3.2 CHROMOSOMES

Question 1

Prokaryotes have two types of DNA:

Answer 1

1. Single chromosomes - consiting of a circular DNA molecule
2. Plasmids

Question 2

Plasmids

Answer 2

small extra DNA molecules that are commonly found in prokaryotes

Question 3

characteristics of plasmids

Answer 3

Naked DNA - not associated with histone proteins
Small circular rings of DNA
Note responsible for normal life processes
Commonly contain survival characteristics
Can be passes between prokaryotes
Self-replication

Question 4

DNA in Eukaryotes

Answer 4

single immensely long linear DNA molecules associated with histone proteins

Question 5

Histone proteins

Answer 5

proteins that are globular in shape and are wider than DNA

Question 6

Identyfing genes

Answer 6

Length
Position of centromere
Locus

Question 7

Homologous chromosomes

Answer 7

a pair of chromosomes/chromatids (one from each parent) that are the same length and contain the same genes in the same location

Question 8

Homologous chromosomes share?

Answer 8

The same structural features
The same genes at the loci position

Question 9

Diploid

Answer 9

Nuclei possessing pair of homologous chromosomes (2n)

Question 10

Haploid

Answer 10

Nuclei possessing only one set of chromosomes (n

Question 11

Female chromosomes

Answer 11

two copies of a large X chromosome (XX)

Question 12

Male chromosomes

Answer 12

one copy of an X chromosome and one copy of a Y chromosome (XY)

Question 13

Autosomes

Answer 13

the remaining chromosomes in the organisms

Question 14

Karyograms

Answer 14

a diagram or photograph of the chromosomes present in a nucleus arranged in homologous pairs of descending length

Question 15

Karyotypes

Answer 15

the number and types of chromosomes in a eukaryotic cell

Question 16

How are karyotypes determined

Answer 16

1. Harvesting cells (from foetus or white blood cells)
2. Chemically inducing cell division, then arresting mitosis while the chromosomes are condensed
3. The stage during which mitosis is halted will determine whether chromosomes appear with sister chromatids or not

Question 17

Karyotyping is used to?

Answer 17

1. Determine the sex of the unborn child
2. Test for abnormalities

Question 18

Down Syndrome

Answer 18

condition where the individual has three copies of chromosome 21 (trisomy 21)
It is caused by a non-disjunction event in one of the parental gametes

Question 19

Cairn’s autoradiography

Answer 19

John Cairns pioneered a technique for measuring the length of DNA molecules by autoradiography
By using tritiated uracil (3H-U), regions of active transcription can be identified within the uncoiled chromosome