Exam 2
What is a recessive lethal allele
need 2 copies of lethal gene homozygous
Incomplete pentetrance defintion
"dominant allele does not always penetrate into the phenotype of the individual"
Color blindness is a sex-linked recessive trait. A female is color blind in one eye, but not both. Select the explanation for this condition. Is it possible for a male to have different color-blindness phenotypes in each eye?
- Random X-chromosome inactivation Yes, in an XXY male with a different active X in each eye
In eukaryotes, extranuclear inheritance occurs when genetic information is transmitted by mechanisms other than through nuclear DNA. Mitochondrial DNA (mtDNA) is an example of one mechanism by which extranuclear inheritance can occur. Select the statements that correctly describe mtDNA.
- mitochondrial chromosomes contain genes that are involved in oxidative phosphorylation -mtDNA organization is more similar to that of prokaryotes than eukaryotes
Which of these choices describe Y-linked traits?
-all male offspring of affected fathers will express the trait -the trait is passed down to a son by his father
A genetic cross with two genes produces 400 offspring, and 20 of them have recombinant phenotypes. What is the recombination frequency for this cross?
.05
If a male bird that is heterozygous for a recessive Z-linked mutation is crossed to a wild type female, what proportion of the progeny will be mutant males?
0
In an X linked recessive disorder, what is the probability than an unaffected father will pass down the disease to her son?
0%
Assume that long ear lobes in humans are an autosomal dominant trait that exhibits 30% penetrance. A person who is heterozygous for long ear lobes mates with a person who is homozygous for normal ear lobes. What is the probability that their first child will have long ear lobes? Use two decimal places for your answer.
0.15
How many Barr bodies would be present in white blood cells of an individual of karyotype 48, XXYY?
1
interference calculation
1- coefficient of coincidence
How can the wild type phenotype of the heterozygote be explained
1. 50% of the normal protein is enough to accomplish the proteins cellular function 2. The heterozygote may actually produce more than 50% of the functional protein
Dominant mutations 3 reasons
1. gain of function 2. DOminant negative 3. Haploinsuciency
What are the 3 stages of X-inactivation?
1. initiation: one of the X chromosomes is targeted for condensation 2. Spreading: that X chromosome is condensed 3. maintenance: remain inactive during future cell divisions
In four-o'clock plants, red flower color is dominant to white flower color. However, heterozygous plants have a pink color. If a pink-flowered plant is crossed with a white-flowered plant, what will be the phenotypic ratios of their offspring?
1/2 pink, 1/2 white
en color blindness is an X-linked recessive trait in humans. Polydactyly (extra fingers and toes) is an autosomal dominant trait. Martha has normal fingers and toes and normal color vision. Her mother is normal in all respects, but her father is color blind and polydactylous. Bill is color blind and polydactylous. His mother has normal color vision and normal fingers and toes. If Bill and Martha marry, what proportions of children with specific phenotypes would they be expected to produce? The answers only include the proportions of some of the possible phenotypes; other phenotypes are also expected to occur but are not included.
1/8 color-blind girls with polydactyly, 1/8 boys with normal vision and normal fingers
Suppose that allele D produces small fingers and allele d produces normal fingers. A heterozygous male with the Dd genotype mates with a homozygous female with the dd genotype. Small fingers is an autosomal dominant trait expressed with 20% penetrance. Determine the probability that their offspring will have small fingers. Report your answer as a percentage without decimal points.
10%
A human male with the chromosome constitution of XXXYY would contain how many Barr bodies in his somatic cells?
2
In chickens the dominant allele Cr produces the creeper phenotype (having extremely short legs). However, the creeper allele is lethal in the homozygous condition. The homozygous recessive genotype results in a normal individual. If two creepers are mated, what will be the phenotypic ratio among the living offspring?
2 creepers: 1 normal
What is gene interaction? List the 4 specific types.
2 or more gene influenced the outcome of one trait 1. epistasis 2. complementation 3. gene modifier effects 4. gene redundancy
Assume that long fingers are inherited as a recessive trait with 80% penetrance. Two people heterozygous for long fingers mate. What is the probability that their first child will have long fingers
20%
How many linkage groups in humans?
22 autosomal linkage groups
A woman is phenotypically normal, but her father had the sex-linked recessive condition of red-green colorblindness. If she has children with a man with normal vision, what is the probability that their first child will have normal vision and their second child will be colorblind?
3/16
A maternal effect can cause the offspring phenotype ratio to depart from that of classic Mendelian inheritance. In a species of snail, the dominant allele N codes for right-handed shell coiling and recessive allele n codes for left-handed shell coiling. If an Nn female with right-handed shell coiling mates with an Nn male, what is the shell coiling phenotypic ratio of their offspring?
4 right handed coil: 0 left handed coil
A recombination frequency of 5% translates to what distance on a genetic map?
5 m.u.
In an X linked recessive disorder, what is the probability than an unaffected mother will pass down the disease to her son?
50%
A gene has three alleles. How many different genotypes are possible at this locus in a diploid organism?
6
X-linked red-green color blindness in humans is a recessive condition. Which of the following statements is true?
A color-blind woman must have had a color-blind father
Lyon hypothesis
A mechanism of X inactivation results: X inactivation has already occurred in any given epithelial cell This pattern of inactivation is passed to all the cells progeny
If a mother has a type A blood and her son has type O blood, what are the possible blood types of her sons father?
A, B, O
In the previous example the s and e alleles are linked on one chromosome and the s+ and e+ alleles are linked on the homologous chromosome, are the genes arranged in the cis or trans configuration?
A. Cis/coupling
Example of multiple alleles
ABO blood group determined by antigen present on the surface of red blood cells
Epistasis often results in modified dihybrid phenotypic ratios. Assume that you obtain one such modified ratio, 9:7, with the gene pairs A and B involved. What would be a possible genotype for a phenotype that would be included with the 9 portion of the modified ratio?
Aa BB
An individual with type A blood and an individual with type B blood mate and have offspring. What blood type is not possible in their offspring? ?
All blood types are possible (A,O,B,AB)
At the molecular level, type A and type B blood differ in which of the following characteristics? ? a. The antigens present on the surface of the red blood cells? b. The type of sugar found on the surface the cells c. The antibodies that are generated against the other type of blood?
All of the aboce
Sarah has chronic bronchitis and frequently ends up hospitalized with pneumonia. She has no family history of cystic fibrosis, a serious recessive genetic disorder which affects the respiratory and digestive tracts. She and her husband, Greg, have one child after undergoing fertility treatments to overcome Greg's infertility. They are surprised when the child is diagnosed with cystic fibrosis and the genetic counselor tells them that they each also have the condition, which causes their bronchitis and infertility. Which of the following explanations would be a reasonable explanation of their situation? A) There are several different alleles of cystic fibrosis, which cause differing forms of the disease. • B) Although the underlying disease is genetic, the severity of the disorder is influenced by environmental variation. • C) Cystic fibrosis displays variable expressivity.
All of the above
Normally in humans a mutant gene on the Y chromosome will be inherited in which of the following ways?
All of the sons of a parent with the mutant gene will receive it but none of the daughters will.
The white-eyed mutation in Drosophila studied by Thomas Hunt Morgan was the first clear case of sex-linked inheritance. When Morgan crossed a white-eyed female with a red-eyed male, what phenotypes were present in the offspring?
All the males had white eyes and all the females had red eyes.
In chickens the females are heterogametic, ZW, and the males are homogametic, ZZ. Most sex-linked genes are only carried on the Z chromosome. Congenital baldness is caused by a recessive sex-linked allele. If a bald male is crossed to a normal female, what would be the expected results in the offspring?
All the males will be normal and all the females will be bald.
Select the definition of a Barr body. The first cloned cat, CarbonCopy (CC), was tabby, while the cat she was cloned from, Rainbow, was calico. The surrogate mother was a tabby. Select the explanation that best explains why CC would never have been identical in pattern to Rainbow.
An inactive x chromosome The pattern of X-chromosome inactivation is established randomly in a cell lineage
What does sex limited mean?
Autosomol It is only found in one sex such as sex organs
The most plausible explanation for why more human males are conceived than females is that _____.
C. Y-bearing sperm are more motile than X-bearing sperm
Which statistical test can be used to determine if two genes are linked?
Chi square test
Example of female as a heterogametic sex
Chickens females are ZW and males are ZZ
A boy has blood-type MN with a genotype of LMLN. His red blood cells possess both the M antigen and the N antigen. What is the relationship between his two alleles for this gene?
Codominance
What type of dominance? A white cow and a Red Bull have a calf that is white with red spots (roan colored)
Codominance
What type of dominance? A mother with type A blood and a father with type B blood have a daughter with type AB blood
Codominance
A man, Joe, has classic hemophilia, an X-linked recessive disease. Classify each person depending on whether or not Joe could have inherited the hemophilia gene from him or her. Who could've or couldn't have he inherited from? Paternal grandfather maternal grandfather paternal grandmother maternal grandmother
Could have: Maternal grandmother maternal grandfather Couldn't have: paternal grandfather paternal grandmother
Huntington Disease
Dominant autosome allele H progressive degeneration of nervous system, demtia and early death
In Caenorhabditis elegans, the level of expression of genes on both X chromosomes of females is reduced by half. What phenomenon is this an example of?
Dosage compensation
Three-point testcrosses are often used to map genes. The two least frequent classes from such crosses usually represent which of the following types of progeny?
Double-crossover progeny
Repulsion chromosomes
Each chromosome contains one wild type and one mutant allele allelic arrangement in which each homologue chromosome has mutant and wild type allele trans configuration
What type of gene action occurs when one gene masks the effect of another gene at a different locus?
Epistasis
Hereditary deafness combination of
Epistasis and multiple gene interactions
In a dihybrid cross of two heterozygous individuals, you expect a 9:3:3:1 phenotypic ratio in the offspring, but observe a ratio of 9:7. What is the most likely explantation?
Epistatic interaction of the two genes
True or False: Modes of inheritance such as incomplete dominance and codominance defy Mendel's laws of segregation and independent assortment.
False
Most common sex chromosome variation in males and females
Females - XXX calles SCA Males- XXY caked klinefelter syndrom
l, or monozygotic, twins develop from a single egg fertilized by a single sperm. Monozygotic twins are genetically identical because they originate from a single zygote that split into two. Caroline Loat and her colleagues examined nine measures of social, behavioral, and cognitive ability in 1000 pairs of both male and female identical twins. Their study found that pairs of male twins tended to be more alike in their prosocial behavior, peer problems, and verbal ability scores than pairs of female twins. Which of the following choices explains this observation?
Females are mosaic for the expression of heterozygous X-linked loci, because females undergo random X-inactivation
In the XX-XO mechanism of sex determination, which of the following statements is true?
Females have two X chromosomes (XX) and males have one X (XO).
How does the heterogametic sex differ from the homogametic sex?
Gametes of heterogametic sex have different sex chromosomes; gametes of homogametic sex have the same sex chromosome
What is holandric genes?
Genes only on Y chromosomes
Which statement explains why the recombination frequency between two genes is always less than 50%
Genes with recombination frequency near 50% are unlinked and have an equal likelihood of being inherited together or separately
Which of the following terms describes the situation, for X-linked genes, in human and Drosophila males who have only one X chromosome?
Hemizygous
Human mitochondrial diseases occurs 2 ways
Human mtDNA is transmitted from mother to offspring vis the cytoplasm of the egg Mitichondrial mutations may occur in somatic cells
What are the 3 different alleles that determine antigen presence on the surface of red blood cells
IA -- antigen A IB--- antigen B I-- no antigens
A heterozygote possesses a phenotype that is intermediate between the homozygous dominant and homozygous recessive phenotypes. This is most likely an example of ________.
Incomplete dominance
Fur color in a species of mouse is controlled by a single gene pair. BB animals are black and bb animals are white. Bb animals have gray fur and each hair is gray. What type of interaction is being shown by the two alleles in heterozygous animals?
Incomplete dominance
Which of the following statements best describes linkage?
It is a condition in which two or more genes do not show independent assortment
Which statement is the definition of a map unit (centimorgan)?
It is the percent chance of a crossover between two locations on a chromosomes
Which of the following statements about a lethal allele is NOT correct? A. Lethal alleles are always recessive. B. Lethal alleles may have a late age of onset. C. Lethal alleles may be caused by mutations in essential genes. D. Lethal alleles may affect one individual differently than another.
Lethal alleles are always recessive
What is Xist
Located on Xic region of gene codes for long RNA, which coats the inactive X chromosome
Drosophila, like humans, have X and Y chromosomes. However, unlike humans, it is the ratio of the number of X chromosomes to sets of autosomes that determines the sex of the fly. A fly has one X chromosome, two sets of autosomes (a diploid set), and no Y. What is its sex?
Male
What is MSY?
Male specific region Not homologous -> "Only on Y" nonrecombing regioun
If there is an X linked recessive disorder in which affected individuals die at a young age, which parent is most likely to pass the gene to their offspring? Which sex is most likely to be affected and show symptoms?
Males are affected more Mothers pass down the gene
Nondisjunction in which parent and what meiosis would give you an individual with XYY
Males in Meiosis 2
Example of genetic anticipation
Mytonic dystrophy
In drosophila is there X inactivation?
NO. There is no X-inactivation observed, instead male X linked genes are transcribed at twice the rate
In Barr body will Tsix be expressed?
No
47, XXX syndrom
Normal set of autosome results in female differential some are normal and don't even know they have XXX sometimes underdeveloped secondary sex characteristics
Which of the following statements is part of the Lyon hypothesis?
One X chromosome in each female cell becomes inactivated and the process of selection is random.
What is genomic imprinting? Paternal Maternal
One gene is silenced through methylation paternal- father gene is silences material- mothers gene is silenced
What is a dominant lethal gene?
Only need one copy to be lethal heterozygous
What is Hemizygous?
Only one copy of a chromosome
What is Tsix
Overaps Xist and expressed in opposite direction only expressed during embryonic development
Prader wills and angel man deletion in what parent?
Paternal deletion = no praderwilis product maternal deletion= no angel man product
Match each phenotype description to its corresponding sex-chromosome genotype in humans. XY with SRY deleted
Phenotypically female but karyotype indicates presence of both sex chromosomes
Match each phenotype description to its corresponding sex-chromosome genotype in humans. XXX
Phenotypically female with some abnormalities and over expression of X chromosome genes
Match each phenotype description to its corresponding sex-chromosome genotype in humans. XO with SRY on an autosome
Phenotypically male but karyotype indicates presence of only X chromosome
Match each phenotype description to its corresponding sex-chromosome genotype in humans. XYY
Phenotypically male with an increase in average stature
Match each phenotype description to its corresponding sex-chromosome genotype in humans. XXY
Phenotypically male with sterility and hypogonadism
Imcomplete penetrance Example
Polydactyly additional fingers or toes sometimes individuals have the dominant allele but don't express the trait
Which of the following statements accurately describes both pleiotropy and polygenic inheritance?
Polygenic inheritance refers to the cumulative effect of two or more genes on a single trait. Pleiotropy refers to a single gene that affects multiple traits
Primary sex ratio vs secondary sex ratio
Primary- proportion of males to females conceived secondary- proportion of each sex born
What does homogaetous means
Producing like chromosomes EX: two X chomsomes
What is PAR?
Psuedoautosomal region (X&Y)- homologous regions Present at both ends of the Y chromosome share homology with regions on X chromosome synapse and recombine with X during meiosis
What is an Ab aB linkage arrangement called?
Repulsion linkage
A karyotype is done on a phenotypically female patient, and it is discovered that she has a Y chromosome. However, the Y chromosome appears to have a deletion. What region is most likely deleted?
SRY
Which gene determines maleness in human?
SRY (sex-determining region) Located adjacent to PAR of the short arm of Y chromosomes controls male development
Definition of haplotype
Set of alleles at two or more loci present in a particular chromosome
Penile hypospadias, a birth defect in male humans in which the urethra opens on the shaft instead of at the tip of the penis, results from an autosomal dominant gene in some families. Females who carry the gene show no effects. What type of trait is this birth defect an example of?
Sex limited trait because the defect occurs only in males and the gene involved is autosomal.
What is the name of a trait that is dominant in one sex but recessive in another?
Sex-influenced
When two genes are linked but quite far apart, their estimated map distance, based on recombination frequencies, is often an underestimation of their true map distance. What is the explanation for this underestimation?
Some double crossover events go undetected since they do not lead to recombinant progeny
Which of the following statements best describes genetic maps?
They are based on recombination frequencies between genes?
A yellow female Labrador retriever was mated with a brown male. Half of the puppies were brown, and half were yellow. Explain how the same female, when mated with a different brown male, could produce only brown offspring.
The first male was bbEe, and the second male was bbEE.
In a testcross involving two heterozygous genes, equal numbers of recombinant and nonrecombinant progeny are produced. From this result, what can be concluded?
The genes are not linked
Anhidrotic ectodermal dysplasia is an X-linked recessive disorder in humans characterized by small teeth, no sweat glands, and sparse body hair. The trait is usually seen in men, but women who are heterozygous carriers of the trait often have irregular patches of skin with few or no sweat glands (see the illustration). Irregular patches of skin lacking sweat glands in heterozygous female carriers of anhidrotic ectodermal dysplasia are caused by __________. the distribution of the patches of skin lacking sweat glands differ among the females depicted in the illustration, even between the identical twins?
The inactivation of the X chromosome with the wild type allele int he cells of the sweat gland lacking patches It is due to random inactivation of different X chromosomes in different cells
A three-point linkage analysis found a coefficient of coincidence value of 1.0. What does this value reveal about the number of observed double crossovers in the progeny?
The number of observed double crossovers was the same as the number of double crossovers predicted by probability
What information about recombination frequencies enables scientists to create linkage maps?
The recombination frequency is proportional to the distance between the two genes
Definition of a mutation
The ultimate source of alleles new phenotye result from changes in functional activity of gene product
Which description best defines a haplotype?
The. group of alleles in close association on a chromosome that are likely to be inherited together
A cross between two short tailed mice results in offspring in the ratio of 2/3 short tailed and 1/3 long tailed. The best explanation for this result is that _____
There is a recessive lethal allele
A cross between two short-tailed mice results in offspring in the ratio of 2/3 short-tailed and 1/3 long-tailed. The best explanation for this result is that _____.
There is a recessive lethal allele
Why do calculations of recombination frequencies between loci that are far apart on chromosomes underestimate the true genetic distance between the loci?
There is an increased probability of double crossover events with increasing distance, such that a gamete can maintain the parental genotype even after many recombination events
T/F females are the homogametic sex
True in humans, false in chickens
Nondisjunction in the first meiotic division in a male human could result at fertilization in
Turner or Klinefelter syndrom
Humans with only one sex chromosome (XO) usually have underdeveloped sexual characteristics and are sterile. What is this condition called?
Turner syndrome
You have read that in guinea pigs, black fur is dominant to white fur. You are surprised then when your two white guinea pigs have all black F1. When you cross the F1, you observe 9:7 black:white. How do you best explain this?
Two genes are responsible for the trait because its not 9:3:3:1 which is when 1 gene is involved
Assume that a single crossover occurs between two genes during meiosis. What would be the consequence of this crossover event?
Two of the four chromatids will be recombinant and two will be nonrecombinant
Bombay phenotype
Type O female yet one parents as type AB blood female found to be homozygous for FUT1 at the fucosyl transferase locus no substrate to make a or b antigens
What is cytoplasmic inheritance
Usually physically passed down from one parent in the mitochondria
Which statement below defines epistasis?
When one locus affects or covers the outcome of another locus
What is the genotype and the sex affected of the following syndrome Turner
X0 Females
In which of the following individuals would you expect to find two Barr bodies in their somatic cells?
XXX
What is the genotype and the sex affected of the following syndrome Klienfelter
XXY males
Which of the following chromosome constitutions would never lead to a viable human baby being born?
YY
In Barr body will Xist be expressed?
Yes
The Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two sons who die of bleeding after circumcision (removal of the foreskin from the penis), any additional sons that she has should not be circumcised. The bleeding is most likely due to the X-linked disorder hemophilia. Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should be. Is this religious law consistent with sound genetic principles?
Yes, the woman is a carrier and half (50%) her sons will be affected. Her sisters may also be carriers, but her brother's sons will get their X chromosomes from their mothers and likely be unaffected.
What is genetic anticipation
a genetic disease has an earlier onset and increased severity in each succeeding generation due to the expansion of unstable regions of DNA
What is the apparent purpose for X inactivation in humans and other mammals?
allows for the levels of expression of the genes on the X chromosome to be similar in males and females
Lethal allele deffintion
an allele that has the potential to cause the death of an organism usually cause mutations in essential genes
How are mitochondrial genes typically inherited?
an individual inherits their mitochondrial DNA from their mother
in a plant species, if the B allele (blue flowers) and the W allele are incompletely dominant, what offspring ratio is expected in a cross between a blue flowered plant and a while flowered plant?
all light blue
Complementation group
all mutations present in any single gene
Duchenne muscular dystrophy is caused by a recessive X-linked allele. A man with this disorder _____.
b) must have inherited it from his mother
For single crossovers, the frequency of recombinant gametes is half the frequency of crossing over because a. a testcross between a homozygote and heterozygote produces 1⁄2 heterozygous and 1⁄2 homozygous progeny. b. the frequency of recombination is always 50%. c. each crossover takes place between only two of the four chromatids of a homologous pair. d. crossovers occur in about 50% of meiosis.C
c. each crossover takes place between only two of the four chromatids of a homologous pair.
Why does X inactivation not affect syndromes such as Turner or Kleinfelter
chromosomes inactivation not in early stages of development for cells destined for gondadal tissue Not all X chromosomes forming Barr bodies are inactivated (15% escape inactivation)
In human blood groups, the face than an individual can have an AB blood type is an example of
codominance
When 2 alleles are both expressed together is known as _____
codominance
A man and a woman are both deaf due to being homozygous for a recessive autosomal mutant allele. However, they are homozygous recessive at different gene loci. If all their children have normal hearing, which of the following has occurred within each child?
complementation
What type of dominance? A pea plant with all purple flowers and a pea plant with all white flowers produce a pea plant with all purple flowers
complete dominance
Temperature dependent sex determination
controls sex determination in reptiles (CROCS) they incubate
Chromosome interference
crossovers in one region decrease the probability of a second cross over cross by
In humans, mitochondrial genetic disorders are inherited from only the mother. The severity of such diseases can vary greatly, even within a single family. What form of inheritance does this represent?
cytoplasmic inheritance
Genomic imprinting
differential expression of genetic material depending on whether it is inherited from the male or female parent
What is TDF
encodes protein that triggers testes formation
Gin of function mutation
enhances function of wild type quantity of gene product increases dominant mutations
A trait, such as height, has high heritability because much of the variation between individuals is the result of genetic variation. However, not all of the variation for height in a population can be attributed to genetic variation alone. Why does genetic variation not always determine the differences in a given trait between individuals?
environmental influences can change gene expression
Bombay phenotype is an example of
epistasis -- mutant FUT1 gene masks expression of Ia and Ib alleles
What does sex linked mean
found on the sex chromosomes
CFTR is an example of
gene with pleiotropic effects it regulates ion transport across cell membranes. Mutant allele causes ion imbalances
A gene whose expression is affected by the sex of the transmitting parent demonstrates which of the following?
genomic imprinting
Human males, with XY chromosomes are ___________ and produce two different kinds of gametes, whereas females with XX chromosomes are ___________ and produce only one kind.
heterogametic homogametic
PKU as an environmental effect
if detected early individuals can be fed a restricted diet essentially free of phenylalanine and remain symptom free
A Barr body is a(n):
inactivated X chromosome, visible in the nucleus of a cell that is normally from a female mammal.
What type of dominance? A moth with red wings and a moth with yellow wings produce a moth with orange wings
incomplete dominance
What type of dominance? a black sheep and a white sheep produce a gray lamb
incomplete dominance
When a heterozygote exhibits a phenotype that is intermediate between the homozygous phenotype is known as _____
incomplete dominance
Which statement best describes human sex determination?
individuals with a Y chromosome are male
What is dosage compensation?
it offsets the difference in active chromosomes between sexes
environmental sex determination examples
limpet positions in the stack teperature in turtles
Loss of function mutation
loss of WILD TYPE function results in generally recessive mutations
47 XYY condition
males are using over 6 feet personality disorders subnormal intelligence
Nondisjunction in which parent and what meiosis would give you an individual with Klinefelter syndrome (XXY)
males in meiosis 1 Females in meiosis 1 or 2
Genomic maternal imprinting mendelian vs non-mendelian
mendelian: silencing impacts phenotypic expressions, depends on parental origin of genes non: depends on how genes are marked, not both inherited
List the ratio of X chromosomes to autosome sets will give you metafemale, female intersex male metamale
metafemale: 1.5 (3X, 2A) female: 1 (3X:3A) or (2X:2A) intersex: 0.75 (3X : 4A) male: 0.5 ( 1X:2A) metamale: 0.33 (1X:3A)
What is pleiotropy
multiple effects of. single gene can be caused because can affect cell function in more than one way expressed in different cell types expressed at different stages of development
Coefficiant of coincidience
observed number of double recombinants divided by expected
How is sex determined in humans?
presence of a Y chromosome
What is heterogamous mean
producing unlike chromomes EX: XY in males
Maternal effect
refers to an inheritance pattern for certain nuclear genes in which the genotype of the mother directly determines the phenotype of her offspring due to the accumulation of gene products that the mother provides to her developing eggs
The water snail
right handed -Dextral Left handed - sinistral ONLY DECIDED BY MOTHER
Complementation analysis
screens number of individuals mutations resulting in same phenotype can predict total number of genes determining a trait
In an allele is dominant in one sex and recessive in another, it is an example of
sex influenced inheritance
Male pattern baldness is an example of _____
sex influenced traits BB genotype is dominant in males and recessive in females
Scurs on cows is an example of ____
sex influenced traits allele B Is dominant in males but recessive in females
A recessive mutant allele of an autosome gene in a species of mouse results in a shorted tail in males when homozygous. However, when homozygous in females, this genotype has no effect, and the mice have normal tails. What is this genetic phenomenon called?
sex limited characteristic
Sex limited inheritance are controlled by what
sex limited inheritance
The phenomenon where half the "normal" level of functional protein is not enough to generate a normal phenotype is called haploinsufficiency. Which of the following situations demonstrates haploinsufficiency?
small eye in mice is caused by loss of one copy of the Pax6 gene
The coat characteristics of arctic foxes and Siamese cats, where proteins in the extremities function differently than in other parts of the body, is an example of _________.
temperature sensitive alleles
Multifactorial characteristics result from which of the following?
the activity of polygenes influenced by environmental factors
Definition of Locus
the chromosomal site where a specific gene is located
what is expressivity
the degree to which a train is expressed
With genetic maternal effect, the phenotype of an individual is determined by which of the following?
the nuclear genotype of the maternal parent
Defintion of interference
the observed double crossover frequency differs from the expected double crossover frequency
What is penetrance?
the percentage of individuals having a particular genotype who express the expected phenotype
what is maternal effect
the phenotype of an individual is determined by the genotype of the mother
In humans, what normally results in the male sexual phenotype?
the presence of the SRY gene on the Y chromosome
Definition of recombination
the process by which a new pattern of alleles on a chromosome is generated
Mapping function
the relation between genetic map and distance and the frequency of recombination
Definition of linkage
the tendency for genes located in close proximity on the same chromosome to be inherited together
What is a pseudoautosomal region
the very genes found on both X and Y chromosomes
Which of the following is not a physical mapping technique?
three point test cross
What gene is most responsible for inhibition of X-inactivation?
tsix
what is penetrance
when a certain percent of the population has it
Epistasis is ___
when one gene can mask the effects of a second gene
When do gene interactions occur
when two or more different genes influence the outcome of a single trait
Coupling chromosomes
wild type ales are found on one chromosome and mutant alleles are found on the other allelic arrangement in which mutants are on the same chromosomes and wild type alleles on the homologue Cis configuration
A young boy is diagnosed with hemophilia A, a recessive, X-linked condition. If neither parent has hemophilia A, what are their genotypes?
xAxa, xAY
