MCB 150 Exam 3 UIUC | 2025/2026 Updated
Guide | Practice Questions & Verified
Answers
Nucleoplasm - answers substance of a cell nucleus
Chromatin Fibers - answers DNA and protein
Nucleolus - answers site for rRNA synthesis and processing assembly of subunits
Nuclear Pore Complex - answers particles can pass through this
Nuclear Lamina - answers Network of proteins that provide attachement for
heterochromatin and give the nucleus shape
Who proposed that there were functional domains of nucleus? - answers Rabl
What can visualize and identify chromosomes? - answers Flourescence
Functional Domains of Nucleus - answers each chromosome occupies a distinct
territory within the nucleus and is arranged in an organized fashion. nuclei are divided
into discrete funtional domains that play an important role in regulating gene expression
and in replication
How many focis of replication are in the human nucleus? - answers greater than 100
The cell cycle consists of what? - answers M phase and interphase (G1, S phase, G2)
G1 Phase - answers cell is growing and preparing for s phase
S phase - answers when DNA synthesis occurs (replication), longest interphase cycle
G2 phase - answers make sure you are ready to go through next round of m phase
M phase - answers mitosis and cytokinesis (division of mother cell into two identical
daughter cells)
Early replication has what gene density? - answers high gene density, euchromatin
Late replication has what gene density? - answers low gene density, heterochromatin
Nucleolus - answers ribosome production facility, site for rRNA synthesis, rRNA
processing, assembly of ribosomal subunits
,what are the 4 types of rRNA? - answers 5s, 5.8s, 18s, 28s
How many copies does the human cell have of 5.8s, 18s, and 28s rRNA genes? -
answers about 280
how many copies does the human cell have of 5s rRNA genes? - answers about 2000
Tandem arrays - answers when 5.8s, 18s, and 28s rRNAS are transcribed by
polymerase 1 into pre rRNA
45S GENES - answers processed into 5.8s, 18s, and 28s rRNAS are found on human
chromosomes 13, 14, 15, 21, and 22
Where are 5s rRNA genes found in huge array? - answers chromosome 1
Nucleolar organizing regions - answers arrays of 45s rRNA genes, nucleolus forms
around these NOR, so if cell is not actively transcribing 45s rRNA genes, there will be
no nucleus
3 distinct regions of nucleolus - answers fibrillar region or center
dense fibrillar region
granular zone
mutations - answers heritable changes in the DNA
What mutations are in single cell organisms? - answers all daughter cells have the
same mutation
What mutations are in multi cell organisms? - answers Either somatic of germ-line
Somatic mutation - answers non sex cell, passed to daughter cells in area
germ line mutation - answers sex cell, passed to new organisms
Why are mistakes in transcription/translation not as critical? - answers many copies of
RNA are produced, RNAS are not heritable over multiple generations
How often do errors in DNA replication occur? - answers 4 mutations in 100 cell
divisions
proof reading - answers 3'-5' exonuclease activity, a DNA polymerase's backspace key
methyl directed mismatch repair in e. coli - answers 1. mutH cuts nonmethylated strand
2. an exonuclease removes base just beyond mismatch
3. DNA polymerase III fills in the gap
, 4. ligase seals the nick
base substitution mutations - answers replace one base pair with another
same sense mutations - answers nucleotide (usually third position) changed to a
different codon that specifies the same amino acid, no effect on protein product/function
missense mutation - answers single nucleotide change results in a codon that codes for
a different amino acid, changes protein product/function
nonsense mutation - answers codon specifying an amino acid is changed to a stop
codon, this causes premature termination, protein is virtually always inactive (null
phenotype)
framshift mutation - answers addition or removal of a small number of bases not
divisible by 3, disrupts normal reading frame in the mRNA, all codons after the change
are altered, usually results in premature appearance of a stop codon (truncation)
What is the effect of an in frame removal of 3 bases? - answers loss of 1 amino acid,
rest of protein is unaffected
Disorders caused by chromosomal level mutations? - answers lymphomas, leukemias,
oncogenes, fragile x syndrome, huntington's disease, infertility, haemophilia A, muscular
dystrophy
What are chromosomal level mutations? - answers insertion, deletion, duplication,
inversion, translocation (reciprocal)
Mitosis - answers division of nucleus
Cytokinesis - answers division of cytoplasm
Inner membrane nuclear envelope - answers lipid bilayer that faces nucleoplasm
Outer membrance nuclear envelope - answers lipid bilayer that faces cytoplasm
Traffic through NPC - answers Small molecules (MW <20kDa) can pass through
(passive diffusion)
Large Molecules (MW >60kDa) require energy, GTP to pass through (active transport)
ex. is RNAS and proteins
Nuclear localization signal or NLS - answers keeps cytoplasmic proteins out of nucleus
bc it needs an NLS to pass through
What is chemical character of example sequence of NLS - answers Pro Lys Lys Lys Arg
Lys Val
Guide | Practice Questions & Verified
Answers
Nucleoplasm - answers substance of a cell nucleus
Chromatin Fibers - answers DNA and protein
Nucleolus - answers site for rRNA synthesis and processing assembly of subunits
Nuclear Pore Complex - answers particles can pass through this
Nuclear Lamina - answers Network of proteins that provide attachement for
heterochromatin and give the nucleus shape
Who proposed that there were functional domains of nucleus? - answers Rabl
What can visualize and identify chromosomes? - answers Flourescence
Functional Domains of Nucleus - answers each chromosome occupies a distinct
territory within the nucleus and is arranged in an organized fashion. nuclei are divided
into discrete funtional domains that play an important role in regulating gene expression
and in replication
How many focis of replication are in the human nucleus? - answers greater than 100
The cell cycle consists of what? - answers M phase and interphase (G1, S phase, G2)
G1 Phase - answers cell is growing and preparing for s phase
S phase - answers when DNA synthesis occurs (replication), longest interphase cycle
G2 phase - answers make sure you are ready to go through next round of m phase
M phase - answers mitosis and cytokinesis (division of mother cell into two identical
daughter cells)
Early replication has what gene density? - answers high gene density, euchromatin
Late replication has what gene density? - answers low gene density, heterochromatin
Nucleolus - answers ribosome production facility, site for rRNA synthesis, rRNA
processing, assembly of ribosomal subunits
,what are the 4 types of rRNA? - answers 5s, 5.8s, 18s, 28s
How many copies does the human cell have of 5.8s, 18s, and 28s rRNA genes? -
answers about 280
how many copies does the human cell have of 5s rRNA genes? - answers about 2000
Tandem arrays - answers when 5.8s, 18s, and 28s rRNAS are transcribed by
polymerase 1 into pre rRNA
45S GENES - answers processed into 5.8s, 18s, and 28s rRNAS are found on human
chromosomes 13, 14, 15, 21, and 22
Where are 5s rRNA genes found in huge array? - answers chromosome 1
Nucleolar organizing regions - answers arrays of 45s rRNA genes, nucleolus forms
around these NOR, so if cell is not actively transcribing 45s rRNA genes, there will be
no nucleus
3 distinct regions of nucleolus - answers fibrillar region or center
dense fibrillar region
granular zone
mutations - answers heritable changes in the DNA
What mutations are in single cell organisms? - answers all daughter cells have the
same mutation
What mutations are in multi cell organisms? - answers Either somatic of germ-line
Somatic mutation - answers non sex cell, passed to daughter cells in area
germ line mutation - answers sex cell, passed to new organisms
Why are mistakes in transcription/translation not as critical? - answers many copies of
RNA are produced, RNAS are not heritable over multiple generations
How often do errors in DNA replication occur? - answers 4 mutations in 100 cell
divisions
proof reading - answers 3'-5' exonuclease activity, a DNA polymerase's backspace key
methyl directed mismatch repair in e. coli - answers 1. mutH cuts nonmethylated strand
2. an exonuclease removes base just beyond mismatch
3. DNA polymerase III fills in the gap
, 4. ligase seals the nick
base substitution mutations - answers replace one base pair with another
same sense mutations - answers nucleotide (usually third position) changed to a
different codon that specifies the same amino acid, no effect on protein product/function
missense mutation - answers single nucleotide change results in a codon that codes for
a different amino acid, changes protein product/function
nonsense mutation - answers codon specifying an amino acid is changed to a stop
codon, this causes premature termination, protein is virtually always inactive (null
phenotype)
framshift mutation - answers addition or removal of a small number of bases not
divisible by 3, disrupts normal reading frame in the mRNA, all codons after the change
are altered, usually results in premature appearance of a stop codon (truncation)
What is the effect of an in frame removal of 3 bases? - answers loss of 1 amino acid,
rest of protein is unaffected
Disorders caused by chromosomal level mutations? - answers lymphomas, leukemias,
oncogenes, fragile x syndrome, huntington's disease, infertility, haemophilia A, muscular
dystrophy
What are chromosomal level mutations? - answers insertion, deletion, duplication,
inversion, translocation (reciprocal)
Mitosis - answers division of nucleus
Cytokinesis - answers division of cytoplasm
Inner membrane nuclear envelope - answers lipid bilayer that faces nucleoplasm
Outer membrance nuclear envelope - answers lipid bilayer that faces cytoplasm
Traffic through NPC - answers Small molecules (MW <20kDa) can pass through
(passive diffusion)
Large Molecules (MW >60kDa) require energy, GTP to pass through (active transport)
ex. is RNAS and proteins
Nuclear localization signal or NLS - answers keeps cytoplasmic proteins out of nucleus
bc it needs an NLS to pass through
What is chemical character of example sequence of NLS - answers Pro Lys Lys Lys Arg
Lys Val
