Unit 5.1 Study Guide: DNA Structure, Protein Synthesis, and Mutations

This flashcard set covers DNA structure, the mechanisms of protein synthesis (transcription and translation), and the various types and effects of genetic mutations.

Double helix

The shape of DNA that resembles a spiral staircase made of two complementary strands with nitrogenous bases in the middle.

Nitrogenous bases

The four molecules ($A$, $G$, $C$, $T$) that make up the steps of the DNA ladder and whose sequence determines the proteins and traits of a person.

DNA replication

The process where DNA makes a copy of itself before cell division so that two new cells have the full amount of chromosomes.

Protein synthesis

The two-step process (transcription and translation) of making proteins using the instructions held in DNA.

Transcription

The first step of protein synthesis where a section of DNA is used as a template in the nucleus to create an mRNA molecule.

mRNA

Messenger RNA; the molecule created during transcription that copies the DNA recipe and carries it to the ribosome.

Translation

The second step of protein synthesis where mRNA instructions are read in the ribosome to build a chain of amino acids.

Codon

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

Amino acid

The individual components that are linked together during translation to form a protein.

Ribosomes

The organelles where translation occurs and mRNA instructions are used to build proteins.

tRNA

Transfer RNA; the molecule that brings the correct amino acids to match each mRNA codon during translation.

Mutation

A change in the DNA sequence that occurs during replication, involving the deletion, addition, or substitution of bases or alterations to chromosomes.

Positive effect (Mutation)

When a mutation makes an organism stronger or better suited to its environment, such as a bird developing a beak better at cracking nuts.

Neutral effect (Mutation)

When a mutation does not cause a change in the amino acid sequence and therefore does not change the protein or affect the organism.

Negative effect (Mutation)

When a mutation changes a protein in a way that makes it harder for an organism to survive or reproduce, such as a fish with weakened fins.

Stop codon mutation

A mutation that causes an early termination signal in the genetic code, making the resulting protein shorter.

Blue-Skin Syndrome mutation

A specific case where a guanine ($G$) base was substituted for cytosine ($C$), changing the amino acid Alanine (Ala) to Glycine (Gly).