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Principles of dizzees > Chromosomes > Flashcards

Chromosomes Flashcards

1
Q

Describe the structure of a chromosome (after replication).

A

Two genetically identical sister chromatids

Joined at a centromere

Telomeres at the end of each chromatid

Heterochromatic and euchromatic sections

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2
Q

What is euchromatin?

A

Lightly packed form of chromatin

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3
Q

What is heterochromatin?

A

Tightly packed form of chromatin

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4
Q

Which form of chromatin does DNA transcription take place on?

A

Euchromatin

Loosely packed - allows enzymes n shit in

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5
Q

What are telomeres?

A

Long section of repeating base sequences at the ends of chromosomes

In mitosis, sections are cut off the 3’ to 5’ strand of DNA for reasons I can’t be bothered typing (end replication problem)

Telomeres protect useful DNA being cut off

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6
Q

Describe the phases of mitotic cell cycle.

A

G1 - cell grows

S - DNA replicates

G2 - Cell prepares to divide

M - mitosis - cell division

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7
Q

List the stages of mitosis.

A 
Prophase 
Metaphase
Anaphase
Telophase
Cytokenesis

(interphase)

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8
Q

What happens in Prophase?

A

Chromosomes condense

Nuclear membrane

Spindle fibres form from the centriole

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9
Q

What happens in metaphase?

A

Chromosomes align on equator of cell

Chromosomes attach to centrioles via spindle fibre

Maximum condensation of chromosomes

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10
Q

What happens in anaphase?

A

Sister chromatids split apart (centromere splits)

Sister chromatids move to opposite poles of the cell, along the spindle fibre

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11
Q

What happens in telophase?

A

New nuclear membranes form

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12
Q

What happens in cytokinesis?

A

Cytoplasm splits and two new daughter cells are formed

Cells are diploid, have 46 chromsomes and are genetically identical

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13
Q

What is the name given to repetitive sequences of DNA, like the ones found in centromeres and telomeres?

A

Satellite DNA

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14
Q

What is the kinetochore?

A

A complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach

One forms per sister chromatid

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15
Q

What are the 2 types of tandemly repeated DNA sequences?

A

Satellite and minisatellite

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16
Q

What are the types of repeated interspersed DNA sequences?

A

SINEs - short interspersed nuclear elements

LINEs - long interspersed nuclear elements

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17
Q

Describe the properties and functions of histones.

A

Positively charged proteins

8 histones come together to form a core

DNA wraps around histone cores to form nucleosomes

Looks like beads on a string

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18
Q

Describe the levels of structure of chromatin.

A

1) DNA chain
2) Nucleosome
3) Chromatin fibre (further wrapping of nucleosomes)
4) Fibre scaffold complex
5) Chromosome

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19
Q

Why is it important that histone proteins are positively charged?

A

DNA is negatively charged

Neutralised by histones and holds it together

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20
Q

What are the 3 types of chromosome, and what are their differences?

A

Metacentric - p arm similar size to q arm

Submetacentric - p < q

Acrocentric - p &laquo_space;q (p has no functional DNA)

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21
Q

What type of cell in the body can not be used for chromosome analysis and why?

A

Red blood cells

No nucleus so no chromosomes

22
Q

Describe the process of chromosome analysis.

A

Blood taken and RBC’s seperated off

Add culture medium to white cell suspension

Incubate 3 days at 37 degrees

Add colchicine

Separate off white cells

Add hypotonic saline

Fix cells

Drop cells onto slide and stain

Analysis and photograph to produce karyotype

23
Q

What does staining of chromosomes show?

A

G-bands

24
Q

Why would you use fluorescent in sutu hybridisation (FISH)?

A

Highlight specific genes or specific parts of genes

25
Q

What are the different types of FISH probes?

A

Unique sequence probes

Centromeric probes

Telomeric probes

Whole chromosome probes

26
Q

Which type of FISH probe is good for determining chromosome number?

A

Centromeric probes

27
Q

What type of cells undergo meiosis?

A

Germ cells

Diploid cells (in ovaries and testes) form haploid cells

28
Q

How does meiosis create genetic diversity?

A

Crossing over (re-combination)

Independent assortment

29
Q

What is Oogenesis?

A

Process of egg formation

30
Q

Spermatogenesis is the process of?

A

Sperm formation

31
Q

Out of sperm and eggs, which has more chance of mutation?

A

Sperm

More cell divisions so more chance of mutation

32
Q

In females, ovulation takes place at birth.

Meiosis normally produces 4 daughter cells, but how is this different in women?

A

Meiosis II produces 1 Ootid and 3 polar bodies

Ootid differentiates into an egg

Polar bodies are degraded

33
Q

What organelle is maternally inherited only?

A

Mitochondria (+ their DNA)

34
Q

What are 3 types of chromosomal abnormalities?

A

Numerical

Structural

Mutational

35
Q

What type of abnormality is associated with down’s, turner’s and patau syndromes?

A

Numerical abnormality

Aneuploidy - wrong number of chromosomes

Down's = Extra 21 
Edward's = Extra 18 
Patau = Extra 13
36
Q

What gives rise to numerical chromosomal abnormalities?

A

Non-disjunction during meiosis

37
Q

Trisomy is more commonly caused by what sex?

A

Maternal

38
Q

Give some examples of sex chromosomes aneuploidy syndromes.

A

Turner syndrome - 45, X

Klinefelter syndrome - 47, XXY

39
Q

What are the types of structural abnormalities of chromsomes?

A

Translocations

Deletions

Inversions

Insertions

40
Q

What are the two types of translocations?

A

Robertsonian - fusion of two acrocentric chromosomes, with loss of the short arms (p arms)

Reciprocal - breaks of 2 chromosomes with the formation of 2 new chromosomes from these

41
Q

How can reciprocal translocations be balanced or unbalanced?

A

If chromosome A and chromosome B translocate, part of B is on A and vice versa

If A and B end up in the same cell after meiosis, then the DNA compliment is the same, and the outcome will most likely be fine

If A and B end up in different daughter cells, then the zygotes will have an unbalanced amount of A or B

Partial trisomy + partial monosomy

42
Q

What is the difference between terminal and interstitial deletion?

A

Terminal = deletion at ends

Interstitial = deletion in the actual chromosome (not the end)

43
Q

What are the two types of inversion, and are the balanced/unbalanced?

A

Paracentric and pericentric

Paracentric = inversion in chromosome not involving centromere

Pericentric = inverted section contains centromere

Balanced rearrangement

44
Q

What are the 2 types of genetic mutation?

A

Germline or somatic

45
Q

What are the different types of coding mutations?

A

Silent - Base change with no effect on coded AA

Missense - Base change causing AA change

Nonsense - Base change causing stop codon

Frameshift - deletion/insertion of a base - codons after are read out of frame

46
Q

What is the difference between transitions and transversions?

A

Transitions = purine to purine or pyrim. to pyrim.

Transversions = purine to pyrim. or pyrim. to purine

47
Q

What are the ways that we can detect mutations?

A

PCR - Polymerase chain reactions

Gel electrophoresis

RFLP - Restriction fragment length polymorphism analysis

ARMS - Amplification refractory mutation system

DNA sequencing

48
Q

Which mutation detection technique involves heating and DNA sample then adding nucleotides, repeatedly?

A

PCR

49
Q

In gel electrophoresis, different DNA fragments are separated based on what feature?

A

Size

DNA fragment ‘bands’ can be compared to other bands to detect differences/mutations to the bands formed from non-mutated DNA fragments (controls)

50
Q

What technique is most sensitive/accurate for detecting mutations?

A

DNA sequencing

51
Q

What is the only lab procedure for DNA analysis that doesn’t involve using an electric field to separate DNA fragments?

A

PCR

Principles of dizzees (28 decks)

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