Types of RNA and Their Functions

This section delves into the three main types of RNA involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Each plays a crucial role in translating genetic information into functional proteins.

Messenger RNA (mRNA)

mRNA carries genetic information from DNA to ribosomes, where it directs protein synthesis.

Definition: Codon - A three-base sequence found on mRNA that codes for a single amino acid.

Transfer RNA (tRNA)

tRNA molecules are recruited to ribosomes to help create specific polypeptide sequences as directed by mRNA.

Vocabulary: Anti-codon - A three-base sequence on tRNA that complements and pairs with mRNA codons.

Highlight: Correct base pairing of tRNA anti-codons with mRNA codons results in the release and addition of an amino acid to a growing polypeptide.

Ribosomal RNA (rRNA)

rRNA forms the functional units of ribosomes responsible for protein assembly.

Example: In the ribosome, if an mRNA codon reads "AUG", the corresponding tRNA anti-codon would be "UAC", bringing the amino acid methionine to start the polypeptide chain.

This page provides essential information for understanding the rrna ap bio definition and how mRNA, tRNA, and rRNA all interact during protein synthesis. It's crucial for students preparing for the AP Biology transcription and translation practice test.

Transcription and the Central Dogma

The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to proteins. This process is fundamental to understanding how cells function and how genetic traits are expressed.

DNA Transcription Process

Transcription is the first step in gene expression, where the information in DNA is transferred to RNA. The process involves several key steps:

1. DNA strand separation
2. RNA nucleotide addition by RNA polymerase
3. Formation of a new RNA strand
4. Exit of RNA to the cytoplasm through nuclear pores

Vocabulary: RNA polymerase - The enzyme responsible for synthesizing RNA by adding complementary nucleotides to the DNA template strand.

Definition: Template strand (antisense strand) - The DNA strand that serves as a blueprint for RNA synthesis.

Highlight: The strand serving as the template depends on the specific gene being transcribed. The gene targeted for transcription is located on the coding strand.

Example: During transcription of a gene, if the template strand sequence is 5'-ATGCTA-3', the resulting RNA sequence would be 5'-UACGAU-3'.

Nucleotide Base Pairing

Understanding the base pairing rules is crucial for comprehending transcription:

• Cytosine pairs with Guanine
• Adenine pairs with Thymine (in DNA) or Uracil (in RNA)

Quote: "mRNA molecules are transcribed copies of particular genes"

This page provides a solid foundation for understanding the transcription AP bio definition and sets the stage for more detailed exploration of RNA types and processing.