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167 Cards in this Set

  • Front
  • Back
The study of..?
Not the study of genes. NOT molecular. Its INHERITANCE PATTERNS!
Biological factos that induce particular traits.
Alternate forms of a given gene, inherited from different parents. (1 copy on each homolog)
The location on a chromosome, often used to refer to the gene at that site.
(Refers to the site on a chromosome of a particular gene.)
An allele which always determines the phenotype.
An allele which only determines phenotype in the absence of a dominant allele.
A mutant allele, or individual with a mutated allele.
Wild Type
An allele that is not mutated, alleles that occur normally in nature. Usually these are dominant alleles. Wild type can also be used to refer to an individual who does not carry a mutated allele.
The combination of alleles in an individual. (ex- the genotype for someone with a Brown eye allele and a Blue eye allele is Bb.)
Observable characteristics. The physical manifestation of the genotype. (ex- the phenotype of a Bb person is Brown eyes.)
To carry both copies of the same allele (Both dominant, BB, or both recessive, bb.)
To have different alleles. (One dominant and one recessive, ex- Bb.)
A homozygous individual.
A heterozygous individual.
Monohybrid Cross
A cross where one gene locus is tracked. (ex- Aa x Aa)
Dihybrid Cross
A cross where two loci are tracked. (ex- AaBb x AaBb)
Trihybrid Cross
A cross where three loci are tracked. (ex- AaBbCc x AaBbCc)
Filial One
The first generation produced in a series of crosses.
Filial Two
The second generation produced ina series of crosses.
Independent Assortment
Inheritance of alleles at one locus does not influence inheritance at other loci.
This is a product of crossing over.
Independent Assortment.
Sex Chromosome
Sex determining chromosome, X or Y.
Any chromosome except X or Y.
X Linked
(Sex Linked)
A gene located on the X chromosome.
Any genen not located on X, or characteristic not associated with X.
blu= blue eye color
blu+= brown eye color
eds= Ehlers Danlos Syndrome
+=wild type
Parent (In Monohybrid Cross)
a typical monohybrid cross begins with two homozygous parents, one dominant and one recessive.
Gametes (In Monohybrid Cross)
The dominant parent can only produce dominant gametes, the other only recessive.
F1 (In Monohybrid Cross)
The first parent must contribute a dominant allele while the other must give a recessive allele, so all first generation progeny must be heterozygous.
F1 Gametes (In Monohybrid Cross)
Each gamete from each parent has an equal chance of inheriting iether allele, so half will carry the dominant form, half recessive.
F2 (In Monohybrid Cross)
How many ways to produce homozygous dominant progeny?
Heterozygous progeny?
Homozygous recessive progeny?
There is only one way to produce a homozygous dominant progeny.
There are two ways to produce heterozygous progeny (dominant from the father, recessive from the mother; recessive from the father, dominant from the mother)
There is only one way to produce homozygous recessive progeny.
What is the ratio of the F2 generation in a Monohybrid Cross?
Homozygous Dominant: Heterozygous: Homozygous Recessive
What is the phenotypic ratio of a Monohybrid Cross?
Because homozygous dominant and heterozygous progeny have the same appearance, the phenotypic ratio is 3:1.
Monohybrid Cross
A cross where one gene locus is tracked.
(ex- AA x aa)
Dihybrid Cross
A cross where two gene loci are tracked.
(ex- BBEE x bbee)
What is the F2 genotypic ratio for a dihybrid cross?
What is the F2 phenotypic ratio for a dihybrid cross?
F1 generation in a Dihybrid Cross?
As with the monohybrid cross, all first generation progeny must be heterozygous.
Where does independent assortment occur in a Dihybrid Cross?
In the F1 Gametes
Inheritance at one allele is ____ of another.
Why is inheritance at one locus independent of another in the F1 gametes of a Dihybrid Cross?
Because meiosis segregation of one pair of homologs is independent of another, and because crossing over shuffles alleles between homologs.
For a heterozygous, dihybrid cross, there are ___ possible combinations of the alleles in the gametes.
F2 Generation in a Dihybrid Cross:
The ___ different types of gametes fromt eh two different parents can combine in ___ different ways.
How can you distinguish an individual's genotype from their phenotype?
Heterozygotes look the same as homozygous dominant. A test cross is a simple procedure for making this determination.
What is the procedure for distinguishing an individual's genotype from their phenotype?
Cross the unknown subject with a homozygous recessive mate. (ex- B? x bb)

If ? is B, all F1 have brown eyes.
If ? is b, f1 ia half brown, half blue eyes.
What is the rational behind a test cross?
Because the test subject is dominant phenotype, they must have at least one dominant allele. The unknown is their second allele. With a test cross this unknown allele must pair with a recessive allele from the mate. That is all the mate has to contribute. Thus, if the unknown allele is recessive, half the F1 will be homozygous recessive. If the test subject is homozygous dominant, all the F1 will be heterozygous with dominant phenotype.
This serves to reveal recessive alleles by guaranteeing that they pair with other recessive alleles.
Test Cross
In a test cross, if the F1 are all dominant phenotype, then the test subject was _____?
Homozygous Dominant
In a test cross, if the F1 are half dominant phenotype, half recessive, then the test subject was _________?
What is the ratio produced whenever you cross a homozygous recessive with a heterozygote?
This is a method for determining genotypic or phenotypic ratios by writing every possible combination in a matrix.
Punnett Squares
Test Cross
Genotypic Ratio?
Phenotypic Ratio?
1:1 (Bb x bb)
1:1 (B x b)
Monohybrid Cross
Genotypic Ratio?
Phenotypic Ratio?
1:2:1 (BB: Bb: bb)
3:1 (B: b)
Dihybrid Cross
Genotypic Ratio?
Phenotypic Ratio?
What kind of test would you do to answer this question-
Are two mutants with the same phenotype (ex- EDS) priduced by different mutations of the same gene OR by defects in separate genes where either mutation results in the same phenotype?
Complementation Test
What is the procedure in a complementation test?
Cross two homozygous mutants with each other.
What is the rational behind the procedure of a complementation test?
Procedure- Cross two homozygous mutants with each other.
Rationale- If the mutations are in the same gene, then the F1 will inherit two mutated alleles for the locus and they will have the condition.
In a complementation test, if the mutated alleles are in separate genes-?
The F1 will all be heterozygous for both loci and they will be healthy. The wild type allele at each locus corrects the defect, and the genes are said to compliment each other.
Complimentary genes are ____ genes.
(If two mutations compliment each other, they are in different genes.)
Non-Mendelian Inheritance
There are genetic interactions other than the autosomal recessive pattern characterized by Mendel. These are known as non-Mendelian inheritance.
What are seven types of Non-Mendelian Inheritance?
1) Semidominance
2) Codominance
3) Polygenic Inheritance
4) Epistasis
5) X linkage
6) Sex Influenced Inheritance
7) Linkage
Partial or incomplete dominance.
Different alleles for a particular gene have equal effects, so that heterozygotes have intermediate phenotypes.
This is an example of what?
In snapdragon flowers, one allele mkes the flower red when homozygous. Another allele makes them white. However, heterozygotes are pink, intermediate between red and white.
What are the phenotypic ratios in semidominance?
The phenotypic ratios are the same as genotypic ratios. (1 red:2 pink:1 white)
Different alleles for a gene that impart independent effects on phenotype.
What is a classical example of Codominance?
A and B blood types.
Homozygotes for the Ia allele are blood type A, which means their RBCs express the A antigen, so they do not produce anti-A antibodies, and they do not react against A type blood. They do reacts against B type transfusions, because B antigens are recognized as foreign.
Homozygotes for the Ib allele react against ___ type blood.
more than two alleles for a given gene
(ex- eye color)
Polygenic Inheritance
To have multiple genes influencing the same trait.
For a gene to mask the phenotype of another gene, at another locus.
This is not a dominant allele masking a recessive allele, this is a gene suppressing the phenotype of a totally separate gene.
In epistasis, the gene that masks the phenotype is called a ___?
The gene that masks the phenotype is said to be ___ to the gene it suppresses.
The suppressed gene is sometimes described as ___?
Epistasis Analysis
This is another type of diagnostic cross. It uses suppressors to determine the order of different genes ina regulatory pathway.
This analysis determines whether a gene acts upstream or downstream of another gene.
Epistasis Analysis
In this type of analysis, we would begin by performing a series of crosses to generate progeny that are homozygous for two loci (ex- bbpp). We would then score these double homozygotes to determine which phenotype is suppressed.
Epistasis Analysis
One gene suppressing another. Used to determine the order of genes in a pathway.
Epistasis Analysis
X Linkage
Genes carried on the X Chromosome
Sex Chromosomes
Sex determining chromsomes, X and Y.
All chromsomes besides X and Y.
X Linked
gene located on X chromosome
A gene not located on X or Y
Males have half as many X linked alleles as females. They carry alleles on their X with no corresponding alleles on their Y. This is because Y only carries a few genes.
Sex Influenced Inheritance
Autosomal gnees, not carried by the X or Y chromosomes, but which are differentially expressed in males and females.
These are usually involved with secondary sexual characterisitics such as body hair, fat distribution and aggression.
Sex Influenced Inheritance
Characteristics of X Linkage
The distinguishing characteristic of X linked recessive alleles is they are passed from affected grandfathers, through unaffected mothers, to affected grandsomes.
These are expressed in males more often than females.
X Linked Genes
What is the key pattern in a Sex Linkage?
Affected Grandfather
Carrier Mother
Affected Son
If a homozygous wild type mother is crossed witha color blind father, what is the F1 generation?
This generations progeny are all wild phenotype, but the daughters are heterozygous carriers, not hte sones. The hemizygous boys have wild type X chromosomes while their Y chromosomes carry no alleles for this locus.
F2 generation if a homozygous wild type mother is crossed with a color blind father.
Because the F1 daughters are heterozygous, they give wild type alleles to half the F2 progeny, and mutated alleles to the other half.
What is the genotype and phenotype of F2 granddaughters iwth a homozygous wild type mother crossed with a color blind father?
The F2 granddaughters are either heterozygous or homozygous wild type. They all have wild phenotypes.
What is the genotype and phenotype of F2 grandsones froma homozygous wild type mother crossed with a color blind father?
The hemizygous grandsons lack an allele on their Y chromosomes so they are either wild phenotype or color blind.
Homozygous wild type mother crossed with a color blind father.
All the F1 children and F2 granddaughters are ____ type, but half the grandsons are ___ and half are ___.
Wild type
Wild type
Color blind
The X linked allele is passed from the father, through his daughters to half his ___.
What is the rational behind dosage compensation?
The X chromosome carries numerous genes while the Y chromosomes carries very few. Most Y linked genes are involved with sex determination. Therefore females, who have two X chromosomes possess twice as many X linked genes as males, who only have one X. To avoid genetic imbalance there must be a mechanism to adjust expression of X linked genes.
X Inactivation
In mammals, the adjustment for dosage compensation is achieved by inactivation one X chromosome in each blastomere. These inactivated X chromosomes become condensed (heterochromatic).
Inactivated, condensed, heterochromatic X chromosomes are known as___?
Barr bodies
When does X chromosome inactivation offur?
Early in embryogenesis, around the 64 cell stage.
How does X chromosome inactivation work?
It is random. One or the other X may be inactivated in each blastomere. This results in body regions where all the cells have the same inactivated X.
Genetic Mosaics
Female mammals, in which certain body regions all have the same inactivated X chromosome.
Anhidrotic Ectodermal Dysplasia
What is it?
What does it demonstrate?
The absence of sweat glands.
Results from genetic mosaics due to inactivation of X chromosomes in the blastomeres.
Why are all calico cats female?
Result of genetic mosaics where cells of a certain area all share the same inactivated X chromosome. Dosage compensation.
When two genes are so close they usually segregate together during inheritance.
This is a violation of the principle of independent assortment.
If two alleles are on the same homolog, they are ___ to each other. If they are on different homologs, they are in the ___ conformation.
Consider two heterozygous loci that are cis to each other. If these loci are far apart there is a great chance of a cross over occurring between them. Whenever this occurs recombinant ___ progeny are produced.
The closer two genes are, the less ____ you see between them.
Recombination (Crossing Over)
Linkage Mapping
Estimating distances between loci by determining recombination frequencies.
Recombination frequency between genes is proportional to the ___?
Distance between the loci
Map Unit
Percent recombination between two loci.
(1 MU = 1%)
How do you determine which are the parental types and which are the recombinant types in linkage mapping?
The parental types have a higher number.
What is the formula for Linkage Mapping?
100 x (Recombinant)/ (Total)
What is the greatest number of map units you can have?
This is because if the distance is greater than 50 MU, there is an equal chance of having an equal or odd number of crossover between the lci, so there is the same chance of producing recombinant or parental genotypes.
What is the criteria for linkage?
Genes that are 50 MU apart or greater are not linked, while if they are less than 50 MU apart, they are linked.
Multifactorial Traits
Characteristics controlled by multiple factors, both genetic and environmental.
What is an example of something that is purely genetic? (Not multifactorial.)
Finger prints
Any trait controlled by multiple genes AND environmental factors. NOT just genetics!
Multifactorial trait
Polygenic Inheritance
For a trait to be controlled by multiple genes
This is the genetic component of a multifactorial trait.
Polygenic Inheritance
For a single gene to control multiple traits.
What is an example of Pleiotrophy?
Cystic Fibrosis
Knock out 1 gene leads to multiple effects.
Multiple alleles in a population for a gene.
For a given locus, there are multiple alleles in the population.
Estimate of how much genetics (as opposed to environment) contributes to a given trait.
Estimate of how much of a trait is controlled by the polygenic component.
Quantitative Multifactorial Traits
Can be assigned a numerical value. (ex- BP, height, weight)
Qualitative Multifactorial Traits
Either occur or dont. These are all or none phenomenon. (ex- heart attacks, nerual tube defects)
A multifactorial trait is influenced by numerous factors. These factors are ___ as well as ___.
Polygenic traits are by definition ___.
This is controlled by an interaction between many different factors, both the multitude of genes that influence the trait, and any environmental conditions that the individual is exposed to.
Multifactorial Traits
Normal Distribution of Multifactorial Traits
Most multifactorial traits fall into a normal distribution (bell shaped curve).
Hardy Weinberg Equilibrium
This is a model explaining how genes and alleles are distributed throughout a population. The model assumes that the distribution, or frequency of each allele, is at steady state.
What is the formular for the Hardy Weinberg Equilibrium?
p2 + 2pq + q2 = 1
p + q = 1
In the Hardy Weinberg Equilibrium,
p = frequency of most abundant allele in the population
q = less abundant allelic frequency (usually the recessive)
Frequency refers to the ___. This is why p and q add up to one.
The fracion of all the alleles in the population.
Carrier frequency
Affected frequency
usually homozygous recessive (aa)
allelic frequencies
p and q
genotypic frequencies
(Hardy Weinber Equilibrium)
p2, 2pq, q2
p2 = ?
2pq = ?
q2 = ?
p2 = unaffected frequency
2pq = carrier frequency
q2 = incidence (frequency of disease or trait)
What is the primary assumption of the Hardy Weinberg model?
That the population is at equilibrium, which is to say gene frequencies are constant.
What is the true definition of evolution?
With this in mind, what is another way to state the primary assumption of the Hardy Weinberg Model?
Evolution is any change in gene frequency.
The population is not evolving.
What are the secondary assumptions of the Hardy Weinberg Model?
Four mechanisms for changing gene frequencies. Must be met for the primary assumption to be valid.
1) Mutation
2) Genetic Drift
3) Migration
4) Selection
A change in gene sequence, usually resulting from an error in DNA replication. Any giben mutation only adds one allele to the population. This represents a minute change in allelic requency, so mutation is considered a minor force driving evolution.
Genetic Drift
Fora generation/s to randomly inherit a disproportionately high or low frequency of a particular allele. A random change.
In small populations such as isolated villages, this can have a much more substantial affect.
Genetic Drift
Emigration of a new population, with gene frequencies different from the native population, resulting in a combined population with frequencies different from either of the original populations.
This is a major factor in modern human populations, where advances in transportation are resulting in intermixing of races around the world.
What is the most important of the secondary assumtions in the Hardy Weinberg Equilibrium?
Forces that influence the chance that an allele will be passed onto future generations. Related to fitness.
The ability to pass genes onto the next generation.
diagrammatic representation of a family history
Index case.
The first family member identified with the inherited trait of interest.
For consanguineous individuals to produce offsprings.
Any two individuals who are descended from a common ancestor. This term usually refers to two individuals with a common ancestor in their recent family history, so that they are closely related.
What is the symbol for an X-linked recessive carrier?
A circle with a darkened circle in the middle.
What is the symbol for a Proband?
A darkened circle or square with an arrow pointing to it.
What are the characteristics for identifying an autosomal recessive inheritance pattern?
1) Tends to skip generations.
2) On the average, 25% of the offspring of carriers will be affected, 2/3 of the unaffected offspring will be carriers.
3) Both parents must be carriers.
4) Common for multiple siblings to be affected (horizontal transmission).
5) Affected offspring will be more common with consanguinity.
What are the characterisitics for identifying an autosomal dominant inheritance pattern?
1) There are usually several generations of affected offspring (vertical transmission).
2) All carriers are affected.
3) On the average, half of a carrier's offspring will be affected.
4) One one parent need be a carrier.
5) Homozygotes are usually rare. Most carriers are heterozygotes.
6) Sporadic cases caused by new mutations may be observable.
What are the characteristics for identifying a Sex Linked inheritance pattern?
1) More males will be affected than females.
2) Transmission will usually be from affected fathers, through carrier daughters, to affected grandsons.
3) No father to son transmission.
4) All daughters of affected males will be carriers.
5) Half the offspring of the female carriers will receive the mutated allele. The sons will be affected, the daughetrs carriers.
6) Sporadic cases caused by new mutations in hemizygous males may be observable.
What are the characterisitics for indentifying a Multifactorial inheritance pattern?
1) Distinguishing characteristic of polygenic traits is familial recurrence without any distinctive inheritance pattern.
2) The more closely related a subject is to an affected relative, the greater the subject's risk of manifesting the trait.
3) The occurrence tends to decline in a family from generation to generation.
4) Risk increases with greater numbers of affected family members.
5) Risk increases with more severe symptoms in family members.
6) If occurrence is frequent in a sex, risk increases for family members of that sex.
Coefficient of Relationship (R)
The fraction of identical genes shared by two relatives.
The number of matings (n) in a line is counted, and 1/2 is multiplied for each mating.
Coefficient of Relationship
Coefficient of Inbreeding (F)
The fraction of homozygous loci resulting from a consanguineous mating.
This can also be thought of as the chance that any given loci will be homozygous due to inbreeding.
Coefficient of Inbreeding (F)