AP Bio Unit 6 (Gene Expression and Regulation) Vocab

Purines

Nitrogenous bases with a double ring structure (A&G)

Pyramidines

Nitrogenous bases with a single ring structure (T&C)

Antiparallel

1 strand runs 5’-3’, the other runs 3’-5’

Plasmids

Small, circular DNA molecules that are separate from the chromosomes

RNA

Ribonucleic Acid helps carry DNA information to control protein synthesis.

DNA

Deoxyribonucleic Acid carries genetic information for the rest of the cell.

Origins of Replication

The place where DNA replication starts

Replication Fork

DNA strands pulled apart by proteins at Origins of Replication

Helicase

Unwinds DNA strands at each Replication Fork

Topoisomerase

Helps prevent strain ahead of the Replication Fork by relaxing supercoiling.

Primase

Initiates DNA replication by adding primers to the Parental Strand

Primers

Short segments of RNA

DNA Polymerase III

Attaches to each primer and moves in 3’-5’ while adding nucleotides in 5’-3’

DNA Polymerase I

Replaces RNA nucleotides with DNA nucleotides

Leading Strand

DNA Polymerase III follows Helicase and only needs 1 Primer

Lagging Strand

DNA Polymerase III moves away from Helicase and needs many primers

Okazaki Fragments

Segments of the lagging strand DNA

DNA Ligase

Joins the Okazaki Fragments forming a continuous DNA strand.

Telomeres

Repeating units of short nucleotide sequences that don’t code for genes

Telomerase

Addes telomeres to DNA

Nuclease

Removes damaged DNA segments/nucleotides

Mismatch Repair

Enzymes remove and replace incorrectly paired nucleotides

Conservative Model

Parental strands direct synthesis of a while new double stranded molecule (fully conserved)

Semi-Conservative Model

Two parental strands make a copy of themselves (1 parental strands + 1 new strand)

Dispersive Model

Parent strand material is randomly dispersed between the 2 daughter molecules (random mix of parental & new DNA)

Rosalind Franklin

X-Ray Crystallography of DNA and discovered a regular and repetitive pattern

Edward Chargaff

Discovered that Adenine = Thymine, and Cytosine = Guanine

Watson and Crick

Combined Franklin’s findings (Helix shape) and Chargaff’s findings (Base pairing) to create the first 3D double helix model of DNA

Meselson and Stahl

Used bacteria and isotopes to discover that DNA replication followed the Semi-Conservative Model

Transcription

The synthesis of RNA using information from DNA

Gene Expression

The process by which DNA directs the synthesis of proteins

Template Strand

The DNA strand being transcribed

Codon

mRNA nucleotide triplets

rRNA

Helps form ribosomes and link amino acids together

tRNA

Carries specific amino acids and attach to mRNA via their anticodon

5’ cap

A modified guanine nucleotide cap added to the 5’ end of pre-RNA

Poly-A tail

50-250 adenine nucleotides added to the 3’ end of pre-mRNA

mRNA

Carries information from the DNA to the ribosomes in the cytoplasm

Redundancy

More than one codon code 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

Alternative splicing

A single gene can code for more than one kind of polypeptide

RNA splicing

Sections of the pre-RNA, called introns, are removed and then exons are joined together

Translation

The synthesis of a polypeptide

Anticodon

A specific sequence of three nucleotides located on a tRNA molecule that is complimentary to a corresponding codon on mRNA

tRNA

Has an anticodon region that is complementary and antiparallel to mRNA and carries the amino acids that mRNA is coding for

Stop codon

A codon in mRNA that causes termination in translation, and does not code for an amino acid.

Operons

A group of genes that can be turned on or off

Promoter

The part of an operon where RNA Plymerase can attach

Operator

The on/off switch of an operon

Inducible

Transcription in an operon is usually off, but can be induced/started (off→on)

Cytoplasmic Determinants

Substances in the maternal egg that influence cells

Allosteric Inhibitor

Substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites will close (Inactive form)

Regulatory Gene

Produces a repressor protein that binds to the operator to block RNA Polymerase

Allosteric Activator

Substrate binds to allosteric site and stabilizes the shape of the enzyme so the active site will remain open

Control elements

Sections of noncoding DNA that serve as binding sites

Histone Acetylation

Adds acetyl groups to histones, which loosens the DNA

DNA Methylation

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

Epigenic Inheritance

Chromatin modifications do not alter the nucleotide sequence of the DNA, but can be heritable to future generations

Gene

Code for related enzymes in pathway of operons

Differentiation

Cells become specialized in their structure and function

Morphogenesis

The physical process that gives an organism its shape

Repressible

Transcription is usually on, but can be repressed/stopped (on→off)

Induction

Cell-to-cell signals that can cause changes in gene expression

Homeotic genes

Map out the body’s structures

Apoptosis

Programmed cell death

Pattern Formation

A “body plan” for the organism

Mutations

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

Genotype

The genetic makeup of an organism

Phenotype

The observable characteristics/traits of an organism

Nondisjunction

When chromosomes do not separate properly in meiosis

Translocation

A segment of one chromosome moves to another

Inversions

A segment is reversed

Deletions

A segment is lost

Horizontal Gene Transfer

Allows prokaryotes to exchange genetic material

Transformation

Uptaking of DNA from a nearby cell

Conjugation

Cell-to-cell transfer of DNA

Transposition

Movement of DNA segments within and between DNA molecules

Point Mutations

Change a single nucleotide pair of a gene

Duplications

A segment is repeated

Transduction

Viral transmission of genetic material

Substitutions

The replacement of one nucleotide and its partner with another pair of nucleotides

Gel electrophoresis

A technique used to separate DNA fragments by size

PCR

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

DNA sequencing

The process of determining the order of nucleotides in DNA