Genotype/Phenotype/Genome content Flashcards
What is the polyadenylation ?
short sequence of the mRNA that has 3 functions:
- Terminator of the transcription (stops the RNA polymerase)
- Protects the mRNA from being digested
- Tells all the proteins to add the poly-A tail (which also protects the RNA from being digested
Complete : __ fuels natural selection
Mutations
What is the definition of an allele?
One of the possible alternative forms of a gene (different alleles may have different phenotypic effects)
What is the definition of a mutation
Heritable change in the DNA sequence or chromosome structure
What is a SNP
Single-nucleotide polymorphism
Variation (between genotypes) in one nucleotide pair
Describe the following:
- Monogenic trait
- Polygenic trait
- Pleitropic gene
Monogenic trait : a trait that is determined by one gene
Polygenic trait : a trait that is determined by multiple genes
Pleiotropic gnee : a gene that has affects multiple traits
The HBB gene is which type of gene ?
Pleiotropic
Difference between homozygous and heterozygous ?
Homozygous : individual with identicals alleles for a gene of interest
Heterozygous : Individual with different alleles at one or more loci
To express a recessive phenotype, the needs to have what ?
Homozygous for the recessive gene
What is a quantitative trait ?
Continuous trait whose expression depends on many genes with small, additive (sometimes interactive or dominants) effects
Describe the differences between quantitative traits and mendalian traits
Mendelian = discrete
Quantitative = continuous
Mendelian = one or a few genes determines the trait
Quantitative = many genes determine
Mendelian = high heritability
Quantitative = low to high heritability
Mendelian = lower influence of the environment
Quantitative = higher influence of the environment
Is Huntington’s disease an example of mendelian or quantitative trait ?
Mendelian
Are height, weight and blood pressure examples of mendelian or quantitative traits ?
Quantitative
True or false : the traits of one genotype can vary if they are affected by the environment
True
When a trait is coded by more than one gene, is the effect of the environment more continuous or discrete ?
Continuous (the variation is no longer discrete)
The phenotype is the result of what addition ?
P = G + E
P= Phenotype
G= genetic effect
E= Environmental effect
How can we calculate a phenotypic variance within a population ?
Vp= Vg + Ve
Vp = Phenotypic variance
Vg = Genetic variance
Ve = Environmental variance
How can we define Heritability (h^2) ?
Proportion of the variance in a trait among individuals that is attributable to differences in genotype (strength of inheritance)
Ex : trait with low heritability = it means that the phenotypic differences between individuals within a population can be attributed mostly to environmental differences (high Ve)
How can we calculate heritability ?
h^2 = Vg/Vp
Vg = Genetic variance
Vp = Phenotypic variance
what does it mean when we say that a trait has a genetic basis?
It means that genes influence the trait in some way
(applies to both mendelian and quantitative traits)
Name reasons why heritibality may be low
- Individuals in a population are similar genetically (low Vg)
- Environmental factors contribute much more to differences between these individuals (high Ve) than genetic differences do
Describe the genome content
- 2% exons
- 24% introns
- 15% unique sequences not found in genes
- 59% repetitive DNA sequences
What are retrotransposons ?
Mobile genetic elements
- they are copied by an RNA intermediate
- They insert themselves at other chromosomal sites, often causing mutations
Describe forward genetics
Trying to find the genes that are responsible for a condition (usually through gene mapping)
