Unit 6: Cell Division

What is the cell theory?

states that all cells come from preexisting cells

What is cell division?

The process by which cells reproduce

All cells contain what?

genes

What are genes?

protein coding sequence in our DNA that makes us, US

When cells divide the genetic information is what?

copied and separated into each daughter cell

DNA (genes) must be what in preparation for this cell division?

packaged tightly

What are chromosomes?

bundle of tightly packed DNA

Where are chromosomes located and why?

the nucleus because thats where DNA is

What are chromosomes composed of?

DNA and protiens

What is the protein in chromosomes called?

histone

What is DNA first coiled around?

histones

After DNA is coiled around a bunch of histones what happens?

the histone complexes are then packed tightly together

The tightly packed bundles of histones and DNA make up what?

chromosomes

Chromosomes are composed 2 identical what?

chromatids

What are chromatids?

identical strands of chromosomes known as sister chromatids

What are these sister chromatids attached to?

a complex protein called centromere

What is the protein that connects the 2 chromatids?

centromere

What is a chromosome composed of?

DNA and proteins (histones)

The number of chromosomes does not correlate to what?

the complexity of an organism

What are homologous chromosomes?

one of two pairs of morphologically similar chromosomes

What is a dipoid?

a cell that contains both chromosomes of a homologous pair

2N refers to

a diploid cell

What is a haploid?

a cell that only has one chromosome of each homologous pair

1N refers to

a haploid cell

What is the cell cycle?

the sequence of five events of cell division: includes 3 phases of interphase, mitosis, and cytokinesis

What is interphase?

the period of cell growth and development that proceeds mitosis

What are the 3 phases of interphase?

G1, S, G2

What is the G1 phase?

Cell growth

What is the S phase?

DNA synthesis

What is G2 phase?

cell undergoes rapid growth to prepare for mitosis, synthesizes necessary enzymes and structures

What is mitosis?

division of the cell nucleus in which the chromosomes of the parent cell divide into two identical sets

What are the phases of mitosis?

prophase, metaphase, anaphase, and telophase

What is early prophase?

breaking down of nucleus and chromosome formation

What is late prophase?

spindle fibers form

What is metaphase?

the line up of chromosomes in the middle of the cell

Where do spindle fibers come from?

centrioles

What are polar fibers?

fibers that go from on centriole to the other centriole

What are kinetochore fibers?

fibers that move the chromosomes to the equator, or center, of the cell

What is meiosis?

the process of nuclear division that reduces the number of chromosomes by half

What is the difference between mitosis and meiosis?

mitosis deals with body cells and meiosis deals with sex cells

What is meiosis I?

first division; homologous chromosomes are separated into separate cells, follows interphase just like mitosis

What are the steps of meiosis I?

Prophase I, Metaphase I, Anaphase I, Telophase I

What is meiosis II?

the second division; chromatids of each chromosome are separated into separate cells

What are the steps of meiosis II?

Prophase II, Metaphase II, Anaphase II, Telophase II

Prophase I?

spindle appears

What is synapis?

Pairing of homologous chromosomes (prophase I)

What is tetrads?

group of two chromosomes, the tetra "four" refers to the amount of chromatids

Metaphase I?

tetrads move to the equator of the cell, they are moved by spindle fibers, and homologous pairs stay together

Anaphase I?

Homologous pairs of chromosomes separate, each chromosome is still composed of 2 chromatids and a centromere

Telephase I?

Cytoplasm divides forming two daughter cells

Meiosis II?

occurs in each cell formed during meiosis I

Prophase II?

chromosomes coil again and new spindle fibers begin to form

Metaphase II?

chromosomes are lined up on the equator of the cell, spindle fibers attach to centromeres

Anaphase II?

centromeres divide, spindle fibers pull each chromatid to the opposite poles

Telephase II?

spindle fibers dissolve, nuclear membrane forms, cells begin to divide (don't fully divide until cytokinesis)

Each new cell created in meiosis is \____________?

haploid

Gametes

sexual reproductive cells

Ootid

egg cell that receives almost all of the cytoplasm

Polar bodies

three other cells that receive very little or no cytoplasm and eventually disintegrate

Each meiotic division results in \______ haploid egg cell.

one

asexual reproduction

the production of offspring from one parent (no union of gametes)

sexual reproduction

production of offspring through meiosis and fusion of gametes

Genetic recombination

results from crossing over and homologous pairs of chromosomes separate independently

Why is sexual reproduction important?

genetic variation

What phase does crossing over occur?

prophase 1 of meiosis

What are the daughter cells of meiosis called?

gametes