nucleus mod 3 biochem exam 1

What can vary about a cell's nucleus?

Shape, size, number, appearance, and location

How many nuclei do most cells have?

One

Which cells may have multiple nuclei?

Hepatocytes

Which mature blood cells lack a nucleus?

Erythrocytes

Where is the nucleus located in most cells?

Near the center

What does leptochromatic describe?

The overall light appearance of a nucleus

What does pachychromatic describe?

The overall dark appearance of a nucleus

What type of chromatin dominates a leptochromatic nucleus?

Euchromatin

What type of chromatin dominates a pachychromatic nucleus?

Heterochromatin

Is a leptochromatic nucleus usually more or less active?

More active

Why does a leptochromatic nucleus look light?

It contains more open available DNA

What organelles are increased in leptochromatic cells?

Rough ER and Golgi

Is a pachychromatic nucleus usually highly active?

No, it has lower protein synthesis

Why does a pachychromatic nucleus look dark?

It contains more tightly packed DNA

What is euchromatin?

Open available DNA that is transcriptionally active

How does euchromatin stain?

Lightly

What is heterochromatin?

Tightly packed transcriptionally inactive DNA

How does heterochromatin stain?

Darkly

Where may heterochromatin be found?

Periphery, around the nucleolus, or scattered in nucleoplasm

Can one nucleus contain euchromatin and heterochromatin?

Yes, usually in different proportions

What do leptochromatic and pachychromatic describe?

The nucleus as a whole

What do euchromatin and heterochromatin describe?

The state of the DNA

What are the 3 main components of the nucleus?

Nuclear envelope, nucleolus, and chromatin

What is the nuclear envelope?

A double membrane separating nuclear material from the cytoplasm

How many membranes form the nuclear envelope?

Two

What is the outer nuclear membrane continuous with?

Rough endoplasmic reticulum

What is the perinuclear space?

Space between the inner and outer nuclear membranes

What is the perinuclear space continuous with?

The space inside the rough ER

What is the nuclear lamina?

A protein mesh lining the inside of the inner nuclear membrane

What proteins form the nuclear lamina?

Lamins

What are nuclear pores?

Openings in the nuclear envelope

What is the function of nuclear pores?

Transport between the nucleus and cytoplasm

Can nuclear pore transport occur in both directions?

Yes

Name an RNA that leaves through nuclear pores

mRNA or tRNA

Name a protein that can enter through nuclear pores

DNA polymerase, RNA polymerase, lamins, or ribosomal proteins

What is the nucleolus?

A dense structure inside the nucleus

What is the main function of the nucleolus?

Synthesis of rRNA

In what cells is the nucleolus especially prominent?

Cells with active protein synthesis

What does the nucleolus contain?

DNA coding for rRNA, rRNA, and proteins

What larger structures are assembled in the nucleolus?

Ribosomal subunits

Where are ribosomal proteins produced?

In the cytoplasm

Where do ribosomal proteins go after production?

Into the nucleolus

Where do ribosomal subunits go after assembly?

Into the cytoplasm

What is chromatin made of?

Double stranded DNA associated with histones

What are histones?

DNA packing proteins

What is the cell cycle?

The sequence of events that produces new cells

What are the 2 broad parts of the cell cycle?

Interphase and mitosis

What phases make up interphase?

G1, S, and G2

What happens during G1?

The cell grows and carries out RNA and protein synthesis

Which interphase phase is usually the longest and most variable?

G1

What happens during S phase?

DNA replication

What does the S in S phase stand for?

Synthesis

What happens during G2?

The cell prepares for mitosis

What does the cell make during G2?

Proteins and organelles needed for daughter cells

What happens during M phase?

Mitosis

What is G0?

A state where differentiated cells leave the active cell cycle

Which cells commonly remain in G0?

Neurons and most muscle cells

Which G0 cells can reenter the cell cycle if needed?

Hepatocytes

What type of cells undergo mitosis?

Somatic cells

How many daughter cells does mitosis produce?

Two

How do mitotic daughter cells compare genetically?

They are genetically identical

What are the 4 phases of mitosis?

Prophase, metaphase, anaphase, telophase

What happens to chromosomes in prophase?

They condense and become visible

What happens to the nucleolus during prophase?

It disappears

What happens to the nuclear envelope during prophase?

It breaks down

When does the mitotic spindle begin forming?

Prophase

What are spindle fibers made of?

Microtubules

What happens during metaphase?

Chromosomes line up at the equatorial plate

What is another name for the equatorial plate?

Metaphase plate

What happens during anaphase?

Sister chromatids separate and move to opposite poles

What pulls sister chromatids apart?

Spindle microtubules

After sister chromatids separate, what are they called?

Chromosomes

What happens to chromosomes during telophase?

They decondense and loosen

What happens to the nuclear envelope during telophase?

It reforms

What happens to the nucleolus during telophase?

It reappears

What is cytokinesis?

The physical separation of the two daughter cells

What forms during cytokinesis?

A cleavage furrow

What is the PMAT memory for prophase?

Pack chromosomes

What is the PMAT memory for metaphase?

Middle

What is the PMAT memory for anaphase?

Apart

What is the PMAT memory for telophase?

Two nuclei forming

Before S phase, how many chromatids make one chromosome?

One chromatid

After S phase, how many sister chromatids make one chromosome?

Two sister chromatids

What joins sister chromatids together?

The centromere region

What gets separated during anaphase?

Sister chromatids

What type of cells undergo meiosis?

Cells that form sperm and egg cells

How many divisions occur in meiosis?

Two

How many final cells does meiosis produce?

Four

Are meiotic daughter cells diploid or haploid?

Haploid

What happens to chromosome number during meiosis?

It is reduced by half

Are meiotic daughter cells genetically identical?

No, they are genetically varied

What process creates variation during meiosis?

Crossing over or genetic recombination

Is there another S phase between meiosis I and meiosis II?

No

What is the key difference between mitosis and meiosis?

Mitosis makes 2 identical cells while meiosis makes 4 varied haploid cells