01:119:115 Lecture 20: Lecture 20_ Microevolution

53 views5 pages

copperseal575

1 Dec 2017

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Some phenotypes are either on or off . Rapid (asexual reproduction) lots of mutations! Population genetics : study of the variability of genetics within a population. Gene pool : all alleles of all genes in a population. Allele frequency : proportion of a specific allele (w/w) in a population. Ex. population alleles are w and are w frequency of each will be 0. 5 f(w) = f(w) = 0. 5 (50%) (think about: could be: birds are ww and ww or all birds are ww) Ideal scenario = describes a population that is not evolving. Population"s frequencies of alleles will remain constant over time. This will continue as long as a large population continues to mate randomly and no outside agents act on the population. Mutations: no , random mating, no natural selection, large population, no . If any of these are not true, allele frequencies are changing! Only mutations in cells that produce gametes can be passed to offspring.

Related Questions

15. Population genetics provides answers for all of thefollowing questions except:

a. What is the frequency ofgenetic disease in a population?

b. What fraction of thephenotypic variation in a trait is the result of geneticvariation?

c. What alleles are most likelyto mutate?

d. Given certain quantifiablevariables, how long is a disease likely to persist?

e. How rapidly can a disease gaina foothold in a population?

16. Which of the following is not one of the assumptions of theHardy-Weinberg law?

a. The population is verylarge.

b. There is non-random matingwithin the population.

c. Mutations in the alleles donot occur.

d. No migration occurs into orout of the population.

e. The ability of all genotypesfor survival and reproduction is the same.

17. The heterozygote genotype frequency term for a gene with twoalternate alleles A (frequency p) and a (frequency q) in theHardy-Weinberg equation is:

a.p² b.q² c.2pq d.(p+q)² e. p+q

18. In humans, brachydactyly is a dominant condition. Sixthousand four hundred people in a population of 10,000 show thedisease (1,600 are BB, 4,800 are Bb) and 3,600 are normalphenotypes (bb). The frequency of the b allele is:

a.0.6 b.0.8 c.0.36 d..48 e. 0.16

19. Fitness is described as:

a. an individualâs ability tosurvive to adulthood

b. an individualâs ability toreproduce

c. an individualâs ability toadapt to change

d. all of the above are true

champagnewallaby382

These all relate to exceptions to the inheritance patterns encountered by Mendel.â

Why do multiple and lethal alleles often result in modifications of the classic Mendelian monohybrid and dihybrid ratios?

Select the four correct statements.

-When an essential gene is mutated, it can result in a lethal phenotype. There are no classic Mendelian monohybrid and dihybrid ratios.

-In the case of codominance, heterozygotes produce gene products from both alleles of a gene. Classic Mendelian monohybrid and dihybrid ratios are modified by codominance.

-In the case of incomplete dominance, the phenotype of the heterozygote is distinct from and often intermediate to the phenotypes of homozygous individuals. Classic Mendelian monohybrid and dihybrid ratios are modified by incomplete dominance.

-Genes exist in a large number of allelic versions and a diploid organism has two homologous gene loci that may be occupied by different alleles of the same gene. This can result in many different phenotypes for traits, which may not follow typical Mendelian ratios.

-When an essential gene is mutated, it can result in a lethal phenotype. This results in a modification of classic Mendelian ratios.

-The phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. The joint expression of both alleles in a heterozygote is called codominance. There are no classic Mendelian monohybrid and dihybrid ratios.

-Genes exist in a large number of allelic versions, but in a diploid organism, only one allele of the gene can occupy one homologous gene loci. Classic Mendelian inheritance cannot explain this phenomenon.

-Each gene produces a unique gene product. The effect of one allele in a heterozygote completely masks the effect of the other. Classic Mendelian genetics cannot explain this phenomenon.

Q1. What is the founder effect?

Sampling error that occurs during the establishment of a newpopulation by a small number of migrants.

Strong natural selection acting on the founders of a newpopulation because the environment they are now living in is sodifferent from the environment they came from.

A phenomenon named after William Founder, who observed that toppredators generally have low genetic diversity.

Rapid population growth following a bottleneck.

Q2. The effects of genetic drift are more pronounced in largerpopulations.

True

False

Q3. Inbreeding tends to increase the proportion of homozygousindividuals in a population (i.e. individuals that have two copiesof the same allele).

True

False

Q4. The effective size of a population is:

The size of an idealized randomly-mating population that is notunder selection and has the same heterozygosity as the actualpopulation.

The size of an idealized randomly-mating population that has thesame heterozygosity as the actual population, but does not loseheterozygosity over time.

The size of an idealized randomly-mating population losinghomozygosity at the same rate as the actual population.

The size of an idealized randomly-mating population losingheterozygosity at the same rate as the actual population.

Q5. Which of the following tends to reduce the effective size ofa population?

Check all that apply:

Increasing the population size.

A biased sex ratio.

Non-random mating.

Q6. If gametes from a gene pool combine randomly to make only asmall number of zygotes, the allele frequencies among the zygotesmay be different than they were in the gene pool because:

The effects of natural selection are more pronounced in smallpopulations.

The effects of genetic drift over several generations are morepronounced with small numbers of gametes.

The effects of differences in frequencies for different allelesare more pronounced with small numbers of zygotes.

The effects of sampling error are more pronounced with smallsamples.

Q7. Genetic drift is different from natural selectionbecause:

In natural selection allele frequencies change because somealleles confer higher fitness, whereas in genetic drift allelefrequencies change because of chance sampling error.

Natural selection acts primarily in large populations, whereasgenetic drift acts primarily in small ones.

Natural selection is a mechanism of evolution, whereas geneticdrift is an outcome of evolution.

Natural selection tends to cause rapid evolution, whereasgenetic drift tends to cause slow evolution.

Q8. Imagine a population evolving by genetic drift in which thefrequency of allele K is 0.65. What is the probability that at somepoint in the future allele K will drift to a frequency of 1?

Q9. A dwindling population of 1000 frogs occupies an isolatedwatershed in Costa Rica. To help preserve the species, scientistscaught 20 frogs to start a new population in a nearby watershed.This species has a gene that affects eye shape. The 1000-memberwild population has two alleles for this gene: R and r, withfrequencies 0.7 and 0.3, respectively. What will be the allelefrequencies of R and r in the 20-member founder population?

The frequencies will be 0.7 for R and 0.3 for r.

The frequencies will be 1.0 for R and 0 for r.

The expected frequencies are 0.7 for R and 0.3 for r. The actualfrequencies could be different.

The founder populations's allele frequencies will necessarily bedifferent than the source population's frequencies.

Q10. For a population containing 90 females and 10 males, whatis the effective population size, N_e ?

chocolateplatypus914

01:119:115 Lecture 20: Lecture 20_ Microevolution

Document Summary

Get access

Related Documents

01:119:115 Lecture Notes - Lecture 20: Allele Frequency, New Weird, Microevolution

01:119:115 Quiz: Lectures 20 and 21: Macroevolution and Microevolution Study Guide Organizers

01:119:115 Lecture Notes - Lecture 20: Allele Frequency, Population Genetics, Zygosity

Related Questions