Lecture 22b Flashcards
What is Lineage Tracing?
This is when we attach a fluorescent protein to a cell & watch to see what forms from that original cell (aka its progeny).
What is “the identification of all progeny of a single cell”?
Lineage tracing
What is Fate Mapping?
A method used in developmental biology to study the embryonic origin of various adult tissues and structures.
What do Fate Maps show?
They show which parts of the embryo will develop into which tissue.
What is an example of Fate Mapping in humans?
Early in development, the human embryo is a disk but the cells in different parts of the disk have already been specified.
Which occurs first: cell determination or cell differentiation?
Cell determination
What is Cell Determination?
This is where a cell is destined/predetermined to become a particular cell type.
What is Cell Differentiation?
When a cell’s morphology and function have changed (usually permenantly) into a specialized cell type.
T/F: There aren’t any specific genes that cause cells to differentiate.
False! Researchers have identified specific genes that cause cells to differentiate into particular cell types.
These genes trigger undifferentiated cells to differentiate into their proper cell fates.
What are the 4 genes that initiate muscle development?
MyoD, Myogenin, Myf5, and Mrf4
What do MyoD, Myogenin, Myf5, and Mrf4 encode for?
Encode transcription factors that contain a basic domain and a helix-loop-helix domain.
What does a Basic Domain do?
Binds DNA and activates skeletal muscle specific genes.
What does a Helix-Loop-Helix Domain do?
It is necessary for dimer formation between transcription factor proteins.
Collectively, what are MyoD, Myogenin, Myf5, and Mrf4 called?
Myogenic bHLH proteins
Where are Myogenic bHLH proteins found?
Found in all vertebrates and even some invertebrates (Drosophila and C. elegans)
When are Myogen bHLH proteins activated?
During skeletal muscle development
What does the expression of Myogen bHLH proteins do?
Expressing them drives muscle development (the production of muscle).
What is the central issue in population genetics?
Genetic variation, specifically, its extent within populations, why it exists, and how it changes over the course of many generations.
What is a Gene Pool?
All of the alleles of every gene in a population.
Who contributes to the gene pool of the next generation?
Only individuals that reproduce contribute to the gene pool of the next generation.
What do Population Geneticists study?
Study the genetic variation within the gene pool and how it changes from one generation to the next.
What is a Population?
A group of individuals of the same species that occupy the same region and can interbreed with each other.
What are Local Populations?
A large population is usually composed of smaller groups, called local populations.
Members of a local population are far ______________ to breed with each other than with members of the general population.
likelier
What separates Local Populations from each other?
Moderate geographic barriers such as distance, rivers, etc.
Populations are typically dynamic and change from one generation to the next in what 3 things?
Size, geographic location, and genetic composition.
What is Polymorphism?
Refers to the observation that many traits display variation within a population.
A gene is ___________________ if it has 2 or more alleles that influence phenotype.
polymorphic
What is a Monomorphic Gene?
A gene that exists mainly as a single allele.
By convention, when a single allele is found in at least 99% of all cases, the gene is considered Monomorphic.
What is the main source of Polymorphism?
Single-nucleotide polymorphisms (SNPs), which account for 83% of genetic variation between people.
T/F: Genetic variation remains static over many generations.
False! Genetic variation changes over many generations.
What is Microevolution?
This describes changes in a population’s gene pool from generation to generation.
Name 5 factors that change allele frequencies.
Mutation, random genetic drift, migration, natural selection, and non-random mating.
What provides the source of genetic variation and drives genetic variability?
Mutations
What are Mutations?
Random events that occur spontaneously at low rates.
Mutagens ______________ the mutation rate.
Higher mutation rate = more variability.
increase
T/F: Mutational variability constitutes evolution by itself.
False! Mutational variability provides the raw material for evolution but does not constitute evolution itself.
Mutation can provide new alleles, but does not act as the major force dictating the final balance.
A new mutation can be what 3 things? What is it often and what is rare?
Beneficial, neutral, or deleterious.
Beneficial is relatively rare. It is more common for a mutation to be neutral or deleterious.
What is a Deleterious mutation?
A mutation that is not good for an organism. It makes it less likely to survive and weakens it.
What is Mutation Rate?
The probability that a gene will be altered by a new mutation, which varies from organism to organism.
What is the expression for Mutation Rate? What is it commonly in the range of per generation?
Number of new mutations in a given gene per generation.
Commonly in the range of 10^-5 to 10^-6 per generation.
What is Random Genetic Drift?
Random changes (usually neutral mutations) in allele frequencies due to chance fluctuations.
In other words, allele frequencies may drift from generation to generation as a matter of chance.
Over the long run, genetic drift favors either the _______ or the ___________ of an allele.
loss, fixation
How does population size impact the rate of random genetic drift?
Bigger population = slower genetic drift
Smaller population = faster genetic drift
Genetic drift ultimately operates in a ______________ manner with regard to allele frequency.
Over the long run, it leads to either allele fixation or elimination
directional
Some populations are geographically broken into small local populations which are more susceptible to what?
Genetic drift
What is Genetic Drift’s impact more significant on?
Small populations or small local populations
In smaller populations, allele frequency fluctuates _____________ from generation to generation.
In larger populations, allele frequency fluctuates ____________ from generation to generation.
substantially, much less
