BSC 114 - EXAM 3

eukaryotic cell vs. prokaryotic

eukaryotic:
- nucleus
- linear DNA
prokaryotic:
- no nucleus
- circular DNA

zygote

development of fertilized cell

cell division does

1. development from fertilized cell
2. growth
3. maintenance and repair of tissues

chromatin types of structure

- tight or loose
easier to move DNA when tightly packaged
** when condensed, genes aren't always turning on

somatic cell

any cell of a living organism other than the reproductive cells.

gametes

Humans = sperm and egg cells
Plants = pollen and ovum
** reproductive

Goal of mitosis

splitting up genetic material

meiosis goal

make offspring have little bit of genetic difference

cytokinesis

division of cytoplasm to produce two genetically identical daughter cells

cells not always identical

in mitosis

2 Big Phases of Cell Cycle

M phase: mitotic phase (mitosis and cytokinesis)
Interphase

G1 phase

receiving of environmental signals
- signal transduction pathway
- a cell receiving its job
- cell growth

S (DNA synthesis) phase

spend energy on making second copy of DNA
- need nucleotides to make DNA
- S-cyclin promotes

G2 phase

receiving signals from environment
- "is it ok to divide?"
- cell growth
- need ATP to power through

Signal transduction pathways control

shifting between different phases of cell cycle

Mitosis 5 Phases

prophase, prometaphase, metaphase, anaphase, telophase

Nucleolus starts dissolving in G2 of interphase

allows chromosomes to condense up
- nuclear envelope dissolves 50% during prometaphase **

metaphase plate

where sister chromatids split in half
- half to souther and northern poles

plant cell cytokinesis

DONT PINCH INWARD
- vesicles that form cellulose, lines up to form cell plate, and grows bigger between cells to help divide them

kinetochore

proteins that anchor the chromatids
- site for spindle fibers to pull sister chromatids apart in anaphase

metaphase

all spindle fibers should be attached to kinetochore part of chromosome
- cell is circular (One half going north/south)

anaphase

asters getting further apart and spindle fibers are getting shorter ... separating two sister chromatids (cell becomes semi ovular)

aster

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

Telophase and Cytokinesis

chromosomes hit opposite ends of cell; you get two new nuclei and two new cells start to form

cytokinesis in animal cell

cleavage furrow
- contractile ring forms and pinches off into two new cells

checkpoints in cell cycle

G1
G2 --> chromosomes condensed together; no turning on genes
M --> mitosis checkpoint

G0 checkpoint

NON-DIVIDE STAGE
cell isn't giving signals ... won't reproduce anymore
- can pop out of G0 and go back into cell cycle

checkpoints are controlled by ...

cyclin-dependent kinases (Cdk)
- G1/S-cyclin promote G phase
- increase concentrations move through cell cycle

cyclin

cell cycle protein activated by joining ... then protein turned on

meiosis makes

four cells with half amount of DNA; DNA should be different in each one
- plants, humans, any eukaryotes

growth factors

released by certain cells and stimulate other cells to divide

density-dependent inhibition

crowded cells stop dividing
- need room to grow so take cells and put them in a new bottle

anchorage dependent

wants to be stable on something
- in order to divide they must be attached to a substratum

Cancer cells

have some form of inhibition but very little
- have growth were you shouldn't have growth
- feed themselves growth factors

transformation

normal cell converted to a cancerous cell

benign tumor

abnormal cells at original site

malignant tumor

invade surrounding tissues and metastasize
- export cancer to other parts of body

Biggest advantage to cancer treat

"personalized medicine"
- sequence own human genome for under $1000

prokaryotic cell development

binary fission
1. double amount of DNA
2. two origins of replication
3. cell splits in half (two genetically identical)
- every 18 mins; also die very fast

cell division

continuity of life is based on reproduction of cells
- distribution of identical genetic material (DNA) to two daughter cells
exception: meiosis

genome

cell's DNA; genetic info
- prokaryote = single DNA
- eukaryote = number of DNA

somatic cell count

46 chromosomes 2 sets of 23
- first is X/Y = sex-linked

sister chromatids

joined copies of original chromosome
- each sister chromatid has a centromere

Interphase accounts for

90% of cell cyle
- G1, S, G2
- cell grows during all phases but chromosomes only replicated during S

spindle apparatus consists of

- kinetochore microtubules --> bind to centromere associated protein
- overlapping nonkinetochore microtubules --> interact via motor proteins
- astral microtubules (asters) --> extend from each centrosome
- centrosomes --> remain attached to spindle microtub

prometaphase

nuclear envelope breaks down; chromosomes undergo active movement as they begin process of aligning at equator

prophase

replicated chromosomes condense
- outside nucleus microtubule spindle assembles between two centrosomes

cell checkpoints regulated by

internal and external signals

Cdk activity controlled by

protein kinases
protein phosphatases
non-enzyme proteins regulating cyclin-Cdk activity

heredity

transmission of traits from one generation to the next

haploid cell

diploid zygote

genes

units of heredity and made up of segments of DNA

n

haploid

2n

diploid

sex of baby is determined by

sperm's DNA

ploidy level of original cell

diploid

ploidy level of final cell

haploid

prophase I

crossing over
- synapsis; recombination
- chiasmata = sites of crossover

metaphase I

homologous chromosomes line up on metaphase plate
- one chromosome at each pole
- microtubules from one pole attached to kinetochore

anaphase I

pairs of homologous chromosomes separate
- one chromosomes moves toward opposite poles

telophase & cytokinesis

each half of cell has a haploid set of chromosomes
- cleavage furrow forms (animal)
- cell plate form (plant)

Prophase II

spindle apparatus forms
- later prophase II (chromosomes move toward metaphase plate)

metaphase II

sister chromatids line up at the metaphase plate
- two sister chromatids of each chromosome are no longer genetically identical

anaphase II

sister chromatids separate
- move as two newly individual chromosomes toward opposite poles

telophase II and cytokinesis

chromosomes arrive at opposite poles; nuclear chromosomes begin condensing

chiasmata

site of crossing over

mitosis vs. meiosis

mitosis:
- no crossing over
- 2 identical cells
- metaphase = sisters line up
- 1 round cyotkinesis
Meiosis:
- don't want identical
- 4 genetically diverse
- prophase I -> genetic diff
- metaphase I -> homologous line up

genetic variation

1. independent assortment of chromosomes
2. crossing over
3. random fertilization (not animals or plants)

karyotype

ordered display of the pairs of chromosomes from a cell

homologous chromosomes (homologs)

two chromosomes of a pair have the same length, centromere position, and staining pattern
- X/Y = sex chromosome
- X = egg
- sperm = X or Y

autosomes

non-sex chromosomes

synaptonemal complex

formation of zipper-like structure
- holds one homolog to other

synapsis

the DNA breaks are closed up so that each broken end is joined to the corresponding segment of the nonsister chromatid

3 unique events of meiosis I

1. synapsis and crossing over
2. alignment of homologous pairs at metaphase plate
3. separation of homologs

locus

gene's specific individual passes all genes to offspring w/o fusion of gametes

fertilization

union of gametes (sperm and egg)
- fertilized egg = zygote
- one set of chromosomes from each parent

gametes are the only

haploid cells in animals

Gametes fuse to form a diploid zygote that divides by

mitosis to develop into a multicellular organism

daughter cell has only

half as many chromosomes as parent cell

Mitosis conserves the number of chromosome sets

producing cells that are genetically identical to the parent cell

Meiosis reduces the number of chromosome sets from

Two (diploid) to one (haploid)

independent assortment

1. homologous pairs of chromosomes orient randomly at metaphase I of meiosis
2. each pair of chromosomes sorts maternal/paternal homologs into daughter cells independently

crossing over

produces recombinant chromosomes
- contributes to genetic variation (combine DNA from two parents into single chromosome)

natural selection results in

the accumulation of genetic variations favored by the environment

sexual reproduction contributes to

genetic variation in a population, which originates from mutations

character

heritable feature that varies among individuals (flower color)

trait

each variant for a character (purple or white color)

true-breeding

plants produce only same variety as the parent plant

hybridization

"crossing" of two true-breeding varieties

P generation

true-breeding parents (parental generation)

Hybrid offspring

F1 generation (first "son" generation)

hybrids self-pollinate

F2 generation

alleles

alternative versions of a gene

homozygote

organism that inherits two alleles of the same type for a given gene

heterozygote

organism that inherits two different alleles for a given gene

phenotype

An organism's physical appearance, or visible traits.

genotype

genetic makeup of an organism

testcross

Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

monohybrids

where heterozygous for the one particular character being followed in the cross

dihybrids

individuals heterozygous for the two characters being followed in the cross