Mitosis and Meiosis

Cell theory

all cellular life is made of one or more cells 

Cells

basic organizational and functional units of all organisms 

Cell division

all parts of a cell divide into new cells and distribute genetic material into daughter cells 

Unicellular cell division 

divide to reproduce daughter cells 

Multicellular cell division

divide to grow and develop new cells 

Daughter cells

get a complete copy of the parent cells genome

Genome

a cells total genetic material

Prokaryotes chromosome

1 circular DNA molecule

Eukaryotes chromosome

more than 1 linear DNA molecule 

Chromosome

molecule of DNA wrapped around proteins

Chromatin

DNA/protein complex in dispersed state

Haploid (n)

contain one complete set of chromosomes 

Diploid (2n)

contain two complete sets of chromosomes

Interphase

time between cell divisions 

Interphase key concepts

cell is highly active: grow & synthesize

cell spends at least 90% of its life in interphase

prepares cell for division

G1 phase

grows and develops cell

Synthesis phase (S)

replicates the cells DNA

Sister chromatids 

identical copies of a single chromosome 

Centromere

the part of a chromosome where the sister chromatids are held together 

How are chromosomes counted?

chromsomoes are counted by the number of centromeres present 

G2 phase 

cell continues to grow and prepares for MITOSIS

Prophase

chromatids condense into chromosomes 

nucleus breaks down 

miotic spindles form

Miotic spindles 

help move chromosomes to the opposite ends of the cell 

Metaphase

chromosomes align at the middle of the cell due to the complete breakdown of the nucleus

Anaphase

sister CHROMATIDS are pulled apart by kinetochores

Kinetochores

proteins attached to centromes

Telophase

new nuclei form around the chromosomes

Cytokinesis

splits the cytoplasm

Result of Mitosis

two identical diploid cells

Cleavage furrow

region where parent cell pinches forward 

Cell plate

new membrane at location of metaphase plate

Prophase I

chromosomes match up with their homologous pairs and cross over

Crossing over

transfer of genetic information

Metaphase I

homologous pairs line up in the middle

Anaphase I

CHROMOSOMES are pulled apart

Telophase I

new nuclei surround the chromosomes

Prophase II

chromosomes condense (no crossing over)

Metaphase II 

chromosomes line up in the middle in a single file line

Anaphase II

CHROMATIDS are pulled apart

Telophase II 

new nuclie forms around the chromatids

Result of Meiosis

4 non-identical haploid cells 

Heredity

transmission of traits from one generation to the next

Variation

differences between individuals

Genetics

the study of heredity variation 

Gametes

reproductive cells that transmit genes from one generation to the next

Asexual reproduction

single parent produces offspring

Unicellular asexual reproduction

reproduce by splitting into two cells 

Multicellular asexual reproduction 

reproduce by fragmentation or budding  

Multicellular fragmentation

parent cell breaks down and each part develops into a new cell

Budding fragmentation

an organism grows onto the parent cell and eventually detaches and develops into a new cell

Advantages of asexual reproduction

fast

low E required

safe

results in lots of offspring 

Sexual reproduction

fusion of 2 gametes to form a zygote

Zygote

diploid cell resulting from fertilization

Costs of sexual reproduction

slow

high E requirement

dangerous

result in few offspring 

Advantages of sexual reproduction

genetic variation

offspring represent novel combinations of parents genes

more likely to survive environmental change / stress

Pros of variation

allows for a population to adapt or survive environmental changes and evolve over time which increases long-term survival

Cons of variation 

if gametes have the same number of chromosomes as parents then the chromosomes will double every generation