DNA, RNA, and Protein Synthesis – Lecture Review

These flashcards review key vocabulary and processes related to DNA structure, replication, RNA types, transcription, and translation.

What does DNA stand for?

Deoxyribonucleic acid

What are the three components of a DNA nucleotide?

A phosphate group, a five-carbon sugar (deoxyribose), and a nitrogenous base

What does DNA stand for?

Deoxyribonucleic acid

What are the three components of a DNA nucleotide?

A phosphate group, a five-carbon sugar (deoxyribose), and a nitrogenous base

Which nitrogenous bases are purines?

Adenine and guanine

Which nitrogenous bases are pyrimidines?

Thymine and cytosine (uracil replaces thymine in RNA)

What shape best describes the DNA molecule?

A double helix

What molecules form the sides (backbone) of the DNA ladder?

Alternating sugar (deoxyribose) and phosphate groups

What molecules form the rungs (steps) of the DNA ladder?

Paired nitrogenous bases held together by hydrogen bonds

State Chargaff’s base-pairing rules for DNA.

Adenine pairs with thymine; cytosine pairs with guanine

Which scientists are credited with discovering the double-helix structure of DNA?

James Watson and Francis Crick

What is the primary function of DNA?

To store genetic information for inherited traits

Define DNA replication.

The process by which DNA makes an exact duplicate of itself

Which enzyme unwinds and separates the DNA strands during replication?

DNA helicase

Which enzyme adds complementary nucleotides during replication?

DNA polymerase

What is a replication fork?

The Y-shaped region where the DNA double helix is separated and replication occurs

How many original strands are present in each new DNA molecule after replication?

One original (parental) strand and one newly synthesized strand

What is the approximate error rate of DNA replication before proofreading?

About 1 error in every million bases

What is a mutation?

Any change in the nucleotide sequence of DNA

What does RNA stand for?

Ribonucleic acid

List three differences between DNA and RNA.

1) Sugar: deoxyribose vs. ribose; 2) Strands: double-stranded vs. single-stranded; 3) Bases: thymine in DNA, uracil in RNA

Name the three main types of RNA.

Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Describe the role of mRNA.

Carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm

Describe the role of tRNA.

Reads the mRNA codon and brings the corresponding amino acid to the ribosome

Describe the role of rRNA.

Combines with proteins to form ribosomes, the site of protein synthesis

Define transcription.

The process of synthesizing an RNA strand using DNA as a template

Which enzyme catalyzes transcription?

RNA polymerase

What is a promoter in transcription?

A specific DNA sequence where RNA polymerase binds to start transcription

What is a terminator in transcription?

A DNA sequence that signals RNA polymerase to stop transcription

What are introns?

Non-coding sections of pre-mRNA that are removed before translation

What are exons?

Coding sections of pre-mRNA that are spliced together to form functional mRNA

Define translation.

The process by which ribosomes synthesize proteins using the information in mRNA

What is a codon?

A three-nucleotide sequence on mRNA that codes for a specific amino acid or start/stop signal

How many possible mRNA codons exist?

64

How many different amino acids are used to build proteins?

20

True or False: Each amino acid is specified by only one codon.

False—most amino acids are specified by more than one codon

Why is the shape of a protein important?

Its shape determines its function, and shape is dictated by the amino acid sequence