AP Bio Unit 6

Why are there different melting points in DNA strands?

Number of H bonds affect the melting points; more G-C (which have three bonds) have higher melting points than A-T (two bonds) due to there being more bonds to break

Where does replication occur?

Prokaryotes: nucleoid regoins

Eukaryotes: nucleus

Function of ligase in DNA replication

Seals gaps in okazaki fragments on lagging strands to create a continuous strand

rRNA function

Composes the ribosome; ribosome is made of rRNA and proteins and has a large and small subunit; catalyzing the formation of peptide bonds; plays a key role in protein synthesis by facilitating translation, as it ensures the correct alignment of mRNA and tRNA.

tRNA function

Transports amino acids to the ribosome; large subunit binds to tRNA, which then transfers amino acids to the ribosome; has an anticodon that complements an mRNA codonand helps translate the mRNA sequence into a polypeptide chain

mRNA function

Carries genetic information from DNA in nucleus to ribosomes in cytoplasm; synthesized during transcription using DNA as the template

Function of intron removal during mRNA processing

Removes non-coding sequences to produce a continuous coding sequences for translation

What is PCR and how does it amplify DNA?

Uses heating, cooling, and synthesis with DNA polymerase to replicate specific DNA sequences, exponentially increasing the amount of DNA

Retovirus dogma violation

uses reverse transcriptase to convert RNA > DNA and integrates into host genome rather than DNA > RNA

Structure of DNA in prokaryotes and Eukaryotes

Pro: circular

Eu: Linear

How does electrophoresis separate DNA frags?

DNA frags move toward the positive end; smaller fragments move faster

Repressible vs. inducible operons

Repressible are usually turned on and can be turned off by a repressor when product is abundant; inducible are usually of and are turned on by inducer when substrate is present

What are the A, P, and E sites in ribosomes?

Binding sites of ribosomes involved in translation

A: Acceptor site for new tRNA

P: peptidyl site for growing polypeptide chain E: Exit site for empty tRNA

What proc

DNA Replication copies DNA, transcription synthesizes RNA from DNA, and translation synthesizes a polypeptide from RNA

DIfferences between RNA and DNA

DNA: Contains T and deoxyribose, double stranded

RNA: Contains U and ribose, single-stranded

Why are DNA Strands anti-parallel

Allows for complementary bases to pair

What is the central dogma of molecular biology

DNA > RNA > Polypeptide

Lagging vs. Leading strands during DNA replication

The leading strand is synthesized continously toward replication fork, the lagging is synthesized discontinously (okazaki fragments) away from the fork

How do mutations affect DNA and Protein synthesis?

Mutations alter nucleotide sequences, which can change STRUCTURE and therefore FUNCTION of proteins

Purpose of DNA sequencing

DNA sequencing determines nucleotide order in a DNA molecule

What happens in translation termination

A release factor binds to the stop codon and hydrolyzes the bond between tRNA and the polypeptide, which releases the protein

How does DNA methylation and acetylation influence gene expression

Methylation inhibits gene expression by tighting DNA around histones

Acetylation relaxes DNA, which promotes transcription

Function of the promotor in transcription

A DNA region where RNA polymerase binds to initiate transcription

What are post-transcriptional modifacations in Eu. mRNA?

These are processes that occur after transcription; the addition of a 5' cap, the addition of a poly-A tail at 3’ end; and the removal of introns through splicing

Describe the translation inititation process

Small ribosomal subunit binds to mRNA and start codon, which recruits the large subunit and the initiator tRNA

Steps of DNA replication

Helicase unwinds, supercoils are relieved by topisomerase, primer synthesized by primase, DNA is synthesized by DNA polymerase, and ligase seals gaps

What are operons and how do they regulate Pro. gene expression?

Operons are gene clusters that are regulated by a single promotor and operator that control the transcription of related genes, allowing for coordinated expression in response to environmental changes

Helicase function in DNA replication

Helicase unwinds the DNA double helix by breaking H onds between bases at the replication fork

Role of Poly-A tail in mRNA stability

Decreases hydrolytic enzyme activity which prolongs the lifespan of the mRNAby protecting it from degradation in the cytoplasm

Location and process of transcripton

Pro: nucleoid region

Eu: Nucleus

Synthesizes RNA from DNA

Ligase

Enzyme that joins Okazaki fragments together during DNA replication

Three stages of translation

Initiation (begin at start codon), elongation (tRNA binding and peptide bond formation), termination (Stop codons with release of polypeptide)

How many H bonds are formed between adenine and thymine, and cytosine and guanine

two H bonds between ___ and ___, three bonds between ___ and ___

What is bacterial transformation

A process by which foreign DNA is inserted into bacteria (often using heat shocking to facilitate plasmid entry) for cloning or genetic modifaction

Significance of 5’ and 3’ ends of DNA and RNA strands?

5’ has a phosphate group, 3’ a hydroxyl group; strands are read 3’ to 5’ and synthesized 5’ to 3’ and are anti-parallel

What is the role of the promotor in transcription?

A promotor is a DNA region where RNA polymerase binds to initiate transcription

What is the purpose of the 5' guanine cap in post-transcriptional modification?

Signals the start of the transcript and facilitates export of mRNA from the nucleus.

Process of translation initiation

Translation begins at the start codon AUG; ribosome assembles around the mRNA and the first tRNA carries methionine to the P site

How do point mutations impact protein synthesis

Causes silent, missense, or nonsense mutations, which can alter amino acid sequences or create stop codons

Where does transcription occur in Eu. and Pro?

Eu: in the nucleus

Pro: Nucleoid region of cytoplasm

How does methylations affect gene expression?

Inhibits RNA polymerase binding to DNA, leading to gene silencing

Role of DNA Polymerase during replication

Synthesizes DNA strands by adding nucleotides to the 5’ and 3’ direction and proofreads for errors

Role of DNA polymerase during transcription

Synthesizes RNA strands by adding ribonucleotides complementary to the DNA template

What are purines and pyrimidines?

Purines are double-ringed bases (Adenine and Guanine), pyrimidies are single-ringed based (Cytosinse and thymine in DNA, uracil in RNA)

Where does translation occur?

In prokaryotes, translation occurs in the cytoplasm, while in eukaryotes, it occurs in the cytosol and Rough ER.

Role of helicase in DNA replication

Unwinds the DNA Helix by breaking hydrogen bonds between bases

Role of helicase in DNA translation

Unwinds the DNA double helix and separates the strands for RNA synthesis during translation

Role of helicase in DNA transcription

Unwinds the DNA double helix and separates the strands for RNA synthesis during transcription.

Enzyme that creates RNA primer during DNA replication

Primase