Chapter 8–DNA Replication, Binary Fission, and Mitosis

Why do unicellular organisms divide?

Reproduce

Why is cell division important in multicellular organisms?

Supply of replacement cells

What type of division do multicellular organisms use...

...for growth and repair?

Mitosis

To produce sex cells?

Meiosis

Sex cells contain ___________ the DNA as other body cells.

Half

What is fertilization?

When two gametes combine and the zygote inherits DNA from both

What is the name of the cell produced by fertilization?

Zygote

What type of cells are produced by meiosis?

Sex cells (gametes)

What is apoptosis?

programmed cell death

What is DNA replication?

The making of two identical copies of DNA starting with one copy.

Why must DNA be replicated before a cell divides?

So each daughter cell receives identical DNA.

Helicase

unwind the DNA

Binding proteins

hold strands apart

Primase

Adds short RNA primers

DNA polymerase

Builds new DNA strands (adds to 3' end, 5'→3')

Ligase

Joins DNA fragments on lagging strand

Topoisomerase

Relieves twisting/tension in DNA

What does it mean that DNA replication is semiconservative?

Each DNA molecule has one parental strand and one newly made strand.

What is the role of RNA primers in DNA replication?

They provide a starting point for DNA polymerase.

What is the difference between the leading and lagging strand?

Leading: continuous synthesis

Lagging: discontinuous synthesis (opposite direction of helicase)

What are Okazaki fragments?

Short lengths of single-stranded DNA made on the lagging strand.

Okazaki fragments are found on the _____________________ strand of DNA.

Lagging strand

Where on the DNA does replication begin?

At origins of replication.

Which organisms divide by binary fission?

Prokaryotes

Is binary fission a sexual or asexual process?

asexual

List the main steps of binary fission:

DNA is replicated

DNA attaches to cell membrane

Cell membrane grows and separates DNA

Cell splits into two identical cells

Why is binary fission considered asexual?

Because it produces two identical cells.

Eukaryotic cells do not divide by binary fission. They divide by

mitosis.

What is the form of DNA when the cell is not dividing?

Chromatin

Replicated chromosomes condense before eukaryotic cell division. What is the term for this condensed, visible DNA?

Chromosomes

DNA wraps around ___________________ proteins, forming bead-like structures called ________________________.

histone, nucleosomes

Those bead-like structures cluster together into

Chromatin.

Why is DNA packaging important before cell division?

So DNA stays tightly packed and does not get lost or damaged during division.