Chromosomes

Question 1

What is a chromosome?

Answer 1

A chromosome is a small segment of DNA that contains information about the organism’s traits.

Question 2

What is the difference between autosomes and sex chromosomes?

Answer 2

• One pair of chromosomes is called the sex chromosomes – called X and Y.
• A female always has two X chromosomes - X X
• A male always has an X and a Y chromosome - X Y
• All other chromosomes are called autosomes – they determine all other characteristics of the organism. E.g., hair colour, eye colour, height, etc

Question 3

What are homologous chromosomes? Why do they pair up?

Answer 3

• pairs of chromosomes that have the similar length, centromere location, and banding pattern
• They pair up to exchange genetic information

Question 4

What is a karyotype chart? How is it used? At what phase of mitosis is cell division halted in order to make a karyotype chart?

Answer 4

• During metaphase, cell division can be halted. The paired chromosomes are stained, collected and organized into a chart based on their height and banding pattern.
• Each organism has a particular set of chromosomes called a karyotype.
• The karyotype chart is organized on pairs from longest chromosomes to shortest chromosomes.
• In humans, the autosomes are numbered 1 – 22 and the sex chromosomes are labeled as X or Y.
• Notice the Y chromosome is much smaller than the X chromosome.

Question 5

Use a karyotype chart to determine a genetic disorder (see Table 4.2 p.179) and gender of an individual.

Answer 5

Autosomes:
- Trisonomy 21: down
- Trisonomy 18: Edward
- Trisonomy 13: Patau
Sex chromosomes:
- XXY: Klinefelter
- XYY: Jacobs
- XXX: Triple X
Monosomy:
- XO: Turner