Chapter 2 - Mitosis and Meiosis

plasma membrane

outer covering that defines the cell boundary and actively controls the movement of materials into and out of the cell

chromatin and nucleolus

2 things found in the nucleus

ribosomal RNA is synthesized and the initial assembly of ribosomes is completed

what occurs in the nucleolus?

cytosol is the gel-like substance inside the cell whereas the cytoplasm includes organelles and substructures

cytosol vs cytoplasm

ribosomes translate mRNA into proteins

what occurs on the rough ER?

synthesizing fatty acids and phospholipids

what occurs at the smooth ER?

• free ribosomes are proteins within the cytosol

• bound ribosomes are proteins for secretion, insertion into membranes, and packaging within certain organelles

free vs bound ribosomes

organize spindle fibers and important for movement of chromosomes

functions of the centrioles

p arm

shorter arm of chromosome

q arm

longer arm of chromosome

metacentric

centrosome located in the middle of chromosome

submetacentric

centrosome located between the middle and end of chromosome

acrocentric

centrosome located close to the end of chromosome

telocentric

centrosome located at the end of the chromosome

pseudo autosomal region

present on both X and Y chromosomes and important for synapsis of chromosomes during meiosis

biparental inheritance which results in alleles

what are 2n genomes a result of?

2n

diploid organisms have __ genomes

G1 → S → G2 → mitosis → G0 (if necessary)

stages of the cell cycle

metabolic activity and growth (preparing for division) and synthesis of new chromosomes to generate sister chromatids

(cell volume has doubled, DNA is replicated, and cell ready for mitosis)

what occurs during interphase?

interphase → prophase → metaphase → anaphase → telophase

order of mitosis

kinetochore microtubules

most directly involved in chromosome migration during prometaphase and metaphase

separase

degrades cohesin when spindle fibers and kinetochore bind

shugoshin

this protects cohesion at the centromere region which separase is degrading it

cyclins

proteins that vary in their concentration throughout the cell cycle

cyclin-dependent kinases

what regulates the cell cycle

crossing over

genetic exchange between members of each homologous pair of chromosomes

bivalents

synapsed pairs of homologous chromosomes in prophase I of meiosis

complex of DNA and proteins found in eukaryotic cells during interphase

what is chromatin?

a complete copy of a chromosome

in karyotype, each half of the “X” is what

1. basis of asexual reproduction in single celled organisms

2. multi-cellular organisms under mitosis for development and growth

3. wound healing/replacement of tissues

4. abnormal mitosis: tumors/cancer

4 implications of mitosis

separation of DNA and nucleus that requires replication of chromosomes and partitioning into 2 daughter nuclei

what is karyokinesis

splits volume into 2, encloses new cells with complete plasma membrane, and organelles replicate themselves new or from existing structures

what is cytokinesis?

1. migration of 2 pairs of centrioles to opposite ends of the cell

2. centrioles establish poles at opposite ends of the cell

3. centrosomes organize cytoplasmic microtubules into spindle fibers that run between the poles (create an axis for chromosomes separation)

4. nuclear envelope and nucleolus begin to break down/disintegrate

5. chromatin begin to condense and chromosomes are easily visible

6. sister chromatid forms held together by cohesion

6 steps of prophase

migration and configuration of chromosome to equatorial plane

occurs during prometaphase and metaphase

• spindle fibers bind to kinetochore which are proteins associated with the centromere and on opposite sides of each paired centromere

• separase degrades cohesin when spindle fibers and kinetochore bind

• shugoshin protects cohesion at centromere region

explain how migration of chromosomes occurs during prometaphase/metaphase

sister chromatids of each chromosome separate (disjunction)

• shugoshin is degraded

• cohesin at the centromere region is cleaved by separase

• sister chromatids of each chromosome are pulled towards the opposite poles of the cell (kinetochore and spindle fibers work with motor proteins)

what occurs during anaphase?

• chromosomes uncoil

• nuclear envelope reforms

• spindle fibers disappear

• nucleolus gradually reforms

reversal of prophase events during telophase

cleavage furrow in animals

cell plate in plants

cytokinesis in animals vs plants

checks for chromosome spindle attachment

metaphase checkpoint

check for nutrients, growth factors, and DNA damage

G1 checkpoint

check for cell size and DNA replication

G2 checkpoint

they behave autonomously during division in mitosis but not is meiosis 1

difference in behavior of maternally and paternally derived chromosomes in mitosis and meiosis 1

tetrads

bivalents give rise to _____

chiasma

represent a point where non-sister chromatids have undergone genetic exchange through crossing over

prophase 1

when does crossing over occur

reductional division

reduces number of centromeres in half (anaphase 1 of meiosis)

nondisjunction

if an error occurs and separation doesn’t happen properly

the haploid number

at completion of meiosis 1, daughter cells contain a set of dyads equal to

equal division

the number of centromeres is not reduced