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P.O.D own flashcards > chromosomes and cell division > Flashcards

chromosomes and cell division Flashcards

1
Q

What is a Telomere and its function. And what happens to these parts during replication?

A

tips of the arms/natural ends of chromosomes
function is to protect the ends from DNA repair machinery
they are lost during replication

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2
Q

p arm

A

shorter arm

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3
Q

q arm

A

longer arm

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4
Q

heterochromatin

A

contains the DNA that the chromosome is not currently using- non-active part of the molecule
enables cell to keep it packaged and inaccessible

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5
Q

DNA replication

A

2 DNA strands are unzipped

DNA plymerases copy DNA info and synthesise complementary strand

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6
Q

which direction does DNA plymerase synthesis in

A

5’ to 3’

called continuous

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7
Q

3’ to 5’ synthesis

A

dis-continuous
completed in a series of fragments
called the lagging strand

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8
Q

what are the small fragments of DNA made during replication called and what do they need ot be initiated by

A

okazaki

RNA primer

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9
Q

End-replication problem

A

on the lagging strand there is a gap at the end where the primer has to stop- can’t fully replicate it

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10
Q

what is the answer to the end-replication problem?

A

telomerase
carries out reverse transcriptase
uses RNA template to template new DNA

chromosomes shorten during a number of division and telomerase detects this and extends them

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11
Q

kinetochore

A

protein complex that binds to microtubules

required for chromosome separation during cell division

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12
Q

kinetochore

A

protein complex that binds to microtubules

required for chromosome separation during cell division

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13
Q

Chromatin structure

A

DNA packaged with histone proteins packaged into units called nucleosomes

octamere nucleuosome structure- 8 histone proteins with DNA wrapped round them
locked in place by histone H1

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14
Q

Histone proteins

A

positively charged

small

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15
Q

solenoid structure

A

the structure of the 30 nm fibre. -secondary chromatin structure which helps to package DNA into the nucleus
- 6 nucleosomes in a turn

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16
Q

solenoid structure

A

the structure of the 30 nm fibre which ultimately becomes the chromosome

  • secondary chromatin structure which helps to package DNA into the nucleus
  • 6 nucleosomes in a turn
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17
Q

purpose of packaging DNA

A
  • Negatively charged DNA neutralised by positive charged histone proteins
  • DNA takes up less space
  • Inactive DNA can be folded into inaccessible locations until required
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18
Q

mitosis

A

IPMAT
interphase
prophase - chromosomes condense, nuclear membrane disappears, spindle fibres form centrioles

metaphase- chromosomes align at equator (metaphase plate), max condensation of chromosomes

anaphase- sister chromatids separate at centromere, move to opposite ends of cell

telophase- new nuclear membranes form- each cell has 46 chromosomes (diploid)

cytokinesis- cytoplasm separates, 2 new daughter cells

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19
Q

fluorescent in situ hybridisation (FISH)

A

a powerful technique used in the detection of chromosomal abnormalities
- uses fluorescent probes that bind to only those parts of the chromosome with a high degree of sequence complementarity for the probes (the probes are complementary to specific parts of chromosome)

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20
Q

meiosis

A

2 rounds of cell division
cell division in germ cells
diploid cells (in ovaries and testes) divide to form haploid cells
chromosomes are passed on as re-arranged copies- allows re-assortment of paternal/maternal genes

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21
Q

meiosis process

A

PMAT-PMAT
essentially the same as in mitosis, except here the non-sister chromatids cross over, forming chiasmata, where they can exchange DNA resulting in variation

the secondary cycle is pretty similar to the first, except the chromosomes are not copied or crossed over. This results in 4 haploid cells being produced instead of 2 diploid cells

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22
Q

spermatogenesis (process of sperm formation)

A

four sperm cells are formed per meiotic cycle, over a course of around 60 days. They undergo many more divisions than eggs, meaning there are more chances for mutations to occur

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23
Q

oogenesis (process of egg formation)

A

Each meiotic cycle produces one ovum and 3 polar bodies and this process occurs over 10-50 years.
These polar bodies mature into ova.

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24
Q

x-inactivation

A

genes present on X chromosome- one needs to be switched off, random inactivation of one in early embryo
so that women don’t make twice as much of proteins encoded by X chromosome genes

25
Q

What 3 types of chromosome abnormalities are there?

A

numerical
structural
mutational

26
Q

numerical abnormalities and name the different autosomal and sex chromosome aneuploidy syndromes.

A

having too many or too little a number of chromosome pairs ie having more or less than 23
autosomal: Trisomy 21, Trisomy 18, Trisomy 13
sex chromosome: X and XXY

27
Q

Trisomy 21

A 
DOWN SYNDROME 
autosomal
Trisomy 21 is a type of numerical chromosome abnormality 
95% caused by non-dysjunction 
can cause an IQ of less than 50
Alzheimer's later in life
28
Q

what is non-dysjunction?

A

homologous chromosomes or sister chromatids not separating

29
Q

Trisomy 13

A

PATAU SYNDROME
autosomal
very few survive past first year of life
90% non-dysjunction

30
Q

Trisomy 18

A 
EDWARD SYNDROME
autosomal
90% non-dysjunction
most die within first month to a year of life
cut 8 in half = E for edward
31
Q

X

A

Turner syndrome
sex chromosome aneuploidy- affects females- 1 less X chromosome
results in neck webbing and widely spaced nipples
intelligence and lifespan are normal
about 97% of babies affects are miscarried or still born but quite rare syndrome 1 in 1500 to 2500

32
Q

XXY

A 
Klinefelter syndrome 
affects males- additional X chromosome
long limbs
infertile, small testes 
50% develop breasts 
mild learning difficulties
33
Q

Structural abnormalities include?

A 
balanced and unbalanced rearrangements
translocation
deletion
insertion
inversion
34
Q

translocation- balanced and unbalanced

A 
balanced= piece of DNA or chromosome breaks off from two chromosomes and swaps to from two new structurally rearranged chromosomes
unbalanced= only one breaks off and swaps
35
Q

deletion

A

lost part of chromosome

36
Q

insertion

A

addition of larger sequence of DNA into chromosome

37
Q

inversion: peri-centric and para-centric

A

rearrangement
piece of chromosome breaks off, turns around and then is reinserted
peri-centric:-both sides of centromere
para-centric:- only at one side of centromere

38
Q

Robertsonian translocation

A

fusion of two acrocentric (centromere is close to the end of chromosome) chromosomes
no loss of genetic info
loss of short arms

39
Q

Mutational abnormalities: somatic and germline?

A

germline- mutations in germ cells- passed on to children

somatic- occurs after contraception in any of the cells in the body except germ cells

40
Q

types of mutations?

A

non coding- doesn’t affect amino acid sequence/protein

coding- silent, missense, nonsense, frameshift

41
Q

Silent mutation

A

no change in amino acid or protien

42
Q

missense mutation

A

changes one of the RNA codons so amino acid sequence is altered- different protein

43
Q

nonsense

A

stop codon is produced

44
Q

frameshift

A

addition or deletion of base pair in DNA so translation is altered/ shifted from that point

45
Q

Point mutation

A

only affects 1 or very few nucleotides in a gene sequence

46
Q

Point mutation

A

only affects 1 or very few nucleotides in a gene sequence

47
Q

Methods of detecting mutations

A 
PCR
DNA sequencing
Gel electrophoresis
ARMS
RFLP
48
Q

PCR

A

in vitro (out of the body, lab etc)
amplifies DNA
heating and cooling stages

49
Q

gel electrophoresis

A

separates DNA fragments by size by applying electric field
DNA is negatively charged
agarose gel matrix

50
Q

DNA sequencing

A

determining order of nucleotides in DNA sequence
very sensitive, robust
gold standard
however expensive

51
Q

what type of mutation is down syndrome caused by

A

translocation
an unbalanced translocation of chromosome 21 can lead to having 3 copies of the long arm
It is more commonly caused by trisomy for the whole of chromosome 21

52
Q

chromosome staining with dyes? what happens

A

When chromosomes are stained with dyes, they appear to have alternating lightly or darkly stained regions. The lightly stained regions are euchromatin and contain genetically active DNA. The dark regions are heterochromatin and are inactive DNA. (think dark, lights off, inactive)

53
Q

when does gametogenesis in males occur? and how many divisions occur?

A

during puberty

54
Q

when does gametogenesis in females occur? how many divisions occur?

A

in the fetus

55
Q

which parent is mitochondrial DNA passed on by?

A

Mother

this is because the egg is bigger and has more space for mitochondria

56
Q

when can you only see chromosomes?

A

when they are dividing

57
Q

what are mismatch repair (MMR) genes?

A

they correct errors that spontaneously occur during DNA replication

58
Q

who do Y-linked conditions occur to only?

A

only in males and in all their male descendants

P.O.D own flashcards (34 decks)

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