Biology Mitosis and Meiosis 🤑😋

Metastasis

the spread of cancer cells from the place where they first formed to another part of the body

Oncogenesis

the formation of a cancer

Viruses

can cause mutations of proto-oncogenes & tumor suppressor genes leading to cancer

Cell Theory

• all living things are made of cells

• cells are the basic unit of life

• all cells come from other cells

Stages of Mitosis

prophase, metaphase, anaphase and telophase

Interphase

Cell grows and carries out normal cell processes

DNA replicates

Chromosome Replication

occurs in S phase and the amount of chromosomes is duplicated

Prophase

the first phase of mitosis and longest: chromatin condenses, nuclear membrane breaks down, nucleolus disintegrates, spindle fibers begin to form

Centromere

structure at center of chromosome where the sister chromatids are attached

Why chromatin condenses

chromatin condenses to make them easier to separate into the two daughter cells

Metaphase

Chromosomes align at the equator

Chromosomes attach to spindle apparatus at the centromere

Anaphase

Microtubules shorten to move chromosomes to the opposite poles

Telophase

Chromosomes reach the poles

Nuclear envelope reforms and nucleolus reappears

chromosomes decondense

Cytokinesis

the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.

Cytokinesis in Plant Cells (has cell wall)

the cell plate forms dividing daughter cells

Cytokinesis in animal cells (no cell wall)

cleave furrow forms at equator of cell and pinches inward to divide the cell in two

Aster

star-shaped structure made up of microtubules that forms around each centriole pair at the poles of a dividing cell

Mitosis in multi-cellular organisms

cells divide for growth, development, and tissue repair (not to create a new individual)

Mitosis in uni-cellular organisms (Mitotic cell division)

the method of asexual reproduction (ex., binary fission, budding)

Apoptosis

programmed cell death (eliminating unwanted or damaged cells which prevents uncontrolled cell growth and is essential for proper development, tissue homeostasis, and preventing diseases like cancer)

Meiosis

cell division happens to create egg and sperm cells which unite to form a new individual (sexual reproduction)

Prophase vs Prophase I

homologous chromosomes are present in Prophase I where they form pairs during synapsis

Metaphase vs Metaphase I

homologous chromosomes line up instead of individual chromosomes

Anaphase vs Anaphase I

in Anaphase I, homologous chromosomes separate (2n →n) rather than sister chromatids splitting

Meiosis II

Occurs after Meiosis I and is very similar to mitosis except for that the number of chromosomes has been halved — produces 4 total haploid cells

Chromatin

long fibers made of DNA and protein molecules

Chromosome

condensed chromatin

Sister chromatids

two identical copies of a chromosome formed after DNA replication, joined at the centromere, and separated during cell division

Homologous chromosome

one of a matching pair of chromosomes, one inherited from each parent

Body cell

a non-sex cell (somatic cell)

Gamete

a sex cell (egg/sperm) (haploid)

Zygote

a fertilized egg

Diploid cell (2N)

a cell containing two homologous sets of chromosomes, one from each parent (46)

Haploid cell (N)

a sex cell containing a single set of chromosomes (23)

steps of interphase

G1 (first gap), S (Synthesis), G2 (second gap)

How meiosis allows for genetic variation

Different possible alignments of chromosomes, (crossing over) the exchange of genetic material between homologous chromosomes, random fertilization of egg by sperm

Outcome of meiosis

a diploid (2N) cell becomes 4 genetically different, haploid (N) cells

Outcome of mitosis

produces 2 genetically identical diploid (2N) cells)

Synapsis

paring of homologous chromosomes

Tetrad

4 sister chromatids of paired homologous chromosomes

Result of crossing over

genetic variety in gametes

Amount of Nuclear Divisions in Mitosis

1 Nuclear Division

Amount of Nuclear Divisions in Meiosis

2 Nuclear Divisions

Difference between Mitosis and Meiosis

Mitosis:

• 1 diploid → 2 daughter diploids

• 1 nuclear divisions

• genetically identical

• reproduce (uni-cellular)

• growth, maintainance, repair (multi-cellular)

Meiosis

• 1 diploid → 4 haploids sex cells

• 2 nuclear divisions

• genetically different

• makes sex cells (sperm/egg/gamete)

How to remember steps of mitosis

PMAT (Prophase, Metaphase, Anaphase, Telophase)

Shortest Stage of mitosis

anaphase

P vs Q arm

P arm is shorter and Q and is longer

they are separated by the centromere

Karyotype

the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism

Edward’s Syndrome

Trisomy in chromosome 18 (3 copies instead of 2)

Down syndrome

Trisomy in chromosome 21 (3 copies instead of 2)

Sex Chromosome

Chromosome 23:

XX → Female

XY → Male

Non-sex Chromosomes

The other 22 pairs of chromosomes are autosomes

Genetic errors in Chromosome 23

in female: XX → X_ (Turner’s Syndrome)

in male: XY → XXY (Klinefelter’s Syndrome)

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division.

Importance of genetic variation

crucial for a species' ability to adapt to changing environments (allows for a range of traits within a population)

Telomeres

a region of repetitive DNA sequences at the end of a chromosome which protect the ends of chromosomes and become slightly shorter with each division