Ch. 3 The Cell Nucleus (E2) Flashcards
A membrane-limited compartment that contains the genome (genetic information) in eukaryotic cells, together with the machinery for DNA replication and RNA transcription and processing.
What is the nucleus?
A non-dividing cell is also called an {…} cell.
Interphase
The interphase cell consists of 4 major components. List them.
1) Chromatin
2) Nucleolus
3) Nuclear envelope
4) Nucleoplasm
This nuclear material contains DNA associated with roughly an equal mass of various nuclear proteins (e.g., histones) that are necessary for DNA to function.
What is chromatin?
In what 2 ways is chromatin organized?
Euchromatin & heterochromatin
A small area within the nucleus that contains DNA in the form of transcriptionally active ribosomal RNA (rRNA) genes, RNA, and proteins, making it the site of rRNA synthesis and contains regulatory cell cycle proteins.
What is the nucleolus?
A double membrane system that surrounds the nucleus of the cell. It consists of an inner and an outer membrane separated by a perinuclear cisternal space and perforated by NUCLEAR PORES.
What is the nuclear envelope?
The outer membrane of the nuclear envelope is continuous with that of the {…} and is often studded with ribosomes.
rER (rough endoplasmic reticulum)
Nuclear content other than the chromatin and nucleolus.
What is the nucleoplasm?
Evaluation of nuclear size, shape, and structure plays an important role in this disease.
What is cancer?
The disappearance of nuclei due to complete dissolution of DNA by increased activity of DNAse as seen in DYING CELLS.
What is karyolysis?
Condensation of chromatin leading to shrinkage of the nuclei (they appear as dense basophilic masses) as seen in DYING CELLS.
What is pyknosis?
Fragmentations of nuclei (these changes are usually preceded by pyknosis) as seen in DYING CELLS.
What is karyorrhexis?
Chromatin, a complex of DNA and proteins, is responsible for the characteristic {…} (i.e., affinity/love for alkaline/basic pH) of the nucleus.
Basophilia
Why is DNA organized as chromatin?
The length of a DNA molecule is MUCH longer than the nuclear diameter, so it must be tightly folded and organized
Further folding of chromatin, such as that which occurs during mitosis, produces these structures.
What are chromosomes?
Chromatin proteins include five basic proteins called {…} along with other {…} proteins.
1) Histones
2) Non-histone
The human {…} encompasses the entire length of human DNA that contains the genetic information packaged in all 46 chromosomes.
Genome
In what year was the sequencing for the human genome completed?
2003
Recent discoveries have revealed that large segments of DNA can vary in numbers of copies. For instance, genes that were thought to always occur in two copies per genome have sometimes one, three, or more copies. Such {…} are widespread in the human genome and most likely lead to genetic imbalances.
CNVs (copy number variations)
A union of genomic sequences encoding a coherent set of potentially overlapping functional products (i.e., polypeptides).
What is a gene?
In general, two forms of chromatin are found in the nucleus: a condensed form called {…} and a dispersed form called {…}.
1) Heterochromatin
2) Euchromatin
Which form of chromatin is densely stained during slide preparation? Heterochromatin or euchromatin?
Heterochromatin
Which form of chromatin is lightly stained during slide preparation? Heterochromatin or euchromatin?
Euchromatin
Which form of chromatin is transcriptionally active (i.e., genes are actively being copied from DNA into mRNA)?
NOTE: Think about the chromatin structure. In which form can chromatin be easily read and transcribed?
Euchromatin
This type of heterochromatin contains the same regions of genetically inactive, highly repetitive sequences of DNA that are condensed and consistently packaged in the same regions of the chromosome when compared with other cells. It is found in large amounts near CENTROMERES and TELOMERES.
What is constitutive heterochromatin?
This type of heterochromatin is not repetitive, and its location within the nucleus and chromosomes varies when compared with other cells.
What is facultative heterochromatin?
Facultative heterochromatin may undergo active transcription in certain cells, such as this inactive X chromosome found in female mammals.
What are Barr bodies?
List 3 locations in which you will find heterochromatin.
1) Marginal chromatin
2) Karyosomes
3) Nucleolar-associated chromatin
The structure that light microscopists formerly referred to as the nuclear membrane actually consists largely of {…} chromatin, which is found at the PERIPHERY OF THE NUCLEUS.
Marginal
Discrete bodies of chromatin irregular in size and shape that are found throughout the nucleus.
What are karyosomes?
Chromatin found in association with the nucleolus.
What is nucleolar-associated chromatin?
