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Genetic diversity and natural selection
Mitosis and meiosis
Gene pools and evolutionary mechanisms
100

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.

100

A human body cell has 46 chromosomes. How many chromosomes does each daughter cell usually have after mitosis?

46

100

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.

200

What is the original source of new alleles?

Mutations.

Mutations change DNA and can create new alleles. Sexual reproduction rearranges existing alleles.

200

When does DNA replication occur (both mitosis and meiosis)?

Interphase (S phase)

200

What is a species

Group of individual organisms that can interbreed in nature and produce fertile, viable offspring

300

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.

300

What separates during anaphase I of meiosis?

Homologous chromosomes

300

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.

400

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)

400

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)

400

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.

500

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

500

State all the key stages in mitosis and briefly explain what happens during each stage

  • Prophase: Chromosomes condense and thicken, nuclear envelope breaks down
  • Metaphase: Chromosomes align in a single file at the center (equator) of the cell guided by spindle fibres.
  • Anaphase: Sister chromatids are pulled apart by spindle fibers and move toward opposite poles of the cell.
  • Telophase: New nuclear envelopes re-form around each set of separated chromosomes, and the chromosomes begin to decondense. At the same time cytokinesis happens whereby a cleavage furrow in animal cells or a cell plate in plant cells separate the cell into two daughter cells
500

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%.