Nucleus Flashcards
Command center of the cell
Nucleus
Contains the molecular machinery to replicate DNA and to synthesize and process all types of RNA
Nucleus
3 types of RNA
rRNA (ribosomal)
tRNA (transfer)
mRNA (messenger)
Appears as a large rounded or oval structure often near the center of the cell
Nucleus
2 FUNCTIONS OF THE NUCLEUS
Cellular Regulation
Production
o Houses genetic material, which directs all cellular activities and regulates cellular structure
Cellular regulation
o Produces ribosomal subunits in nucleolus and exports them into cytoplasm for assembly into ribosomes.
Production
(3) COMPONENTS OF THE NUCLEUS
• Nuclear Envelope
• Chromatin
• Nucleoli or Nucleolus
Forms a selectively permeable barrier between the nuclear and cytoplasmic compartments
Nuclear envelope
Nuclear envelope:
Has two concentric membranes separated by a narrow _________
perinuclear space
Nuclear envelope:
are continuous with RER
Outer nuclear membrane
Nuclear envelope:
is associated with a highly organized meshwork of nuclear space proteins called the nuclear lamina
Inner nuclear membrane
Stabilizes the envelope/ membrane
Nuclear lamina
The inner and outer nuclear membranes are bridged at ________
nuclear pore complexes
Regulates movement of macromolecules between the nucleus and the cytoplasm
nuclear pore complexes
Consists of the DNA and its attendant proteins in DNA a largely uncoiled state
Chromatin
Group of proteins and DNA
Chromatin
Two types of chromatin
Heterochromatin
Euchromatin
- appears as coarse, electron-dense material and as intensely basophilic clumps in the light microscope
Heterochromatin
- finely dispersed granular material in the electron microscope and as lightly stained basophilic areas in the light microscope
Euchromatin
A small, dense mass of heterochromatin present in females but not males
CHROMATIN
“___________” (or_______) is one of the two X chromosomes present in female.
Sex chromatin
Barr body
DNA in chromatin is extensively packaged by associating with basic proteins called______
histones
provides structural support for a chromosome.
Histones
A protein associated with
DNA
Histones
Each long DNA double helix with its associated proteins is a ______
chromatid
After DNA replication, two
“chromatids held together by complexes of cohesion proteins make up each _______
chromosome
A DNA molecule with part or all of the genetic material (Genome) of an organism.
Vectors of heredity
Chromosome
One copy of a newly copied chromosome which is still joined to the original chromosome by a single centromere.
CHROMATID
Condensed form of DNA
cells are actively dividing
CHROMOSOME
contain genes determining whether an individual will develop as a female or a male.
X and Y sex chromosomes
In addition to the pair of sex chromosomes, cells contain pairs of______.
autosomes
Each of these pairs of chromosomes contains one chromosome originally derived from the mother and one derived from the father.
The members of each chromosomal pair are called________.
homologous
2 types of chromosomes
Sex Chromosomes
Autosomes
Chromosomes that are not sex chromosomes
These are pairs 1-22 on a human karyotype
Autosomes
Chromosomes that determine gender
XX = female
XY - male
These are the 23rd pair on a human karyotype
Sex chromosomes
Cells of most tissues (somatic cells) are considered_____ because they contain pairs of chromosomes.
diploid
Sperm cells and mature oocytes are_____, with half the diploid number of chromosomes, each pair having been separated during meiosis.
haploid
One copy of each chromosome
Haploid
Two copies of each chromosome
Diploid (2n)
Spherical, highly basophilic subdomain of nuclei in cells, actively making proteins
Nucleolus
Intense basophilia of nucleoli is due not to heterochromatin but to the presence of densely concentrated _______
Nucleolus: ribosomal RNA
Site of most of the synthesis of __________ and assembly of ribosome subunits
ribosomal RNA (rRNA)
