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Describe how populations with substantial genetic differences can form. What is the role of natural selection?
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Ch. 21 - Population and Evolutionary Genetics
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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TOC.tableOfContents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
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Capitolo 21, Problema 12
Under what circumstances might a lethal dominant allele persist in a population?
Guida verificata passo dopo passo1
Understand what a lethal dominant allele is: it is an allele that causes death when present in just one copy (heterozygous or homozygous state), typically preventing individuals from reproducing.
Consider that for a lethal dominant allele to persist, it must be passed on before the lethal effect occurs, meaning the allele's harmful effect happens after the individual has reproduced (late onset).
Recognize that if the lethal effect occurs after reproductive age, individuals can still pass the allele to offspring, allowing the allele to remain in the gene pool.
Another circumstance is if the allele has incomplete penetrance or variable expressivity, meaning not all individuals with the allele show the lethal phenotype, so some carriers survive and reproduce.
Also, new mutations can introduce the lethal dominant allele into the population continuously, balancing the loss of individuals who die from the allele.
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Lethal Dominant Alleles
A lethal dominant allele causes death when present in just one copy, often before reproductive age. Such alleles typically reduce an individual's fitness drastically, making their persistence in a population unusual unless specific conditions allow carriers to reproduce.
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Percorso guidato
04:37
Variations on Dominance
Heterozygote Advantage and Delayed Onset
Lethal dominant alleles may persist if their harmful effects appear after reproductive age, allowing carriers to pass the allele to offspring. Additionally, if heterozygotes have some survival or reproductive advantage, the allele can be maintained despite its lethality.
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13:04Hardy Weinberg
Mutation-Selection Balance
New lethal dominant alleles can continuously arise through mutation, balancing their removal by natural selection. This mutation-selection balance can maintain the allele at low frequencies in the population despite its negative effects.
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05:54Natural Selection
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One of the first Mendelian traits identified in humans was a dominant condition known as brachydactyly. This gene causes an abnormal shortening of the fingers or toes (or both). At the time, some researchers thought that the dominant trait would spread until 75 percent of the population would be affected (because the phenotypic ratio of dominant to recessive is 3 : 1). Show that the reasoning was incorrect.
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Domanda del libro di testo
Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?
wAA = 1, wAa = 0.99, waa = 0.98
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Domanda del libro di testo
Assume that a recessive autosomal disorder occurs in 1 of 10,000 individuals (0.0001) in the general population and that in this population about 2 percent (0.02) of the individuals are carriers for the disorder. Estimate the probability of this disorder occurring in the offspring of a marriage between first cousins. Compare this probability to the population at large.
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Domanda del libro di testo
If the initial allele frequencies are p = 0.5 and q = 0.5 and allele a is a lethal recessive, what will be the frequencies after 1, 5, 10, 25, 100, and 1000 generations?
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Domanda del libro di testo
Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?
wAA = 0.8, wAa = 1, waa = 0.8
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