Chapter 8 Flashcards
The diversity of life is based on the same or different genetic code?
Same genetic code
A genetic information molecule must be able to do three things:
- Be able to contain large amounts of complex information.
- Have a mechanism for faithful replication.
- Must encode the phenotype
Johann Miescher discovered
Nuclein in white blood cells
Phoebus Levene discovered
DNA is composed of linked, repeated nucleotides
Albrecht Kossel discovered
DNA had 4 nitrogenous bases
Erwin Chargaff showed
A=T and G=C
Franklin and Chargoff
Did not get a noble prize
Replication (property of the genetic material of cells)
The genetic material must be stored and transmitted from generation to generation.
Gene expression (property of the genetic material of the cell)
The genetic material must control the phenotype of the organism
Mutation (property of the genetic material of the cell)
The genetic material must undergo variations that allow natural selection to work
Fred Griffith
Showed that something in a virulent strain of bacteria could transform a non-virulent strain of streptococcus pneumonia into a virulent again.
Oswald Avery, Colin Macleod & Maclyn McCarty
Showed that DNA is the transforming principle
Bacteriophage
Viruses that affect bacteria
Hershey and Chase
Found DNA not protein is the genetic material in bacteriophage
HIV destroys lymphocytes called what
Helper T Cells
Pyrimadines
T & C
Purines
A & G
James Watson and Francis Crick found this based on work by Franklin and Wilkins and Chargaff
DNA is a double stranded helix
Primary Structure
Nucleotide structure and joining of nucleotides together
Secondary Structure
Three dimensional, stable, helical structure
Tertiary Structure
Complex packing arrangement of DNA around proteins
DNA is a structure of nucleotides which consist of :
A phosphate group, a 5 carbon sugar, a nitrogenous base (purines and pyrimadines)
Purines
double ring structure, forms a covalent bond with 1’ carbon of deoxyribose
Pyrimidines
single ring structure, attached by covalent bond to the 1’ carbon of the pentose sugar
Phosphate groups
makes DNA acidic and always bonded to the 5’ carbon of the sugar
anything with “tide” on the end has
deoxyribose, base, and phosphate
“side” on the end
deoxyribose or ribose sugar and base
Nucleotides are joined by what
Phosphodiester linkages
A-T
2 H bonds
C-G
3 H bonds
The two strands are held together by what
Hydrogen bonds with are weak compared to phosphodiester groups
What makes DNA more stable?
Stacking interactions
DNA - deoxyribonucleic acid
Organized by complimentary bases to form double helix
Replicates before cell division
Provides instruction for every protein in the body
Three forms of the different secondary structures DNA can make
B-DNA, A-DNA, Z-DNA
B-DNA
most stable form, has plenty of water, forms right handed (alpha helix), diameter is 2nm, two antiparallel polynucleotides
A-DNA
Dehydrated samples, also right handed, shorter and wider than B-DNA
Z-DNA
less likely to happen, left handed
Negatively supercoiling
Underrotated, requires less energy to separate into two strands
Bacterial chromosomes are what kind of supercoiling?
Negatively
Plasmids
Small circular DNA molecules that carry additional genes
Prokaryotic DNA is what shape
circluar and not free to rotate
Topoisomerases
Enzymes that add or remove supercoils from DNA
Occurs only in chromosomes with fixed ends
2 states of condensation found in interphase DNA
Euchromatin (less condensed, contains actively transcribed genes)
Heterochromatin (highly condensed, transcription, centromeres, telomeres, and other specific places on chromosomes
Histones
probably organizes DNA
Nonhistone proteins
probably regulate gene expression
How is DNA packaged onto chromosomes
DNA is wound around histones and forms a nucleosome, linkers of DNA separate nucleosomes.
This DNA is coiled to form a solenoid or a helix
The helix or solenoid DNA is looped onto a core of non-histone protein
This whole structure forms a supercoil
Histones
contain several lysine residues at the N terminal ends
Are + charged
Interact with negatively charged phosphate groups of DNA
Holds DNA tightly and transcription is discouraged
Acetylation of histones
Neutralizes the charge on the lysine’s, then histones loosen their hold on DNA and transcription is enhanced
Deacetylation of histones
Replace the + charge on the lysine’s, and histones tighten their hold on DNA, and transcription is repressed
1 degree coiling of DNA
DNA double helix
2 degree coiling of DNA
Around histone core
3 degree coiling of core
Core + linker forms solenoid or a helix
4 degree coiling of DNA
DNA + histone protein + non-histone protein
Centromeres
constricted region of a condensed chromosome where the DNA does not appear to be replicated
kinetochores
Attachment points on the centromeres and are protein structures.
Telomeres
Are natural ends of linear chromosomes
Telomeres have 3 essential functions
Prevent degradation of chromosome ends by deoxyribonuclease
Prevent fusion of ends of chromosome with other chromosome
Facilitate replication of linear DNA molecules without loss of coding material
Tandem repeats of short nucleotide sequences
TTAGGG may be repeated hundreds of times
Enzyme telomerase
Adds nucleotides to the lagging strand
Most telomeres end in what?
A single stranded G rich region
Shelterin
Protein complex that binds to the telomere and protects the ends from being repaired as a single stranded DNA break
POT
Protection Of Telomeres
bind to the G rich single stranded sequence
Translation
carries information from RNA to protein
Transcription
Transfers information from DNA to RNA
Replication
carries genetic information between generation DNA to DNA
how does bacterial DNA distinguish from viral DNA
Methylation
