12.3 Analytical Approaches in Genetics Flashcards
What are biometric techniques in terms of genetics?
They are quantitative approaches to biological data. Examples include things like Punnett squares to mapping of chromosomes to Hardy-Weinberg Equilibrium.
What are Punnett squares?
They predict the relative genotypic and phenotypic frequencies that will result from the crossing of two individuals.
What is a monohybrid cross?
What is the P generation?
What is the F generation?
Monohybrid cross refers to the Punnett square with only one trait, i.e. PP x pp
P Generation= parent generation
F Generation= filial or offspring.
In a Punnett square, what will the the crossing of two heterozygotes create?
Genotype: 1:2:1, for example PP, Pp, Pp, pp
Phenotype 3:1, 3 large Ps and one little
What is a test cross on genetics?
Also called a back cross.
It is used to determine an unknown genotype.
The organism with an unknown genotype is crossed with an organism known to be homozygous recessive.
If 100% are of dominant phenotype, then likely it is homozygous dominant.
if 50% are dominant phenotype, then likely heterozygous.
If 0% are not, then then unknown type was homozygous recessive.
What is a dihybrid cross?
This is an extension of a Punnett square, using the inheritance of two different genes.
This is possible for unlinked genes, due to Mendel’s second law of Independent assortment.
If both parents are heterozygous for a dihybrid cross, what pattern will the offspring be in?
They will be in a 9:3:3:1 Distribution
If both parents are heterozygous for a dihybrid cross, what pattern will the offspring be in?
They will be in a 9:3:3:1 Distribution
What are sex-linked traits?
They are x-linked traits, and generally recessive.
Generally only come out when the offspring is a male, because if it were in a female, it would usually have the extra dominant trait to compensate.
How are sex-linked traits written using a Punnett square?
You put the trait in subscript next to the X (female).
How are sex-linked traits written using a Punnett square?
You put the trait in subscript next to the X (female).
What is the point called where two chromosomes meet in Meiosis I and swapping over occurs?
called the chiasma.
What is the recombination frequency?
This is the liklihood that two alleles are separated from each other during crossing over.
It is porportional to the distance between the two genes on the chromosome.
Genes that are real close together have a recombination frequency close to 0%
Genes that are far apart have that close to 50% (note that the max is 50%)
What are genetic maps?
They represent the relative distance between genes on a chromosome.
One map unit or centimorgan corresponds to a 1 percent chance of recombination occurring between two genes.
For example, if two genes were 25 map units apart, there would be a 25 percent of total gametes would show recombination between the two genes.
What is the allele frequency?
How often an allele appears in a a population.
For example if we took 50 of mende’s plants, we would collect 100 alleles (two from each plant)
What is the Hardy Weinberg equation?
p+q=1 Frequency of alleles in the population
p2 + 2pq + q2=1 provides information about the frequency of genotypes and phenotypes of the population
Remember there will be twice as many alleles as individuals in a pouplation because each invidiaul has two autosomal copies of each gene.
For each of the crosses below, what is the phenotypic ratio seen in the offspring?
