chapter 3- Chromosomes

Question 1

What is John cairns technique for measuring the length of DNA molecules by autoradiography?

Answer 1

1) cells were grown for 2 generations in culture medium containing tritiated thymidine
2) cells were then placed onto a dialysis membrane and cell walls were digested by enzyme lysosome - cells burst to release DNA
3) thin film of photographic emulsion was applied to surface of the membrane
4) end of two month period film was developed and examined

• images could be measured

Question 2

What type of proteins do eukaryotes chromosomes have

Answer 2

Linear DNA associated with histone proteins

Question 3

In eukaryote species what chromosomes are there?

Answer 3

Different chromosomes that carry different genes

Question 4

What are homologous chromosomes?

Answer 4

They have the same sequence of genes but not necessarily the same alleles for those genes

Question 5

What do haploid nuclei have?

Answer 5

One chromosome of each pair - contain 23 chromosomes

ex: gametes have haploid nuclei- each egg and sperm cell have 23 chromosome

Question 6

What do diploid nuclei have?

Answer 6

Have pairs of homologous chromosomes - has two chromosomes of each type- contain 46 chromosomes

Question 7

What does the number of chromosomes feature? And what does this mean?

Answer 7

It is a characteristic feature of members of a species - organisms with a different number of chromosomes are unlikely to be able to breed

Question 8

How is sex determined

Answer 8

By sex chromosomes

Question 9

What chromosomes do not determine sex (all other chromosomes) ?

Answer 9

Autosomes

Question 10

What are the 2 chromosomes that determine sex?

Answer 10

X chromosome

Y chromosome

Question 11

What sex chromosome must all humans have and why?

Answer 11

All humans have at least one X chromosome as it had many genes which are essential in both males and females

Question 12

Which chromosome determines whether it is a boy or girl and why?

Answer 12

Y chromosome is found in guys and one gene in causes fetus to develop into a boy- SRY or TDF

Question 13

What chromosomes do sons/ daughters receive

Answer 13

Female: X from mother X from father
Male: X from mother y from father

Question 14

What do karyograms show??

Answer 14

Shows the chromosomes of an organism in homologous pairs of decreasing length

Question 15

When are chromosomes visible?

Answer 15

In mitosis, with cells in metaphase

Question 16

How can kayeograms show if a child is downs?

Answer 16

3 copies of chromosome 21 - trisomy 21

Question 17

What chromosomes do prokaryotes have?

Answer 17

Have one chromosome consisting of circular DNA molecule containing all the genes needed for the basic life processes of the cell- called naked