The Cell Part V Flashcards
special form of cell division
MEIOSIS
sex cells divide this type
MEIOSIS
chromosome number is reduced from diploid (2n) to haploid (n)
MEIOSIS
occurs in developing germ cells (spermatozoa and oocytes), fertilization results in diploid zygotes
MEIOSIS
doubling of DNA content in S phase
MEIOSIS
Affected by 2 successive cell divisions that give rise to 4 haploid cells
- accompanied by recombination of maternal and paternal genes by crossing over and random assortment.
MEIOSIS
2 STAGES OF MEIOSIS:
A. REDUCTIONAL DIVISION (MEIOSIS I)
B. EQUATORIAL DIVISION (MEIOSIS II)
occurs following the interphase during which 46 chromosomes are duplicated giving the cell a 4 CDNA content (total DNA content of the cell).
REDUCTIONAL DIVISION (MEIOSIS I)
5 stages of Prophase I:
a) LEPTOTENE
b) ZYGOTENE
c) PACHYTENE
d) DIPLOTENE
e) DIAKINESIS
chromatin condenses into visible chromosomes
LEPTOTENE
each contains 2 chromatids joined at the centromere.
LEPTOTENE
homologous maternal and paternal chromosomes pair and make physical contact (synapsis) via the synaptonemal complex, forming a tetra
ZYGOTENE
chiasmata are formed
PACHYTENE
crossing over occurs
PACHYTENE
random exchange of genes between segments of homologous chromosomes
PACHYTENE
increasing genetic diversity
PACHYTENE
chromosomes continue to condense
DIPLOTENE
chiasmata can be observed indicating sites where crossing over has taken place
DIPLOTENE
nucleolus disappear
DIAKINESIS
Chromosomes are condensed maximally
DIAKINESIS
nuclear envelope disappears
DIAKINESIS
begins soon after completion of meiosis I, following a brief interphase without DNA replication
EQUATORIAL DIVISION (MEIOSIS II)
separation of sister chromatids and distribution into 4 daughter cells (gametes) each containing the haploid number of chromosomes
EQUATORIAL DIVISION (MEIOSIS II)
Structure:
Phospholipid bilayer containing cholesterol and proteins (integral and peripheral) and some carbohydrates (externally)
Plasma Membrane
Structure:
forms a selectively permeable boundary of the cell.
Plasma Membrane
acts as a physical barrier to enclose cell contents
Plasma Membrane
regulates material movement into and out of the cell
Plasma Membrane
establishes and maintains an electrical charge difference across the plasma membrane
Plasma Membrane
functions in cell communication
Plasma Membrane
Short, numerous (many) membrane extensions supported by microtubules which occur on exposed membrane surfaces of some cells
Cilia
which occur on exposed membrane surfaces of some cells
Cilia
Long, singular (only one) membrane extension supported by microtubules
Flagellum
present in sperm cells
Flagellum
propels sperm
Flagellum
Numerous thin membrane folds projecting from the free cell surface;
Microvilli
supported by microfilaments
Microvilli
Large structure enclosed within a double membrane;
Nucleus
contains chromatin, nucleolus, and neoplasm
Nucleus
houses the DNA that serves as the genetic material for directing protein synthesis.
Nucleus
double membrane boundary between cytoplasm and nuclear contents
Nuclear Envelope
continuous with rough endoplasmic reticulum
Nuclear Envelope
separates nucleus from cytoplasm
Nuclear Envelope
openings through the nuclear envelope
Nuclear Pores
allow passage of materials between the cytoplasm and nucleoplasm, including ribonucleic acid (RNA), protein, ions, and small water-soluble molecules.
Nuclear Pores
large, prominent structure within the nucleus
Nucleolus
functions in synthesis of ribosomes
Nucleolus
contents of cells between the plasma membrane and nuclear envelope
Cytoplasm
responsible for many cellular processes
Cytoplasm
viscous fluid medium with dissolved solutes (e.g., ions, proteins, carbohydrates, lipids)
Cytosol
provides support for organelles
Cytosol
serves as the viscous fluid medium through which diffusion occurs
Cytosol