GEN BIO - Cellular Reproduction

Chromosome

Is a thread-like structure located inside the nucleus of most living cells

• Chromatid

• Centromere

• Telomere

• P arm

• Q arm

Parts of chromosome:

Chromatid

Is 1 of 2 identical halves of a duplicated chromosome

Centromere

The attachment points of the 2 chromatids of a chromosome

Kinetochore

Is in the middle of centromere, it is where the spindle fibers attach

Telomere

Keeping the shape

p arm

Upper arms of the chromosome

q arm

Lower arm of the chromosome which is usually longer

1. Interphase

2. Cell Division

2 Stage of Cell Cycle

Interphase

• Cell growth and chromosome replication

• Growth & preparation

1. G1 - First Gap Phase

2. S - Synthesis Phase

3. G2 - Second Gap Phase

3 Stages of Interphase

G1 - First Gap Phase

• The cell grows physically larger

• Copies organelles and synthesizes the molecular building block, it will need in later stages

• Doubles the part of organelles inside the cell

• Preparation for DNA synthesis

S - Synthesis Phase

• The cell synthesizes a complete copy of DNA

• Each chromosome is replicated, resulting two identical sister chromatids

• DNA synthesis (replication)

G2 - Second Gap Phase

• The cell continues to grow, synthesize proteins and organelles and prepares to enter mitosis

G0 - Gap Zero

• Cell are unlike to divide but still continue to perform normal function

Quiescent Stage

Cells enter G0 phase temporarily

Senescent Stage

Cells enter G0 phase permanently

Spindle Fibers

Ang hahatak sa schomosome para mag divide

G1 - First Gap Phase

• Cell carries out its normal metabolic functions (example: during G1 phase, an intestinal cell performs its primary duty to absorb nutrients)

• Cells increase their size

• Cell prepares for DNA synthesis

S - Synthesis Phase

• DNA synthesis (replication) occurs: cells make a copy of its genetic material in the form of nuclear DNA

• Cells spend considerable amount of time and energy to make its chromosomes

G2 - Second Gap Phase

• Cells continue to carry out their normal functions and also undergo further growth and synthesis of RNA and proteins

• This stage contains a critical “checkpoint” before transitioning o the next stage which is cellular division

G1 Checkpoint

• Restriction point to enter S phase

• Checks DNA damage and favorable conditions

• Availability of growth factors

• Can direct cell into quiescence (G2) if conditions are not favorable

S Checkpoint

• Checks for DNA damage before/during replication

• Prevents reduplication of DNA

G2 Checkpoint

• Allows entry into mitosis

• Checks DNA damage

• Ensures DNA is duplicated

M Checkpoint

• During mitosis allows entry to anaphase

• Ensures all chromosomes aligned of metaphase plate and attached to the spindle fiber

Mitosis

Is the process of cell division in eukaryotic cells where a single cell divides into two genetically identical daughter cells

Two identical cells

Mitosis is results of two _____________

Asexual Reproduction

Mitosis is what type of reproduction

• Prophase

• Metaphase

• Anaphase

• Telophase

Four Main Phases - Mitosis

Prophase

• the repeated coiling of chromosomes occurs resulted to its thicker and shorter structure - condensing - thickening

• The two chromatids are still attached at the centromere

Metaphase

• Chromosomes align at the equatorial plane

• Each spindle fiber from both centrosomes connect to each chromosome through its kinetochore

Centriole

the two opposite poles the helps form chromosomes in a straight line

Anaphase

• Spindle fibers begin to contract and become shorter

• Centromeres divide

• The single chromatids move towards the opposite poles

Telophase

• The chromosomes are now at the opposing poles of the spindle

• Two sets of chromosomes are surrounded by new nuclear membranes, completing the nuclear division process known as karyokinesis

karyokinesis

The nuclear division process is known as

Cytokinesis

• After telophase, the cell’s cytoplasm and organelles divide in a process called ______________

• New identical cell is present

Meiosis

Is a specialized type of cell division that is critical for sexual reproduction

different set of cell

Meiosis produces _____________

• Crossing Over

• Independent Assortment

Genetic Diversity Two Key Processes:

Genetic Diversity

Unique traits

Crossing Over

• During the first stage of meiosis, homologous chromosome pair up and exchange segments of their DNA

Homologous Chromosome

Two pairs of chromosomes

Sister chromatid

two identical copies of a chromosome that are joined together by a centromere

Recombinant Chromatids

Are chromatids that have new combinations of genes

Independent Assortment

The process by which homologous chromosomes randomly align at the center of the cell during metaphase I of meiosis

Meiosis I

This is the “reductional” division, where homologous chromosomes are separated

Prophase I

Chromosomes condense and homologous chromosomes pair up (synapsis) and exchange genetic material through crossing over

Synapsis

Paired up of homologous chromosomes

Tetrad

Group of four chromatids

Metaphase I

The pairs of homologous chromosomes line up at the center of the cell

Anaphase I

The homologous chromosome pairs are pulled apart to opposite ends of the cell

Telophase I

The cell divides intro two new cells, each with half the number of chromosomes

Interkinesis

Resting (at the end of meiosis I)

Meiosis II

This is the “equational” division, similar to mitosis, where sister chromatids are separated

Diploid

Two sets of chromosomes

Haploid

one set of chromosomes

Meiosis I

Separation of homologous chromosomes

Meiosis II

Separation of sister chromatids (in meiosis)

Prophase II

The chromosomes condense again in each of the two new cells (in meiosis)

Metaphase II

The chromosomes line up at the center of each cell (in meiosis)

Anaphase II

The sister chromatids are pulled apart and move to opposite poles (in meiosis)

Telophase II

Four new haploid cells are formed each with a single set of chromosomes

Four Haploid Cells

Determines sexual reproduction

Sperm Cell

Four Haploid Cells in male

Egg cell

Four Haploid Cells in female

Mitosis

Results in two genetically identical diploid cells

Mitosis

It is used for growth, repair, and asexual reproduction

Meiosis

Results in four genetically unique haploid cells

Meiosis

It’s used for sexual reproduction, ensuring that the number of chromosomes remains constant across generations and introducing genetic diversity