Genetic diversity and natural selection
What is genetic diversity?
A. The diverse number of genes in an individual
B. The number of organisms in an ecosystem
C. The range of genetic differences within a species
D. The changes an individual makes during its lifetime
C.
Genetic diversity describes genetic differences, including different alleles, within a species.
A human body cell has 46 chromosomes. How many chromosomes does each daughter cell usually have after mitosis?
46
What is a population’s gene pool?
A. All organisms in an ecosystem
B. Only the dominant alleles in a population
C. The chromosomes in one gamete
D. All the alleles of all the genes in that population
D.
A gene pool includes all allele copies present in a population.
What is the original source of new alleles?
Mutations.
Mutations change DNA and can create new alleles. Sexual reproduction rearranges existing alleles.
When does DNA replication occur (both mitosis and meiosis)?
Interphase (S phase)
What is a species
Group of individual organisms that can interbreed in nature and produce fertile, viable offspring
A desert mammal produces concentrated urine to conserve water. What type of adaptation is this?
Physiological
Producing concentrated urine is an internal body process, so it is a physiological adaptation.
What separates during anaphase I of meiosis?
Homologous chromosomes
For an autosomal gene, how many allele copies are present in 20 diploid individuals?
40 alleles in total
reason: Each diploid individual has two copies of the autosomal gene, so 20 × 2 = 40 allele copies.
Why can high genetic diversity help a population survive environmental change?
Genetic diversity increases the chance that there are some individuals that have the variation can survive and reproduce under new conditions (they have the selective advantage in the new selection pressure)
What is a key role of meiosis in humans?
Producing haploid cells for sexual reproduction (create more genetic variation by independent assortment and crossing over)
A gene has only two alleles, A and a. If A has a frequency of 0.65, what is the frequency of a?
0.35
All allele frequencies for a gene add to 1, so a = 1 − 0.65 = 0.35.
Explain how bacteria can evolve to be antibiotic resistant after someone use antibiotic treatment?
Some bacteria are resistant before antibiotic treatment. The antibiotic (selection pressure) selects among existing variants of bacteria by killing or inhibiting susceptible bacteria. Bacteria that have the alleles that allow them to survive are more likely to survive and reproduce so the allele frequency for antibiotic resistance in the population increase over time
State all the key stages in mitosis and briefly explain what happens during each stage
A population has 40 copies of a gene. Twelve are allele A. What is the frequency of A?
Allele frequency = 12 ÷ 40 = 0.30, or 30%.