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Specialities > Chromosomes > Flashcards

Chromosomes Flashcards

1
Q

What does each eukaryotic chromosome contain?

A

Linear chromosomes

Telomere

Centromere

Heterochromatin

Euchromatin

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2
Q

What does the centromere do?

A

Hold the chromosome together

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3
Q

What are telomeres?

A

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

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4
Q

Why do telomeres need to be protected?

A

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

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5
Q

What is the process of DNA replication?

A

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

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6
Q

In what direction does DNA polymerase add new nucleotides?

A

5’ to 3’ direction

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7
Q

What are okazaki fragments?

A

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

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8
Q

How much base pairs are lost during mitosis and why?

A

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

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9
Q

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

A

They are recognised by telomerase and become extended

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10
Q

What is mitosis?

A

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

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11
Q

What are the phases of mitosis?

A

1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
5) Cytokinesis

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12
Q

What happens during prophase?

A

Chromosomes condense

Nuclear membrane disapears

Spindle fibres form from the centriole

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13
Q

What happens during metaphase?

A

Chromosomes aligned at the equator of the cell

Attached by fibre to each centriole

Maximum condensation of chromosome

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14
Q

What happens during anaphase?

A

Sister chromatids seperate at centromere

Seperate longitudinally

Move to opposite ends of the cell

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15
Q

What happens during telophase?

A

New nuclear membrane forms

Each cell contains 46 chromosomes (diploid)

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16
Q

What happens during cytokinesis?

A

Cytoplasm seperates

Two new daughter cells

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17
Q

During what phase are chromosomes most condensed?

A

Metaphase

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18
Q

In what phase can chromosomes be seen?

A

Prophase

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19
Q

What is the spindle made from?

A

Microtubules

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20
Q

What do centromeres do during mitosis?

A

Join sister chromatids and bind to microtubules

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21
Q

What is the site of kinetochore?

A

Centromeres

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22
Q

What are centromeres composed of?

A

Repeated DNA sequences known as satellite DNA

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23
Q

What is satellite DNA?

A

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

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24
Q

What is kinetochore?

A

Multiprotein complex that attaches to microtubules from each pole

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25
Q

What do both sides of kinetochore need to be captured?

A

So that each daughter cell has the same amount of chromosomes

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26
Q

What are the 2 forms of chromatin?

A

Heterochromatin

Euchromatin

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27
Q

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

A

Heterochromatin is condensed with silent genes

Euchromatin is open with active genes

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28
Q

What is chromatin?

A

The part of a chromosome that contains the coding information

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29
Q

Why can euchromatin code for proteins?

A

Open structure can be accessed by RNA polymerase

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30
Q

How many base pairs are there in our genome?

A

3 billion

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31
Q

What are extragenic sequences?

A

DNA that is repeated

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32
Q

What kind of sequences are lots of our DNA?

A

Extragenic sequences

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33
Q

What are the 2 kinds of extragenic sequences?

A

Tandemly repeated DNA sequences

Highly repeated interspersed DNA sequences

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34
Q

What are examples of tandermly repeated DNA sequences?

A

Satellite DNA

Minisatellite DNA

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35
Q

What are examples of highly repeated interspersed DNA sequences?

A

SINEs (short interspersed nuclear elements)

LINEs (long interspersed nuclear elements)

36
Q

How much of our DNA is repeated sequences?

A

A huge amount

37
Q

What are nucleosomes?

A

Formed from the packaging of DNA and histone forming chomatin

38
Q

How many base pairs are around a core of a nucleosome?

A

146 base pairs (1.8 turns)

39
Q

What is the core of a nucleosome made of?

A

8 histones

40
Q

How many different kinds of histone proteins are there?

41
Q

What charge do histones have?

A

Positive charge

42
Q

What are nucleosome further wrapped to form?

A

‘Solenoid’ structures

43
Q

What does the further wrapping of nucleosomes compact DNA by a factor of?

44
Q

What are the 4 levels of condensing chromatin structure?

A

Level 1 (nucleosome)

Level 2 (chromatin fibre)

Level 3 (fibre-scaffold complex)

Level 4 (chromosome)

45
Q

Why does DNA and histine combine?

A

Negatively charged DNA is neutralised by positvely charged histone

46
Q

Why is DNA packaged?

A

Negatively charged DNA is neutralised by positively charged histone

DNA takes up less space

Inactive DNA can be folded into inaccessible locations until required

47
Q

What locks DNA in place in the nucleosome?

A

Histone H1

48
Q

What is a karyotype?

A

Number and appearance of chromosomes

49
Q

What is the process of viewing a karyotype?

A

1) Blood extracted
2) Red blood cells seperated
3) Add culture medium to white cells and incubate for 3 days at 37oC
4) Add colchicine
5) Seperate white cells
6) Add hyptonic saline
7) Spread cells onto slide and stain
8) Photograph and produce karyotype

50
Q

How do male and female chromosomes differ?

A

Males have a X and a Y chromosome

Females have two X chromosomes

51
Q

Where are the chromosomes from each pair from?

A

One is from the mother and one is from the father

52
Q

What are the 3 types of chromosomes in a karyotype?

A

Metacentric (P and Q arms are the same length)

Sub metacentric (P arm is shorter than the Q arm)

Acrocentric (P arm is so short that is is not functional)

53
Q

What are the P and Q ares like in metacentric chromosomes?

A

The same length

54
Q

What are the P and Q arms like in submetacentric chromosomes?

A

P arm is shorter than the Q arm

55
Q

What are the P and Q arms like in acrocentric chromosomes?

A

The P arm is so short it is not functional

56
Q

What can be used to life up specific sequences of interest?

A

Fluorescent in situ hybridisation (FISH)

57
Q

What are the different kinds of fluorescent in situ hybridisation probes?

A

Unique sequence probes

Centromeric probes

Telomeric probes

Whole chromosome probe

58
Q

What is the centromeric probe used for?

A

Determining chromosome number

59
Q

What is the telomeric probe useful for?

A

Detecting subtelomeric rearrangments

60
Q

What is the whole chromosome probe useful for?

A

Detecting translocation and rearrangements

61
Q

What are probes unique to?

A

Specific genes

62
Q

What is a spectral karyotype?

A

A karyotype where each chromosome pair is labelled a different colour

63
Q

What is meiosis?

A

Cell division in germ cell

64
Q

What are diploid cells?

A

Cells that have two complete sets of chromosomes (46 chromosomes)

65
Q

What are haploid cells (gametes)?

A

Contains 23 chromosomes

66
Q

What happens during meiosis?

A

1) Diploid cells in the ovaries and testis divide to form haploid cells
2) Chromosomes are passed on as rearranged copies which creates genetic diversity (paternal and maternal chromosomes exchange parts)

67
Q

What is oogenesis?

A

Process of egg formation

68
Q

What is spermatogenesis?

A

Process of sperm formation

69
Q

Why is there more of a chance for a mutation in sperm than eggs?

A

Sperm goes through more cell divisions than eggs do

70
Q

What is gametogenesis?

A

The process in which cells undergo meiosis to form gametes

71
Q

What is formed by meiosis from one cell in a male?

A

4 gametes (sperm)

72
Q

What is formed by meiosis from one cell in a female?

A

One egg and three polar bodies

73
Q

When does male gametogenesis commence?

74
Q

When does female gametogenesis commence?

A

Early embryonic life

75
Q

How long goes male gametogenesis take?

A

60-65 days

76
Q

How long does female gametogenesis take?

A

10-50 years

77
Q

How many mitosis occur in gamete formation in males?

78
Q

How many mitosis occurs in gamete formation in females?

79
Q

What is the gamete production per meiosis in males?

A

4 spermatids

80
Q

What is the gamete production per meiosis in females?

A

1 ovum and 3 polar bodies

81
Q

What is the gamete production in men?

A

100-200 million per ejaculation

82
Q

What is the gamete production in females?

A

1 ovum per mentrual cycle

83
Q

What is fertilisation?

A

Two haploid cells (egg and sperm) form 1 diploid cell (zygote) which develops into an embryo

84
Q

What determines whether the embryo is male or female?

A

Whether the sperm contains a X or a Y chromosome

85
Q

Where does the mitochondria in a embryo come from?

A

Mother because the egg is where most of the cytoplasmic fluid is from

86
Q

What happens to the X chromosomes in a zygote if they have two?

A

Both are active, but in early embryonic life one X chromosome is randomly switched off

87
Q

What do chromosome abnormalites result due to?

A

Too many chromosome

Too little chromosomes

Insertion

Translocation

Deletion

Duplication

Inversion

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