bio unit 7

Unit 7 Test Study Guide – Cell Cycle, DNA Replication, Mitosis

Cell Cycle and Regulation

Vocabulary

Benign – tumor that stays in one place and is less harmful
Malignant – cancer that spreads through the body
Metastatic – stage 4 cancer that has spread to other organs

Cyclins – proteins that regulate and control progression through the cell cycle

Interphase – G1, S, G2 phases when the cell grows and prepares for division

Sexual reproduction – egg + sperm; offspring genetically different

Asexual reproduction – produces two genetically identical daughter cells

Key Concepts

Why cells divide

  1. Growth

  2. Repair damaged tissue

  3. Replace old/dead cells

  4. Reproduction (especially asexual organisms)

Difference Between Sexual and Asexual Reproduction

Sexual

Asexual

Two parents

One parent

Egg and sperm

No gametes

Offspring genetically different

Offspring genetically identical

Meiosis

Mitosis

Phases of the Cell Cycle

G1 (Gap 1)

  • Cell grows

  • Organelles produced

  • Normal cell functions

S Phase (Synthesis)

  • DNA replication occurs

  • Chromosomes are copied

G2 (Gap 2)

  • More growth

  • Cell prepares for mitosis

  • DNA checked for errors

M Phase (Mitosis + Cytokinesis)

  • Nucleus divides (mitosis)

  • Cytoplasm divides (cytokinesis)

Interphase vs Mitosis

Interphase

  • G1, S, G2

  • Cell grows and copies DNA

  • Longest part of cycle

Mitosis/Cytokinesis

  • Cell actually divides

What controls the cell cycle?

  • Cyclins

  • Checkpoints

  • Genes

Two important genes:

Proto-oncogenes

  • Act like the gas pedal

  • Promote cell division

Tumor suppressor genes

  • Act like the brakes

  • Stop or slow cell division

If mutations happen → cancer

Restriction Point

  • Checkpoint in G1

  • Cell decides whether to divide or enter G0

G0 Phase

  • Resting phase

  • Cell leaves the cycle and stops dividing

  • Example: nerve cells

DNA Replication

Vocabulary

Chromatin – loose DNA form in the nucleus

Condensed chromosome – tightly packed DNA visible during mitosis

Chromatid – one half of a duplicated chromosome

Centromere – area where sister chromatids attach

Nucleosome – DNA wrapped around histone proteins

Histone – protein DNA wraps around

Semiconservative replication – each new DNA molecule has

  • 1 old strand

  • 1 new strand

Antiparallel – DNA strands run in opposite directions

  • one 5’ → 3’

  • other 3’ → 5’

Structure of DNA

DNA is made of nucleotides

Each nucleotide contains:

  • phosphate group

  • deoxyribose sugar

  • nitrogen base

Bases:

  • A (adenine)

  • T (thymine)

  • C (cytosine)

  • G (guanine)

Base Pairing Rules

A pairs with T
C pairs with G

Example:

Original strand
ATTCGCGTA

Complementary strand
TAAGCGCAT

DNA Replication

Where: nucleus
When: S phase
Why: so each new cell has a full set of DNA

Enzymes in DNA Replication

Helicase

  • unwinds DNA helix

Topoisomerase

  • prevents DNA from tangling

Primase

  • adds RNA primer

DNA Polymerase

  • adds nucleotides to new strand

Ligase

  • joins fragments together

Leading vs Lagging Strand

Leading strand

  • built continuously

  • follows helicase

Lagging strand

  • built in fragments (Okazaki fragments)

  • moves opposite direction

End Product of DNA Replication

Two identical DNA molecules
(each contains one old strand + one new strand)

Mitosis

Vocabulary

Mitosis – division of the nucleus

Cytokinesis – division of the cytoplasm

Cleavage furrow – pinching of animal cells

Cell plate – new wall forming in plant cells

Order of Mitosis Phases

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase

  5. Cytokinesis

Events in Each Phase

Prophase

  • chromosomes condense

  • nuclear membrane breaks down

  • spindle fibers form

Metaphase

  • chromosomes line up at middle (metaphase plate)

Anaphase

  • sister chromatids pulled apart

Telophase

  • nuclear membranes reform

  • chromosomes decondense

Cytokinesis

  • cell splits into two daughter cells

Plant vs Animal Mitosis

Animal Cells

  • cleavage furrow forms

  • membrane pinches inward

Plant Cells

  • cell plate forms

  • new cell wall develops

Fill-in Question

Mitosis is the division of the nucleus
Cytokinesis is the division of the cytoplasm

Cancer Cells vs Normal Cells

Cancer cells:

  • divide uncontrollably

  • ignore checkpoints

  • can spread through body (metastasis)

Normal cells:

  • follow cell cycle checkpoints

  • stop dividing when necessary

Two regulation methods discussed:

  1. Cyclins controlling checkpoints

  2. Genes (proto-oncogenes and tumor suppressors)

✅ Tip for your test:
Most teachers LOVE asking these:

  • Complementary DNA strand

  • Order of mitosis phases

  • Leading vs lagging strand

  • Difference between mitosis & cytokinesis

  • Proto-oncogene vs tumor suppressor

If you want, I can also make you a super short “cheat-sheet version” that fits perfectly on the Cell Cycle Wheel so you can copy it by hand and have almost every answer during the test.