Card Set Information
Larger cells = more volume but not as much surface area so what is done to increase SA?
What are prions?
Misfolded proteins � heritable infections proteins
� Create more prions
� Make a pathogenic phenotypes � plaques
� Mad cow disease
RNA, DNA, histones, non histone proteins, and non nuclear constituents
DNA has a neg charge
Replication � lose a small part of our DNA
Telomerase � elongates out telomers
Turns off after a certain point
Cancers � can figure out how to turn telomerase back on
Repeats of identical � no specific purpose
Functions of the Genetic Materia
l The genetic material must replicate, control the growth and development of the organism, and allow the organism to adapt to changes in the environment.
Functions of the Genetic Material
� Genotypic Function
� Phenotypic Function
: Gene Expression
� Evolutionary Function
� Genes are located on chromosomes.
� Chromosomes contain proteins and nucleic acids.
� The nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
The genetic material must perform three essential functions:
the genotypic function�replication, the phenotypic function�gene expression, and the evolutionary function�mutation.
Proof that Genetic Information is Stored in DNA
In most organisms, the genetic information is encoded in DNA. In some viruses, RNA Is the genetic material.
infectious naked RNA molecules
infectious, heritable proteins.
The genetic information of most living organisms is stored in
deoxyribonucleic acid (DNA).
In some viruses, the genetic information is present in
ribonucleic acid (RNA).
Viroids and prions are infectious naked molecules of RNA and protein, respectively.
DNA is usually double-stranded, with adenine paired with thymine and guanine paired with cytosine.
RNA is usually single-stranded and contains uracil in place of thymine.
� Complementary Base Pairs (A with T, G with C
� Antiparallel Strands
� Right-handed double helix (B-DNA)
DNA usually exists as a double helix, with the two strands held together by hydrogen bonds between the complementary base pairs
: adenine paired with thymine and guanine paired with cytosine.
The complementarity of the two strands of a double helix makes DNA uniquely suited to store and transmit genetic information.
The two strands of a DNA double helix have ___ chemical polarity.
RNA usually exists as a single-stranded molecule containing what instead of thymine.
The functional DNA molecules in cells are negatively
Chromosome Structure in Prokaryotes and Viruses
The DNA molecules of prokaryotes and viruses are organized into negatively supercoiled domains.
The DNA of Prokaryotes and Viruses
� ?Prokaryotes are monoploid.
� ?Most viruses and prokaryotes have a single set of genes stored in a single chromosome, which contains a single molecule of nucleic acid.
The DNA molecules in prokaryotic and viral chromosomes are organized into negatively
Bacterial chromosomes contain circular molecules of DNA segregated into about ___domains.
Chromosome Structure in Eukaryotes
Eukaryotic chromosomes contain huge molecules of DNA that are highly condensed during mitosis and meiosis. The centromeres and telomeres of eukaryotic chromosomes have unique structures.
� ?Structural role in chromatin
� ?Present in amounts equivalent to amounts of DNA
� ?Major histone types
: H1, H2a, H2b, H3, and H4
� ?Basic proteins
� ?Arginine and Lysine are Abundant
� ?Highly conserved proteins
� ?Each chromosome is unineme
� ?Each chromosome contains a single large molecule of DNA
Pulsed-Field Gel Electrophoresis Can Separate Large DNA Molecules
� ?Two electric fields at 90�are applied alternately.
� ?Very large DNA molecules can be separated this way.
� ?This technique can separate whole chromosomes from one another.
� ?DNA is labeled with 3H-thymidine, spread on a microscope slide, and covered with emulsion.
� ?Molecules nearly as long as a Drosophila chromosome are observed.
� ?These data support that each chromosome is one molecule of DNA.
Levels of DNA Packaging
� ?2-nm double-stranded DNA molecule
� ?11-nm nucleosomes
� ?30 nm chromatin fiber
� ?Organization around a central scaffold
� ?Constricted region of the chromosome
� ?Necessary for proper segregation of chromosomes in mitosis and meiosis
Functions of telomeres
� �Protect the ends of linear DNA molecules from deoxyribonucleases
� �Prevent fusion of chromosomes
� �Facilitate complete replication of the ends of linear DNA molecules
Most telomeres contain repetitive sequences and a distinct structure.
Eukaryotic chromosomes contain repetitive DNA
Evidence for repetitive DNA
� �Satellite bands
� �DNA renaturation experiments
� �In situ Hybridization
Each eukaryotic chromosome contains one giant molecule of DNA packaged into 11-nm ellipsoidal beads called
?The condensed chromosomes that are present in mitosis and meiosis and carefully isolated interphase chromosomes are composed to
30-nm chromatin fibers.
At metaphase, the 30-nm fibers are segregated into domains by
scaffolds composed of nonhistone chromosomal proteins.
The centromeres (spindle-fiber-attachment regions) and telomeres (termini) of chromosomes have unique structures that facilitate their functions.
Eukaryotic genomes contain repeated DNA sequences, with some sequences present a million times or more.