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Flashcards in Chromosomes Deck (87)
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1

What does each eukaryotic chromosome contain?

Linear chromosomes

Telomere

Centromere

Heterochromatin

Euchromatin

2

What does the centromere do?

Hold the chromosome together

3

What are telomeres?

The ends of DNA which need to be protected because when DNA gets damaged cells have mechanisms to repair it and so need to recognise blunt ends, important do not try to repair natural ends of chromosomes

4

Why do telomeres need to be protected?

To prevent cells trying to repair natural ends of chromosomes, they recognise blunt ends

5

What is the process of DNA replication?

1) Strand unwinds and hydrogen bonds connecting bases are broken

2) RNA primer initiates DNA synthesis

3) DNA polymerase copies the information and makes a complimentary strand (daughter strand on each new DNA)

4) Lagging strands need to be initiated by RNA primer and connected by DNA ligase

6

In what direction does DNA polymerase add new nucleotides?

5' to 3' direction

7

What are okazaki fragments?

The sections of DNA present on the lagging strand that need to be connected

8

How much base pairs are lost during mitosis and why?

100 base pairs are lost each time due to the gap at the end of the lagging strand due to the primer

9

What happens when chromosomes become to short due to bases being lost during each mitosis cycle?

They are recognised by telomerase and become extended

10

What is mitosis?

Cell division that results in two daughter cells that have the same number of chromosomes as the parent cell

11

What are the phases of mitosis?

1) Prophase

2) Metaphase

3) Anaphase

4) Telophase

5) Cytokinesis

12

What happens during prophase?

Chromosomes condense

Nuclear membrane disapears

Spindle fibres form from the centriole

13

What happens during metaphase?

Chromosomes aligned at the equator of the cell

Attached by fibre to each centriole

Maximum condensation of chromosome

14

What happens during anaphase?

Sister chromatids seperate at centromere

Seperate longitudinally

Move to opposite ends of the cell

15

What happens during telophase?

New nuclear membrane forms

Each cell contains 46 chromosomes (diploid)

16

What happens during cytokinesis?

Cytoplasm seperates

Two new daughter cells

17

During what phase are chromosomes most condensed?

Metaphase

18

In what phase can chromosomes be seen?

Prophase

19

What is the spindle made from?

Microtubules

20

What do centromeres do during mitosis?

Join sister chromatids and bind to microtubules

21

What is the site of kinetochore?

Centromeres

22

What are centromeres composed of?

Repeated DNA sequences known as satellite DNA

23

What is satellite DNA?

DNA that does not code, but forms the site of kinetochore

24

What is kinetochore?

Multiprotein complex that attaches to microtubules from each pole

25

What do both sides of kinetochore need to be captured?

So that each daughter cell has the same amount of chromosomes

26

What are the 2 forms of chromatin?

Heterochromatin

Euchromatin

27

Which is heterochromatin and euchromatin is condensed with silent genes and open with active genes?

Heterochromatin is condensed with silent genes

Euchromatin is open with active genes

28

What is chromatin?

The part of a chromosome that contains the coding information

29

Why can euchromatin code for proteins?

Open structure can be accessed by RNA polymerase

30

How many base pairs are there in our genome?

3 billion