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Flashcards in Chapter 17 Deck (47):
1

Gene expression

Process by which DNA directs protein synthesis

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How does RNA's structure differ from DNA's?

1. Sugar is ribose instead of deoxyribose
2. Single stranded
3. Uracil instead of Thymine
4. Nonhelical

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Why must only eukaryotic pre-mRNA go through RNA process?

It must pass through the nuclear envelope

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Primary trasnscript

Initial RNA transcript from a gene (pre-mRNA)

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What does RNA polymerase do?

-Pries DNA strands apart
-Hooks RNA nucleotides together

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What is the stretch of DNA that is transcribed?

Transcription unit

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Where does the RNA polymerase attach to to start initiation?

Promoter

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What is the TATA box?

Stretch of nucleotides in the promoter region

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What do transcription factors do?

Bind to promoter to signal RNA polymerase to come over to the promoter

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What signals RNA polymerase to bind to the promoter?

Transcription factors

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What does the transcription initiation complex consist of?

RNA polymerase II and transcription factors

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How does DNA reallign so quickly after RNA polymerase transcribes the template strand?

Previous RNA stretches peel away

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What happens in termination for eukaryotes?

RNA strand is cut from the polymerase that continues to transcribe past the DNA strand

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What three things occur in RNA processing?

-Introns are cut away
-5' cap is added
-Poly-A tail is added

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What are the functions of the 5' cap and poly-A tail?

-Facilitate export of mRNA
-Protect mRNA from hydrolytic enzymes
-Help ribosomes attach to 5' end

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Introns

Noncoding sequences between coding sequences

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What does RNA splicing do?

Removes introns and joins exons

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What do spliceosomes consist of?

small sibonucleicproteins (snRNP) and proteins

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Spliceosomes are a type of what?

Ribozyme

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Ribozyme

RNA molecule that functions as an enzyme

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What performs RNA splicing?

Spliceosomes

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What properties of RNA allow it to function as an enzyme?

1. Can form 3D shape from ability to pair with itself (specific structure)
2. Some bases in RNA contain functional groups
3. May hydrogen bond with other nucleic acid molecules (adding specificity)

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What is alternative RNA splicing?

Fact that some genes can form different polypeptide types depending on which parts are treated as exons during splicing

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Why can the number of different proteins an organism can produce be larger than its number of genes?

Alternative RNA splicing

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Domains

Discrete regions of proteins

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How can exon shuffling result in new proteins?

Introns provide more area for crossover of exons

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What are ribosomes made up of?

Proteins and ribosomal RNA (rRNA)

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What are the three binding sites of ribosomes?

E site, P site, A site

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What is the start codon that the small ribosomal subunit stops at?

AUG

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What is the initiator tRNA carrying to pair with codon AUG?

Methionine

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What brings the large subunit the complete the translation initiation complex?

Initiation factors

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What does the translation initiation complex consist of?

Both ribosomal subunits, mRNA, initial tRNA

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In translation, protein factors aid in each of the three processes. Which factors are used in each and how?

1. Initiation: initiation factors bring in large subunit
2. Elongation: elongation factors help to add amino acids in polypeptide chain
3. Termination: release factors hydrolyze polypeptide chain

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When does termination in translation occur?

When a stop codon in mRNA reaches the A site

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When stop codon in the mRNA reaches the A site what happens?

Release factor accepted at A site to hydrolyze bonds and split polypeptide

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Polyribosome

String of ribosomes translating 1 strand of mRNA at the same time

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How are polypeptides usually made functional after translation?

1. Polypeptide chains modified
2. Completed proteins sent to specific sites

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WHat are some types of post-translational modifications?

-Enzymes cleave polypeptides
-Polypeptides come together

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What are the 2 types of ribosomes?

Free and bound

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Free ribosomes make proteins for/that ___, bound ribosomes make proteins for ____

-that function in cytosol
-for endomembrane system/for secretion

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What are polypeptides destined for ER/secretion marked by?

Signal peptide

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A signal peptide calls for what to bring the ribosome to the ER?

Signal-reception particle (SRP)

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Mutation

Change in genetic material of a cell or virus

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What are the 2 categories of point mutations

1. Substitutions
2. Insertions/deletions

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What are the 3 types of point mutation substitituions?

1. Silent mutation creates the same amino acid
2. Missense mutation still codes for amino acid
3. Nonsense mutation changes amino acid codon to stop codon

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What are frameshift mutations?

Alteration of reading frame from insertion/deletion

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How can mutations arise?

-Spontaneously during DNA replication, recombination, or repair
-From mutagens