cell cycle, mitosis ,and meiosis

the cell cycle

90% of the time interphase

-cell growth

-DNA Replication

-cell functions

10% of the time M phase

why is mitosis important?

allows cells to reproduce making exact identical copies of themselves

mitosis stages

interphase

DNA replicates each chromosome has 2 chromatids now

46 ,46 - 46 ,92

Prophase

• Chromatin condenses into visible chromosomes

• Nuclear membrane breaks down

• Centrioles move to opposite poles

• Spindle fibers form

Metaphase

• Chromosomes line up in the middle of the cell

• Spindle fibers attach to centromeres

Anaphase

• Sister chromatids are pulled apart

• Move to opposite poles

Telaphase

• Chromatids reach opposite ends

• Nuclear membranes reform

Cytokenisis

• Cytoplasm divides

• Forms 2 identical diploid daughter cells

independant assortment

Random alignment of homologous chromosomes in Metaphase I of meiosis that creates genetic variation in gametes.

what is crossing over

exchange of DNA segments between homologous chromosomes during Prophase I of Meiosis.

what is a homologous chromosome?

A pair of chromosomes—one maternal and one paternal—that carry the same genes at the same loci but may have different alleles.

what are recombinant chromosomes?

Recombinant chromosomes are chromosomes that contain a new mix of maternal and paternal DNA after crossing over during Prophase I of Meiosis.

explain prophase 1 in meosis

Prophase I

• Chromosomes condense

• Homologous chromosomes pair up (synapsis)

• Crossing over occurs → recombinant chromosomes form

• Nuclear membrane breaks down

• Spindle fibers form

explain metaphase 1 in meosis

Metaphase I

• Homologous chromosome pairs line up in the middle

• Independent assortment occurs (random alignment)

explain anaphase in meosis 1

Anaphase I

• Homologous chromosomes separate

• Sister chromatids stay together

explain telophase and cytokinesis in meiosis 1

Telophase I + Cytokinesis

• Cell splits into 2 haploid cells

• Chromosomes are still duplicated

explain prophase 2 in meiosis

Prophase II

• Spindle fibers reform

• Nuclear membrane breaks down (if it reformed)

Explain metaphase 2 in meiosis

Metaphase II

• Chromosomes line up individually in the middle

explain anaphase 2 in meiosis

Anaphase II

• Sister chromatids separate

explain telophase 2 in meiosis

Telophase II + Cytokinesis

• Nuclei reform

• Cell divides

what is the main purpose of meosis

production of gametes

what is a zygote?

A zygote is the fertilized egg formed when sperm + egg fuse during fertilization.

haploid sperm (n) + haploid egg (n) → diploid zygote (2n)

what is ploidy

number of sets of chromosomes