Lecture-reproduction and cellular level

Genome

-a cell’s entire complement of DNA

-all sources of DNA is considered

Prokaryotic Genome

-the genome is composed of a single, double stranded circular DNA molecule

-region in the cell containing the genetic material (nucleid)

-some prokaroytes also have smaller loops of DNA (plasmids) located outside of the DNA

eurkortic Genome

-in eukaroyes, the nuclear genome is made up of several double straded, linear DNA molecules

-DNA is bound to proteins to form complexes (chromosomes)

-each species has charcteristic number of chromosomes

-DNA is in the nucleus, chlorplast or mitchondria

Human genome

Human somatic cells (not involved in producing eggs or sperm) have 46 chromosomes

-23 matched pairs of chromosomes

-cells that are diploid and refered to 2n where n is the number of chromosome pairs

Gametes (sperm and eggs) are haploid (n) and each contains 23 chromosomes, one from each pair

Humologus chromosomes

-the matched pairs of chromosomes

-they are the same length and regions (genes) in the same locations (loci)n

-genes code for proteins and determine spefic charcteristics in orgnaims

-each copy of the homologus pair orginates from a different parent

-the copies of the genes themsleves may or may not be identical

-variation in individuals within species is caused by spefic combination of genes inherited from both parents

cell cycle

is an ordered series of events, cell growth, DNA replication, and cell division into two daughter cells

-interphase and the mitotic phase

interphase-the cell grows and DNA is replicated

mitotic phase- the replicated DNA and cytoplasmic contents are separed and the cell dividies

Interphase

-when the cell undergoes normal processes while also preparing for cell division

-many interal and exteral conditions must be met

-three stages of interpjase are G1. S and G2

G1

-first gap and little change is visible

-biochemical activity

-the cell is accumulating the molecular building blocks of DNA as well as accumulating energy reserves for the tasks that lay ahead

S phase

-DNA replicates

-results in the formation of two identical copies of each chromosome

-these two copies are sister chomatid and they are cconnection at the region centromere

centrosome-duplicated and will rise to the mitotic spindle the appartus that orchestrates the movements of the chromosmes

G2

-second gap and the cell replenishes its energy stores

-some organelles are duplicted and the cytoskelton is dismantled

-the cell may grow in size as it completes all the prepartions for the mitotic phase

difference between gamates and somatic cells

gamates-reroductive cells

somatic cells-non reproductive

Mitotic phase

-to make two daughter cells the contents of cystoplasm must be divided

-is multistep process during which the duplicated chromosomes are aligned, separted and moved to opposite poles of the cell

-cell is divided into two new identical daughter cells

cytoskinesis- physical separtion of the cytoplasmic compentents into two new daughter cells

Mitosis

1. prophase

2. prometaphase

3. metaphase

4. anaphase

5. telophase

Prophase

-chromosomes condense and become visible

-spindle fibers emerge from the centrosomes

-nuclear envelope breaks down

centrosomes move towards opposite poles

Prometaphase

Chromosomes continue to condense

-kinetochores appear at the centromeres

-mitotic spindle microtubles attach to kinetochores

metaphase

-chromosomes are lined up at the metaphase plate

-each sister chromatid is attached to a spindle fiber orginating from the opposite plates

anaphase

centrosomes spilt in two

-sister chromatids now are chromosomes pulled toward opposite poles

certain spindle fibers begin to elongate the cell

telophase

chromosomes arrive at the opposite poles ansd begins to decondense

-nuclear envelope material surrounds each set of chromsomes

-mitoic spindle breaks down

-spindle fibers continue to push poles apart

cytokinesis

animal cells- a cleavage furrow separtes the duaghter cell

plant cells- a cell plate, the precurosor to a new cekll wall separtes the daughter cell

G0 phase

not all newly formed daughter cells immediately enter interphase, closely followed by the mitotic phase

-some cells exit the cell cycle and enter an active stage (G0)

-some cells enter G0 temporaily while others remain permantenlty