lecture 20 Flashcards
what in the genome do we find variability within the species and what do we find to be the same?
all individuals of a species share the same set of genes with slightly different alleles.
what makes up the unique genetic information in humans?
the genome. for humans it is 22 autosomes and the x and y chromosomes.
how is a dna denatured?
it is dissolved in saline solution and warmed
how is dna denaturation measured?
the more relative absorbance of 260nm light, the more the dna has separated
what is the temp that the two strands separate from one another?
melting temp
what will make the melting temp higher?
more gc bonds because there are more h bonds to break and the size of the genome
what is renaturation or reannealing?
single stranded dna molecules are capable of reassociating
what experiments do we see renaturation or reannealing?
pcr, southern blot, northern blot
what does how fast the dna reannealing show?
how complex the organism is
what does the symmetrical curve of bacterial and viral dna fragments suggest
that there is not a lot of repetitive sequences
what does bacterial and viral genome having a symmetrical curve suggest about the genes?
that genes are arranged in a linear array. one gene after the next with not a lot of repeated sequences.
how do the reannealing curves look for plants and animals?
they have three broad classes of dna sequences with different curves. not symmetrical
how do the three classes of dna sequences differ from one another?
the number of times their nucleotide sequence is repeated
what are the names of the three broad classes of dna sequences in plants and animals?
- highly repeated fractions
- moderately repeated fractions
- nonrepeated fractions
why are highly repeated sequences able to reanneal to one another faster?
since they have sequences repeated over and over, it is easier for the two strands to find each other and reanneal to one another
what is the name of the dna sequence in plants and animals that are less abundant together and more scattered throughout genome?
moderately repeated fractions. takes a bit longer because they are more scattered for complementary strands to find one another and reanneal to one another.
special exceptions to moderately repeated fractions. What do they encode for?
SINES, LINES, genes that encode for Trna and Rrna
what part of the DNA renaturation for plants and animals are similar to virus and bacteria renaturation curve?
the nonrepeated fraction
why do nonrepeated fractions take longer to renature?
Because it is the sequences that encode for genes and therefore it is more unique with not many repeated sequences. It takes more time for complementery mate to find sequence and reanneal.
what percent of the dna sequence has highly repeated sequences?
1-10%
what are the three categories of highly repeated sequences?
- satellite dna
- minisatellite dna
- microsatellite dna
how many base pairs are satellite DNAs?
5-200 base pairs. there are several million base pairs together
how many base pairs are minisatelllite DNAs?
10-100 base pairs repeated around 3000 times.
how many base pairs are microsatellite DNAs?
1-9 base pairs present in clusters of around 10-40 base pairs. more spread throughout genome
what composition varies from organism to organism?
highly repeated fraction dnas
why do minisatellite DNAs tend to be so variable amongst organisms?
the number of repeats increase or decrease from one generation to the next due to unequal crossover whenn homologous chromosomes pair up during mitosis
why are minisatellite DNAs so important in dna fingerprintig and why are they so commonly used in csi shows?
minisatellite dnas are highly variable even within family. it makes it so that we can see how closely related two different individuals are
how are mini satelllites processed to see if a defendent matches the dna of a crime scene?
gel electrophoresis is used. dna is digested with restriction endonucleases and dna fragments are separated by size using gel electrophoresis. they are compared to that of the crime scene dna
what are microsatellite DNAs involved in? (disease)
microsatellite repeats are typically implicated in genetic disorders like huntingtons disease where CAG is repeated more than the normal 6-35 times.
how do we determine where s specific repeated sequence or gene is within the chromosome?
fluorescence in situ hybridizatioin or fish
how are satellite DNAs detected within the chromosome?
a fluroescent dye is attached to a probe with the complementery sequence repeated sequence.
how are fluorescent probes attached to the chromosomes?
using hot salt, then the probe is added
how are fluorescently tagged probed genes or dna sequences visualized?
immunofluorescent microscopy
what percentage of the genome consists of moderately repeated sequences?
20-80%
how many times are moderately repeated fraction repeated within the genome?
anywhere from a few times to tens of thousands of times scattered throughout genome
do moderately repeated sequences have a coding function
no, they do not code for protein or rna. the exceptions are rrna trna and histones
how do we find moderately repeated sequences within the genome?
scattered or interspersed.
what are the types of moderately repeated sequences and what do they stand for
- sines = short interspersed elements
- lines= long interspersed elements
how much of the genome is made up of long interspersed elements?
21%
what kind of sequence exhibits mendelian patterns of inheritance and localize to a particular part of the chromosome?
nonrepeated sequences
what do nonrepeated fractions code for?
virtually all proteins in the body other than the histones
how much of the genome is comprised of nonrepeated sequences?
1.5%
how do nonrepeated sequences give rise to similar proteins within the body?
some genes get duplicated over time and over time, they gave rise to protein families that have different genes that are related but not identical for slightly different functions
