Genetics Final Study Set 1
Telophase
Nuclear membrane begins to reform around each separated chromosome Chromosomes begin to condense Cleavage furrow forms
Prometaphase
Nuclear membrane fully breaks apart into vesicles Centrosomes move to opposite ends of cell Spindle apparatus fully formed Kinetochore microtubules begin to form and capture sister chromatids
Metaphase
Sister chromatids align along the metaphase plate Kinetochore microtubules are attached to each dyad on opposite poles
Anaphase
Sister chromatids are pulled apart towards opposite poles of cell Chromatids become individual chromosomes Kinetochore microtubules shorten, which move the chromosomes to opposite ends of the cell Polar microtubules lengthen to elongate the cell
Prophase
Sister chromatids condense Microtubules begin to form the spindle apparatus Centrosomes begin to move apart Nuclear membrane begins to break
Okazaki Fragments
Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
Transcription Initiation
RNA polymerase binds to promoter
Iron Regulatory Protein
RNA-binding protein that influences the two mRNAs that encode ferritin and the transferrin receptor
Chargaff's Rule
% adenine = % thymine; % cytosine = % guanine
rho-Independent Termination
1. Stem-loop causes RNA polymerase to pause 2. During this pause, the weakly bound U-rich sequence is not able to hold the RNA-DNA hybrid together, causing termination
rho-Dependent Termination
1. rho protein binds to the rut site in RNA and moves towards the 3' end 2. RNA polymerase transcribes a region that forms a stem-loop and then proceeds to the terminator 3. Stem-loop causes RNA polymerase to pause 4. During this pause, the rho protein proceeds to the open complex and separates the RNA-DNA hybrid
Complete Turn of Helix =
10 bp and 3.4nm
5' Cap
7-methylguanosine cap structure is recognized by cap-binding proteins
Telomerase
An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells
Operator
DNA element at one end of the operon that is the binding site for the repressor, which regulates expression by controlling access of RNA polymerase to the promoter
Hemimethylation
DNA sequence with one methylated strand and one unmethylated strand
Promoters
DNA sequences that direct the exact location for initiation of transcription as well as specifies the direction of transcription
Cis-Acting Elements
DNA sequences that only affect a particular nearby gene on the strand that they are on TATA Box Enhancers Silencers
Combination Control
Describes the way in which groups of transcription regulators work together to regulate the expression of a single gene One or more activator proteins One or more repressor proteins
Positive Control Conditions for lac Operon
Glubose Absent, Lactose Present
Negative Control Conditions for lac Operon
Glucose Present, Lactose Absent Glucose Present, Lactose Present
I+ Z- Y+ / F' I- Z+ Y+
I+ is dominant to I-
I+ Z+ Y+
I+ is inducible
I- Z- Y+ / F' I+ Z+ Y-
I+ is trans-acting
I- Z+ Y+
I- is constitutive
Coding Strand
The strand of DNA that is not used as a template during transcription; also called the sense strand.
Stop Codons (Translation Termination)
UAG UAA UGA
O+ Z+ Y+ / F' O+ Z- Y+
Z+ is dominant to Z- (synthesis of both enzymes is induced)
Pachytene (Prophase 1)
a bivalent has formed and crossing over has occurred
Iron Response Element
a cis sequence found in certain mRNAs whose stability or translation is regulated by cellular iron concentration
Basal Transcription
a low level of transcription resulting from just the core promoter
Genomic Imprinting
a marking process that occurs during gametogenesis in which an offspring expresses a gene that is inherited from one parent but not both
Enzyme Adaptation
a particular enzyme only appears in the cell after the cell has been exposed to the enzyme's substrate
Trans-Acting Factors
a regulatory protein that binds to a regulatory element in the DNA and modifies its expression
Transformation
a segment of DNA from a dead bacterium is absorbed by a living bacterial cell and incorporated into the bacterial chromosome
A Site
accepts incoming aminoacyl-tRNA (charged-tRNA)
Gram-Positive
acteria that have a thick peptidoglycan layer that stains purple when Gram stain is used
CpG Islands - CpG Sites
adjacent C-G base pairs
Small Effector Molecules (Allosteric Effectors)
affect transcription regulation by binding to regulatory proteins (repressors/activators)
Translation Elongation
amino acids are added to the polypeptide chain one at a time
Antisense RNA
an RNA strand that is complementary to mRNA, which when synthesized will regulate translation
preRC
assembly of this structure begins eukaryotic replication
Auxotrophs
bacteria that are unable to synthesize essential nutrients
Gram-Negative
bacteria that have a thin peptidoglycan layer that stains pink when Gram stain is used (more dangerous)
Conjugation
bacterial DNA is transferred from one to another through direct contact
Coupling
bacterial mRNA transcription and translation occurs at the same time in the cytoplasm
oriC
bacterial origin of replication
Specialized Transduction
bacteriophage genetic material can cut itself out (excise) of the host chromosome, which could imprecisely cut out some of the host chromosome with it
Corepressors
bind to repressors and cause them to bind to DNA
MCM Helicase
binding of this protein complete DNA replication licensing
H3K9me3
binds to heterochromatin protein 1 (HP1) to direct histone deacetylation and DNA methylation, resulting in repression
GAL80
blocks GAL4 from activating transcription
Full Methylation
both DNA strands are methylated
Proteolytic Cleavage
breaking of bonds between amino acids in proteins
DNA Helicase
breaks hydrogen bonds between DNA strands
Catabolite Repression
caused by presence of glucose, lactose will break down into glucose and galactose, which will stop lac operon expression via CAP
G2 Phase
check to make sure that cell has all materials needed for cell division
Exonucleases
cleave a covalent bond between two nucleotide at one end of a strand
Endonucleases
cleave bonds within a strand
Swi2-Snf2
coactivator of transcription: repositions the nucleosome and exposes the promoter
Exporter
complex of 10 to 15 proteins encoded by the F factor that pumps DNA/relaxase into the recipient cell during conjugation
trp mRNA Leader Sequence
contains an attenuator region and two tryptophan codons
Mediator
controls the switch to the elongation phase in eukaryotic transcription
G1 Phase
copies of organelles are made, checks that materials needed for DNA replication are present, and checks for any present mutations
H2A, H2B, H3, H4
core histones, form an octamer through a pair of each
DNA Methyltransferase
covalently attaches methyl groups to DNA, inhibiting eukaryotic transcription by inhibiting the binding of an activator protein
DNA Ligase
covalently links the DNA backbones in Okazaki fragments together
Avery, Macleod, and McCarty
discovered that DNA was the genetic material by purifying each macromolecule, only treatment with DNase eliminated transformation
Watson and Crick
discovered the double helix structure of DNA based on the work of other scientists
Barbara McClintock
discovered transposable elements by studying corn
AG-GU Rule
each intron is cut at each end and these intron ends almost always have GU at the 5' end and AG at the 3' end
GAL1, GAL2, GAL7, and GAL10
encode enzymes that catalyze steps in the biochemical pathway that converts galactose into glucose
trpL
encodes a short peptide called the leader peptide
lacl Gene
encodes the lac repressor protein
trpR
encodes the trp repressor protein
Transcription Termination
end of RNA synthesis occurs when the short RNA-DNA hybrid of the open complex is forced to separate, which releases the newly made RNA as well as the RNA polymerase
DNA Replication Licensing
ensures that DNA replication is initiated only once per cell cycle and prevents genetics material that could lead to instability or disease from being replicated
Aminoacyl-tRNA Synthetase
enzyme that attaches an amino acid to specific tRNAs There are 20 of these enzymes, one for each amino acid
Phosphatase
enzyme that removes phosphate group from another enzyme
Shine-Dalgarno Sequence
facilitates the binding of mRNA to the 30S subunit in prokaryotes
F+
formed after a bacterial cell with F factor conjugates with an F- cell do not transfer any of their chromosome to recipient cell
cAMP
formed from ATP in the presence of low glucose
Hfr Strain
formed when an F factor integrates into the bacterial chromosome, then transferring a portion of the bacterial chromosome to a recipient cell during conjugation
Heterogamous
gametes are morphologically different
Isogamous
gametes are morphologically similar
Generalized Transduction
genes picked up by the phage can come from any part of the bacterial genome
Operon
group of genes operating together
Housekeeping Genes
groups of genes that express a relatively constant level of expression in most cells and tissues of an organism
Naturally Competent Bacteria
have the ability to freely absorb DNA from the environment
Enhanceosomes
help recruit transcriptional machinery
Sex-Influenced Traits
heterozygous males and females have different phenotypes
Heterochromatin
highly condensed chromatin
P Site
holds the tRNA that is linked to the growing polypeptide chain
Upstream Activator Sequences (UAS)
if deleted, genes are silent
X-Inactivation
in females, compensates for the single X chromosome in males by inactivating extra X chromosomes to turn them into Barr bodies, which is maintained throughout somatic cell division
Inducer
increases transcription by binding to either regulatory protein Binding to a repressor will cause stop it from inhibiting transcription Binding to an activator will cause it to bind to DNA
Allolactose
inducer molecule that binds to lac repressor and prevents it from binding to DNA strand
GCN5
interacts with histones using acetyltransferase to activate genes
Ferritin
iron storage protein
Single-Stranded Binding Proteins
keep the strands of DNA separate during replication
GAL4
key regulator of pathway with 2 domains: Activation domain required for regulatory activity DNA-binding domain associates with UAS
H1
linker histone binds to DNA linker region helps organize adjacent nucleosomes
ter Sequences (only found in prokaryotes)
locate on the opposite side of the oriC
Euchromatin
loosely packed chromatin
Attenuation
mechanism by which an operon transcribes some but not all of its products
Torpedo Model
model for eukaryotic termination: 1. An exonuclease binds to the 5' end of the RNA that is still being transcribed and degrades it in the 5' to 3' direction 2. Exonuclease catches up to RNA pol II and causes termination
Allosteric Model
model for eukaryotic termination: RNA polymerase II is destabilized and dissociated from the DNA after transcribing the polyA signal sequence
Conservative Model
model where both parental strands stay together after replication
Semiconservative Model
model where double-stranded DNA contains one parental and one daughter strand after replication
Dispersive Model
model where parental and daughter DNA segments are interspersed in both strands after replication
Polycistronic mRNA
molecules of mRNA that code for multiple proteins
Translational Repressors
most common translational regulatory protein, inhibiting translation
polyA Tail
most mature mRNAs have a string of adenine nucleotides at their 3' ends that is enzymatically added after the gene is transcribed
Transposon
moved to a new target site in DNA turing simple transposition
Retrotransposon
moved via an RNA intermediate during retrotransposition
Transcription Elongation
new nucleotides are added to RNA strand
Maternal Effect
non-Mendelian inheritance pattern where the genotype of the mother directly affects the phenotype of the offspring
Diakinesis (Prophase 1)
nuclear membrane breaks apart and prophase 1 ends
Epigenetics
occur when a modification of a gene or chromosome affects gene expression, but the modification is not permanent over many generations
Incomplete Penetrance
occurs when a dominant trait is not expressed in and individual that carries it
Incomplete Dominance
occurs when a heterozygote has an intermediate phenotype between its parental phenotypes
Variable Expressivity
occurs when individuals have the same genetic composition but express a spectrum of traits
Material Inheritance
occurs when organelles, such as mitochondria or chloroplasts, are transmitted via the egg
Epistasis
occurs when the alleles of one gene mask the phenotypic expression of the alleles of a different gene
Codominance
occurs when the heterozygote expresses both alleles at the same time without having an intermediate phenotype
Overdominance
occurs when the heterozygote has an advantage and greater reproductive success over homozygotes
Complementation
occurs when two individuals with similar recessive phenotypes produce offspring with a wild-type phenotype
O+ Z- Y+ / F' Oc Z+ Y
operator is cis-acting
Oc Z+ Y+
operator is constitutive (lac operon is always expressed regardless of lactose presence)
O+ Z+ Y+
operator is inducible (synthesis of both enzymes is induced)
Synapsis
pairing of two chromosomes that occurs during meiosis
Enhancer-Blocking Insulators
prevent enhancer activation
Operon Components
promoter, operator, structural genes
GAL3
promotes GAL operon expression Both a sensor and inducer
Archibald Garrod
proposed that there was a relationship between genes and protein production through study of homogentisic acid oxidase
Relaxosome
protein complex that recognizes origin of transfer (DNA sequence) and makes a cut in the DNA during conjugation
tus
protein that binds to ter sequences, stopping the movement of the replication fork
Transferrin
protein that transports iron in the blood
Transcription Factors
proteins that bind to regulatory elements and influence the rate of transcription
Meiosis 2
reduces the 2 daughter cells from meiosis 1 from diploid to haploid (2n→1n, two sets of chromosomes to one) starts with half the genetic content seen in mitosis
Regulatory Transcription Factors
regulate the rate of transcription of target genes by influencing the ability of RNA polymerase to begin transcription of a gene
Xic
regulates X-inactivation
Repressors
regulatory protein that binds to cis-acting regulatory DNA element, such as a promoter or enhancer, to inhibit transcription (negative control)
Activators
regulatory protein that binds to cis-acting regulatory DNA elements to increase or activate transcription of an adjacent promoter (positive control)
Silencers
regulatory sequences that inhibit transcription
Enhancers
regulatory sequences that stimulate transcription
Core Promoter
relatively short DNA sequence within eukaryotic genes necessary for determining the precise start point of transcription
Induction
relief of repression of a gene/genes under negative control
Topoisomerase II (DNA Gyrase)
removes positive supercoiling ahead of the replication fork
DNA Polymerase I
removes the RNA primer and replaces it with DNA
DNA Pol II, IV, and V
repair and replicate damaged DNA
Nucleosome
repeating structural unit of eukaryotic chromatin
Sister Chromatids
replica of eukaryotic chromosomes formed before cell division
Leptotene (Prophase 1)
replicated chromosomes condense
S Phase
replication of chromosomes
General Transcription Factors (GTFs)
required for binding of RNA polymerase to core promoter
Regulatory Elements
short DNA sequences that affect the ability of RNA polymerase to bind to the core promoter (often found in the -50 to -100 region)
AraC Protein
singular binding protein in the arabinose operon that is an: activator in the presence of arabinose repressor without arabinose present
Allosteric Site
site on a protein that binds to a small effector molecule, modifying the activity of its active site
DnaA Boxes
sites for the binding of DnaA protein
GATC Methylation Sites
sites that help to regulate DNA replication
AT-Rich Regions
sites where the DNA strands separate
ORC
six subunit complex that acts as the first initiator in eukaryotic DNA replication
RNA Interference
small RNAs called microRNA (miRNAs) and short, interfering RNA (siRNAs) silence the translation of mRNA
Inhibitors
small effector molecule that binds to activators and prevent them from binding to DNA
Methionine
start codon in eukaryotes
Formylmethionine
start codon in prokaryotes
Senescent
state of cells when their telomeres are too short, causing them to lose their ability to divide
lacY
structural gene that codes for permease which transport lactose into the cell
lacZ
structural gene that modifies lactose into allolactose and cleaves the lactose molecule in order to yield glucose and galactose
Frederick Griffith
studied Streptococcus pneumoniae to discover transformation
Jacob and Monod
studied enzyme adaptation by analyzing lactose metabolism in E. coli
40S, 60S
subunits of eukaryotic ribosomes
30S, 50S
subunits of prokaryotic ribosomes
Is
super-repressor mutation that prevents expression even in the presence of an inducer
Zygotene (Prophase 1)
synapsis begins and the synaptonemal complex begins to form
Diplotene (Prophase 1)
synaptonemal complex dissociates
Primase
synthesizes RNA primer
DNA Polymerase III
synthesizes new DNA only in the 5' to 3' direction
E SIte
tRNA that has given up its amino acid is let go by the ribosome at this site
Ubiquitination
targets a protein for degradation using ubiquitin
Template Strand
the DNA strand that is transcribed
DNA Pol III Holoenzyme
the complex of all 10 subunits of DNA pol III
Feedback Inhibition
the final product in a pathway inhibits an enzyme that acts early in the pathway
Law of Segregation
the two copies of a parental gene separate into individual copies, with one from each parent being passed down to offspring
Sex-Limited Traits
traits expressed only in one sex, causing sexual dimorphism
X-Linked Inheritance
traits found on X chromosome are more common in males than females unless the trait is dominant
Blending Hypothesis
traits from each parent blend together to form an intermediate offspring
Spermatogenesis
two cells produced, one stays a spermatogonial cell while the other becomes a primary spermatocyte (which goes through both stages of meiosis)
Heterogametic
two different types of gametes
Law of Independent Assortment
two genes will randomly sort their alleles during meiosis
Sporophyte
undergoes meiosis to produce haploid spores, which then divide by mitosis to produce the gametophyte
Meselson and Stahl
used light and heavy nitrogen to distinguish daughter and parental strands in bacterial DNA replication
Hershey and Chase
used radioactive phosphorus to label DNA and radioactive sulfur to label proteins in T2 phages (transduction)
Testcross
used to map distance between two or more linked genes done by breeding an individual heterozygous for 2+ genes with an individual that is homozygous recessive for the same genes
Positive-Effect Variegation (PEV)
when genes are relocated to heterochromatic regions, causing genes to be silenced
G0
when no cell division occurs and the cell is only maintaining homeostasis
Synteny
when two or more genes are located on the same chromosome and are linked
Isoacceptor tRNAs
when two or more tRNAs that differ at the wobble base are able to recognize the same codon
Prototrophs
wild-type bacteria that grow on minimal media