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Flashcards in chapter 3- Chromosomes Deck (17)
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1
Q

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

A

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
2
Q

What type of proteins do eukaryotes chromosomes have

A

Linear DNA associated with histone proteins

3
Q

In eukaryote species what chromosomes are there?

A

Different chromosomes that carry different genes

4
Q

What are homologous chromosomes?

A

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

5
Q

What do haploid nuclei have?

A

One chromosome of each pair - contain 23 chromosomes

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

6
Q

What do diploid nuclei have?

A

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

7
Q

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

A

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

8
Q

How is sex determined

A

By sex chromosomes

9
Q

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

A

Autosomes

10
Q

What are the 2 chromosomes that determine sex?

A

X chromosome

Y chromosome

11
Q

What sex chromosome must all humans have and why?

A

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

12
Q

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

A

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

13
Q

What chromosomes do sons/ daughters receive

A

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

14
Q

What do karyograms show??

A

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

15
Q

When are chromosomes visible?

A

In mitosis, with cells in metaphase

16
Q

How can kayeograms show if a child is downs?

A

3 copies of chromosome 21 - trisomy 21

17
Q

What chromosomes do prokaryotes have?

A

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

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