Exam 27: Chromosomes and Cell Division

One out of every 800 to 1000 infants born will have three copies of chromosome 21 (trisomy 21), a condition known as ________.

Human cells that have completed telophase I will each contain ________ chromosomes, which will be in a(n) ________ form.

Why is meiosis II needed for gamete (egg and sperm) production?

Explain two important sources of genetic variation in meiosis. Evolutionarily speaking, why do you think is it important that meiosis involves recombination of the genes?

The ________ cells are those body cells of humans that contain 23 chromosomes.

What are the results of nondisjunction, and why are these chromosome alterations so detrimental to an individual?

A picture of the arrangement of an individual's chromosomes by size and centromere location is called a(n) ________.

Which of the following combinations of sex chromosomes results in Klinefelter syndrome?

Crossing over in prophase I and ________ in metaphase I increase the genetic variation from one generation to another.

In which phase of meiosis I do homologues separate?

Each cell contains two chromosomes with genes for the same traits; these chromosomes are called ________.

Children born with Down syndrome have inherited an extra chromosome, so their diploid number is 47 rather than 46 chromosomes. What is this genetic condition called?

A process in which a sister chromatid inherited from the mother and a sister chromatid inherited from the father pair up and form tetrads and exchange DNA to form genetically diverse gametes is called ________.

Suppose a researcher claims to be able to make a hybrid animal that is a cross between a goat and a horse. This animal has been termed "gorse." The normal diploid number for a goat is 60, and the normal diploid number for a horse is 62. Ignore the ethics here, and answer the following. Based on normal meiosis, a goat gamete (haploid) should have ________ chromosomes, whereas a horse gamete (haploid) should have ________ chromosomes. This means we would expect our hybrid gorse to contain a total of ________ chromosomes per cell. Let's assume our researcher beats the odds and that this hybrid "gorse" survives. Even if the hybrid survives, it is likely that it will be sterile. Referring to the above numbers, you can see that a problem is likely to occur when the hybrid produces its gametes. Explain what that problem will be.