Unit IV Recitation Quizzes and Learning Objectives
how many sets of histone molecules are in each nucleosome
8
first step of DNA replication
DNA primase initiate DNA replication; form RNA primers on both strands at a replication fork
series of DNA coiling
DNA wrapped around histone proteins (form nucleosome); nucleosome compacted into chromatin fibers; chromatin fibers coil into looped domains; looped domains compacte, forming chromosomes
transcription termination
RNA polymerase recognizes a termination sequence of bases; RNA polymerase separates from the template DNA; in Eukaryotic RNA polymerase adds 10-35 nucleotides to mRNA after it passes termination
fourth step of DNA synthesis
RNA primer is degraded and gaps filled in with other DNA polymerase; leaves a nick
DNA is duplicated during __________ of the cell cycle
S phase
what 3 molecules are involved in translation
mRNA, tRNA, and ribosomes
nontemplate strand
may not code for a protein
The correct number of chromosomes is maintained during sexual reproduction by
meiosis, which reduces the chromosome number by half
The mitotic spindle is made of:
microtubules
difference between mitosis and cytokinesis
mitosis is process in which cell information is duplicated and separation in two begins; cytokinesis is when cytoplasm divides
_________ are the building blocks of DNA
nucleotides
telophase I
one of each pair of homologous chromosomes is at each pole; cytokinesis occurs
During which phase does crossing-over occur
prophase I
Homologous chromosomes undergo synapsis during
prophase I
4 stages of M phase
prophase, metaphase, anaphase, telophase
Which of the following represents the overall sequence of events during mitosis?
prophase, metaphase, anaphase, telophase
translation initiation
small subunit binds to mRNA; initiator tRNA binds to start codon in mRNA (AUG); large ribosomal subunit bonds
In essentially all organisms, the AUG codon codes for:
the initiation of translation
transcription
the synthesis of RNA molecules complimentary to DNA
what base is different in DNA
thymine
A sequence of bases located upstream from a reference point occurs
towards the 5' end of the mRNA sequence
The final product of DNA replication is
two DNA molecules, each of which contains one new and one old DNA strand
Introns in pre-mRNA are known to:
undergo excision, whereby they are spliced out of the message
what base is different in RNA
uracil
template strand
used for transcription
plant cell cytokinesis
vesicles gather on midplane; small vesicles fuse together forming larger vesicles (eventually one large vesicle); new cell walls and new plasma membrane formed
can template and nontemplate strands switch with each different gene
yes
does more than one codon specify most amino acids
yes
Initiation of transcription requires:
a promoter sequence
kinetochore
a protein structure to which microtubules bind during mitosis
The 5' end of each Okazaki fragment begins with
a separate RNA primer
The 5' end of each Okazaki fragment begins with:
a separate RNA primer
During prophase I, each chiasma represents:
a site of crossing-over
The 3' end of eukaryotic pre-mRNAs are changed by:
adding 100−250 adenine nucleotides
translation elongation
adding amino acids to a growing polypeptide; hydrogen bonds formed between tRNA and mRNA; ribosome shifts one codon to the right
Uracil forms a complementary pair with __________ in RNA and __________ in DNA.
adenine; adenine
nonsense mutation
amino acid converted to a stop codon prematurely
Ribose differs from deoxyribose by having
an extra hydroxyl group
During which of the following stages of meiosis do the sister chromatids separate?
anaphase II
RNA polymerase
binds nucleotides to RNA
A site
binds the tRNA delivering the next amino acid
P site
binds the tRNA holding the growing chain
Single Strand Binding Protein (SSB)
binds to single strands of DNA and prevents the helix from reforming before it can be used as a template for replication
Topisomerase
breaks one or both DNA strands preventing excessive coiling during replication and rejoins them in a more relaxed configuration
which direction is RNA synthesized
5' to 3'
If a DNA template strand has a sequence of 3'TACAATGTAGCC5' then the RNA produced from it will be which sequence
5'AUGUUACAUCGG3'
start code
AUG
Which of the following adds new nucleotides to a growing DNA chain
DNA polymerase
second step of DNA replication
DNA polymerases extend the leading and lagging strand copies from the RNA primers in a 5' -> 3' direction
Which of the following is NOT a criterion for an organism's genetic material?
The genetic material must be dynamic, changing rapidly in response to changes in the environment
G2 function
cell growth, increased protein synthesis
G1 function
cell growth, normal metabolism, positive signals sends to S phase
mutagens
chemical and radiation
early prophase
chromosomes condense, spindles form, centrioles migrate to poles
telophase
chromosomes decondence, spindle disassemble, nuclear envelope forms, cleavage furrow begins forming
metaphase II
chromosomes line up along cell's midplane
chromosome
condensed DNA
What type of bond links nucleotides
covalent
significance of meiosis
creates genetic diversity
how is genetic diversity formed by meiosis
crossing-over and independent assortment; sexual reproduction
The sources of genetic variation during meiosis are
crossing-over and the random assortment of maternal and paternal chromosomes
cytokinesis
cytoplasmic division; cleavage furrow deepens as waistband tightens, pinches cells apart
DNA from any source contains about the same amount of guanine as __________
cytosine
Which purine base forms 3 hydrogen bonds when binding its complementary nucleotide
guanine
meiosis I
homologous chromosomes separate
anaphase I
homologous chromosomes separate and move to opposite poles; sister chromatids remain attached at their centromere
prophase I
homologous chromosomes synapse and exchange segments by crossing-over; nuclear envelope breaks down
release factor
hydrolysis bond between peptide chain and tRNA
3 stages of transcription
initiation, elongation, termination
The cell cycle of a typical somatic cell consists of ___________ and M phase
interphase
2 stages of cell cycle
interphase, M phase
splicing
involves snRNPs (small nuclear riboneucleoprotein complexes); RNA within intron may splice itself without enzyme
A replication fork
is a Y-shaped structure where both DNA strands are replicated simultaneously
If a cell is in G2:
it has twice the amount of DNA present in telophase
Eukaryotic chromosomes consist of
linear DNA molecules complexed with nucleosomes
The enzyme DNA ligase is responsible for:
linking short DNA segments
DNA ligase
links Okazaki fragments by joining the 3' end of the new DNA fragment to the 5' end of the adjoining DNA
transposons
movable sequences of DNA that "jump" into the middle of a gene, inactivate it
telophase II
nuclei form at opposite poles of each cell; cytokinesis occurs
late prophase
nucleolus disappears, nuclear envelope breaks down, chromosomes captured by spindle, chromosomes move towards midline
promotor
nucleotide sequence in DNA to which RNA polymerase and associated proteins initially bind
helicase
opens the double helix at replication forks by disrupting the hydrogen bonds that hold the two strands together
homologous chromosomes
paired chromosome, carry information about the same genetic trait, but not always the same information
dispersive replication
parent and new strands become randomly mixed
A ______ bond holds the amino acids of a growing polypeptide chain together during the elongation stage of translation
peptide
what type of bond joins amino acids to form proteins
peptide bonds
The nucleotides within DNA are composed of a:
phosphate group, deoxyribose sugar and nitrogenous base
Griffith
pneumococcus into mice; S strain (virulent) R strain (avirulent); living S cells, mice die; killed S cells mice live; living and killed R cells live; killed S + live R large portion die
nucleosome
positively charged histones associated with DNA (negative charge from photon groups) forming a protein core around which DNA winds
Watson & Crick
proposed model of DNA
ribosome subunits
protein and rRNA
missense mutation
protein function may be changed; one amino acid different
Which of the following is NOT a component of the translation machinery
protein polymerase
histones
proteins that facilitate chromosome packaging
Is adenine a purine or pyrimadine?
purine
mutational hot spots
regions of DNA more likely than others to undergo mutation
what sugar is RNA
ribose
molecular chaperones
ribosome-associated proteins help fold newly synthesized polypeptide chain into 3D shape
where is the site of translation
ribosomes
Avery, MacLeod, McCarty
separated S cells; separated S cells into lipids, proteins, polysaccharides, and nucleic acids; tested each part to see if it could transform R cells into S cells; lipids, polysaccharides, proteins did not cause transformation; nucleic acids were tranformed
meiosis II
separates chromatids
codon
sequence of 3 consecutive bases
triplet code
series of codons that specifies amino acid sequence
base substitution 3 types
silent, missense, nonsense
mRNA
single RNA strand that carries information for making a protein
tRNA
single RNA strand that folds back on itself to form a specific shape; transfers amino acid to ribosome
mitosis
single cell division which produces 2 daughter cells that are genetically identical
haploid
single set of chromosomes
anaphase II
sister chromatids separate, and chromosomes move to opposite poles
anaphase
sister chromatids separate, chromatids move towards respective poles, pulled by shortening of spindle
__________ contain identical DNA sequences and are held together by __________ during mitosis
sister chromatids; centromeres
chiasmata
sites of prior crossing-over
The information carried by DNA is incorporated in a code specified by the:
specific nucleotide sequence of the DNA molecule
metaphase
spindle microtubules line up chromosomes at cell's metaphase plate; each chromatid faces opposite pole, pushed along spindle
binary fission
splitting in two
translation termination
stop codon reached; protein release factor binds to mRNA; remaining parts of translation complex dissociate
rRNA
structural part of ribosome with catalytic function needed during protein synthesis
backbone of DNA
sugar-phosphate backbone
DNA primase
synthesizes short RNA primers on the lagging strand that begins replication of the leading strand
Which of the following contains the anti-codons used during translation?
tRNA
E site
tRNA that have delivered amino acids exit the ribosome
Meselson & Stahl
tested DNA replication; supported semiconservative replication
During prophase I of meiosis, homologous chromosomes lie side by side. This phenomeon is known as
tetrad formation
metaphase I
tetrads line up on cell's midplane; tetrads held together at chiasmata
Frameshift mutations result from:
the insertion or deletion of one or two base pairs
dimensions of DNA
0.34 nm, 3.4 nm, 2.0 nm
how many strands is RNA
1
sister chromatid
1 of 2 identical replicated chromosomes
how many chromatin are in a chromosome
2
how many strands is DNA
2
semiconservative replication
2 chains separate, each strand pairs with new complementary nucleotides to replace the missing pair
Which of the following best describes semiconservative replication
A DNA molecule consists of one parental strand and one new strand
fifth step of DNA synthesis
Okazaki fragments linked by a DNA ligase that repairs nick to form continuous strand
stop codes
UAA, UGA, UAG
conservative replication
2 parent strands remain together, 2 newly synthesized strands would form second double helix
transcription elongation
2 phosphate are removed from each nucleotide as they are added to the 3' end of the RNA; remaining phosphate becomes part of the sugar-phosphate backbone; last nucleotide has exposed 3' hydroxyl
diploid
2 sets of chromosomes
aminoacyl-tRNA synthetases
20 enzymes (1 for each amino acid); covalently links tRNA to amino acids
In a human cell at prophase I, there are __________ tetrads
23
How many nucleotides are contained in a single codon?
3
3', 5' phosphodiester linkage
3' carbon of one sugar is linked to 5' carbon of next sugar
structure of DNA
3' carbon of one sugar is linked to 5' carbon of next sugar
Which of the following nucleotide sequences represents the complement to the DNA strand 5' − AGATCCG- 3'?
3' − TCTAGGC- 5'
One of the mRNA codons specifying the amino acid leucine is 5'-CUA-3'. Its corresponding anticodon is
3'-GAU-5'
mRNA modification (post transcription)
5' cap (stabilizes and allows ribosomes to bind), poly-A tail at 3' end (exports mRNA from nucleus, stabilizes mRNA, initiation of translation)
Central Dogma
DNA codes for RNA, which codes for proteins
Which of the following causes the unwinding of the DNA double helix
DNA helicase
third step of DNA replication
DNA polymerase slides along; leading strand toward fork, lagging strand away from fork; Okazaki fragments are short segment of strand beginning with RNA primer
3 stages of interphase
G1, S, G2
What enzyme is responsible for the synthesis of mRNA
RNA polymerase
transcription initiation
RNA polymerase recognizes a promoter, unwinds the RNA double helix and initiates transcription
silent mutation
a change in a base that yields the same polypeptide sequence
DNA replication
a chromosome becomes duplicated so that it consists of two identical sister chromatids that later separate at anaphase; genetic material must be precisely duplicated and distributed to the daughter cells
centromere
a point of chromosome constriction that binds kinetochore proteins; links sister chromatids
To prevent disastrous consequences, the eukaryotic cell cycle is controlled by
a series of cell cycle checkpoints
Hershey & Chase
bacteria, 35S, 32P, viruses; S in protein, P in nucleic acid; S in supnatant (not injected into cell); P in pellet (injected into cell)
Watson-Crick model
because nucleotides pair with each other in complimentary fashion, each strand of the DNA molecule could serve as a template for synthesizing the opposite strand
small subunit
binding site for mRNA, initiation proteins
EPA site
binding sites for tRNA
Cytokinesis in plant cells begins with the formation of a(n)
cell plate
gametes
cells produced in meiosis; reproductive cells
significance of mitosis
cells receive identical chromosomes; growth and repair of body tissues
check points
check for proper coding before continuing in cell cycle
During prophase, __________ is(are) compacted into visible chromosomes
chromatin
prophase II
chromosomes condense again following brief period of interkinesis; DNA does not replicate again
S phase function
chromosomes replicate & histone synthesis
genetic code
codons for amino acids and for start and stop signals
scaffold protein
coiled chromatin attaches to larger nonhistone proteins
zygote
combination of 2 gametes (egg & sperm cell unite)
Hydrogen bonds can form between guanine and __________, and between adenine and __________.
cytosine; thymine
frameshift mutation
deletions or insertions
what sugar is DNA
deoxyribose
DNA components
deoxyribose (pentose sugar), phosphate, one of four nitrogenous bases
In an animal cell, a zygote (fertilized egg) contains the __________ complement of chromosomes
diploid
ploidy of zygote
diploid
meiosis
diploid cell undergoes genetic rearrangement and two successive nuclear divisions; resulting in 4 genetically different haploid daughter cells
introns
do not code; get removed
Nucleosomes are best described as
eukaryotic DNA associated with histone proteins
exons
expressed sequences that are parts of the protein-coding sequence
ploidy of gametes
haploid
what bonds hold together nitrogenous bases
hydrogen bonds
where does transcription occur
in the nucleus
where does translation occur
in the ribosomes
The RNA segments laid by DNA primase are responsible for
initiating DNA synthesis
Interrupted coding sequences include long sequences of bases that do not code for amino acids. These noncoding sequences, called __________, are found in __________ cells.
introns; only eukaryotic
In DNA replication, the lagging strand
is synthesized as a series of Okazaki fragments
The kinetochore serves which of the following functions
kinetochores attach to microtubules during mitosis
DNA polymerase
links nucleotide subunits to form a new DNA strand complementary to a DNA template
tRNA recognizes codons in the:
mRNA strand
DNA serves as the template for
mRNA, tRNA, and rRNA
