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More Genetics

Terms in this set (42)

when you can determine a organism's phenotype but not their genotype?
when the organism has a dominant phenotype but its genotype is AA or Aa
what are three ways you could figure out an organisms genotype
1. sequence the DNA
2. test cross
3. look at a pedigree
what is a test cross
when you cross the organisms with a homozygous recessive organism whose phenotype and genotype (aa) you know. If any of the organisms display the recessive phenotype the unknown organism was definitely heterozygous. If all are dominant, the unknown organism was probably homozygous dominant.
why would an unknown organism probably be homozygous dominant if you mixed the unknown organism with a homozygous recessive organism and you got kids that were all dominant.
Some of Mendel's crosses were nowhere near his predicted ratios (3:1, 9:3:3:1) this was because of random chance. In order for the data to be more reliable, there must be at least 100 trials to prevent sampling error.
What is a pedigree?
a chart that shows the passage of a trait through many generation. Getting a large sample size in a human family is not possible-therefore we turn to pedigrees instead.
what does an autosomal trait mean?
traits that are inherited as simple dominant and recessive alleles
What are other ways of inheritance besides autosomal?
incomplete dominance and codominance
what is incomplete dominance
sometimes, the phenotype of a heterozygote is a blend (average) of the phenotypes of the opposite homozygotes. (an example would be a mix of yellow allele and blue allele and you get green)
what is codominance
some traits are inherited such that the phenotype of the heterozygote is a simultaneous expression of 2 alleles separately from one another (an example would be having a red and white cow because it is showing red and white at the same time)
what is the phenotypes and genotypes of A blood and what are the antibodies
-A
-AA or AO
-B
what is the phenotypes and genotypes of B blood and what are the antibodies
-B
-BB or BO
-A
what is the phenotypes and genotypes of AB blood and what are the antibodies
-AB
-AB
-none
what is the phenotypes and genotypes of O blood and what are the antibodies
-O
-OO
-A and B
what is an important question to ask when transfusing blood?
what antibodies does the recipient have that would attack (agglutinate) the donor's type of incoming blood
what is the most important thing to identify for a transfusion
recipient's antibodies
what is the universal donor of blood
O
what is the universal recipient of blood
AB
if a mothers blood is type A and her child's is O, what type of blood can the father NOT be?
AB
what does it mean if blood is positive or negative
any trait that can be represented as a simple +/- is simply due to the presence or absence of a single protein. This is basically inherited as an autosomal trait.
what does it mean if your blood is +
they must have at least one + allele
what does it mean if your blood is -
they must have 2 negative alleles
what are polygenic traits
traits that are not controlled by a single gene, which makes them harder to trace through a pedigree.
what is an example of a polygenic trait?
-height.
-People are not just short/tall-there is continuous variation within the population. Due to a combination of the expression of multiple genes.
what are sex-limited traits
occur in only one gender or the other
what is an example of a sex-limited trait
milk production in females or pattern baldness in males
what are sex-linked traits
coded for by genes found on the x chromosome and are therefore expressed disproportionately between genders because male and females do not get the same number of x chromosomes
what are the chromosomes for males and females
males: xy
females: xx
what is unique about the y chromosome for mammals and flies
the chromosome is very short and has very few genes (ex. color blindness, muscle dystrophy, hemophilia are sex-linked recessive traits)
what does autosomal dominant look like
A_
what does autosomal recessive look like
aa
what does sex-linked recessive look like
x^n x^n or x^n y
what does sex-linked dominant look like
n^N x^_ or x^N y
what is holandric?
trait carried on the Y (females will NOT show)
why does mendel's law of assortment not work with all genes?
alleles must be coded for by genes on the same chromosomes. Genes that are inherited following the principle of independent assortment are found on different chromosomes. If alleles are connected to each other on the same chromosome, they will not be inherited independently!
what is a linkage group?
a group of genes that tend to be inherited together because they are on the same chromosome
Sometimes, alleles that are connected on the same gene can still be separated from one another during meiosis even though they're on the same chromosome...how?
crossing over occurred so alleles got traded and recombined.
what is genetic recombination
anytime a new combination of DNA is created. This occurs during crossing over because there's anew linkage of alleles than was found in the parent's cells.
what is the recombination frequency
a measure of the total recombination between two linked genes expressed as a percentage (there is always an 18% recombination frequency)
what can you use the recombination frequency for
can be used to determine the distance between two alleles on a chromosome and can effectively be used to map genes on a chromosome.
how can you map genes on a chromosome by recombination frequency
if two genes are close together on a chromosome, the likelihood of randomly cutting between them to separate them from one another is very low. Therefore, the further apart two genes are from one another, the more likely they are to be randomly separated from one another
what does it mean if there is a high recombination frequency
the further the genes are from one another on the chromosome
what does it mean if there is a low recombination frequency
the closer together the genes are on the chromosome
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