5/1 Flashcards
what is a dominant mutant
it is a mutation that alters a gene in a way that creates a phenotype that is present when there is only one copy of the mutant allele
what is incomplete dominance
it is when a heterozygote exhibits a phenotype that is an intermediate between corresponding homozygotes
with an incomplete dominant phenotype, is the 3:1 ratio for a self-cross expected?
no, a 1:2:1 ratio may be observed
what would the phenotypes and their ratios be when a pink flower is crossed with a white
1 pink 1 white
if a trait looks dominant at first glance, does that mean it is fully dominant?
no, it could be incompletely dominant but it would need to be examined more closely to see the phenotype
what is an essential gene
they are genes that are essential for survival
what is the phenotype of an essential gene being lost?
it leads to a lethal phenotype
what is a lethal allele
it is a gene that has the potential to cause death
what is a nonessential gene
it is a gene that is not essential for survival, a mutation here is not lethal
where do lethal alleles come from
they are typically a result of mutations in essential genes and are usually inherited in a recessive nature
why is inbreeding harmful in the case of lethal alleles
it increases the chance of creating a double recessive which will cause the lethal allele to be active
why are dominant lethal alleles persisting in the environment
they tend to exert their effects later in life, meaning that they can pass their allele on before they are affected and die
what is the difference between a conditional allele and a conditional lethal allele
a conditional allele is a trait that will appear under certain conditions
a conditional lethal allele is an allele that will kill an organism under certain conditions (dominant)
what is a semilethal allele
it is an allele that will kill some individuals in a population but not all
why do semilethal alleles kill some but not all
there are other genes involved in the genetic background and environmental factors that may prevent the detrimental effects of the semilethal allele
what is the manx cat and creeper an example of
these are examples of dominant lethal alleles. When they are homozygote, they will kill the organism, but when they are heterozygote they will be incompletely dominant
what are multiple alleles
more than two alleles for a gene that follow a dominance hierarchy
when an animal has dark fur due to low temperatures, but this allele does not directly kill them, what type of allele is it?
it is a temperature sensitive conditional allele, it is not lethal
what is codominance
they are multiple alleles that are expressed in a heterozygous individual
how is the ABO system expressed in blood types
the A and b are codominately expressed where the O allele is recessive (ii)
for safe blood transfusion what blood types must be matched?
A with A or i
B with B or i
O with i only
A+B with A, B, or i
what is heterozygote advantage
it is the phenomenon where the heterozygote type has an advantage over homozygotes
in sickle cell anemia, how is the HAHS type more advantageous than the HAHA or HSHS type
the HAHS type is weaker and will rupture before the parasite for sickle cell can propagate
