Biology Unit 5

this class sucks ass

How long is the DNA in our cells if it was stretched out?

6ft

How long would the DNA from ALL of your cells be?

It would be ale to stretch to the sun and back 61 times

How does all of our DNA fit in a single eukaryotic cell?

DNA packaging

Genome

total genetic material in an organism

as organisms get bigger…

their genome size increases

Chromatin

Loosely wound substances found in eukaryotic cells that consists of DNA wrapped around histone proteins (form of DNA in non actively dividing cells)

Histones

family of proteins that are associated with DNA packaging in the form of chromatin

photo of histone

nucleosome

fundamental subunit of chromatin

What is a nucleosome composed of?

a little less than two turns of DNA wrapped around a set of eight proteins called histones

dna composition

octamer

chromosome

tightly wound (condensed) substance found in dividing eukaryotic cells. Essentially the chromatin gets more tightly packed/wound

chromosome photo

chromatid

one-half of two identical threadlike strands of a replicated chromosome

chromosome & chromatid photo

centromere

the region of a chromosome where chromatids are joined

labelling a chromosome

benefits of chromosomal packaging?

easy to move around the cell during cell division

disadvantages of chromosomal packaging?

difficult to access the genes during transcription

chromosome #…

increases as organism becomes more complex

Prokaryotic DNA Characteristics

circular, single chromosome, naked (not bound with histone proteins), compact (few repetitive sequences or introns)

prokaryotic DNA image

prokaryotic chromosomes image

eukaryotic chromosome image

genophore

DNA found in a prokaryotic cell

plasmids are in…

prokaryotes

plasmid

a small dna molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. Mostly associated with prokaryotic cells

organelle dna

mitochondria/chloroplast, some like yeast can have plasmids too

prokaryotic DNA organization

single loop of naked DNA (no histones)

prokaryotic number of chromosomes

1

prokaryotic extra genetic material

plasmids (rings of extra non-essential DNA

eukaryotic dna organization

dna is wrapped around histone proteins (linear)

eukaryotic number of chromosomes

multiple, normally multiples of 2

eukaryotic extra genetic material

mitochondra, chloroplast, occasionaly plasmids like yeast

asexual reproduction

no exchange of genetic material

sexual reproduction

exchange of genetic material

continuity of life is based on…

cell division

unicellular organisms

organisms where division of one cell reproduces the entire organism

multicellular organisms

organisms that depend on cell division for development from a fertilized cell, growth, and repair

cell division is an integral part of what?

the cell cycle

what does cell division result in? (most of the time)

daughter cells with identical genetic information, DNA

what do some specialized types of cell division produce

non-identical daughter cells (gametes, or sperm and egg cekks)

asexual reproduction example

mitosis & binary fission

sexual reproduction example

meiosis

cell cycle

the series of events that take place from when a cell forms until when it divides to produce daughter cells, the life of a cell

cell cycle consists of…

interphase, mitosis, and cytokinesis

interphase

cell growth and copying of chromosomes in preparation for cell division

mitotic phase

mitosis and cytokineses

cell cycle image

interphase subphases

G1, S, and G2

G1 phase

first growth phase. the cell carries out routine functions, grows larger, and makes new proteins and organelles

S phase

“synthesis”, when dna is replicated

G2 phase

second growth phase. the cell prepares for division by forming microtubules and other organelles or molecules that they cell may need to divide

interphase is not a what

resting phase

% of cell cycle that is interphase

90%

when is dna duplicated in cell cycle?

s phase

cell cycle control system function

direct the sequential events of the cell cycle

what is the cell cycle control system regulated by?

internal and external controls

cell cycle control system is similar too..

a clock

checkpoints

places in the cell cycle control system where the cell cycle stops until a go ahead signal is received

different checkpoints

G1 checkpoint, G2 checkpoint, M checkpoint

G0

a phase where the cell is not preparing to divide, and therefore is not going to progress through the cell cycle. cells will perform normal metabolic processes during G0. some cells can re-enter the cell cycle after being in G0, althought some cells are in terminal G0 and cant re-enter the cell cycle

what are the types of regulatory proteins involved in cell cycle control

cyclins and cyclin-dependent kinases (cdks)

relationship between cyclin and cdks

cycle activates cdks

what does the activity of cyclins and cdks do?

fluctuate during cell cycle

mpf

maturation-promoting factor, a cyclin-cdk complaex that triggers a cell’s passage past the g2 checkpoint into the m phase

fluctuation of mpf activity and cyclin concentration during the cell cycle

molecular mechanisms that help regulate the cell cycle image

cdks are…

always present but not always active

cdks are activated when…

a cyclin binds to it

mpf function

go signal for the g2 checkpoint, allows cell to enter m phase

eukaryotic cell division consists of…

mitosis and cytokinesis

mitsosis

division of the nucleus

cytokinesis

division of the cytoplasm

why can’t prokaryotes perform mitosis

they do not have a nucleus, and sincce mitosis is the division of the nucleus, they cant do it

phases of mitosis

prophase, metaphase, anaphase, telopahse

cytokinesis occurs simultaneously with

telophase

g2 of interphase

formation of the centrosomes, structures that will direct formation of mitotic spindle

centrioles

component of the centrosomes in animal cells.

prophase

mitotic spindle grows, chromatin condenses into chromosomes, mitotic spindle attaches to chromosomes (microtubules), nuclear envelope breaks down

mitotic spindle

apparatus of microtubules & centrosomes that controls movement during mitosis

where/when does the assembly of the mitotic spindle begin?

during prophase in the centrosome

as the mitotic spindle grows..

the centrosome replicates, forming 2 centrosomes that migrate to opposite ends of the cell

kinetochores

protein structures that are located in the centromere region where microtubules attach and help to facilitate chromosome movement

where do spindle microtubules attack to move the chromosome?

on the kinetochore

metaphase

the chromosomes line up at the metaphase plate.

what does the m checkpoint do

checks to make sure the chromosomes have lined up at the metaphase plate during metaphase before anaphase begins

nonkinetochore microtubules

microtubules from opposite poles that overlap and push against each other, elongating the cell

anaphase

sister chromatids separate and move along the kinetochore microtubules towards opposite ends of the cell

during anaphase, what direction do chromosomes move?

towards spindle

telophase/cytokinesis

genetically identical daughter nuclei form at opposite ends of the cell. nuclear membrane reforms, chromosomes unwind back into chromatin

animal cell cytokineses

occurs by a process known as cleavage, forming a cleavage furrow, pinching inwards until the cells separate

plant cell cytokinesis

cell plate forms during and grows outwards

binary fission (prokaryotes)

the chromosomes replicates and the 2 daughter chromosomes actively move apart as the cell divides

why did mitosis probably evolve from binary fission

prokaryotes evolved before eukaryotes

certain protists (eukaryotes) exhibit what type of cell division?

mix between binary fission and mitosis

regulatory proteins

proteins inside and outside the cell that control cell cycle, stop/go signals

internal regulators

proteins that respond to events inside a cell and allow the cell cycle to proceed only when certain events have occured, ex cyclins/cdks

external regulators

proteins that respond to events outside the cell, often directing cells to speed up or slow down the cell cycle