DNA Transcription

what is the role of DNA in a cell

stores genetic information — it acts as a living instruction manual for the cell.

what are catalysts in a cell

are molecules that help read DNA and build proteins.

function of proteins

• Build cell structures

• Run biochemical reactions

• Are sometimes exported outside the cell

How does the cell use DNA to make proteins?

Catalysts read the DNA instructions and use them to build the proteins needed by the cell.

What dies living archive mean when referring to DNA

It means DNA stores active, usable instructions that the cell constantly refers to.

what are exported proteins used for

They do jobs outside the cell — like enzymes, hormones, or signals for other cells.

what happens to DNA when a cell divides

The cell makes a copy of its DNA so that each daughter cell gets one.

what is DNA replication

It’s the process of making a copy of DNA before cell division.

why is accuracy in DNA replication important

Because mistakes can cause health problems or affect inherited traits.

what do daughter cells receive after cell division

Each one gets a complete, copied set of the original DNA.

what can happen if DNA is not copied correctly

The new cells may be unhealthy or have genetic defects.

what is the shape of DNA called

A double helix (twisted ladder)

What are the building blocks of DNA

nucleotides

what are the 4 types of DNA nucleotides

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

what is each DNA nucleotide named after

The nitrogenous base it contains

What are the base pairing rules in DNA?

A pairs with T, and C pairs with G

How does DNA structure help with accurate replication?

Each strand acts as a template, ensuring the correct nucleotide pairs are made

what is complementary base pairing in DNA

A system where A pairs with T, and C pairs with G

What happens to DNA strands during cell division?

They separate (unzip) and each becomes a template for a new strand

What ensures accurate DNA copying?

Complementary base pairing rules (A–T, C–G)

what is the result of DNA replication

Two identical DNA molecules, each with one original strand and one new strand

What type of replication does DNA use?

Semi-conservative replication (one old + one new strand per DNA)

Do all cells in the body have the same DNA?

Yes, all cells in a multicellular organism have the same DNA.

Why do different cells do different things if they have the same DNA?

Because they express different genes depending on their function.

What is gene expression?

It’s the process where cells turn on specific genes to perform their role.

What do nerve cells express?

Genes for neurotransmitters (chemicals that send signals)

What do muscle cells express?

Genes for protein filaments needed for contraction

What determines which genes a cell expresses?

The function or role of the cell in the body

What is transcription?

It's the first step in decoding DNA, where RNA polymerase makes an RNA copy of part of the DNA.

What enzyme is used during transcription?

RNA polymerase

Which DNA strand is used during transcription?

Only one strand (template strand)

What are three main differences between RNA and DNA?

• RNA is single-stranded, DNA is double-stranded

• RNA has ribose, DNA has deoxyribose

• RNA uses uracil (U) instead of thymine (T)

Does RNA form a helix like DNA?

No, RNA folds into complex shapes due to internal base-pairing

What does A in DNA pair with in RNA?

Uracil (U)

What does mRNA do?

It carries the genetic code from DNA to the ribosome for protein-making.

Why is mRNA called a transcript?

Because it is a copied version of a gene’s instructions.

What is the role of rRNA?

It forms the main structure of the ribosome, where proteins are made.

What does tRNA do during protein synthesis?

It brings the correct amino acids to the ribosome to help build proteins.

What are the three types of RNA involved in gene expression?

mRNA, rRNA, and tRNA

Match the RNA type to its role:

• mRNA = Messenger

• rRNA = Ribosome

• tRNA = Transport

How many RNA polymerases do eukaryotic cells have?

Multiple, with each one specialized for different RNA types

How many RNA polymerases do prokaryotic cells have?

Only one RNA polymerase for all RNA types.

What are some roles of the lesser-known RNA types?

They may regulate gene expression and defend against viruses.

What is the difference between RNA polymerase in prokaryotes and eukaryotes?

Prokaryotes have one RNA polymerase; eukaryotes have multiple specialized ones

What is an example of a function of regulatory RNAs?

They can turn genes on or off and help fight viruses.

Which RNA type is the most variable?

mRNA (messenger RNA)

What types of proteins are usually encoded by abundant mRNAs?

Structural proteins

What types of proteins are usually encoded by rare mRNAs?

Signaling proteins

How long can structural protein mRNAs last in eukaryotic cells?

Over 10 hours

How short-lived can signaling protein mRNAs be?

Less than 10 minutes

Why are signaling protein mRNAs often short-lived?

Because cells need quick, temporary signals, not long-lasting ones.

What is a transcriptome?

The complete set of mRNA molecules in a cell at a given time.

Does every cell in a multicellular organism have the same DNA?

Yes, but they use different parts of it (different gene expression

What does the transcriptome reveal about a cell?

Which genes are being expressed (turned on) in that cell.

Why don’t bone cells make insulin even though they have the gene for it?

Because the insulin gene is not transcribed in bone cells.

Does the transcriptome stay the same in all cells?

No, it varies based on cell type and cell activity.

What’s the difference between genome and transcriptome?

• Genome = all the genes in a cell (same in all cells)

• Transcriptome = only the active/expressed genes (varies per cell)

What are ribosomes made of?

rRNA and proteins

What are polyribosomes?

Clusters of ribosomes making proteins at the same time

Where can ribosomes be found in eukaryotic cells?

Floating freely or attached to internal membranes (like rough ER)

What do membrane-bound ribosomes make?

Proteins for membranes or for secretion

How much of the ribosome’s mass is made of rRNA?

About half

How many proteins are in a ribosome?

• ~60 in prokaryotes

• Over 80 in eukaryotes