AP Bio Unit 6 Vocabulary

Covers topics such as DNA and RNA structure, replication, transcription and RNA processing, translation, regulation of gene expression, general gene expression, cell specialization, mutations, and biotechnology.

Purines

Nucleotides with a double ring structure.

• IE: Adenine and guanine

Pyrimidines

Nucleotides with a single ring structure.

• IE: Cytosine, thymine, and uracil

Antiparallel

The opposite of parallel; the two strands run in opposite directions.

One strand runs 5’ to 3’ and the other runs 3’ to 5’.

Plasmids

Small, circular DNA molecules that are separate from chromosomes.

• Contain useful genes for a particular environment

• Typically not required for survival

RNA

Ribonucleic acid (polymer that creates proteins via translation)

• Single stranded

• A=U and C=G

DNA

Deoxyribonucleic acid (polymer containing genetic information)

• Double stranded

• A=T and C=G

Origin of Replication

The origin (place) at which the sequence of replication starts and DNA is opened to form the replication fork.

Topoisomerase

An enzyme that prevents strain ahead of the replication form by relaxing supercoiling.

Helicase

An enzyme that unwinds the DNA strands at each replication fork.

Replication Fork

The active area in which DNA replication takes place.

Primase

An enzyme that initiates replication by adding primers (short segments of RNA) to the parental DNA strand.

DNAP III

An enzyme that attaches to each primer on the parental strand, moving in the 3’ to 5’ direction, adding nucleotides to the new stand in the 5’ to 3’ direction.

Leading Strand

The strand in which DNAP III follows helicase and only one primer is required.

Lagging Strand

The strand in which DNAP III moves away from helicase and requires many primers.

Okazaki Fragments

Segments of the lagging strand

DNA Ligase

The enzyme that joins okazaki fragments together to form a continuous DNA strand.

Primers

Short segments of RNA that serve as the foundation for DNA synthesis.

Telomeres

Repeating units of short nucleotide sequences that do not code for genes.

• Form a cap at the end of DNA to help to postpone erosion

• Added by telomerase

Telomerase

The enzyme responsible for the creation of telomeres.

Mismatch Repair

When enzymes remove and replace the incorrectly paired nucleotide(s) of a mismatch.

Nuclease

An enzyme that can remove segments of nucleotides if the segments of DNA are damaged, allowing those segments to be replaced by other enzymes.

DNAP 1

Adds nucleotides to new DNA strand and proofreads the added bases

• Also repairs mismatches

Gene Expression

The process by which DNA directs the synthesis of proteins.

Transcription

The synthesis of RNA using information from DNA, which allows for the “message” of DNA to be transcribed.

• Occurs in the nucleus

Translation

The synthesis of a polypeptide using information from RNA.

• Occurs at the ribosome

• Nucleotide sequence becomes an amino acid sequence

mRNA

Carries information from the DNA (at nucleus) to the ribosomes (in cytoplasm).

• Synthesized during transcription using a DNA template

tRNA

Useful in the process of translation, with each carrying a specific amino acid. Allow information to be translated into a peptide sequence.

• Can attach to mRNA via their anticodon

Anticodon

A complimentary codon to mRNA that is located on tRNA.

rRNA

Helps in forming ribosomes and linking amino acids together.

Codons

mRNA nucleotide triplets that code for amino acids.

Template Strand

The strand of DNA that is transcribed in the process of transcription.

• Also known as the noncoding strand, minus strand, or antisense strand

Redundancy

In terms of genetics, this refers to the fact that more than one codon codes for each amino acid.

Reading Frame

The codons on the mRNA must be read in the correct groupings during translation to synthesize the correct proteins, so they must be read in the right frame.

5’ Cap

The 5’ end of the pre-mRNa receives a modified guanine nucleotide “cap".

Poly-A Tail

The 3’ end of the pre-mRNA receives 50-250 adenine nucleotides.

RNA Splicing

When sections of the pre-mRNA, called introns, are removed and the exons are joined together.

Alternative Splicing

When a single gene can code for more than one kind of polypeptide and splicing occurs.

Stop Codon

A codon that does not code for an amino acid, but rather signals for a release factor hydrolyzing the bond that holds the polypeptide to the P site.

When this is added and mRNA reaches the A site of the ribosome, termination occurs (step 3 of translation).

Operons

A group of genes that can be turned on or off

• Consist of promoter, operator, and genes.

Promoter

The part of an operon where RNA polymerase can attach.

Operator

The part of an operon that is the on/off switch.

Genes

The part of an operon that codes for related enzymes in pathways.

Repressible

A type of operon in which transcription is usually on, but can be repressed (stopped).

Inducible

A type of operon in which transcription is usually off, but can be induced (started).

Regulatory Gene

A gene that produces a repressor protein that binds to the operator to block RNA polymerase from transcribing the gene.

• Always expressed, but at low levels

• Binding of a repressor to an operator is always reversible

Allosteric Activator

Substrate that binds to allosteric sites and stabilizes the shape of an enzyme so that the active sites remain open (remain in the active form).

Allosteric Inhibitor

Substrate binds to allosteric sites and stabilizes the enzyme shape so that the active sites are closed (in the inactive form).

Histone Acetylation

Adds acetyl group to histones, which loosens the DNA.

• A form of eukaryotic gene expression regulation.

DNA Methylation

Adds methyl groups to DNA, which causes the chromatin to condense.

• A form of eukaryotic gene expression regulation.

Control Elements

Sections of non coding DNA that serve as binding sites, where gene expression can be increased or decreased by binding of activators or repressors.

Cytoplasmic Determinants

Substances in the maternal egg that influence cells.

Induction

Cell to cell signals that can cause a change in gene expression.

Pattern Formation

A “body plan” for the organism that is influenced by both cytoplasmic determinants and induction.

Homeotic Genes

Genes that map out the body structures.

Apoptosis

Programmed cell death.

• Allows structures to take their form.

• Critical in cell differentiation.

Morphogenesis

The physical process that gives an organism its shape.

Differentiation

The process by which cells become specialized in their structure and function.

Epigenetic Inheritance

A form of inheritance in which a parent’s experiences, through epigenetic changes, are passed down to offspring.

Mutations

Changes in the genetic material of a cell, which can alter phenotypes.

• A primary source of genetic variation

Substitution

A mutation in which one nucleotide and its partner are replaced with another pair of nucleotides.

Nondisjunction

A mutation where chromosomes do not separate properly in meiosis, which results in the incorrect number of chromosomes.

• Ex: Down Syndrome - Trisomy 21

Translocation

A mutation where a segment of one chromosome moves to another.

Inversions

A mutation where a segment is reversed.

Duplications

A mutation where a segment is repeated.

Deletions

A mutation where a segment is lost / deleted.

Horizontal Gene Transfer

A form of exchange of genetic material in prokaryotes through the movement of material between different organisms (and different cells).

Transformation

The uptaking of DNA from a nearby cell.

Transduction

The viral transmission of genetic material.

Conjugation

The cell to cell transfer of DNA.

Transposition

The movement of DNA segments within and between DNA molecules.

Point Mutations

Changes in a single nucleotide pair of a gene.

Genotype

An organism’s sequence of DNA.

Phenotype

The observable expression of a genotype.

Gel Electrophoresis

A technique used to separate DNA fragments by size.

• DNA is loaded into wells on one end of a gel and an electric current is applied.

• DNA fragments are negatively charged so they move towards the positive electrode.

PCR (Polymerase Chain Reaction)

A method used in molecular biology to make several copies of a specific DNA segment.

• Segments of DNA are amplified

• Results analyzed using gel electrophoresis

DNA Sequencing

The process of determining the order of nucleotides in DNA.