; in this form it is called
chromatin.
during cell division, the DNA in eukaryotic cells is tightly packed and coiled into structures called
chromosomes.
prokaryotic chromosomes
consist of a circular DNA molecule.
division plate formation begins during
cytokinesis
Homologous chromosome
each cell has 2 copies of each chromosome- one from mom and one from dad.
Chromatids
each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
chromosome numbers
each species has a certain number od chromosomes in each cell.
X X sex cells are
female
zygotes
fertilized egg cells
ovum
functional haploid cell formed in female gametogenesis.
During meiosis the resulting gametes have ________ the number of chromosomes as the parent cell.
half
eggs and sperm are ______ cells
haploid
in meiosis, the cell is resting metabolically with no physical division during
interkinesis
The steps of mitosis:
interphase, then PMAT- prophase, metaphase, anaphase, telophase, then interphase again with 2.
crossing over is important because
it increases the genetic variation in the progeny.
chromatin
less tightly coiled DNA- protein complex found in cells when they aren't going though cell division.
X Y sex cells are
male
polar bodies
non-functioning haploid cells formed in female gametogenesis.
In oogenesis, a diploid reproductive cell divides meiotically to produce
one haploid gamete
tetrads may be found in
only in late prophase I and metaphase I of the first meiotic division.
G2 phase
period of interphase when synthesis of organelles occur.
S phase (late interphase)
period of the cell cycle when DNA is replicated. centriole also replicated
G1 phase (interphase)
period of the interphase when cell growth and development takes place.
oogonia
primary germ cell undergoing meiosis in females.
spermatagonia
primary germ cell undergoing meiosis in males.
oogenesis
production of female gamete
in mitosis and meiosis, centrioles begin to migrate to opposite poles of the cell during
prophase
in mitosis and meiosis, chromatin assembles into chromosomes during
prophase
crossing over may occur in which phase of meiosis I?
prophase I
in which phase of meiosis do tetrads form?
prophase I
The steps of meiosis
prophase I, metaphase I, anaphase I, telophase I,
the steps of meiosis II
prophase II, metaphase II, anaphase II, and telophase II
histones
special proteins that wrap around DNA, forming chromatin networks. found in the chromosomes of eukaryotic cells but not prokaryotic cells.
spindle
structure that helps move chromosomes apart.
cytokinesis occurs during which phase of meiosis?
telophase
in mitosis and meiosis, spindle disappears, nucleoli reappear, and nuclear membranes reform during
telophase
Synapsis
the fusion of chromosome pairs at the start of meiosis. Chromosomes line up next to their homologues.
binary fission
the process of cell division in prokaryotes.
cell cycle
the series of changes that a cell undergoes from the time it forms until it divides.
autosomes
unisex chromosomes(all of them accept for the xx/xy ones)