Genomes Flashcards
What is a gene?
A gene is a sequence of DNA nucleotides
The sequence holds a “code” with all of the information needed to make protein or RNA, can code for more than one protein
Alleles are the “forms” of the gene- Found in physical location of chromosome- locus. DNA and genome are the same in all cells. Use switches to turn on and off genes, control of gene expression.
The genome in general
A genome includes all the genetic information for a given species
Human genome: all the genetic information on the 22 autosomal plus the sex chromosomes (x and y)
In higher eukaryotes the genome is composed of mostly non coding regions. It is speculated that only 3-5% of DNA in humans actually codes for genes
Non coding DNA
no information, does not code for proteins or RNA. However noncoding DNA Controls which genes are turned on or which proteins are translated
Simple representation of a gene
Promoter region- Series of base pairs. recognized by proteins so that it can be transcribed.
Protein coding region- most information carried in DNA. In protein coding regions: introns (non coding, found in genes, only transcribed ) exons (protein coding, will be translated)
Organism complexity
With increasing complexity there is an increase in the number of genes
Decreasing gene density
Larger genome, more genes, decreasing gene density (number of genes per number of base pairs)
Amount of DNA
DNA of bacterium is about 1000times as long as the length of the cell
The DNA of a human cell is about 100,000 times the cell diameter and consists of about 3 x 10^9 base pairs
Many plants have more DNA than humans. Polyploidy- entire genome is doubled during the evolutionary history of the plant
Size of genome does not indicate size of organism
Chromosomes
Linear array of genes, DNA wrapped around histone proteins to form nucleosomes
Each chromosome in a cell contains only one single DNA molecule
Circular in DNA but linear in eukaryotic cells
Circular DNA also found in mitochondria, chloroplasts and some viruses (endosymbiosis)
Centromere
In the center of the chromosome
Telomeres
End of chromosomes, Common microsatellite, has a sticky end complimentary to other telomeres. Chromosome fusion can result
Closely related species
May have different number of chromosomes due to fusion
Similar DNA sequences different chromosomal anatomy. Can cause a speciation event
Ape chromosomal arrangements
Overall DNA sequence very similar, but humans have one chromosome where apes have 2
Between the genes
Non coding regions and repetitive DNA
• Satellite, minisatellite and microsatellite DNAs refer to repetitive sequences, reanneal more rapidly than a unique sequence of DNA - number of repeated, genetic fingerprint
Analysis of these sequences forms the basis for DNA fingerprinting and act as markers in complex genomes, many times being used for mapping other genes
Location of these repeated sequences can be determined using FISH with a repeat sequence as the probe
Hybridization
Hybridization can occur between two complimentary strands (don’t have to be exactly complimentary)
If you have a mixture of Nucleic acid strands, those that are complimentary will anneal more readily
Temperature important- more GC higher temp needed
Probes
Can be used to find complimentary sequences in larger fragments by fluorescence
