UAFS Chapter 4 Genetics
What are the two types of mutation effects?
1. Loss-of-Function 2. Gain-of-Function
Mating an agouti mouse and a yellow mouse will always result in a _____ ratio of agouti and yellow among progeny
1:1 ratio
What subunit in flowering plants provides an example of a loss-of-function mull mutation?
26S proteosome
THe 4 different human blood types are caused by how many alleles?
3
What does haploinsufficient mean?
A single copy is NOT sufficient to produce the wild-type phenotype in the heterozygous genotype
Multiple alleles of a single gene can display what?
A variety of dominance relationships that establish an allelic series.
In certain circumstances, the ___ allele can be both dominant and recessive
A^Y
The ABO blood types are produced by what?
Alleles whose protein products produce dominance or codominance depending on the genotype.
What can happen in incomplete penetrance?
An allele does not always have the expected effect on the phenotype.
What does genetic dissection do?
Analytic approach to identify the step-by-step events making up a genetic pathway.
What are catabolic pathways and what do they do?
Breakdown of compounds into intermediate compounds and often into elemental constituents.
What gene is responsible for coding for coat color in mammals?
C gene
What is the dominance relationships in the allelic series for gene C?
C>c^ch>c^h>c
Chapter 4 Summary
Chapter 4 Summary
Chapter notecards
Chapter notecards
The cross of a pure breeding white flower with a pure breeding red flower produces a white flower with red spots.
Codominance
_________ leads to a heterozygous phenotype different from the phenotype of either homozygous parent. It is also characterized by the detectable expression of both allele in heterozygotes.
Codominance
Which mode of inheritance results in both alleles being detected equally in heterozygous phenotypes?
Codominance.
What are the epistasis types and their ratios?
Complementary gene interaction (9:7) Duplicate gene action (15:1) Dominant gene interaction (9:6:1) Recessive epistasis (9:3:4) Dominant epistasis (12:3:1) Dominant suppression (13:3)
These pathways direct normal growth, development, and differentiation of body parts and structures
Developmental pathways
What does single-gene- traits mean?
Different forms of a trait can be transmitted to offspring by the segregation of alleles of a single gene; summarizes the observation that inherited variation for one gene can
How are alleles manifested in sex-limited and sex-influenced traits?
Differently in each sex.
What do developmental pathways do?
Direct normal growth, development, and differentiation of body parts and structures.
A dominant mutation that behaves as a loss-of-function, often due to blocking the formation or normal function of a multimeric protein complex
Dominant negative mutation
Neomorphic mutation is what kind?
Gain of function
Mutations that identify alleles that have acquired a new function or have their expression altered in a way that gives them substantially more activity than the wild-type allele
Gain-of-function mutations
The result of the influence of environmental factors (i.e. non genetic factors) on the expression of genes and on the phenotypes of organisms
Gene-environmental interaction
If wild type T1 is expressed in T1T1, but not expressed in T1T2 or in T2T2, is
Haploinsufficient
What does incomplete dominance produce?
Heterozygotes with phenotypes that differ from those of either homozygote but are closer to one homozygous phenotype than the other.
c^h represents ________ coat color where the feet and ears are fully pigmented but the body isn't; siamese cats have this
Himalayan
Which coat color gene is a temperature-sensitive allele?
Himalayan (c^h)
A common example of delayed age of onset in humans is _________ disease
Huntington's Disease
A type of gain-of-function mutation that produces a gene product that is indistinguishable from that of the wild-type allele, but is present in a greater amount and thus induces a higher level of activity; usually dominant
Hypermorphic mutation
Gain-of-function mutations: ________ results in a gene product that is the same as the original but induces a greater level of activity and is functionally in "overdrive". ______ results in a gene product that has a completely different function than the original had
Hypermorphic mutation Neomorphic mutation
The mutant agouti allele, A^Y, is what type of gain-of-function mutation? Is it dominant or recessive?
Hypermorphic; dominant
A mutation results in an enzyme that is partially active compared to the wild-type allele. This type of leaky mutation is classified as
Hypomorphic
The recessive c gene c^ch produces a phenotype called chinchilla. This allele is what type of loss-of-function mutation?
Hypomorphic
Codominant alleles are both equally detected in what?
In the heterozygous phenotype.
PKU is caused by the absence of the enzyme phenylalanine hydroxylase
Just know this cuz she'll probably ask about it and I don't want to make a question because that's a long word to remember
What can lethal alleles do?
Kill gametes, prevent the gestational development of certain classes of progeny, or have their lethal effect later in life.
What are anabolic pathways and what do they do?
Lead ultimately to the production of an end product such as a pigment, amino acid, hormone, or nucleotide.
A type of loss-of-function mutation that results in a partial loss of gene function; implies that a small percentage of normal functional capability is retained by the mutant allele but at a lower level than is found for the wild-type allele
Leaky mutation aka hypomorphic mutation again with the stupid double names
What type of allele is often detected as a distortion in segregation ration, where one class of expected progeny is missing
Lethal allele
Certain single-gene mutations are so detrimental that they cause death early in life or terminate gestational development. These life-ending mutations effect genes whose products are essential to life. These are called ______
Lethal genes
This mutation effect results in a significant decrease or in the complete loss of the functional activity of a gene product
Loss-of-function
What do loss-of-function mutations and gain-of-function mutations do?
Loss-of-function: Decrease or eliminate gene activity. Gain-of-function: Can cause over-expression or result in new functions.
What happens in genetic heterogeneity?
Mutations in different genes can produce the same phenotype.
A type of gain-of-function mutation that produces a gene product that is functional, but have structures that differ from the wild-type gene product. The altered structures lead the mutant protein to function differently than the wild-type proteins; usually dominant
Neomorphic mutation
A type of loss-of-function mutation that results in a complete loss of gene function in comparison to the wild-type gene product; produce no functional gene product and are often lethal in a homozygous genotype
Null mutation aka amorphic mutation because God forbid something in science just have one name we have to memorize two names for the same thing
A mutation resulting in an inactive gene product is classified as
Null/amorphic
What does haplosufficient mean?
One (haplo) copy is sufficient to produce the wild-type phenotype in the heterozygous genotype
What happens in variable expressivity?
Organisms with the same genotype have different degrees of phenotypic expression.
The alteration of multiple, distinct traits of an organism by a mutation in a single gene
Pleiotropy
Quiz Questions
Quiz Answers
A loss of function is dominant or recessive?
Recessive
Are loss-of-function mutations usually dominant or recessive?
Recessive (but can sometimes be dominant. They're just almost always recessive)
What are gene interactions?
Refers to the ways genes collaborate or interact to influence a phenotype
What do signal transduction pathways do?
Responsible for reception of chemical signals, such as hormones, that are generated outside a cell and initiate a response inside a cell.
_________ traits are those in which the phenotype corresponding to a particular genotype differs depending on the sex of the organism carrying the genotype
Sex-influenced
Which phenomenon explains difference in the inheritance patterns of the appearance of chin beards in female/male goats?
Sex-influenced trait
These pathways are responsible for reception of chemical signals, such as hormones, that are generated outside a cell and initiate a response inside a cell
Signal transduction pathways
Epistasis is revealed by what?
Six alternative ratios that are modifications of the 9:3:3:1 ratio expected among the progeny of a dihybrid cross.
What causes the hylomorphic c^h allele to be unstable and result in the distinctive fur pattern?
Temperature
What causes the allelic series in coat color?
The amount of tyrosinase that is produced. The more produced, the more dominant
What is gene interaction?
The collaboration of multiple genes in the production of a single phenotypic character or a group of related characteristics.
The interaction of allelic products determines what?
The dominance relationship between alleles.
What do biosynthetic pathways result from?
The expression of genes whose products help build complex compounds of molecules that are the end product of the pathway.
The failure to detect genetic complementation from the cross of two similar mutant organisms identifies what?
The mutant alleles are being carried by the same gene.
What does it mean that c^h is a temperature-sensitive allele?
The tyrosinase enzyme produced is unstable and is inactivated at a temperature very near the normal body temperature of most mammals. That's why the body is one color since it's warmer, and the feet are another color since they're further away
Genetic complementation produces progeny with what?
The wildtype phenotype from parents that are pure-breeding for similar mutant phenotypes. The detection of genetic complementation means the mutations occur in different genes.
What do anabolic and catabolic pathways reveal?
They reveal the necessity for several genes to work together to produce the wild-type phenotype for a trait; they also show that the mutation of any of the participating genes could block or alter the wild-type phenotype.
How do signal transduction pathways operate?
Through the release of a signaling molecule that is part of a sequence of steps culminating the in activation or repression of gene expression in response to an intracellular or extracellular signal.
What do pleiotropic mutations affect?
Two or more distinct and seemingly independent attributes of the phenotype.
When testing someone's blood type, clumping occurred with the Anti-A antigen, but not with the Anti-B. This indicates that the person's blood type is _____
Type A
In blood types, what two types are codominant to each other?
Type A and type B
When testing someone's blood type, clumping occurred with both the Anti-A and Anti-B antigen was added. This indicates that the person's blood type is ____
Type AB
When testing someone's blood type, clumping did not occur when Anti-A was added or when Anti-B was added. This indicates that the person's blood type is ____
Type O
Production of wild-type proteins from all three genes is necessary to produce what?
Wild-type eye color, and hereditary eye color mutations result from the mutation of one or more of the genes.
In mice, wild-type coat color is a brown color called ______
agouti
With multiple alleles, an order of dominance emerges among them based on the activity of each allele's protein product. This forms a sequential series known as a(n) _______
allelic series
An example of sex-limited traits in mammals if the development of ____ and the ability to produce ______ in females
breasts; milk
Produces no enzymatic activity and is a fully null allele that does not produce a functional gene product. Homozygosity for this allele produces an albino phenotype
c
If the correspondence between genotype and phenotype holds true every time, that is, the genotype always code for the same phenotype every time, this is called _________
complete penetrance
When the abnormalities of lethal alleles do not appear until after affected organisms have had an opportunity to reproduce and transmit the mutation to the next generation, this is called _________
delayed age of onset
If wild-type R phenotype is expressed in homozygous RR and heterozygous Rr, but not present in rr, then it is _________
haplosufficient
When the dominance of one allele over another is not complete, it is called ___________
incomplete dominance
When traits display _______, two pure-breeding parents with different phenotypes produce F1 heterozygotes having a phenotype different from that of either parent. This F1 phenotype is intermediate between the parental forms, but usually more closely resembles one more than the other
incomplete dominance
Polydactyly is expressed when an individual has extra fingers and/or toes. This is an example of ________
incomplete penetrance
Traits for which nonpenetrant individuals occasionally or routinely occur are identified as displaying __________
incomplete penetrance
A locus possessing three or more alleles is said to have _________. ABO blood type is an example of this
multiple alleles
If an organism with a particular genotype fails to produce the corresponding phenotype, it is called _______
nonpenetrant
Differences in gene expression between the sexes can result in the appearance of _____. Both sexes typically carry the genes for this, but the genes are expressed in just one sex.
sex limited traits
Beards in male goats vs beardless in female goats are an example of ________ traits
sex-influenced
In ____________, there is a potential limitation of gene expression to one sex but not the other
sex-limited gene expression
The observation that inherited variation for one gene can produce a mutant phenotype rather than a wild-type phenotype
single-gene trait
The dominance of one allele over another is determined by
the protein product of that allele
Each individual organism can posses at most ____ alleles at a locus
two because diploid
What enzyme does C gene produce?
tyrosinase
In ___________, the same genotype produces phenotypes that vary in degree or form of expression of the allele of interest
variable expressivity