AP Bio - Unit 6: Gene Expression and Regulation

Twisted ladder with rigid rungs

Adenine(A), Thymine(T), Guanine(G), and Cytosine(C)

Adenine(A) and Guanine(G)

Thymine(T) and Cytosine(C)

The chain on the right side runs in one direction whereas the left side of the chain runs in the opposite direction, upside-down direction

The making of DNA from an existing DNA strand; semiconservative; Each of the daughter molecules has one old strand and one new strand

The replication of DNA begins at the orgins of replication

Helicase enzymes unwind the parental double helix exposing the nucleotides to be replicated

The unwinding of the double helix causes tighter twisting ahead of the replication fork. Topoisomerase is an enzyme that helps relieve the strain by breaking and reforming DNA strands

Breaks and reforms DNA strands

DNA polymerase catalyzes the elongation of new DNA at the replication fork. DNA polymerase requires RNA primers to start DNA replication.

DNA polymerase adds nucleotides to the growing chain one by one working in a 5’ to 3’ direction. DNA polymerase can only add new nucleotides to the 3’ end.

The strand that runs 3’ to 5’ is copied in a series of segments and forms the lagging strand.

5’ to 3’ strand

3’ to 5’ strand

When the strand that runs 3’ to 5’ is copied in a series of segments.

The lagging strand is synthesized in separate pieces which are then sealed together by DNA ligase forming a continuous DNA strand

Separate pieces in the lagging strand

Short, repetitive nucleotide sequences that do not contain genes

Activated by a mutation; An enzyme that prevents degradation and renders the cancer cells “immortal“

A one double-stranded, circular DNA molecules associated with a small amount of protein

Linear DNA molecules associated with large amounts of protein

DNA and proteins packed together

Becomes less accessible to transcription enzymes which reduces gene expression

Process by which DNA directs the synthesis of proteins

Transcription and translation

Each gene codes for a polypeptide which can be or can constitute a part of a protein

The synthesis of RNA using DNA as a template; Takes place in the nucleus of eukaryotic cells

Produced during transcription; Carries the genetic message of DNA to the protein-making machinery of the cell in the cytoplasm, the ribosome

The cytoplasm in eukaryotic and prokaryotic cells and Rough ER of eukaryotic cells

Yields the final mRNA; Pre-mRNA goes through this process

Transcription and translation

The production of a polypeptide chain using the mRNA transcript and occurs at the ribosomes

DNA to RNA to Protein

mRNA base triplets ; Written in the 5’ to 3’ direction

1 strand of DNA that is transcribed

mRNA triplet

An enzyme that separates the two DNA strands and connects the RNA nucleotides as they base pair along the DNA template strand

5’ to 3’

DNA sequence at which RNA polymerase attaches

DNA sequence that signals the end of transcription

Entire stretch of DNA that is transcribed into a RNA molecule

Assist the binding of RNA polymerase to the promoter so transcription may began

A modified Guanine nucleotide (GTP) that is added onto the 5’ end of the mRNA

A group of 50 to 250 adenine nucleotides added to the 3’ end

Large portions of the newly synthesized RNA strand are removed; Occurs in Eukaryotic cells

Sections of the mRNA that are spliced out

Sections of the mRNA that remain and subsequently spliced together by a spliceosome

Play a major role in catalyzing the excision of the introns and joining of the exons

When RNA serves a catalytic role

Allows for different combinations of exons resulting in more than one polypeptide per gene

Proteins often have a modular architecture consisting of discrete structural and functional regions

Transfer amino acids from the cytoplasm to the mRNA at the ribosome for assembling the polypeptide chain; Specific for a particular amino acid

Nucleotide triplet that pairs with a complementary codon on the mRNA

Makes up ribosomes

Holds the tRNA that carries the growing polypeptide chain

Holds the tRNA that carries the amino acid that will be added to the chain next

Exit site for each tRNA

Initiation, Elongation, and Termination

• A small ribosomal subunit binds to mRNA in such a way that the first codon of the mRNA strand is placed in the proper position

• The tRNA with anticodon UAC hydrogen bonds to the first codon

• The large ribosomal subunit attaches allowing the tRNA with methionine to attach to the P site

• Anticodon pairs with the complementary mRNA codon in the A site; Hydrolysis of GTP occurs

• An rRNA molecule of the large ribosomal subunit catalyzes the formation of a peptide bond between amino group of the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site

• The ribosome translocates the tRNA in the A site to the P site and the empty tRNA in the P site is moved to the E site where it is released

A stop codon in the mRNA is reached and translation stops; A release factor binds to the stop codon and the polypeptide is freed from the ribosome

Sequence of the leading 20 or so amino acids ; Serves as a cellular zip code by directing proteins to their final destination

Alterations of just one nucleotide base pair of a gene

Additions and losses of the nucleotide pairs in a gene

Causes the mRNA to be read incorrectly on each remaining codon

Substances or forces that interact with DNA in ways that cause mutations

Exclusive to prokaryotes; Clusters of genes; Consists of an operator, promoter, and genes

Controls the access of RNA polymerase to the genes; Found within the promoter site or between the promoter and the protein coding genes

Where RNA polymerase attaches

Entire stretch of DNA required for all the enzymes produced by the operon

Produce repressor proteins that may bind to the operator site; Occupies the operator site in order to turn off the operon

Normally off but can be activated; Normally catabolic; Ex: lac operon

Binds to and inactivates the repressor protein

Normally on but can be inhibited; Normally anabolic

Expression of different genes by cells with the same genome

Addition of methyl groups to DNA; Causes DNA to be more tightly packed which reduces gene expression

Acetyl groups added to amino acids of histone proteins which makes the chromatin less tightly packed and encourages transcription

Enhances gene expression

DNA sequences far from the gene; Bounded to activators

Proteins bounded to enhancer regions

Process by which cells become specialized in structure and function

Gives an organism its shape

Maternal substances in the egg that influence the course of early development

Series of events that lead to observable differentiation of a cell

Sets up the body plan and is a result of cytoplasmic determinants

Sets up the body plan and is a result of cytoplasmic dterminants

Master control genes that control several other genes at one time

Cancer causing genes

Genes that code for proteins responsible for normal cell growth; Become Oncogenes when a mutation occurs

A gene whose products normally inhibit cell division

Surrounds the genetic material

Surround the protein shell and aid viruses in infecting their hosts

Viruses that infect bacterial cells

Viruses can only infect a very limited variety of hosts

Ends in the death of the host cell by rupturing it

The bacteriophage’s DNA becomes incorporated into the host cell’s DNA and is replicated along with the host cell’s genome

• Destroy the foreign DNA of the phage by cutting it up

• Used to cut strands of DNA at specific locations(restriction sites)

RNA viruses that use the enzyme reverse transcriptase to transcribe DNA from an RNA template

Viruses pick up pieces of the first host’s DNA and carry it to the next cell to be infected