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Larger cells = more volume but not as much surface area so what is done to increase SA?
Folding
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What are prions?
- Misfolded proteins � heritable infections proteins
- � Create more prions
- � Make a pathogenic phenotypes � plaques
- � Mad cow disease
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Chromatin contains?
RNA, DNA, histones, non histone proteins, and non nuclear constituents
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Replication � lose a small part of our DNA
Incomplete pricess
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Telomerase � elongates out telomers
- Turns off after a certain point
- Aging
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Cancers � can figure out how to turn telomerase back on
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Satellite bands
Repeats of identical � no specific purpose
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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.
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Functions of the Genetic Material
- � Genotypic Function: Replication
- � Phenotypic Function: Gene Expression
- � Evolutionary Function: Mutation
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Chromosomes
- � Genes are located on chromosomes.
- � Chromosomes contain proteins and nucleic acids.
- � The nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
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The genetic material must perform three essential functions:
the genotypic function�replication, the phenotypic function�gene expression, and the evolutionary function�mutation.
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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.
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Viroids are
infectious naked RNA molecules
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prions are
infectious, heritable proteins.
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The genetic information of most living organisms is stored in
deoxyribonucleic acid (DNA).
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In some viruses, the genetic information is present in
ribonucleic acid (RNA).
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Viroids and prions are infectious naked molecules of RNA and protein, respectively.
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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.
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DNA Structure
- � 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.
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The complementarity of the two strands of a double helix makes DNA uniquely suited to store and transmit genetic information.
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The two strands of a DNA double helix have ___ chemical polarity.
opposite
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RNA usually exists as a single-stranded molecule containing what instead of thymine.
uracil
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The functional DNA molecules in cells are negatively
supercoiled.
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Chromosome Structure in Prokaryotes and Viruses
The DNA molecules of prokaryotes and viruses are organized into negatively supercoiled domains.
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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.
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The DNA molecules in prokaryotic and viral chromosomes are organized into negatively
supercoiled domains.
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Bacterial chromosomes contain circular molecules of DNA segregated into about ___domains.
50
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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.
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Histone Proteins
- � ?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
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Eukaryotic Chromosomes
- � ?Each chromosome is unineme
- � ?Each chromosome contains a single large molecule of DNA
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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.
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Autoradiography
- � ?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.
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Levels of DNA Packaging
- � ?2-nm double-stranded DNA molecule
- � ?11-nm nucleosomes
- � ?30 nm chromatin fiber
- � ?Organization around a central scaffold
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Centromeres
- � ?Constricted region of the chromosome
- � ?Necessary for proper segregation of chromosomes in mitosis and meiosis
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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
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Most telomeres contain repetitive sequences and a distinct structure.
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Eukaryotic chromosomes contain repetitive DNA
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Evidence for repetitive DNA
- � �Satellite bands
- � �DNA renaturation experiments
- � �In situ Hybridization
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Each eukaryotic chromosome contains one giant molecule of DNA packaged into 11-nm ellipsoidal beads called
nucleosomes.
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?The condensed chromosomes that are present in mitosis and meiosis and carefully isolated interphase chromosomes are composed to
30-nm chromatin fibers.
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At metaphase, the 30-nm fibers are segregated into domains by
scaffolds composed of nonhistone chromosomal proteins.
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The centromeres (spindle-fiber-attachment regions) and telomeres (termini) of chromosomes have unique structures that facilitate their functions.
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Eukaryotic genomes contain repeated DNA sequences, with some sequences present a million times or more.
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