DNA, Protein Synthesis, and Mutations – Review Flashcards

These question-and-answer flashcards review key points on DNA structure/function, protein synthesis (transcription and translation), and mutations, including their types, effects, and causes.

What organelle contains the master set of instructions for cell specialization and function?

The nucleus.

What molecule carries the genetic instructions within the nucleus?

DNA (deoxyribonucleic acid).

Describe the overall shape of a DNA molecule.

A double-stranded helix resembling a twisted ladder.

What forms the ‘sides’ (backbone) of the DNA ladder?

Alternating phosphate groups and pentose (deoxyribose) sugars.

Name the four nitrogenous bases in DNA.

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

Which base pairs with adenine in DNA?

Thymine (A–T pairing; “Apple-Tree”).

Which base pairs with cytosine in DNA?

Guanine (C–G pairing; “Car-Garage”).

Give two primary functions of DNA.

(1) Provides instructions for all cell functions and heredity. (2) Can replicate, mutate, and thereby drive evolution.

What is chromatin?

A combination of DNA and histone proteins that is loosely coiled inside the nucleus.

When a cell is about to divide, chromatin coils up to form what structure?

Chromosomes.

How many chromosomes are in a normal human somatic cell?

46 chromosomes (23 pairs).

What sex chromosomes are found in human males?

XY.

Define a gene.

A small segment of DNA located on a chromosome that codes for a specific protein.

State the ‘one gene – one protein – one function’ concept.

Each gene directs the production of one particular protein, which performs one specific function in the cell.

List two structural protein examples.

Muscle fibers (actin/myosin) and keratin in hair/nails.

List two functional protein examples.

Enzymes (speed reactions) and antibodies (fight infection).

Where in the cell does transcription occur?

In the nucleus.

What molecule is produced during transcription?

Messenger RNA (mRNA).

Name the enzyme that links RNA nucleotides during transcription.

RNA polymerase.

Which base replaces thymine in RNA?

Uracil (U).

After transcription, where does mRNA travel?

Through nuclear pores to the cytoplasm/ribosome.

Where does translation take place?

At ribosomes in the cytoplasm.

What is a codon?

A sequence of three mRNA bases that codes for a specific amino acid.

What codon signals the start of translation?

AUG (methionine).

What molecule brings amino acids to the ribosome?

Transfer RNA (tRNA).

What is an anticodon?

A three-base sequence on tRNA complementary to an mRNA codon.

What happens to a protein after the ribosome finishes translation?

It moves to the Golgi apparatus for folding, packaging, and transport.

Why does protein function depend on shape?

Because the specific 3-D shape determines how a protein interacts with other molecules; altering shape can destroy function.

Define mutation.

Any change in the nucleotide sequence of DNA.

Differentiate chromosomal and gene (point) mutations.

Chromosomal mutations affect large DNA segments or entire chromosomes; gene mutations alter one or a few bases within a single gene.

Name four types of chromosomal mutation involving segments.

Deletion, duplication, inversion, and translocation.

What chromosomal condition causes Down’s syndrome?

Trisomy 21 – an extra chromosome #21.

Give three types of gene (point) mutation.

Substitution, deletion, and insertion (addition).

Why are deletion and insertion often more harmful than substitution?

They cause frameshift mutations that alter every codon downstream.

Provide an example of a negative (harmful) gene mutation.

Sickle-cell anemia or cystic fibrosis.

Provide an example of a positive (beneficial) gene mutation.

Mutation conferring resistance to HIV infection.

Provide an example of a neutral mutation.

The white coat (Spirit Bear) mutation that doesn’t alter survival.

Define mutagen.

Any physical, chemical, or biological agent that increases mutation rates in DNA.

Give three examples of mutagens.

UV radiation, cigarette smoke, and certain viruses such as HPV.

What is a carcinogen?

A mutagen specifically known to cause cancer.