L3 Flashcards
what is spacer DNA
unique non coding DNA
what are non coding functional sequences
do not produce proteins but still important
what are human globin genes for
codes for oxygen carrying molecule in humans
what is a heme
iron carrying molecule
true or false, eukaryotic genomes tend to be larger than prokaryotes
true
true or false, there is no relationship between genome size and phenotypic complexity
true
true or false, the number of genes in a species is often lower than expected when compared to the size of its genome
true
true or false, there is no strong relationship between genome size and number of genes
true
which has fewer genes but a larger genome in a given number of base pairs, eukaryote or prokaryote
eukaryote
true or false, of the genomes sequenced so far, humans and other mammals have the lowest gene density
true
what do the genes of most bacteria consist of
genes for proteins tRNA or rRNA with the remaining consisting of non transcribed regulatory regions
true or false, in eukaryotes the vast majority of DNA neither encodes protein nor is transcribed into RNA of known function
true
true or false, humans have 10 000 times as much non coding DNA as bacteria
true
what are unique sequence DNA
aka spacer DNA
mainly consist of genes which in addition to coding regions contain intervening sequences that are not translated ( has exons and introns).
true or false, gene related regulatory sequences and introns account for 20% and 5% of the human genome respectively, the remainder is 15% unique non coding DNA
true
what are pseudogenes
non functional gene within a family of genes
why have some genes evolved into tandem arrays
this is because cells need a large amount of products of those genes
what is the purpose of telomeres
it acts as a cap stabilizing the end of the chromosome and stops it from being degraded; the G rich strand often protrudes beyond the complementary C-rich strand at the end of the chromosome
true or false, special proteins bind to the single-strand sequence protecting the telomere from degredation
true
what does the telomeric sequence solve
solves the problem of replicating the ends of a linear DNA molecule
what enzyme can extend the G-overhang
telomerase (reverse transcriptase)
where is telomerase present
in single-celled organisms, germ cells, early in embryonic cells and certain somatic cells
true or false, most somatic cells have little or no telomeras activity
true
true or false, once the telomeres have shortened beyond a critical point the chromosome becomes unstable
true
what are centromeric repeats
highly repeat sequences with no known function
what are centromeric repeats also known as and what type of chromatin are they usually
aka satellite DNA, usually heterochromatic, short A-T rich tandem repeats flanking the centromeres
what are variable number of tandem repeats (VNTRs)
A DNA sequence consistent of variable number of tandem repeat units
what are the two principal families of VNTRs
microsatellites and minisatellites
what is a microsatellite
The repeat unit in microsatellite is 2-6 bp long
most common is repeat CA complement GT
what is a minisatellite
between 15-100 bp long
what uses do mini and micro satellites have
can be used in DNA fingerprinting and paternity tests
What are transposable elements
are mobile DNA sequences found in the genome of all organisms; they make up 45% of the human DNA; able to insert into many different locations in the genome
how do transposable elements cause mutation
often cause mutation either by direct insertion into gene or by promoting DNA rearrangement such as chromosome deletions, duplication, inversions
what are the classes of transposable elements in eukaryotes
retrotransposons and DNA transposons
What are retrotransposons
make RNA copies of themselves which are then reverse transcribed into DNA and inserted into chromosome;
the RNA is copied into DNA by enzyme reverse transcriptase
what do you call the mechanism which retrotransposons transpose
copy and paste, because they leave a copy behind
what is the enzyme which is encoded by transposon
transposase
what are two types of retrotransposons
LINE and SINE
what is LINE
long interspersed elements; have an element which encodes reverse transcriptase but lack LTRs
what is SINE
short interspersed elements; are non autonamous LINEs
what do you call the most abundant SINE in humans
Alu
How do we survive with so much mobile DNA in our genome?
- most transposable elements are found in the introns and therefore are removed during RNA splicing
- the vast majority of mobile elements are currently inactive and cannot move or increase in copy number
- most are relics and have been inactivated by mutations
- some are rendered inactive by host regulatory mechanisms
what is the overall frequency of mutation due to class 2 elements in humans
low, 0.2% of all mutations
