BIOL 1020 Cell division & DNA replication

LECTURES 7-8

In what organisms does division of one cell reproduce the entire organism?

Unicellular organisms

What 2 things do multicellular organisms depend on cell division for?

Growth/development and repair

What does chromatin do during cell division (what does it turn into)?

Condenses into chromosomes

The centromere is where _______ _________ are attached

“Sister chromatids”

What is the role of H2A, H2B, H3, H4?

Makes core part of nucleosome

What is the role of H1?

Prevent uncoiling of DNA by fixing it on the surface of nucleosome

What is linker DNA?

Segment of DNA connecting individual nucleosomes

Structure of metacentric chromosome

centromere is centered, arms are equal

Structure of sub-metacentric chromosomes

Centromere placed slightly closer to one end

Structure of acrocentric chromosome

Centromere placed extremely close to one end

Structure of telocentric chromosomes

“Terminally placed chromosome,” looks like a circle with 2 little legs

Why do RBCs lose their nuclei?

To make more space for carrying oxygen

What is the division in mitosis vs cytokinesis?

Mitosis divides genetic material, cytokinesis divides the cytoplasm (creating 2 identical cells)

Who developed dyes to observe chromosomes in 1882?

Walther Flemming (personal reminder: Asher Fleming from gilmore girls)

Spindle fibers (mitotic spindle) are made of what? Additionally, what protein is your answer made of?

Microtubules, made of tubulin

Telophase is essentially the opposite of the effects in ___phase.

“Pro,” phase

During what phase does the centrosome replicate?

Interphase

What is an aster?

Radial array of short microtubules

What 3 things does the spindle include?

Centrosomes, spindle microtubules, asters

How do microtubules shorten?

They depolymerize (break down into monomers) at their kinetochore ends

What do nonkinetochore microtubules from opposite poles do instead of attaching to kinetochores?

Overlap and push against each other (elongates cell, pushes spindle poles apart)

In what phase do nuclei form at opposite ends of the cell

Telophase

In animal cells, cytokinesis occurs by a process known as _______, forming a ______ ______.

“Cleavage,” “cleavage furrow”

What forms in plant cells during cytokinesis?

A cell plate

What is binary fission?

The method by which prokaryotic cells reproduce

What is mitosis said to have developed from?

Binary fission

T/F: Mitochondria and chloroplasts divide independently within eukaryotic cells by binary fission

True

Evidence for cytoplasmic signals comes from experiments looking at cell cycle progression in __________ cells

“mammalian”

Sequential events of the cell cycle are directed by a distinct _____ ______ ______ _______

“cell cycle control system”

T/F: The cell cycle control system is regulated by only external controls

F: It is regulated by both internal and external controls

Two types of regulatory proteins involved in cell cycle control

Cyclins and cyclin-dependent kinases (Cdks)

What does the MPF (maturation-promoting factor) trigger when enough of it accumulates?

Triggers a cell’s passage past the G2 checkpoint into M phase

During what phase is the cyclin component of MPF degraded?

Anaphase

What checkpoint is the most important for many cells?

G1 checkpoint

If the cell does not receive the “go-ahead” signal, it will exit the cycle, entering the nondividing state known as ___ phase

“G0”

If a cell will not pass the M checkpoint, then enter anaphase until all chromosomes are properly attached to spindle fibres, is this an internal or external signal example?

Internal signal

Are growth factors an internal or external factor?

External

Platelet-derived growth factor (PDGF) made by platelets stimulate other cells to _______

“divide”

What is anchorage dependence?

When a cell must be attached to a substratum to divide

What type of cells exhibit anchorage dependence

Animal cells

Density-dependent inhibition is an ______ factor in which crowded cells stop dividing

“external”

What type of cells exhibit neither density-dependent inhibition nor anchorage dependence?

Cancer cells

What did HAYFLICK and MOORHEAD find about cells?

That cells divided a maximum of 50 times + Long lived animals had larger division limits (vise versa)

HAYFLICK and MOORHEAD’s conducted their research on ____ cells from humans

“lung”

How many times will the typical normal human fetal cell divide?

50-70 times

What is the Hayflick limit?

The limit on cell replication imposed by the shortening of telomeres with each division

What is the end stage of the Hayflick limit called?

Cellular senescence

A normal cell is converted to a cancerous cell by a process called?

Transformation

Cancer cells not eliminated by the immune system form?

Tumors

If abnormal cells remain only at the original site, it is a?

Benign tumor

________ tumors invade surrounding tissues and can metastasize

“Malignant”

T/F: Cancer cells can divide with no limit

True

What does metastasis result in?

Exporting of cancer cells to other parts of the body (where they may formed more tumors)

How can localized tumors be treated?

High-energy radiation (damages the DNA in cancer cells)

The role of DNA in heredity was first discovered by studying _______

Bacteria

Discovery of genetic role of DNA began with research by ______ ______ in 1928

“Frederick Griffith” (the mouse experiment guy)

What is a bacteriophage?

A virus that affects specifically bacteria

What is the protective coat surrounding a virus made of?

Usually protein

The Hershey-Chase experiment showed that DNA is the genetic material of __ phage

“T2”

What was showed in the Hershey-Chase experiment concerning E. coli cells during infection?

Showed that only one of the two components of T2 enters an E. coli cell during infection

In 1950, who reported that DNA composition varies from one species to the next?

Erwin CHARGAFF

The observation that A // T and C /// G became known as ________ rules, as well as any number of A bases = T bases, vise versa.

“Chargaff’s”

The basic of Chargaff’s rules was not understood until the discovery of the _______ helix

“double”

Watson and Crick built ______ of the double helix

“models”

Did Watson or Crick build a model in which the backbones were antiparallel?

Watson

More hydrogenous bonds = can live at ______ temperatures

“higher”

How many origins of replication do eukaryotes vs bacteria have?

Eukaryotes may have hundreds or thousands… bacteria just one

What is helicase?

The enzyme that unzips the double helix @ replication forls

What are single-stranded binding proteins?

Bind to and stabilize single-stranded DNA

What is topoisomerase?

Enzyme that corrects “overwinding” by breaking/rejoining DNA strands

What is primase?

Synthesizes RNA primers

DNA polymerases cannot initiate synthesis of a?

Polynucleotide

DNA polymerases can only add nucleotides to an existing _’ end

“3”

What is the rate of elongation (___ nucleotides/sec) in bacteria vs human cells?

Bacteria (500n/sec), human (50n/sec)

Each nucleotide added to growing DNA strand is a ________ _________

“Nucleoside triphosphate”

dATP supplies ______ to DNA and is similar to ATP of energy metabolism

“adenine”

What is the difference between dATP and ATP?

dATP is deoxyribose while ATP has ribose (sugar difference)

As each new nucleotide is added to the growing DNA strand, it loses ___ phosphate groups as a molecule of pyrophosphate

“two”

DNA polymerases add nucleotides only to the free _’ end of a growing strand

“3”

A new DNA strand can elongate only in ’_ to _’ direction

“5” to “3”

Okazaki fragments are joined by ___ ______, also known as the “chemical glue”

“DNA ligase”

pg 128

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