MCAT LLJ15 Flashcards
Cellular __________________ describes the state of cell cycle arrest in aging cells
Senescence
Cell _____________________ describes the process when cells become committed to a certain developmental fate
Determination
Cell ________________ describes the process by which cells transform into more specialized cell types.
Differentation
True or false: Cell differentiation is irreversible
This statement is false. Cell differentiation in most cases does not reverse itself in normal human physiology, although cancer cells can become less differentiated, and pluripotency can be artificially induced.
What stem cell types are naturally found in adults?
Somatic stem cells, which include hematopoietic, intestinal, and mesenchymal stem cells, are found in adults
Mesenchymal somatic stem cells develop into ________________, _________________, and ______________ cells of the body
Adipose
Bone
Liver
What does totipotent mean?
A cell can differentiate into any cell type
When are cells totipotent?
Within the first 24 hours after fertilization
__________________ stem cells can give rise to all cell types of the body (but not the placenta).
Pluripotent
_________________ stem cells can develop into a limited number of cell types in a particular lineage.
Multipotent
Why is the lac operon considered negatively inducible?
The lac operon is referred to as under negative control because it involves a repressor. The lac operon is considered inducible because lactose metabolism is induced (i.e. turned on) instead of turned off, by certain environmental conditions
Regarding the lac operon: the ______________ binds to the operator, RNA polymerase binds to the _________________, allolactose binds to the ____________ to cause it to dissociate, and the CAP protein binds to the CAP binding site.
Repressor
Promoter
Repressor
In the trp operon, tryptophan binds to the _______________, which then binds the operator and halts transcription
Repressor
An individual is experiencing symptoms related to the lack of a specific protein. However, genetic analysis finds no mutation in the gene encoding this protein. If a mutation does indeed exist, it would most likely be found:
A mutation in the promoter sequence would prevent initiation of transcription entirely, resulting in a total lack of the relevant protein
____________________ and _________________ are forms of pre-transcriptional silencing
Methylation
Acetylation
Post-transcriptional silencing includes ___________________
RNA interference
The expression of lactose metabolism is blocked by the repressor binding to the operator, which blocks the activity of RNA polymerase. In order to express these genes, ________________ binds to the repressor, causing it to dissociate from the operator. For lactose metabolism genes to be strongly expressed, the CAP protein binds to the CAP binding site, facilitating RNA polymerase activity.
Allolactose
Place the elements of the lac operon in order from 5’ to 3’
The CAP binding site, the promoter, the operator, and structural genes lacZ, lacY, and lacA.
The RNA-induced silencing complex (RISC) is a ribonucleoprotein that uses RNA fragments to target complementary mRNA transcripts. This process is most accurately characterized as:
RNA interference
The lac operon is negatively ________________
Inducible
The trp operon is negatively _____________
Repressible
True or false: Promoters may occur thousands of base pairs away from the transcription start site of target genes.
This statement is false. Regulatory elements such as enhancers may be thousands of base pairs away from the start site of target genes, but promoters tend to be in close proximity upstream of target genes.
Messenger RNA (mRNA) is single-stranded RNA transcribed from DNA that will be translated at the ribosome into protein. __________________ and ______________________ are single- and double-stranded RNA sequences, respectively, that target complementary mRNA sequences for destruction, which is known as RNA silencing.
microRNA
small interfering RNA (siRNA)
_________________ and _______________ are regulatory sequences that are bound by repressors and activators, respectively, to regulate expression of target genes. RNA polymerase initially binds the promoter sequence before transcribing the target gene.
Silencers
Enhancers
Place the following events of the acrosome reaction in the correct order: sperm travels through the zona pellucida, sperm travels through the corona radiata, sperm nucleus enters egg, and sperm travels through the Fallopian tubes
The correct order of events are as follows: first, the sperm travels through the Fallopian tubes, before reaching the oocyte and surrounding layers. It then travels through the corona radiata, then the zona pellucida. The sperm nucleus entering the egg is the last major event of the acrosome reaction, after the sperm has travelled up the Fallopian tubes and penetrated the outer layers of the egg.
Arrange the following stages of early embryonic development in the proper order from earliest to latest: morula, zygote, gastrula, and blastocyst.
Zygote, morula, blastocyte, gastrula
The urinary bladder derives from the __________________.
Endoderm
The _________________ differentiates into the muscles, blood, bone, heart, kidneys, and gonads
Mesoderm
The skin, eyes, nervous system, and nose derive from the _________________
Ectoderm
A rod of ___________________ cells forms the notochord
Mesoderm
The formation of the notochord induces the formation of the _________________ just above it from ectoderm cells
Neural plate
The neural plate invaginates to create neural folds and a central neural groove. The folds then meet and fuse to form the _________________
Neural tube
The notochord forms during neurulation, which occurs after ______________. The blastocoel forms during ____________________. This is a process that precedes gastrulation. Polar body formation occurs during ________________. This is a process that precedes gastrulation.
Gastrulation
Blastula development
Oogenesis
_____________ is a tumor suppressor protein that is encoded by the TP53 gene
p53
What are the two major functions of p53?
To initiate DNA repair as needed and to initiate apoptosis when DNA damage is too extensive
____________________ are genes that normally promote cell growth and division but can lead to cancer when they get mutations that cause them to express their protein product at inappropriately high levels
Proto-oncogenes
_______________ strain refers to the strain created by eclipsing substituents on neighboring atoms
Torsional
Epoxides form a small, 3-membered ring between a single oxygen and two carbons. This implies a high degree of ________________ strain, which is why epoxides are far more reactive than their parent group, ethers, despite also featuring an oxygen bound to two different carbon atoms
Angle
________________________ are isomers that differ in spatial arrangement of atoms, rather than order of atomic connectivity
Stereoisomers
______________________ is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds
Conformational
A _________________ is an atom bound to at least three unique groups such that a new stereoisomer is formed if two of these groups are switched
Stereocenter
What is the equation for enatomeric excess?
enantiomeric excess = (observed optical rotation*100) / specific rotation
! The number of stereoisomers of a molecule is equal to ______________, where n denotes the number of chiral centers in the molecule
2^n
