37 terms

Genetics ch4 Study Guide

explain X linked white eyed mutation in relation to drosophila
How was this mutation figured out
white eyes are an X linked mutation meaning the mutation is attached to the X chromosome
this mutation was figured out via reciprocal crossing which doesn't show the same mendelian ratio as is normally expected
Explain Hemizygous
pertains to males who can't be heterozygous or hemizygous in regard to X linked mutations because they only have one X therefore they are hemizygous
What kind of a pattern of inheritance does X linkage result in
a criss cross pattern where males always inherit their mothers homozygous X linked mutation because they are hemizygous.
What is the resulting offspring from a mother homozygous for x linked color blindness who has children with a normal vision male?
What will be the result from their sons offspring with a normal vision lady? What will be the result of their daughters offspring with a normal vision man
F1 generation: the sons will be hemizygous for the X linked trait.
The daughters will be heterozygous for the X linked trait thus they will be carriers.
F2 generation: The sons children with normal lady will not have the X linked trait. The daughters offspring with a normal vision male will be some carrier daughters some normal sons and some color blind sons.
What is an X-Linked Lethal disorder
Basically an X linked disorder that leads to death or debilitation before maturation.
what gender does this occur in and why
occurs in males due to the fact that they are hemizygous. Can't occur in females because they are always carriers. otherwise they would be dead or their mate would be dead
What are carriers
Refers to females who are heterozygous for a recessive mutation
What is an example of an X linked lethal disorder
Duchene Muscular Dystrophy
what is sex limited influenced - give an example
refers to autosomal traits that are limited to a certain sex. An example is recessive rooster feathering. HH or Hh means hen feathers seen in both hens and roosters. hh means rooster feathers in roosters and hen feathers in hens. This sex limited autosomal trait is due to hormonal factors.
What is sex influenced - give an example
refers to an autosomal trait that varies in expression according to sex. An example is the homozygous pattern baldness. So bb means not bald in both male and female. Bb means bald in males and not bald in females. BB means bald in males as well as females but later in life and to a different degree for females.
What effect does the environment have on an individuals genetic background?
Expression of genes is not only influenced by genetic makeup and hormones but also due to external environment. This is seen in drosophila with the mutation for no eyes.
What is penetrance?
Penetrance refers to the percentage of subjects in which mutant gene is expressed at least some.
What is expressivity?
refers to the degree that a mutation is expressed. seen in drosophila with mutation for no eyes ranges from normal eyes to absence of 1 or both
what is genetic suppression
mutant genes such as suppressor of forked or hairy wing will completely or partially restore the normal phenotype in forked or hairy wing homo or hemizygous mutations
what are suppressor genes
Genetic background that modifies primary gene effects
what is the position effect
refers to the fact that the position of a gene may effect its expressivity. This can occur due to a a chromosome being rearranged or relocated. Normal expression is especially changed if the new location is close to heterochromatin which is tightly coiled inactive gene region
What effect does temperature have on an animals phenotypic expression: give examples?
A certain temperature can keep a gene from being expressed. this is seen in himalayan rabbits who are white except in their feet and paws because these are the only locations warm enough for pigmentation genes to function
what are conditional mutations?
mutations whose expression is affected by something like temp
What is a permissive condition?
gene is able to function at temperature or certain condition
What is a restrictive condition?
gene is nonfunctional at temperature or conditions
Explain onset of genetic expression. What are a few examples of diseases.
What can be concluded from this?
Genetic expression refers to the fact that some genes are expressed at different times such as prenatal, teen, adult.
Some diseases such as huntington's disease or tay sachs are examples. The diseases aren't seen until the mutant gene is expressed.
Demonstrates that gene products play an essential role at certain life stages, internal physiological environment changes with age.
Explain genetic anticipation and provide examples
refers to the fact that some inheritable genetic mutations appear earlier and are more serious in successive generations.
An example is myotonic dystrophy
Explain genomic imprinting
refers to a portion of a gene that is silenced following fertilization this influences the phenotype.
Is genomic imprinting permanent
no it is reversible in subsequant generations
Describe examples of human genomic imprinting
Imprinting of Chromosome 15 causes Prader Willi Syndrome when occurs through the sperm. Known as Angelman syndrome when inherited through the egg.
What is extranuclear inheritance? What is its effect on mendelian patterns of inheritance?
refers to organelle heredity and maternal effect. Basically inheritance that occurs due to genes or some kind of silencing that does not originate from the nuclear DNA
What is organelle heredity
Refers to heredity due to DNA found in the mitochondrial and DNA found in the chloroplast
What is the maternal effect
occurs following fertilization when the development of the zygote is influenced by gene products of only one parent which is usually the mother
Where does organelle inheritance usually come from. Why is it hard to study?
Comes from the mother mainly due to the fact that she contributes more organelles
It is hard to study especially ibecause have many mitochondria and chloroplast without all being effected.
What is heteroplasmy
Refers to a situation where have some mitochondria or chloroplasts in the cytosol with a mutant gene and some without
How is organelle heredity seen in four o'cock plants
regardless of pollen source the resulting branch of flowers corresponds to the ovule source
Explain mitochondrial mutations
Basically occur due to genes in the mitochondria most of the time seen in a mutation that affects cellular respiration
Explain Poky and Petite Yeast
Poky is basically a slow growing bread mold this is due to a mitochondrial mutation that inhibits some form of cellular respiration in regard to the electron transport chain.
Petite yeast is small because of mutation that limits cellular respiration to anaerobic respiration
Two reasons mtDNA may be vulnerable to mutations
1. repair mechanisms aren't as good as in nuclear DNA
2. there is a lot of mutagenic free radicals that accumulate in mitochondria
Describe 3 criteria to attribute to mitochondrial mutation
has maternal rather than mendellian inheritance pattern.
affect the bioenergetic processes
must be able to find at least one mutation in mitochondria or chloroplast
Explain Myoclonic Epilepsy Ragged Red Fiber Disease
Occurs due to mitochondrial mutation. have maternal transmission
muscles look ragged red due to abberant mitochondria
heteroplasmy keeps the disease from being lethal
Explain Leber's hereditary optic neuropathy
occurs due to mitochondrial mutation - this mutation affects eye vision