Chromosomes, Cell Division, Meiosis and Chromosome Abnormalities Flashcards Preview

Principles of disease (Ross Lilley) > Chromosomes, Cell Division, Meiosis and Chromosome Abnormalities > Flashcards

Flashcards in Chromosomes, Cell Division, Meiosis and Chromosome Abnormalities Deck (21)
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1

basic structure of linear chromosomes

regions of chromosome:
telomeres
centromere
heterochromatin
euchromatin

2

the end-replication problem and how it is solved

primers need to be used when replicating DNA on the lagging strand. Most of these primers are replaced by DNA when they detach, however the very end primer is not able to be replaced, this means a short sequence of DNA is lost with each replication of DNA. To combat this telomeres exist at the end of chromosomes, they are repeating sequences that contain no genes. So instead of genetic material from genes being lost, non-functional DNA from telomeres is lost instead.

3

euchromatin

-open structure, less dense
-active genes

4

heterochromatin

-condensed structure
-silenced genes

5

centromere

constricted region joining sister chromatids, formed of repetitive satallite DNA.

6

kinetochore

protein complex that forms on centromere and allows the attachment of spindles

7

extragenic sequences of DNA

-tendemly repeated sequences: satellite and minisatellite DNA.
-SINEs (short interspersed nuclear elements
-LINEs (long interspersed nuclear elements

8

chromatin

DNA-protein complex

9

packaging of DNA

1. DNA is wrapped around histone protein, forming nucleosomes.
2. These nucleosomes are wrapped up themselves, 6 per turn.
3. This structure is then wrapped again.
4. then again to form a chromosome

10

purpose of packaging of DNA

-Negatively charged DNA neutralised by positive charged histone proteins
-DNA takes up less space
-Inactive DNA can be folded into inaccessible locations until required

11

primary laboratory technique for chromosome number abnormalities

Fluorescent in situ hybridisation (FISH)

12

types of FISH

-unique sequencing probes
-centromeric probes
-telomeric probes
-whole chromosome probes

13

centromeric probe function

Useful for determining chromosome number

14

Telomeric probe function

-Useful for detecting subtelomeric rearrangements
-Often present in children with unexplained mental retardation

15

Whole chromosome probes function

Useful for detecting translocations and rearrangements

16

sequence of events in meiosis I

prophase- homologous chromosomes condense and pair up.
metaphase- pair of homologous chromosomes line up on equator, spindle forms
anaphase- spindles contracts, separating pair
telophase-chromosomes are moved to opposite poles
cytokinesis

17

sequence of events in meiosis II

similar to mitosis except cells are haploid to begin with.
prophase- chromosomes condense
metaphase- chromosomes line up on eqautor and spindle forms
anaphase- spindle contracts and sister chromatids are pulled apart
telophase- sister chromatids are dragged to opposite ends of the cell
cytokinesis

18

what is satellite DNA?

large arrays of tandemly repeating DNA sequences.
found at centromeres and telomeres

19

what is mini-satellite DNA?

short arrays of tandemly repeating DNA sequences.
used for DNA fingerprinting

20

what are SINEs?

short interspersed nuclear elements, highly repeated short DNA sequences interspersed throughout the DNA

21

what are LINEs?

long interspersed nuclear elements, highly repeated long DNA sequences interspersed throughout the DNA