Gene Structure and Genome Organization
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The self-replicating genetic structures of cells containing the cellular DNA that bears in its nucleotide sequence the linear array of genes.
Chromosomes
Three important DNA sequences
telomere, replication origin, and centromere
The position at which the DNA helix is first opened and has binding sites for the initiator proteins and DNA regions that are especially easy to open.
Replication origin
Sequences that serve as attachment for kinetochore that link chromosomes to mitotic spindles. Ensures equal distribution of chromosomes to daughter cells when a cell divides.
Centromere
Sequences at the ends of eukaryotic chromosomes that help stabilize the chromosomes. Enable the ends of chromosomes to be efficiently replicated.
Telomere
General telomere motif
(TxGy)n where x and y = 1 to 4 n = 20-100 in single celled eukaryotes; 1, 500 in mammals
A gene is a portion of a chromosome that determines or affects a single character or phenotype.
Classic definition
The classic definition of gene is based what precedences?
Laws of inheritance (Gregor Mendel) and Chromosome Theory of Inheritances (Thomas Hunt Morgan)
“Particles” that determine traits occur in pairs and are separated into gametes during meiosis
Principle of segragation
Alleles at one locus segregate into gametes independently of alleles at other loci.
Principle of independent assortment (no gene linkage)
Explain the beadle and tatum experiment?
When spores were exposed to mutagenic agents, mutants lacked one or another specific enzyme
A gene is a segment of genetic material that determines or codes for one enzyme (one gene-one enzyme hypothesis).
Beadle and tatum molecular definition
The beadle and tatum experiment involves an prototropic organism called?
Neurospora crassa
What is the underlying reason for the development of one gene-one polypeptide definition of a gene?
Many genes code for proteins that are not enzymes There are genes that code for a polypeptide of a multi-subunit protein
Variant forms (alleles) of genes that occur in > 1% of the population
polymorphisms
A gene is all the DNA that encodes the primary sequence of some final gene product which can either be a polypeptide or an RNA with a structural or catalytic function.
current definition, syn. smallest unit of heredity, a transcriptional unit
Different forms of a gene at the same locus on homologous chromosomes
Allele
Where does polymorphism come from?
inaccuracy during DNA replication
Includes all the genes which carry the information for making the proteins required by the organism.
Genome
General trend in the organism’s level of tropism and number of genes?
the lower the organism is, the higher the number of protein coding genes
Non living characteristics of viruses
acellular do not grow (only in number but not size) and divide Outside the cell they possess DNA or RNA but never both
Living characteristics of viruses
reproduce but only within living host mutate
An intact infectious viral particle is called a
virion
Virion is composed of
capsid nucleic acid envelope (for some)