Nucleus, Chromatin, Nucleolus Flashcards
What are the major regions of the cell?
cytoplasm + nucleus = protoplasm
What are the functions of the nucleus?
- stores genetic information of the cell
- where DNA is transcribed
- where chromosomes are localized
- where chromosomes are replicated
What are the structural components of the nucleus?
nuclear envelope, nuclear pores, nucleoplasm, nucleolus, chromatin, nuclear skeleton
What lines the inner nuclear membrane?
nuclear lamina
What is the function of the nuclear lamina?
- stabilize nuclear envelope
- support chromatin - acts as an attachment site for chromatin
What is the structure of the nuclear envelope?
outer membrane and inner membrane with perinuclear space between them
What is the outer membrane and perinuclear space of the nucleus continuous with?
rough endoplasmic reticulum
What is the function of nuclear pores of nuclear envelope?
controls movement of substances into and out of the nucleus
What is the nuclear pore complex?
proteins attached to the nuclear pore + nuclear pore e.g. nucleoporins
What is transported out of the nucleus and what is transported in?
RNA and ribosomal subunits needed for protein synthesis are transported out and proteins are transported in
What is the function of nuclear matrix?
- keep cell shape
- support chromatin fibers
What is responsible for the basophilic characteristic of the nucleus?
chromatin
What is chromatin?
long strand of DNA and associated proteins in an uncoiled state
What are the types of chromatin?
euchromatin and heterochromatin
What is Euchromatin?
light, loosely packed, active - light staining material
What is Heterochromatin?
dense, tightly packed, inactive - dark staining material
What are the 3 locations for heterochromatin?
- peripheral of the nucleus
- karyosomes
- near nucleolus
What is facultative heterochromatin?
chromosome material that can either be heterochromatin or euchromatin e.g. inactive X chromosome
What is constitutive heterochromatin?
chromosome material that can only be heterochromatin e.g. Y chromosome
What are chromosomes?
long molecule of DNA and associated proteins that carry hereditary information that has been tightly packed (condensed) and replicated forming 2 sister chromatids that are held together by cohesions
What is the structure of chromosomes?
two sister chromatids connected at the centromere
Types of chromosomes?
- metacentric - centromere is in the middle
- submetacentric - centromere is between middle and end
- acrocentric - the centromere is placed close to the end
- telocentric - centromere is placed at the end
How are these types of chromosomes developed?
centromere is placed at different points on the chromosome
Describe the shorter arm?
is always placed above the centromere - the p arm (petite)
Describe the longer arm?
is always placed below the centromere - the q arm
How are chromosomes characterized?
- length
- position of the centromere
- banding pattern
Ends of the chromosome are called?
telomeres
What are nucleosomes?
chromatin fundamental unit - strand of DNA wrapped around 8 histones twice
What are the 43 chromosomes in a human being?
22 pairs of autosomal chromosomes and 1 pair of sex chromosomes
What are karyotypes?
chromosome pairs sorted according to their morphology
What is a Barr body?
dense mass of heterochromatin present in females but not males - inactivated X chromosome
What can Barr bodies be used to identify?
sex of the fetus
What is the nucleolus?
condensed component of eukaryotic cells - basophilic
What makes up the nucleolus network?
pars fibrosa + pars granulosa = nucleolonema
What are 3 functions of the nucleolus?
- site for initial ribosomal assembly
- RNA synthesis
- contains DNA, RNA and proteins
