AP Biology Unit 6: Gene Expression and Regulation

AP Biology Unit 6 Gene Expression and Regulation study guide.

DNA & RNA

DNA (deoxyribonucleic acid) is the molecule that carries genetic information in cells, while RNA (ribonucleic acid) plays a crucial role in translating this information into proteins, facilitating gene expression.

Prokaryotic Organisms & Eukaryotic Organisms

Prokaryotic organisms are single-celled organisms without a nucleus, and the chromosomes are circular, whereas eukaryotic organisms have a defined nucleus and linear chromosomes.

Plasmids

small, circular DNA molecules found in bacteria, often used in genetic engineering to transfer and replicate genes.

Purines

are a type of nitrogenous base in nucleotides, consisting of adenine and guanine, crucial for DNA and RNA structure. They are characterized by a double-ring structure, allowing them to pair with pyrimidines during base pairing in nucleic acid sequences.

Pyrimidines

are a type of nitrogenous base in nucleotides, consisting of cytosine, thymine, and uracil, which play a key role in the structure of DNA and RNA. They are characterized by a single-ring structure and pair with purines during base pairing in nucleic acid sequences.

5’ to 3’ direction

refers to the orientation of nucleic acid strands, indicating the direction in which nucleotides are added during DNA and RNA synthesis, with the 5' phosphate group at one end and the 3' hydroxyl group at the other.

Replication is a semiconservative process

in which each new DNA molecule consists of one original strand and one newly synthesized strand. This method ensures genetic fidelity during cell division, as each daughter cell receives an exact copy of the DNA.

Helicase

is an enzyme that unwinds and separates the two strands of DNA during replication, allowing each strand to serve as a template for the synthesis of new complementary strands.

Topoisomerase

is an enzyme that relieves the tension and supercoiling in DNA during replication by cutting and rejoining the DNA strands. This action prevents tangling and allows the replication fork to progress smoothly.

DNA polymerase

Requires RNA primers to initiate DNA synthesis.

DNA polymerase

is an enzyme that synthesizes new DNA strands by adding nucleotides to a pre-existing chain, using the original DNA strand as a template. It also has proofreading capabilities to ensure accuracy in DNA replication.

Lagging strand

is one of the two strands of DNA being replicated. It is synthesized discontinuously in short segments called Okazaki fragments, as the DNA unwinds, due to its orientation being 3' to 5'.

Leading strand

is the DNA strand that is synthesized continuously in the same direction as the replication fork, allowing for smooth, uninterrupted synthesis as DNA unwinds.

Ligase

Joins the fragments on the lagging strand.

mRNA

is a type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized.

tRNA

is a type of RNA that helps decode mRNA sequences into proteins by carrying specific amino acids to the ribosome during protein synthesis.

rRNA

is a type of RNA that, alongside proteins, makes up the ribosomes, which are the sites of protein synthesis in cells.

RNA polymerase

is an enzyme that synthesizes RNA from a DNA template during the process of transcription, playing a crucial role in gene expression.

Noncoding strand

is the DNA strand that is not used as a template for RNA synthesis during transcription, serving as a complement to the coding strand.

5’ to 3’

The enzyme RNA polymerase synthesizes mRNA molecules in the 5’ to 3’ direction by reading the template DNA strand in the 3’ to 5’ direction.

Eukaryotic cells mRNA transcript

is processed by adding a 5' cap and a poly-A tail before it leaves the nucleus for translation. Excision of introns and retention of exons.

Translation of mRNA

is the process by which ribosomes synthesize proteins using the mRNA sequence as a template, translating codons into amino acids.

Prokaryotic organisms translation of mRNA

occurs in the cytoplasm simultaneously with transcription, as prokaryotes lack a defined nucleus.

Translation

Involves energy and many sequential steps including initiation, elongation, and termination.

Initiation

is the first phase of translation where the ribosome assembles around the start codon of the mRNA, and the first tRNA molecule is brought to the ribosome.

Elongation

is the second phase of translation during which the ribosome moves along the mRNA, adding amino acids to the growing polypeptide chain as each corresponding tRNA brings the appropriate amino acid.

Termination

is the final phase of translation where the completed polypeptide chain is released from the ribosome once a stop codon on the mRNA is encountered.

retroviruses

are RNA viruses that insert a copy of their genome into the DNA of a host cell, typically using the enzyme reverse transcriptase.

Regulatory sequences

are regions of DNA that influence the transcription of nearby genes by binding transcription factors and other regulatory proteins.

Epigenetic changes

refer to heritable changes in gene expression that do not involve changes to the underlying DNA sequence. Examples include DNA methylation and histone modification.

Phenotype

is the observable physical and biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

operons

are clusters of genes under the control of a single promoter in prokaryotic cells, allowing coordinated expression of genes involved in related functions.

lac operon

is a set of genes required for the metabolism of lactose in E. coli, regulated by the presence or absence of lactose.

Mutations

are permanent changes in the DNA sequence of a gene that can lead to alterations in phenotype. Mutations can be caused by various factors such as environmental exposure or errors in DNA replication.

Mutations can be

detrimental, beneficial, or natural depending on the environmental context.

electrophoresis

a laboratory technique used to separate DNA, RNA, or proteins based on their size and charge.

PCR

(Polymerase Chain Reaction) is a method used to amplify specific segments of DNA, making millions of copies from a small initial sample.

DNA sequencing

is a method used to determine the precise order of nucleotides within a DNA molecule.