Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
41 Cards in this Set
- Front
- Back
|
population genetics:
-Deals with the extent and pattern of genetic variation among individuals within a population and between populations -Main focus is understand the ... of genetic variation -At the heart of genetic variation are ... and occasionally ... |
maintenance
polymorphisms mutations |
|
|
Usefulness in medical genetics
provides knowledge about different disease genes that are common in different populations necessary for clinical diagnosis and genetic counseling -practical use in genetic counseling for ... disorders -estimations of ... carriers of recessive alleles very important in determination of allele ... for risk calculations |
autosomal recessive
heterozygote frequencies |
|
|
... - all the alleles for all the genes in a population
|
gene pool
|
|
|
different forms of genes are called ...
|
alleles
|
|
|
For any one individual, one gene is represented by two different alleles on homologous chromosomes.
-one allele is inherited ..., the other .... |
paternally
maternally |
|
|
Individual members of a population have ... alleles.
-the number of alleles for any particular gene can vary -one gene may have only two representative alleles while another gene may have several representative alleles. |
different
|
|
|
... - shared by all of the individuals in a population
1. All the alleles present at a given ... OR 2.Collectively all the ... for the genes in a population |
Gene pool
locus alleles |
|
|
...
-Cell surface chemokine receptor -Promotes HIV infection ... -Non-functional protein -Lack of receptor expression on surface leads to resistance against HIV infection |
CCR5
ΔCCR5 |
|
|
The size differences between CCR5 and ΔCCR5 alleles are easily distinguished by ....
|
PCR
|
|
|
Using PCR, determine if individuals are ... for either the CCR5 allele or ΔCCR5 allele or ... for both: CCR5/CCR5, ΔCCR5/ ΔCCR5 or CCR5/ ΔCCR5
Take a ... to determine absolute numbers of individuals who are homozygous or heterozygous. |
homozygous
heterozygous random sample |
|
|
The size of a gene pool at a given locus is ... the number of individuals in the population because each autosomal genotype consists of ... alleles
An alternate way of calculate the allele frequency of ΔCCR5 is simply to subtract the allele frequency of CCR5 from 1. 1-0.906=0.094 |
twice
two |
|
|
What is this?
Allows for the determination of what proportion of the population express various genotypes based on established allele frequencies |
Hardy-Weinberg Equilibrium
|
|
|
Hardy-Weinberg Equilibrium
Two components: 1. The expression of autosomal traits by heterozygotes (Aa) ... by distinguished from expression by homozygotes (AA) 2. Allele frequency and genotype frequency ... change from generation to generation-Hardy-Weinberg Equilibrium |
cannot
do NOT |
|
|
Hardy-Weinberg Equation
p= frequency of ... in the population q= frequency of ... in the population Since A and a are the only two alleles found at this locus, p+q=... Frequency of the three genotypes AA, Aa, and aa is given in terms of the binomial expression ... |
A
a 1 (p+q)^2 =p^2+2pq+q^2 |
|
|
Hardy-Weinberg Equation
Assuming that p is the frequency of allele A and q is the frequency of allele a in a gene pool, alleles will combine randomly into genotypes with the following frequencies: -Chance that two A alleles combine is p2 -Chance that two a alleles combine is q2 -Chance that one A allele and one a allele pair is ... -2 comes from the possibility that the A allele could be inherited from the mother and the a allele from the father and vice versa |
2pq
|
|
|
Hardy Weinberg Assumptions
1. Population size is ... and matings are ... with respect to the locus in question -offspring produced by different individuals with different genotypes will be ... -assume no change in the ... of any particular genotype -... is measured by the number of offspring produced in the next generation that survive and reproduce -probability of passing one’s genes to the next ... 2. Maintaining a constant ... A. No appreciable rate of new ... B. No selection against any particular ... -all individuals with all genotypes are equally capable of matting and passing on their genes -selection is the impact of forces (state of environment) that determine the relative fitness of a genotype in the population -affects the frequency of the allele concerned C. No ... in or out of the population OR There is no significant immigration of individuals from a population with allele frequencies very different from the endogenous population 3. ... locus |
large
random balanced fitness fitness generation allele frequency mutations phenotype migration Autosomal |
|
|
Is the following population, at the indicated genotype frequencies, in Hardy Weinberg equilibrium? (hint: p^2 + 2pq + q^2 = 1)
AA, 0.25, Aa, 0.50, aa, 0.25 Yes or No? |
Yes
|
|
|
In a real population most mating are ... random
In a population the following are observed: -Stratification -Assortive Mating -Consanguinity and inbreeding |
NOT
|
|
|
... - violation of the principle of random mating for any locus
-three distinct but related phenomena account for non-random mating -significant ... in the number of shared genotypes -all bring about an ... in the frequency of autosomal recessive disorders by increasing the frequency with which carriers of an autosomal recessive disorder mate |
Non-random mating
increase increase |
|
|
1. ...
-restriction of mating to members of one particular subgroup -occurs in populations in which there are a number of subgroups that remain genetically separate -in US these groups are Caucasians, African-Americans, numerous Native American, Asian and Hispanic groups |
Stratification
|
|
|
2. ... Mating
-choice of mate based on a particular trait -tend to be positive attributes -individual chooses mate that resemble themselves (stature, intelligence, talent) -characteristics that are in part determined by genetics -choose of mate based on opposing traits is called ... mating |
Assortive
negative assortive |
|
|
3. ... mating
-... is relationship by descent from a common ancestor (second cousin or closer) -allow for uncommon alleles to become homozygous -recessive disorders that result from ... matings are rare and unusual |
Consanguineous
consanguinity consanguineous |
|
|
extensive ... exist between individuals in a population
-variations are found are similar ... in all human populations |
polymorphisms
frequencies |
|
|
Other times there are observed ... differences
- some alleles, present in all population groups, demonstrate drastic differences in frequencies among population groups -while other allelic variants are restricted to certain populations and not present in al members of the group |
ethnic
|
|
|
Factors that contribute to deviations from the Hardy Weinberg Equilibrium
Mutations Natural Selection Gene Flow (...) Genetic Drift -... Affect -... Advantage |
Migration
Founders Heterozygote |
|
|
Mutations and Natural selection:
-The frequency of an allele in a population represents a balance between the ... at which mutant alleles appear through mutations and the ... of selection. -Selection is the forces that affect the biological fitness of a genotype in the population, thus affecting the ... of allele concerned -Transmission of an allele to successive generation is dependent on the ... of the allele |
rate
effects frequency fitness |
|
|
Fitness number of offspring produced in the next generation that survive and reproduce
1. Fitness of ...-mutant allele just as likely to be represented in next generation as normal allele 2. Fitness of ...-mutant allele death or sterility -so in a genetic sense, a mutation that prevents reproductions is just as lethal as one that causes an early miscarriage -neither is transmitted to the next generation |
1
0 |
|
|
Natural selection
-more readily impacts ... disorders because the disease-causing allele is readily exposed to affects of selection -... allele frequencies -significantly lower impact on ... disorders because disease-causing allele is hidden by heterozygotes |
dominant
lower recessive |
|
|
what is this?
-Slow diffusion of genes across a reproductive barrier -Involves a large population and a gradual change in the gene frequencies |
gene flow (migration)
|
|
|
Migration
change in allele ... by the gene flow gene of migrant populations with characteristic allele frequencies are merged into the gene pool of a population into which they migrated -the term migrant is used broadly, NOT necessarily geographical, can be racial, ethnic or cultural |
frequency
|
|
|
Gene flow (migration):
Example is the ... of the ΔCCR5 allele originated in Caucasians and diffused into easterly populations -highest in western Europe and Russia -declines in Middle East and India -almost absent in Africa and Fareast |
frequency
|
|
|
... is the result of random effects of environment or other chance occurrences that are independent of the genotype
|
Genetic drift
|
|
|
... leads to a high frequency of a mutant allele in a population founded by a small ancestral group when one or more of the founders was a carrier of the mutant allele
|
Founder effect
|
|
|
Genetic Drift
accounts for increase or decrease of certain genetic ... in small, isolated population operating in a ... population has significant consequences on allele frequency -same effects would not alter the allele frequencies of a ... population result of random effects of environment or other chance occurrences that are ... of the genotype (ex. War, Tsunami) |
diseases
small large independent |
|
|
Founder Effect
type of ... break off of a small ... from a larger population new group is a ... sampling of the larger population and may have different allele frequencies than larger population one of the founding members of the group carries a ... allele -allele frequency in subpopulation is much higher than in larger population from which it was derived -... mating choices |
genetic drift
subpopulation random rare fewer |
|
|
Genetic Drift and Founder Effect
One example: High incidence of Huntington disease (autosomal ...) in Lake Maracaibo, Venezuela Another Example: High incidence of Ellis-van Creveld syndrome (autosomal ...) among the Old Order Amish -large families with high frequency of consanguineous marriages -short-limb dwarfism, polydactyl, abnormal nails and teeth and congenital heart defects |
dominant
recessive |
|
|
-Historically, the maintenance of a polymorphism necessary for survival of the species, that came at the cost of individual ...
-Prior to therapeutic intervention, individuals lacking the sickle cell allele were unable to survive in regions where ... was endemic -Individuals ... for the sickle cell trait are able to control malarial infection -Individuals ... for the sickle cell allele are also able to control malarial infection, but typically die of sickle cell anemia |
survival
malaria heterozygous homozygous |
|
|
Heterozygote Advantage
-mutant alleles deleterious in ... -environmental conditions in which heterozygotes, FOR SOME DISEASES, have increased ... not only over homozygotes for the mutant allele but also over homozygotes for the normal allele -leads to an increase in the frequency of an allele that is ... in homozygotes because the heterozygotes greatly outnumber the homozygotes in the population |
homozygotes
fitness detrimental |
|
|
Malaria and the Sickle Cell Trait
-prior to therapeutic intervention, individuals lacking the ... allele were unable to survive in regions where malaria was endemic |
sickle cell
|
|
|
Sickle cell anemia
1. ... for the sickle cell allele -individuals with sickle cell anemia are homozygous for the mutant allele -upon exposure to low-oxygen conditions, RBCs lose their healthy, round shape and become sickled -the sickle shape causes the RBCs to lodge in capillaries, resulting severe bouts of pain and lead to organ damage, strokes and anemia 2. ... -individuals who carry one mutant allele and one normal allele show a mixed phenotype -experience sickling only under extreme conditions -do not experience ill effects of disease, yet carry sickle cell trait -..., parasite responsible for malarial infection, is unable to establish a produce infection cycle in either heterozygotes or homozygotes 3. Homozygotes for the normal allele -greatest chance of passing on genes successfully with regards to the sickle cell allele, yet, they have the greatest chance of dying from ... |
Homozygotes
Heterozygotes Plasmodum flaciparum malaria |
|
|
The highest frequency of sickle cell allele is found in West Africa, where there is the highest level of ... infections.
-the allele frequency is dropping in populations that have migrated out malarial endemic regions -the allele frequency is dropping in endemic regions where medical and mechanical intervention is available |
malarial
|
