Chapter 14: RNA and Gene Expression

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Questions and Answers

What is the role of the ribosome in translation?

To synthesize amino acids

To translate tRNA into mRNA

To assemble amino acids into a polypeptide chain (correct)

To transcribe mRNA into tRNA

What is the function of the lac repressor in the lac operon?

To synthesize lactose

To translate the lac mRNA

To transcribe the lac genes

To bind to the operator and block transcription (correct)

What is the role of tRNA in translation?

To bring amino acids to the ribosome (correct)

To assemble amino acids into a polypeptide chain

To synthesize amino acids

To translate mRNA into protein

What is the purpose of the TATA box in eukaryotic gene expression?

To mark the beginning of a gene Signup and view all the answers

What is the result of a frameshift mutation?

The reading frame of the genetic message is shifted Signup and view all the answers

What is the role of homeotic genes in development?

To control the identity of body parts Signup and view all the answers

What is the purpose of epigenetic marks?

To influence patterns of gene expression Signup and view all the answers

What is the result of a point mutation?

A single amino acid is changed Signup and view all the answers

What is the role of transcription factors in gene expression?

To bind to DNA sequences and regulate gene expression Signup and view all the answers

What is the purpose of the promoter in gene expression?

To initiate transcription Signup and view all the answers

What is the role of RNA in the process of gene expression?

To copy genetic code from DNA into another molecule Signup and view all the answers

What is the main difference between RNA and DNA?

RNA uses the sugar ribose instead of deoxyribose Signup and view all the answers

What is the function of messenger RNA (mRNA)?

To carry genetic instructions from DNA to the ribosomes Signup and view all the answers

What is the role of ribosomal RNA (rRNA)?

To provide a platform for protein synthesis Signup and view all the answers

What is the function of transfer RNA (tRNA)?

To carry amino acids to the ribosomes Signup and view all the answers

What is the process of copying a base sequence from DNA to RNA called?

Transcription Signup and view all the answers

What is the role of RNA polymerase in transcription?

To bind to DNA and separate DNA strands Signup and view all the answers

What is the function of promoters in transcription?

To bind RNA polymerase to DNA Signup and view all the answers

What is the genetic code?

A language with four letters: A, C, G, and U Signup and view all the answers

What is a codon?

A three-base sequence that specifies a single amino acid Signup and view all the answers

Study Notes

Write### Codons and Amino Acids

64 possible codons are used to specify 20 amino acids and 3 stop codons
UGG specifies the amino acid tryptophan
CUA and CUG specify the amino acid leucine
To interpret codons, start at the mid-circle with the first letter of the codon, move out to the 2nd ring to find the second letter, and find the third letter in the third ring

Translation

Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains
Translation is the process of decoding an mRNA message into a protein
Steps in translation:
- Begin when a ribosome attaches to an mRNA molecule in the cytoplasm
- As each codon passes through the ribosome, tRNA molecules bring the proper amino acids into the ribosome
- The ribosome attaches these amino acids to the growing chain
Each tRNA molecule carries only one kind of amino acid
Each tRNA molecule has three unpaired bases called an anticodon, which is complementary to a codon on the mRNA

Gene Regulation and Expression

Prokaryotic gene regulation: cells control which genes they express to conserve energy and resources
Operons: groups of genes that are regulated together
Lac Operon: a group of genes that are regulated together to break down lactose
Promoters and operators:
- Promoter: site where RNA polymerase can bind to begin transcription
- Operator: site where DNA-binding protein (lac repressor) can bind to DNA
Lac repressor blocks transcription, but lactose can bind to the repressor protein, causing it to fall off the operator, allowing transcription to occur

Eukaryotic Gene Regulation

Similar to prokaryotic gene regulation
TATA box: a sequence of DNA found about 25-30 base pairs before the start of a gene, which helps position RNA polymerase
Transcription factors:
- Some open up tightly packed chromatin to help attract RNA polymerase
- Others block access to certain genes, like prokaryotic repressor proteins
- Some bind to DNA sequences in regulatory regions of eukaryotic genes, controlling gene expression

Cell Specialization and Development

Cell differentiation requires genetic specialization
Gene regulation allows multicellular organisms to reproduce
Homeotic genes:
- Control the development and differentiation of body parts
- Found in clusters, with each gene controlling the development of a specific body part
- Exist in DNA of other animals, including humans
Epigenetics:
- Cells can regulate the state of chromatin by attaching chemical groups to DNA and histone proteins
- Epigenetic marks don't change DNA base sequences but influence patterns of gene expression over long periods of time

Mutations

Heritable changes in genetic information
Types of mutations:
- Point mutations: involve changes in a single base pair
- Insertions and deletions: involve changes in the number of bases in DNA
- Chromosomal mutations: involve changes in the number or structure of chromosomes
Frameshift mutations: occur when one or many bases are inserted or removed from DNA, changing the "reading frame" of the genetic message
Mutations can have harmful or beneficial effects on an organism

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This quiz covers the role of RNA in gene expression, its structure, and how it helps decode genetic instructions from DNA. Learn about the importance of RNA in protein synthesis.