Section 3 - Chromosomes

Question 1

DNA is found in the nucleus of ____________ cells.

Answer 1

eukaryotic

Question 2

In each human chromosome, roughly how many genes are contained?

Answer 2

Between a couple of hundred and a few thousand genes

Question 3

How many pairs of chromosomes do humans have?

Answer 3

23

Question 4

Describe homologous pairs

Answer 4

With the exception of the sex chromosomes (X and Y), both chromosomes in a pair are the same size and carry the same genes - they are known as homologous pairs. Chromosomes in a homologous pair usually have different alleles (different versions of the gene).

Question 5

What is an X-shaped chromosome?

Answer 5

One chromosome attached to an identical copy of itself

Question 6

When is a homologous pair of chromosomes X-shaped?

Answer 6

Just after the DNA has been replicated (e.g. in cell division)

Question 7

What is each side of the X-shaped chromosome referred to?

Answer 7

As a chromatid

Question 8

What is the bit in the middle of an X-shaped chromosome called?

Answer 8

Centrometre