Week 1 & 2: Mitosis, Meiosis, Cell Cycle and Principles of Mendelian Inheritance

BIOL*1090

Cell division is the process by which cells make more _____

cells

Cell division occurs for _______,__ _______,__ ______,__ and _____

Growth

cell replacement

healing

reproduction

Cell division occurs either by ____ or ______

mitosis

meiosis

An example of mitosis

hair stem cells

An example of meiosis

germ/sex cells

What are mitotic cells?

Stem cells

What are all the stem cells?

Neural

follicle

mammary

muscle

intestinal

epithelial

haematopoetic

Eukaryotes store DNA in _______

nucleus

Prokaryotes store DNA in _______

cytoplasm

Eukaryote genomes are large and _______

linear

Prokaryote genomes are small and _______

circular

How many phases are there in interphase?

4

G1 phase (Gap 1)

growth, cellular metabolism

S phase (synthesis)

DNA replication; chromosome duplication

G2 phase (Gap 2)

preparation for mitosis

M phase (mitosis)

chromosomal separation and cytokinesis

Interphase

time between successive mitoses (G1 + S + G2)

What are quiescent cells?

Cells that are not actively cycling and exit cell cycle

Quiescent cells enter ____ phase

G0 phase

T or F: a neuron with its axon and dendrites would be QUIESCENT to cell cycle

true

How many homologous chromosomes are there?

22

Centromeres become chromatids in ____ phase

S

Step 1: Prophase

* chromosomes condense
* centrosomes radiate microtubules & migrate to opp poles

Step 2: Prometaphase

microtubules of mitotic spindle attach to chromosomes

Step 3: Metaphase

Chromosomes align in the center of the cell

Step 4: Anaphase

sister chromatids separate and travel to opp poles

Sister chromatids become individual chromosomes when _______

the centromere splits

Step 5: Telophase

* Nuclear envelope reforms
* chromosomes DEcondense

It takes ______ hours to complete 1 cell cyles

24

What is ploidy?

\# of complete chromosome sets in cell

What is haploid?

Cell with one complete set of chromosomes

What is an example of a haploid cell?

* sperm cell
* egg in vertebrates

What is a diploid cell?

Cell with two complete sets of chromosomes

* one from mother, other from father

What is an example of a diploid cell?

* somatic cell (leaf, skin, or stem cell in colon)

T or F: when the number of DNA changes, the ploidy levels in mitosis CHANGE

False

Mitosis results in two _____________

diploid daughter cells

In mitosis, each daughter cell is genetically _______

identical

Mitosis can continue in _________

perpetuity

Meiosis occurs in ______ cells

germ (sex)

Meiosis results in __ ______ daughter cells

4 haploid

In meiosis, each daughter contains _____ number of chromosomes as parent

half

In meiosis, each daughter cell is genetically _______

unique

Meiosis is a ________ event

terminal

In Prophase I, chromosomes first becomes visible as ____________

thin threads

In Prophase I, homologous chromosomes condense and undergo _________

synapsis

What is synapsis?

gene-for-gene pairing

When synapsis in Prophase I is complete, each pair of homologous chromosomes forms a ____________

bivalent

In Prophase I, the chromosomes shorten/thicken and _________ between non-sister chromatids become apparent

chiasmata

Prometaphase I

Spindles attach to kinetochores on chromosomes

Metaphase I

Homologous pairs line up at cell center with bivalents randomly oriented

In mitosis spindle fibers attach to kinetochores that __________

oppose each other

In meiosis, the kinetochores are oriented _______

side by side (mono-orientation)

In Metaphase, all _____ chromosomes align in one plane

46

In metaphase, there is NO ___________

recombination

In Metaphase I, ___ pairs of homologous chromosomes align in one plane

23

Anaphase I

* Homologous chromosomes separate
* sister chromatids do NOT separate

Telophase I & cytokinesis

daughter cells are ready to move into prophase II

After cytokinesis of Meiosis I, the ploidy level would be ___

n

Prophase II

* Nuclear envelope breaks down
* chromosomes condense

Prometaphase II

Spindles attach to kinetochores on chromosomes

Metaphase II

Chromosomes align in center of cell

Anaphase II

Sister chromatids separate

Telophase II & cytokinesis

* nuclear envelope reforms
* cytoplasm divides

What are the similarities between metaphase and metaphase II?

* mitotic spindles attach to both sister chromatids
* sister chromatids separate
* chromosome alignment along equatorial plate

What are the differences between metaphase and metaphase II?

* only 1 homologues in metaphase II
* only recombines chromosomes in meiosis
* half # of chromosome in metaphase II

Meiosis I arrest is released in one of a few oocytes during each __________

menstrual cycle

Meiosis II arrest is released upon _______

fertilization

Why can’t cell division occur all the time?

Uncontrolled division can lead to cancer

What controls the progression through the cell cycle?

* proteins that appear/disappear in cyclical fashion
* enzymes becoming active/inactive in cyclical fashion

What is the name for proteins that appear/disappear cyclically?

cyclins

Cyclins bind to and activate __________ to control cell cycle progression

cyclin-dependent kinases (CDK)

Cyclin-CDK complexes ______ that promote cell division

phosphorylate target proteins

What helps prepare cell for mitosis?

M cyclin-CDK

What helps initiate DNA synthesis?

S cyclin-CDK

What prepares cell for DNA replication?

G1/S cyclin-CDK complex

The DNA replication checkpoint checks for the presence of what?

unreplicated DNA

DNA replication checkpoints occurs at the end of what phase?

G2 before the cell enters mitosis

DNA damage checkpoint checks for what?

Damaged DNA

DNA damage checkpoint occurs before what phase?

S phase

Spindle assembly checkpoint checks for what?

all chromosomes being attached to spindle

Spindle assembly checkpoint occurs when?

Before the cell progresses with mitosis (Before anaphase)

At the DNA damage checkpoint, genes inhibiting the cell cycle are turned on/off by phosphorylated p53?

on

Where is p53 found?

in the nucleus

DNA damage activates what?

protein kinases

What do protein kinases do?

phosphorylate p53

What does phosphorylated p53 act as?

Transcription factor turning on genes that inhibit the cell cycle

What does inhibiting the cell cycle do?

Gives cell time to repair damaged DNA

Oncogene

cancer-causing gene

proto-oncogenes

normal genes important in cell division that have the potential to become cancerous if mutated

tumor suppressors

genes that encode proteins whose normal activities inhibit cell division

Normal cells (cancer development)

inactivation of 1st tumor suppressor gene

benign cancer (cancer development)

activation of oncogene

malignant cancer (cancer development)

inactivation of 2nd tumor suppressor gene

metastatic cancer (cancer development)

inactivation of 3rd tumor suppressor gene

Stem cells in the colon

slowly proliferating \~1x every 2 days

Transit-amplifying cells (colon)

* fast
* \~1x every couple hours

gene

inherited factor (encoded in DNA) helping to determine characteristics

allele

one of two or more alternative forms of a gene

locus

specific place on chromosome occupied by an allele

genotype

set of alleles possessed by individual organism