Bio I Test 4

Summer 2026. Uphadyaya

What are the 3 reasons why cells divide

Growth and development

Repair / regeneration

Reproduction

What is the only reason for bacteria (single celled life) to divide?

Reproduction

Most bacteria have how many chromosomes? What shape is it?

Most have 1 chromosome, circular shape

What is the process for bacteria undergoing cell division

Binary Fission

What are somatic cells?

“Body” cells. Cells that are not sex cells

The cell cycle only occurs in what type of cells

Eukaryotic cells

What happens in the S phase of interphase? G1 and G2?

S phase: DNA replication

G1: Most of growth. Prep for next phase. Inspects DNA

G2: Final touches of growth. Prep for next phase. Inspects DNA

What is the G₀ phase?

Phase of no cell division

What happens during the M phase?

Mitosis and Cytokinesis

Which type of cells are continuously dividing? Divide based on need? Rarely or never divide?

Continuously: Skin, GI tract, blood

Need based: Liver

Rare or never: Neurons and muscles

What cells can leave G₀? What cells cannot leave G₀?

Leave G₀: Need based

Cannot leave G₀: Rare or never

Define chromatin

Complex of DNA and the protein that it is wrapped around

What are histones

The protein that DNA wraps around in a chromatin

During the M phase, what happens to the chromatin

It packs together so tightly that individial chromosomes become clearly visible

Define chromosome

1 DNA molecule and associated proteins

What are the main 3 characteristics of a chromosome

Linear

Contain hundreds to thousands of genes

Human cells have 46 chromosomes

Define replicated chromosome

Chromosome that has copied itself in preparation for cell division

Define chromatids

One of the two identical components that make up a replicated chromosome. Contains 1 molecule of DNA each

What is the genome of a cell?

Total genetic information possesed by an organism

Does every cell contain the human genome? How many genes is it?

Every human cell contains the human genome. ~ 20,500 genes long

What happens during Prophase

Chromosomes condense

Centrosomes begin to move toward poles

Spindle begins to form

What happens during Prometaphase

Nuclear envelope disintegrates

Microtubules grab chromosomes by centromeres (kinetochore)

What happens during Metaphase

Chromomes are aligned in the middle of the cell

What happens during Anaphase

Chromosomes are pulled apart

Cell elongates

What happens during Telophase

Two new nuclear envelopes form

Chromosomes decondense