In a cell with three chromosome pairs, each pair lines up at the middle of the cell with no regard for how the other pairs are lined up, so either member of a pair may go to either new cell. Which source of variation is this?

While homologous chromosomes lie paired together as a tetrad, matching segments are traded between the two chromosomes before the pair separates. Which source of variation is this?

An ovary releases one egg out of the many it could have released, and one sperm out of millions is the one that reaches it. Which source of variation does that particular pairing represent?

As DNA is copied in a cell that will go on to make sperm, one base is copied wrongly and the error is never repaired, so the cell now carries a form of a gene neither parent had. Which source of variation is this?

During one meiotic division a homologous pair fails to separate, so one gamete receives both members of that pair and another gamete receives neither. What is this event called?

A change in the DNA has to reach the next generation before it can add variation to a population. In which cell would such a change be passed on?

At what point in meiosis do homologous chromosomes trade segments with each other?

A woman carries alleles A and R together on one chromosome of a pair, and a and r together on its partner. One egg she produces carries A and r on a single chromosome. Which event produced that chromosome?

In a fruit fly, the alleles for body color sit on one chromosome pair and the alleles for wing shape on a different pair. A gamete carries the father's body-color allele along with the mother's wing-shape allele. Which event best explains this?

Two brothers with the same two parents differ in eye color, height and blood type, yet neither one carries an allele that his parents do not have. What best explains how different they are?

A karyotype made from a newborn's cells shows three copies of chromosome 21 rather than two. Which event during the making of a gamete accounts for this?

A child carries an allele found in neither parent. It arose from a mutation in the egg or sperm the child came from. Can the child pass this allele on to their own children?

An organism has 5 pairs of homologous chromosomes. Counting only the different ways whole chromosomes can be combined, how many chromosomally different gametes can it produce?

Human cells carry 23 pairs of homologous chromosomes. Ignoring the trading of segments, which expression gives the number of chromosomally different gametes one person can make?

Counting only whole-chromosome combinations, a certain organism can make 128 different gametes. How many pairs of homologous chromosomes does it have?

A fruit fly has 4 pairs of homologous chromosomes, so whole-chromosome combinations alone give 16 different gametes. What does the trading of segments between homologous chromosomes do to that number?

Crossing-over, independent assortment and random fertilization all give offspring allele combinations their parents did not have. Which process is the original source of the alleles being combined?

Which statement about crossing-over is accurate?

A population of bacteria reproduces only by copying itself, with no gametes and no meiosis. Why can its descendants still end up genetically different from the original cells?

Two populations of related organisms are compared: one reproduces sexually and one reproduces asexually. Why does the sexual population usually carry more genetic variation?