Biology Flashcards
What does the nucleolus do? Is it membrane-bound in the nucleus? What cells is it in?
site of rRNA synthesis (ribosome assembly)
Not membrane-bound
All nuclear cells (so no anuclear cells like RBCs)
ER is the synthesis site for three things mainly:
lipids
hormones
proteins
A macrophage phagocytizes a radioactive-labeled bacterium. Where in the cell do we expect to see it?
a) ER
b) Golgi
c) mitochondria
d) lysosomes
Lysosomes
Macrophages consume and destroy pathogens, so bacterium is sent to lysosomes for breakdown
What function does the Golgi have:
I. glycosylation
II. lipid synthesis
III. protein sorting
I and III only
- glycosylation: protein modification where glycans attach to proteins and lipids
- lipid synthesis happens in the ER, not Golgi
- protein sorting is a classic fxn
Pinocytosis is an example of:
endocytosis
Na+ and K+ channels are ____-gated channels whereas Cl- channels that are mediated by GABA are ____-gated channels
voltage; ligand
Where does ß-oxidation of long-chain fatty acids take place?
peroxisomes (has a shit ton of H2O2)
What major role does clathrin play?
vesicle coating
hemidesmosomes vs desmosomes
hemidesmosomes are cell-basement
desmosomes are cell-cell
what are two major things that happen during prophase?
- the unraveled DNA (chromatin) will condense into chromosomes
- centrioles create cell poles along which the chromosomes will align
List out the sequence of the fertilization stage in embryonic development, from the diploid primary oocyte undergoing its 1st meiotic division to the formation of the zygote.
diploid primary oocyte →meiosis I→ haploid secondary oocyte → sperm meets secondary oocyte in fallopian tube most of the time → sperm releases acrosomal (digestive) enzymes that help penetrate the zona pellucida → sperm grows out acrosomal process that fuses with oocyte’s cell membrane to inject pronucleus into oocyte → Ca2+ release → allows secondary oocyte to undergo meiosis II → ovum (mature egg) + pronucleus of sperm = zygote (1-cell)
During fertilization, the Ca2+ release after the sperm’s pronucleus enters the secondary oocyte also does what and for what purpose besides just initiating meiosis II?
triggers cortical rxn
Ca2+ released → cortical GRANULES are released which make zona pellucida IMPASSABLE (to PREVENT POLYSPERMY!)
List out the progression of the zygote’s growth in the morulation and blastulation stages.
zygote → morula → blastula → gastrula (“My Baby Grows”)
morula: solid mass of undifferentiated cells
What are the two components of the blastula and what do they each consist of?
blastocoel (cavity in blastula) + outer cells
outer cells = trophoblast + inner cell mass
trophoblast: extraembryonic (ultimately not part of embryo) cells that give rise to placenta, chorion, and amniotic sac that all support fetus as it grows
inner cell mass: consisted of embryonic (pluripotent) stem cells that will then undergo gastrulation
What is gastrulation? What are the three primary germ layers?
the process of when the INNER MASS CELLS develop into 3 primary germ layers: ectoderm (epiblast), mesoderm, endoderm
What does the ectoderm (epiblast) give rise to?
hair, epidermis, eyes, nervous system, EPITHELIUM OF UPPER RESPIRATORY TRACT
What does the mesoderm give rise to?
systems: musculoskeletal, circulatory, genitourinary, lymphatic
others: adipose and connective tissue, adrenal cortex
What does the endoderm give rise to?
internal organs: lungs, pancreas, liver, bladder, GI TRACT, OVARIES, DISTAL URINARY TRACT
T/F: Neurulation happens after gastrulation, and once the neurulation is complete, embryogenesis is completed.
TRUE
After neurulation, embryogenesis is completed and then the fetus keeps growing until all its organs have matured enough
What structure does the anterior part of the baby’s spinal column derive from? What germ layer cells does it derive from?
notochord
mesodermal (musculoskeletal, so in charge of making bone such as spinal column)
Cells from what structure ultimately develop into the CNS? That structure comes from what?
____ releases molecules that cause cells from which germ layer to fold inward and create what a ____ down the length of the embryo surface?
neural tube, which comes from neural groove
Notochord, ectodermal (gives rise to nervous system), groove (which is the neural groove)
What cells develop the PNS and where are those cells located? What other things do these cells develop into?
neural crest cells
located around the neural tube
other: melanocytes, calcitonin-producing cells in the thyroid, sensory and autonomic ganglia
What cells develop the PNS and where are those cells located? What other things do these cells develop into?
neural crest cells
located around the neural tube
other: parasympathetic NS (nerves), melanocytes, calcitonin-producing cells in the thyroid, sensory and autonomic ganglia
If the neural tube does not completely close, what condition does this lead to?
spina bifida
T/F: sympathetic and parasympathetic NS is autonomic, unlike the somatic NS which is voluntary
TRUE
SPNS, PSPNS, and ANS = involuntary
SNS = voluntary
Parasympathetic vs sympathetic NS based on primary NT it releases and their association with glycogen
Para NT: acetylcholine (plays a role in ↓ HR) VS Symp NT: norepinephrine
Para: ↑ glycogen storage VS Symp: depletion of glycogen storage to usable glucose
T/F: Sodium leak channel and sodium/potassium pumps are moderated by APs.
FALSE: they are NOT moderated by APs
Where do voltage-gated sodium channels primarily exist? What do they propagate?
along the axon
APs
When do voltage-gated calcium channels open? What does this allow?
When AP reaches the axon terminal
allow Ca2+ influx → NT release
What structure maintains the negative membrane potential in order to prepare the cell membrane for an AP and how does it do this?
Na+/K+ pump
moves more cations out of the cell (3 Na+ out) than it brings into the cell (2 K+ in)
Depolarization is primarily facilitated by:
voltage-gated sodium channels
Repolarization is primarily facilitated by:
voltage-gated potassium channels
Hyperpolarization occurs for why and for what?
voltage-gated potassium channels stay open longer than needed
To get back to resting potential!
summation
integration of multiple subthreshold signals and can trigger an AP
When does depolarization occur in terms of AP?
START of AP, once it has already been triggered
When does repolarization occur in terms of AP? For what purpose?
AFTER AP has already been triggered
To bring membrane potential back to resting state
When does hyperpolarization occur in terms of AP? Specifically after what stage in AP firing?
AFTER AP has already been triggered
after REPOLARIZATION
Where does the sensory nerve transmit impulses from and to? What is an example of a sensory nerve?
sensory organs → CNS
ie. nerve impulse from OPTIC NERVE → visual cortex → occipital lobe
Where does the effector nerve transmit impulses from and to? What is an example of an effector?
CNS → effectors (ie. muscles, glands)
T/F: Motor nerves are specialized effector nerves which transmit impulses to muscles only
TRUE
Where does the autonomic nerve exist? What is it connected to and what does it do?
spinal cord + brainstem
internal organs
control involuntary actions
The parasympathetic and sympathetic nervous systems are both ____ systems to one another that act on organs such as the ____, _____, and _____ system.
antagonistic
heart, eyes, digestive system
What is the pathway of a simple reflex arc? Does it directly involve higher-order structures like the brain? What is the spinal cord’s role in simple reflex arcs and what does this allow?
afferent (sensory) → interneuron → efferent (motor)
No
houses interneurons b/w afferent and efferent neurons, allowing for fast transmission by circumventing the need for processing in the brain
What gland does the sympathetic NS act upon to increase blood sugar levels during the “fight-or-flight” response? What is the primary hormone released by the gland to do this?
pancreas
glucagon
The sympathetic NS sends impulses to the adrenal gland, releasing what hormone?
norepinephrine
T/F: epinephrine and norepinephrine are primarily released by the adrenal gland, specifically the adrenal cortex.
FALSE
It is the adrenal gland, but specifically adrenal MEDULLA!!
What gland does the parasympathetic NS act upon to decrease blood sugar levels during the “rest-or-digest” response? What is the primary hormone released by the gland to do this?
pancreas
insulin
T/F: Dendrites receive and transmit chemical (NTs) impulses directly but do not receive nerve (electric) impulses directly.
FALSE
They ONLY receive chemical impulses directly and do not receive nerve impulses directly
THEY DON’T TRANSMIT JACK SHIT, BOTH CHEM AND ELEC!
rapid/methodical firing of subthreshold excitatory and inhibitory neurons would result in:
canceling each other out
methodical firing of subthreshold excitatory neurons would result in:
not enough additive effect to generate AP
rapid firing of subthreshold excitatory neurons would result in:
summation, which would most likely result in AP!
T/F: Not all hormones are proteins or produced in the brain, but all are chemical messengers used by glands to communicate with cells and tissues
TRUE
Glucagon is released by _____ in pancreas to ____ blood glucose levels
α-cells
increase
trophic vs direct hormones
trophic: act on other endocrine glands to facilitate the release of direct hormones (more indirect pathway)
direct: act directly on tissues or cells
DNA _____ of ___ and ____ bases at gene promotors can inhibit transcription by hindering the ability of ___ polymerase to transcribe
methylation
A + C
RNA
The addition of ___, ____, and ____ groups to _____ can make DNA more accessible for transcription by decreasing their ____ for DNA.
methyl, ACETYL, phosphate (“MAP groups on the histone!”)
histone
affinity
RNA polymerase I vs II vs III based on what genes they transcribe
I: rRNA genes (EXCEPT for 5S rRNA gene)
II: mRNA, miRNA, snRNA, snoRNA genes
III: tRNA and 5S rRNA genes
RNA polymerase I vs II vs III based on where they reside
I: nucleolus (core of nucleus)
II and III: nucleoplasm (cytoplasm in nucleus)
RNA polymerase I vs II vs III based on what process they PRIMARILY catalyze
I: transcription of ONLY rRNA (EXCEPT 5S rRNA)
II: DNA-directed mRNA synthesis
III: transcription of small untranslated RNAs (ie. tRNAs)
Which ribosomal subunit binds to the mRNA first? Which one has the A, P, and E sites?
small
large
3 general steps that happen in the initiation stage of translation
- small subunit binds to mRNA before the start codon
- AUG on mRNA is paired with either Met/fMet tRNA
- large subunit locks in place, bringing A, P, and E sites with it
3 general steps that happen in the elongation stage of translation
- aminoacyl tRNA (tRNA w/ AA) binds at the A site
- The growing AA chain on the aminoacyl tRNA at the P site gets transferred over to aminoacyl tRNA at the A site by peptidyltransferase
- The aminoacyl tRNA at the A site (with the new AA + the existing growing chain) moves over to the P site, and the now empty tRNA on the P site moves over to the E site → exits the ribosome to be recycled
3 general steps that happen in the termination stage of translation
- stop codons read by the ribosome
- a protein called release factor comes + binds to the A site which releases the new protein (polypeptide chain)
- The ribosome subunits separate and release the ribosome from the mRNA + tRNAs
What are the 3 stop codons?
UAA = U Are Annoying UGA = U Go Away UAG = U Are Gone
Prokaryotes vs eukaryotes in the initiation stage of translation in terms of what the small subunit binds to (step 1) and what the AUG on mRNA is paired with (Step 2)
Step 1
Pro: binds to Shine-Dalgarno sequence
Euk: binds to 5’ cap (NOT THE SAME THING AS KOZAC SEQ!)
Step 2
Pro: fMet tRNA
Euk: Met tRNA
List the scale (from smallest → largest) of DNA organization, starting from the DNA double helix.
DNA double helix → nucleosomes (10 nm chromatin) → nucleofilament (30 nm chromatin) → loops attached to scaffolding proteins (30 nm fiber forms) → heterochromatin (higher-order packaging)
Everything before heterochromatin is euchromatin!
euchromatin vs heterochromatin in terms of DNA wounding, accessibility for transcription, and activity levels.
Euchromatin vs heterochromatin (in this order, respectively)
DNA wounding: unwounded (loose) VS highly wounded (tight)
Accessibility for transcription: accessible VS inaccessible
Activity levels: more active VS less active
Southern blot vs PCR in terms of its purpose and when gel electrophoresis is executed
Southern blot vs PCR (in this order, respectively)
Purpose: to ID + quantify cells VS to mass-produce DNA
GE: denaturing as well as hybridizing DNA w/ probe is done AFTER GE VS denaturing + hybridizing DNA to desired primer is done BEFORE GE
Which enzyme catalyzes transcription? What guides the enzyme where to bind and what does it bind to itself in order to do this?
RNA polymerase II
transcription factors (TF) bind to response elements (located in promoter regions of every gene)
General TFs vs Specific TFs in terms of function and purpose
General vs specific TFs (in this order, respectively)
Fxn: recruits RNA Pol II and unwinds DNA helix VS binds to specific enhancers (specific response element only found in some genes)
Purpose: ensures transcription happens (transcription cannot happen without general TFs) VS regulate gene expression by acting as enhancers or repressors
2 general steps that happen in the initiation stage of transcription (What do TFs may have to do with this?)
- RNA polymerase II binds to a specific region (different in pro and euk) in the promotor (upstream of the actual start site) that signal the binding site for RNA polymerase
- DNA helicase unwinds DNA
(TFs may bind to the promoter to help signal that RNA Pol should bind + may aid in unwinding DNA)
2 general things RNA polymerase does simultaneously in the elongation stage of transcription
- matches RNA bps based on template (antisense) strand
2. catalyzing new phosphodiester backbone that binds between growing mRNA and next RNA nucleotide
What is rho protein? What process is it involved in for which organisms?
a protein that combines onto a specific RNA sequence
prokaryotic termination stage of transcription
Explain the rho-dependent mechanism for prokaryotic termination stage of transcription
Rho binds onto a specific RNA sequence which introduces steric strain → tugs on RNA and pulls it away from RNA pol → mRNA is immediately ready to be translated
RNA pol seals DNA strands and detaches to go find another gene to transcribe
Explain the rho-independent mechanism for prokaryotic termination stage of transcription
GC rich seq in DNA is transcribed to GC rich seq of mRNA → GC rich mRNA seq forms a little loop which introduces steric strain → tugs mRNA away from DNA → mRNA is immediately ready to be translated
RNA pol seals DNA strands and detaches to go find another gene to transcribe
Prokaryotes vs eukaryotes in the initiation stage of transcription in terms of:
- what region of the promoter the RNA pol binds to
- what base pairs that region is rich in
- how far away it is from the actual start site
Region of promoter RNA pol binds to
Pro: Pribnow Box (aka -10 sequence, or even TATA box)
Euk: TATA box
Base pairs the region is rich in
Pro and Euk: A + T
Distance from actual start site
Pro: 10 bp upstream (aka -10 sequence)
Euk: 25-35 bp upstream
What are the 5 components of a mature eukaryotic mRNA that has undergone post-transcriptional modifications?
- 5’ cap
- 5’ UTR
- Exons only
- 3’ UTR
- 3’ Poly-A tail
5’ cap structure and fxn
structure: backward guanine nucleotide (G)
fxn: PREVENTS mRNA degradation by exonuclease (this enzyme recognizes the 5’ cap and can’t chew it off!)
What is the 5’ UTR? Is it generally translated into protein? What is its significance? What important sequence does it contain for pro and euk?
An untranslated region next to the 5’ cap and directly upstream of exons
No
ribosome relies on it to bind mRNA and initiate translation
Pro: Shine-Dalgarno sequence
Euk: Kozak sequence
What are the 3 things that PCR requires? Does it also require restriction enzymes?
primers (complementary to DNA that flanks target seq)
nucleotides (dNTPs)
DNA polymerase (Taq polymerase)
NO
What is the significance of the 3’ poly-A tail? What are the downstream effects the longer the poly-A tail is?
DELAYS mRNA degradation (exonucleases can STILL chew of As one by one)
LONGER poly-A tail → ↑ time mRNA intact → ↑ total protein prod.
What is the 3’ UTR? Is it generally translated into protein? What is its significance? Is it in both pro and euk?
An untranslated region next to the exons and directly upstream of the 3’ poly-A tail
No
often forms secondary structures that help stabilize the mRNA OR
recognized by specific enzymes that degrade transcript
Yes
T/F: Both prokaryotes and eukaryotes have 5’ cap and 3’ poly-A tail
FALSE
Pro does NOT have any of those! Only have 5’ and 3’ UTR
What process is cell differentiation and specialization regulated by?
a) translation
b) transcription
c) alternative splicing
d) post-translational modification
B
SELECTIVE TRANSCRIPTION
What is leakage in evolution?
gene flow, the introduction of new alleles from one species to another
incomplete penetrance
a genetic trait is expressed in only a proportion of the population
variable expressivity
degree of phenotypic variation in individuals with the same genotype
Some people that have the mutated BRCA 1 gene get breast cancer but some don’t. Is this incomplete penetrance or variable expressivity?
incomplete penetrance
heterozygous vs hemizygous
heterozygous vs hemizygous (in this order, respectively)
each chromosome has the copy of the gene vs only one chromosome has the copy of the gene
What means nullizygous? What doe these mutations cause?
2 null alleles for the same gene
complete loss of fxn
multifactorial inheritance
more than 1 factor or multiple genes cause an inherited condition
cytoplasmic inheritance
transmission of genetic material outside the nucleus from parent to offspring
ie. microorganism in a symbiotic relationship with its eukaryotic host confer its beneficial phenotype to offspring
What is hybrid vigor? What are 4 examples of traits that can experience hybrid vigor? What can this increase the chance of?
improved traits in hybrid offspring
growth rate, biomass, stress tolerance, fertility
fitness
What is the probability of double crossover?
the pdt of their recombinant frequencies
T/F: when the question shows you two sister chromatids and shows you the distance of the genes, the probability of crossover occurring between the genes can be directly translated by the literal portrayal by the lengths between them
TRUE
T/F: There are more Y-linked than X-linked disorders
FALSE
There are more X-linked than Y-linked disorders because the X chromosome is bigger
T/F: X-linked recessive disorders are more common in females and X-linked dominant disorders are more common in males
FALSEEE!!!
X-linked recessive = more common in MALES b/c only need one recessive allele to get the disease
X-linked dominant = more common in FEMALES b/c has two X chromosomes, which increases the risk of inheriting the X chromosome that’s dominant for the disease
What is a mutagen? What are two things that mutagens result in?
DEF: agents that cause genetic mutations
What is a mutagen? What are two things that mutagens result in in terms of cell differentiation and cell division?
DEF: agents that cause genetic mutations
↓ degree of cell differentiation
uncontrolled cell division
T/F: Meiosis is consisted of 2 rounds of DNA replication and followed by 2 rounds of cell division
FALSE
1 ROUND OF DNA REPLICATION + 2 ROUNDS OF CELL DIVISION
T/F: non-sister chromatids of homologous chromosomes exchange genetic material in meiosis
TRUE
What is a tetrad? What is it formed by? What stage of meiosis is it in? What are two components of it?
DEF: group of 4 sister chromatids of a homologous pair of chromosomes
formed by synapsis
Prophase I
pair of homologous chromosomes + synaptonemal complex (zipper-like structure associated with the synapsis of homologous chromosomes)
