E153 final Ques ons and answers updated 2026
genes are distributed __________ along the chromosome,some por ons of the eukaryo c
chromosome are characterized by very low gene density values
unevenly
Chromosomal banding pa erns reflect gene density
dark bands are?
faint bands are?
dark bands are gene depleted, faint bands are gene enriched
gene density correlated with gc content, gc content varies across genome, isochore model of
genome orginiza on is
mostly vertrbates genomes can be envisoned by a mosiac of alterna ng pieces called isochores
display diffrent levels of gc content and gene density
giemsa staining
AT rich-
GC rich-
at- dark band
gc- faint bands
Chromosomal regions with high gene density values also feature high gc content and
correspond to faint bands upon Giemsa staining
genome size in prokaryotes is correlated with number of genes but in eukaryotes the size varies
tremendously
genes represent small frac on of genome in some eukaryo c species
genome size and organismal complexity are poorly connected, c value paradox, 1st aspect lack
of precise correla on between organismal complexity and genome size if proxy used for
complexity is genes then its g value paradox, c value amount of dna in haploid cell
genes represent a small frac on of genome in some eukaryo c species
coding component of genome represents small por on in eukaryo c genomes, 47% of genome
is diffrent types of repeats
less complex organisms have more compact and coding efficent genomes, higher gene density
, genome size in eukaryotes influnced by mul ple factors, factors: regulatory sequnce complexity,
number of genes include more copies of genes, whole genome duplica on events, presence of
long introns-longer gene-larger genome
major contributor to diffrence in genome size in eukaryotes is the frac on of genome wide
repeats, c value paradox second aspect- rela vely closely related species can differ greatly in
genome size
diffrences in genome size among eukaryotes is due to longer genes and par culary extra
noncoding dna than diffrences in number of genes, genome size depends on strenght of diffrent
processes with opoosed effects
classes of transposable elements
transposons, mobile elements or genome wide or interspred or complex repeats, diversity of
dna segments tht can in a process called transposi on, move duplicate from one loca on in
genome to other
rna transposons= retrotransposns= class 1
two types
NonLTR retroelements
Lines-autonomus, ORF ORF2 AAA
Sines- non autonomus blocks then AAA
then retrovirus like elements which include, rertroelement LTR, have LTR, autonomus- LTR gag
pol LTR
or non autonomus LTR-gag-LTR
CLASS II DNA TRANSPOSON
IR-tranpose-IR autonomus
non autonomus IR-deleteion-IR
transposi on events can be conserva ve or replica ve, conserva ve no increase in copy and
paste, replica ve increase in copy and paste, type of repeats are dna transposons via dna
intermediate or an rna transposons, retrotransposib then transcrip on and reverse
transcrpi on, then retrotransposon copy
transposi on can occur in both soma c cells and in germ line
rna transposons- LTR cytoplasm (reverse transcriptase)
non-LTR Nucleus (reverse transcriptase)
most of rest of eukaryotes have genomes that harbor larger frac on of TEs
genes are distributed __________ along the chromosome,some por ons of the eukaryo c
chromosome are characterized by very low gene density values
unevenly
Chromosomal banding pa erns reflect gene density
dark bands are?
faint bands are?
dark bands are gene depleted, faint bands are gene enriched
gene density correlated with gc content, gc content varies across genome, isochore model of
genome orginiza on is
mostly vertrbates genomes can be envisoned by a mosiac of alterna ng pieces called isochores
display diffrent levels of gc content and gene density
giemsa staining
AT rich-
GC rich-
at- dark band
gc- faint bands
Chromosomal regions with high gene density values also feature high gc content and
correspond to faint bands upon Giemsa staining
genome size in prokaryotes is correlated with number of genes but in eukaryotes the size varies
tremendously
genes represent small frac on of genome in some eukaryo c species
genome size and organismal complexity are poorly connected, c value paradox, 1st aspect lack
of precise correla on between organismal complexity and genome size if proxy used for
complexity is genes then its g value paradox, c value amount of dna in haploid cell
genes represent a small frac on of genome in some eukaryo c species
coding component of genome represents small por on in eukaryo c genomes, 47% of genome
is diffrent types of repeats
less complex organisms have more compact and coding efficent genomes, higher gene density
, genome size in eukaryotes influnced by mul ple factors, factors: regulatory sequnce complexity,
number of genes include more copies of genes, whole genome duplica on events, presence of
long introns-longer gene-larger genome
major contributor to diffrence in genome size in eukaryotes is the frac on of genome wide
repeats, c value paradox second aspect- rela vely closely related species can differ greatly in
genome size
diffrences in genome size among eukaryotes is due to longer genes and par culary extra
noncoding dna than diffrences in number of genes, genome size depends on strenght of diffrent
processes with opoosed effects
classes of transposable elements
transposons, mobile elements or genome wide or interspred or complex repeats, diversity of
dna segments tht can in a process called transposi on, move duplicate from one loca on in
genome to other
rna transposons= retrotransposns= class 1
two types
NonLTR retroelements
Lines-autonomus, ORF ORF2 AAA
Sines- non autonomus blocks then AAA
then retrovirus like elements which include, rertroelement LTR, have LTR, autonomus- LTR gag
pol LTR
or non autonomus LTR-gag-LTR
CLASS II DNA TRANSPOSON
IR-tranpose-IR autonomus
non autonomus IR-deleteion-IR
transposi on events can be conserva ve or replica ve, conserva ve no increase in copy and
paste, replica ve increase in copy and paste, type of repeats are dna transposons via dna
intermediate or an rna transposons, retrotransposib then transcrip on and reverse
transcrpi on, then retrotransposon copy
transposi on can occur in both soma c cells and in germ line
rna transposons- LTR cytoplasm (reverse transcriptase)
non-LTR Nucleus (reverse transcriptase)
most of rest of eukaryotes have genomes that harbor larger frac on of TEs
