8.4.1 Independent Assortment

Question 1

independent assortment

Answer 1

• In meiosis, homologous chromosomes are sorted into daughter cells independently of one another. This phenomenon is referred to as independent assortment.
  • Independent assortment helps to explain the high amount of variation among offspring

Question 2

note

Answer 2

• Review: During the early part of meiosis, homologous chromosomes pair up and meet along the metaphase plate. During anaphase I the homologues separate and migrate to opposite ends of the cell. This separation of homologues is called disjunction.
• Homologous chromosomes have genes on them that control the same trait. The genes on homologous chromosomes do not have to be identical. For example, one person might have the gene for blue eyes on one chromosome of a homologous pair, and the gene for brown eyes on the other
• In meiosis, homologous chromosomes undergo independent assortment. In the example, either of the t-containing chromosomes could have ended up with either of the r-containing chromosomes. In other words, the separation of a homologous pair of chromosomes during anaphase I is independent of the separation of any other homologous pair.
• The more genes there are, the more genetic combinations are possible. In the first example, we were looking at two pairs of genes (Tt and Rr), thus we had four different possible genetic combinations for the gametes that result from meiosis. The combinations include: TR, Tr, tR, and tr.
• If we were to look at twenty-three different pairs of genes then there would be 2^23 different combinations. The odds of producing a gamete with the same combination of genes are next to impossible considering the number of genes that are present in an organism; thus independent assortment contributes to a high level of genetic variation among the offspring of organisms.

Question 3

Which statement regarding independent assortment is true?

Answer 3

• Independent assortment is the result of the random orientation of homologous pairs of chromosomes along the metaphase plate

Question 4

True or false?

Homologous chromosomes randomly align at the metaphase plate during meiosis.

Answer 4

• true

Question 5

Which of the following statements is not true regarding independent assortment?

Answer 5

• The arrangement of chromosomes before synapsis determines how chromosomes will be separated

Question 6

If a cell has a diploid number of six chromosomes, and crossing over does not take place between the homologous chromosomes, how many different chromosomal combinations are possible in the resulting daughter cells after meiosis? (Each homologous pair consists of a maternal chromosome and a paternal chromosome).

Answer 6

• 8

Question 7

During anaphase I of meiosis

Answer 7

• homologous chromosomes separate and migrate to opposite poles