Lecture 1 Flashcards
Genetics
Genetics uses manipulation of genes/genomes to study how genes function in fundamental biological processes
Gene
A heritable unit. usually corresponds to a locus on a usually continuous stretch of RNA or DNA. encodes a diffusible gene product
What do we mean by diffusible gene product
Mobile gene product
What are the gene products encoded by a gene?
either RNA or protein or both
Gene locus
specific place on chromosome where the gene is
What are the two functions of a gene
Operational Function
Transmission Function
Operational Function of a gene
contains information encoding a gene product (usually an RNA and a protein)
Transmission Function of a gene
a gene carries information from one generation to the next
Centromere
Middle part of chromosome
Chromatid
A “strand” of a chromosome
T/F regulatory sequences are not included in our definition of gene
False
Gene includes both regulatory sequences and the transcribed region
Genomics
The study/cataloging of entire genomes and their gene products
Genetics vs. genomics approach
Genomics: Identify genes that RESPOND to a stimulus
Genetics: identify genes that are REQUIRED for a biological process
How does the genomic approach work
Compare tissues from individuals that receives stimulus vs. those that didn’t
How does the genetic approach work
Find mutants that don’t perform the response
Forward genetics
genes are first identified because of their mutant phenotype. Later, the mutations are mapped to the corresponding gene, and the gene is then characterized by molecular/cellular/biochemical tools.
Advantage of forward genetics
Unbiased, you can identify genes no one has ever linked to the biological process you’re studying
Disadvantage of forward genetics
Slow. Identifying mutated gene can be tricky.
Reverse genetics
You mutate the gene of your choice. This approach may be used to remove the entire gene or just change specific sequences to alter/test its function.
Advantage of reverse genetics
Extremely specific and versatile, allows you to manipulate genes with high precision.
Disadvantage of reverse genetics
Biased (tests the known unknowns).
You may waste your time
The gene you “knocked out” may not have an obvious phenotype.
Tests only a single gene at a time.
Is the following forward or reverse genetics?
You are studying eye development in the mouse. After mutagenizing mice, you identify several mutant mouse strains that display a range of eye phenotypes. After identifying the genes that are mutated, you are studying how these genes relate to eye development.
Forward
Is the following forward or reverse genetics?
You want to know in which process a particular gene is involved or how a specific mutation affects the function of the gene product (e.g. enzyme activity).
Reverse
Is the following forward or reverse genetics?
You are studying immune responses in Drosophila. In a computer search, you find a gene that has some similarity to a known regulator of the anti-bacterial defense system. To test whether this new gene plays a role in immunity, you remove the entire gene and test whether the resulting flies are immune-compromised.
Reverse
Is the following forward or reverse genetics?
You let the animal “tell you” what genes are required in a specific process.
forward
In the car factory analogy, what is the biochemists approach?
Take car apart, work hard all day to analyze components car is made off, and see how they relate to each other.
In the car factory analogy, what is the geneticist’s approach?
Disable individual workers in the morning (before they enter the factory) by tying their hands and watch at the end of the day how it affects the cars coming out of the factory.
Cell biology
Study cells directly (e.g. by Microscopy) to learn about fundamental cellular processes
Biochemistry
Study biological phenomena on a molecular level to understand the mechanistic aspects of a process (e.g. protein-protein interactions)
What discipline does modern molecular genetics fall under?
All four
Genomics, genetics, biochem, cell biology
Preformatism
We used to think that sperm contained a preformed human
What would happen without reduction of genetic information?
You would get 100% of genetic information from mom, and 100% from dad, the child would have double the amount of genetic information, the enxt gen would have quadruple, etc
T/F the mixing of parental genetic information is random, each parent can “donate” any fraction, as long as the two fractions add up to 100%
False
The mixing of genetic ingo is 50% + 50%
What can dna do?
Encode information
Be replicated
Be passed on
Have variation
Most common definition of genotype
The genetic information with respect to a single gene or a group of genes.
Less common def of a genotype
Entire genetic information inherited by an organism: Refers to ALL of the specific information stored in the genome.
Genotype vs. genome
Genotype: refers to information stored in genetic material
Genome : refers to the genetic material itself
Definiton 1 of phenotype
The form taken by some character (or group of characters) in a specific individual (e.g. high blood pressure, be it due to genetic or environmental factors (e.g. obesity).
Definition 2 of phenotype
Any detectable manifestation of a specific genotype, regardless of whether it is morphological, behavioral, physiological or molecular etc. (e.g. a change in enzyme activity or the ability to run longer distances or run faster).
Extended pheotypes
Proposed by Richard Dawkins
Argues that phenotypes should not be limited to organismal traits
Would apply to gene-dependent, visible impacts on habitats, driven by behaviors
Reaction norm
Certain traits have flexibility and respond differently to different environments
Ex: limiting nutrients can restrict growth
What definition of pheotype would apply here:
You have two genetically identical plants, but one was exposed to stress and is shorter
Definition 1. Genetically similar but phenotypically different
What is the Central dogma of molecular biology
DNA codes RNA through transcription
RNA codes Protein through translation
Gene expression
Information stored in DNA is accessed through the process of transcription (‘copying’) into (messenger) RNA molecules
Genetic variation
Describes differences among individuals within a population
Polymorphisms
relatively frequent discontinuous variants in a population
Morphs
An individual with a polymorphism
race/subspecies
form a geographically isolated and distinct population.
Mutants
Rare discontinuous variants in a population
Mutation
a process that introduces a lasting change into the genetic material (DNA or sometimes RNA). If the change occurs in the germline, the mutation can be passed from parent to offspring. In somatic cells, mutations are transferred to daughter cells.
Point mutation
A type of mutation that affects only a single nucleotide. This may cause changes in gene expression and / or affect the function of the corresponding gene product.
Chromosomal alterations and changes in number
multiple genes are affected by the loss, rearrangement, reattachment of a chromosome
Continuous variation
Refers to traits for which the phenotypes change gradually
Discontinuous variation
Traits that fall into distinct groups
Is this continuous or discontinuous variation:
adult height in human beings
Continuous
Is this continuous or discontinuous variation:
human eye color
Discontinuous
Is this continuous or discontinuous variation:
Morphs and mutants
Discontinuous
Alleles
different versions of the same gene in a population (or in a single cell)
T/F alleles that occur in regulatory region isn’t considered in our definition of allele
False
refers to any sequence differences
Chromosome
a linear piece of DNA (and associated proteins)
What did Walter Sutton and Theodor Boveri do
propose that chromosomes are the carrier of genes
Looked at gametes
Found chomosome are in nuclei
notice that the chromosome movements parallel the behavior of Mendel’s genes
Mendel’s genes must reside on/within chromosomes
Break down structure of chomosome
Chomosome ⇒ dna-protein supercoil ⇒ dna ⇒ gene
Chomosome location in prokaryote
Nucleoid
Chomosome location in eukaryote
Nucleus
