Biology

Gregor Mendel

Concept of particulate inheritance and established basic genetic principles

Chromatin

Discovered in late 1800s, found to be the material of chromosomes (Chroma=colored; Soma=body)

Griffith Experiment

Experimented w/ two strains of Streptococcus pneumoniae, virulent strain (s form) was coated with a polysaccharide capsule (caused infected mice to die of blood poisoning), mutant strain (R form) lacked the capsule and was non-virulent

Avery Experiment

Avery, MacLeod, and McCarty. Worked with Streptococcus strains (used dead S and live R). First removed nearly 99.98% of the dead S material. Treated dead S remains with Proteases. Transforming principle was not changed by the removal of protein. Dead S remains would still transform R strains into virulent strains.

Proteases

Enzymes to degrade/break down proteins

Transforming Principle (Avery Experiment)

TRANSFORMING PRINCLIPLE RESEMBLED DNA IN SEVERAL WAYS: Same Chemistry as DNA, not affected by lipid and protein extraction, not destroyed by protein- or RNA-digesting enzymes, destroyed by DNA digesting enzymes. EVIDENCE THAT THE HEREDITY MATERIAL WAS DNA.

Hershey Chase Experiments

Final experimental evidence that pointed to DNA as hereditary material. Team studied viruses that infect bacteria. Viruses have simple structure: core of DNA surrounded by a protein coat.
Final experimental evidence that pointed to DNA as hereditary material, viruses attach themselves to the surface of bacteria and inject their genes inside. Infected bacterial cells make hundreds of copies of new viruses, which then burst out of the cell to infect new cells.

Hershey Chase Experiments 2

Hershey and Chase used radioactive isotopes to "label" (tag) the DNA and the protein of the viruses, some viruses were grown so their dna contained radioactive phosphorus, other viruses were grown so their protein coats contained radioactive sulfur.

Bacteriophage

A virus that infects a bacterium

Mutagens

Chemical that causes mutation

Nucleotides

Base pair (bind together the phosphate backbone of DNA)
-central deoxyribose sugar
-Phosphate group
-Organic Base
(Thymine, Adenine, cytosine, guanine)

Purines

Double ring structure
(adenine and guanine)

Pyrimidines

Single rings
(cytosine and thymine)

Chargaffs Rule

DNA has a regular structure (equal amounts of purines and pyrimidines)
Amount of A=Amount of T
Amount of C=Amount of G

Crick and Watson

Deduced that the structure of DNA was a double helix
-Two strands of DNA bind together by their bases
-Purine-pyrimindine binding across strands keeps DNA molecule a constant thickness
--Base pairing

Conservative Replication

two strands of DNA completely seperate to act as templates for the assembly of two new strands
-After replicating, orginal strands rejoin

Semiconservative Replication

The DNA unzips and new complementary strands are assembled using each strand as a template
-One original strand is preserved in each double helix created

Dispersive Replication

Replication results in both original and new DNA dispersed among the two daughter strands (impossible)

Meselson and Stahl

Determined correct replication model
-used radioactive isotopes of 15N to label thymine in growth medium
-They found that DNA replication was semiconservative.

Semiconservative DNA replication requires several enzymes

1. DNA polymerase
2. Helicase
3. DNA Ligase

DNA Polymerase

adds the correct complementary nucleotide to the growing daughter strand
-can only add nucleotides to the end of an existing strand of a primer

Helicase

unzips the DNA to expose the templates
-This creates a replication fork

DNA Ligase

Seals fragments of DNA together

DNA repair

invovles comparing the daughter strand to the parent DNA template to check for mistakes

Mutation

Results from errors in replication
-can involve changes, additions, deletions to nucleotides.

Recombination

causes change in the position of all or part of a gene

Somatic cell mutations

Not passed to future generations, but passed to all other somatic cells derived from it (cancers)

Germ-line cell mutations

these mutations will be passed to future generations (occur to Gametes)
-Important for evolutionary change

Bases substitution

changes the identity of a base

Insertion

Adds base/s

Deletion

removes base/s

Frame shift mutation

may alter entire protein or protein will not be synthesized at all

Transposition

Occurs when the individual genes move from one place in the genome to another
(called transposons or jumping genes)

Chromasomal Rearrangement

Sometimes entire regions of chromosomes may change their location or undergo duplication
(occurs with Hox genes)

Genomics

A field that compares the entire DNA content of different organisms

Genome

All the genes + other DNA

DNA sequencing

Process that allows scientists to read each nucleotide in a strand of DNA

Single-copy

found in only one copy at a particular location on a chromosome

Segmental Duplications

Blocks of genes that have been copied over from one chromosome to another

Multi-gene families

Groups of similar genes

Tandem Clusters

Groups of genes located together

Non coding DNA

Introns (blank genes that are eventually cut out)

Structural DNA

Tightly coiled DNA

Repeated sequences

simple sequence repeats (SSR's) that are scattered about chromosomes

Duplicated sequences

Other repeated sequences

Transposable elements

DNA sequences that jump from one location on a chromosome to another (Alu)

Genetic engineering

moving genes from one organism to another
(new gene combinations called Recombinant DNA)

Cleaving DNA

Cutting the source and vector DNA

Producing recombinant DNA

Placing DNA fragments into vectors and then transferring the DNA into the target cells

Cloning

DNA bearing vectors reproduce in cultures

Screening

Selecting the particular cells that have recieved the gene of interest

Luciferase

enzyme found in fireflies

Nuclear Transplants

removing a nucleus from a donor cell and transplanting it into an enucleated egg

Genetic Imprinting

DNA is conditioned by the parental environment
-affects the ability of a gene to be read

Genes

Information contained in DNA is stored in blocks called genes.
-code for proteins
-Proteins determine cells characteristics (shape, function)

Central dogma

basis of human existance (DNA, RNA, Proteins)

Gene Expression

Gene information is used to direct the production of particular proteins (two stages)

Transcription

A messenger RNA (mRNA) is made from a gene within the DNA

Translation

Process of using the mRNA to direct the production of a protein

How RNA differs from DNA

RNA has a ribose sugar in each nucleotide, Uracil replaces Thymine as a base

Cells use three kinds of RNA

Messanger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)

RNA polymerase

Produces the mRNA copy of DNA during transcription

Promoter

Rna polymerase binds to a DNA site called the Promoter

Genetic Code Dictionary

determined from trial and error experiments to work out which codons matched with which amino acids
-same genetic code is used by all living things

Codons

Translation requires the reading of 3-base units on the mRNA molecule
-Each codon corresponds to a particular amino acid

Ribosomes

Protein making factories in the cell
-Ribosome=Complex of proteins and ribosomal RNA (rRNA)
-Ribosomes have two subunits

Anticodon

3-Nucleotide sequence anticodon is complementary to 1 of the 64 codons of the genetic code

Activating Enzymes

Match the amino acids with their proper tRNAs

Exons

Coding regions

Introns

Non-coding regions

Primary RNA transcript

When a eukaryotic cell first transcribes a gene, it produces a pRNAt of the entire gene

Alternative splicing

by using different combinations of the same exons, different proteins can be created

Gene expression

Cells control gene expression through the timing of gene transcription

Repressor

Genes can be turned off by the binding of a repressor (protein that binds to the DNA and blocks access to the promoter)

Activator

Genes get turned on, a protein that makes the promoter more accessible to RNA polymerase

Operon

Segment of DNA containing a cluster of genes that are transcribed as a unit

Enhancers

Eukaryotic genes have special sequences called enhancers that help guide RNA polymerase to the promoter at the begining of a gene