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BioChemistry > Chromosomes And Chromosomes Abnormality > Flashcards

Chromosomes And Chromosomes Abnormality Flashcards

1
Q

Describe how DNA is packed from strands to chromosome

A

1 DNA is doubled stranded molecule
2 warps twice around octameric core of Histone proteins forming a nucleosome
3 numerous nucleosomes resemble beads on a string
4 H1 protein added in between nucleosomes and its is packed into a 30nm fiber
5 fibre bound to scaffold protein and we have euchromatin
6 add more scaffold protein to euchromatin and we have heterochromatin
7 further condense heterochromatin to form chromosome

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2
Q

Describe the centromere structure and function

A
  • it is found at the center of chromosomes
  • rich in AT sequences
  • embedded in heterochromatin
  • attachment site for kinetochore microtubule during cell division
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3
Q

Describe telomere structure and function

A
  • found at ends of all linear chromosomes
  • called shelterin together with its histones
  • AGGGTT sequence used to reconstitute ends after division
  • maintain integrity of chromosome
  • helps repair proteins recognize true ends from breaks
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4
Q

Name of short and long arms of chromosomes

A
  • p ( petite arm )

- q arm

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5
Q

How are the arms positioned relative to the centromere

A
  • p arms above

- q arms below

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6
Q

What is non-disjunction and list the 2 types

A

-it is the abnormal separation of chromosomes during replication / division

1 primary non-disjunction
2 secondary

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7
Q

Describe 1• non-disjunction

A
  • occurs at 1st meiotic division
  • a chromosome pair will not separate into the 2 daughter cells but goes into 1 cell
  • 2 of the daughter cells will have extra chromosomes and the other 2 will be short a chromosome
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8
Q

Describe 2• non disjunction

A
  • occurs at 2nd meiotic division
  • a chromosome is split but will enter one daughter cell
  • a progeny will have an extra chromosome and other will be short one
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9
Q

What is the effect of cross over and synapsid to chromosomes

A

-the chromosomes will be recombined with new genetic material

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10
Q

Describe the Y chromosome , PAR region , SRY and how it determines sex

A
  • 122 genes essential for normal development
  • has pseudo-autosomal region ( PAR ) capable of recombination with the X region
  • determines gender at 1 genes called Sex determining region Y ( SRY ) which codes for protein that determines organism towards a maleness development
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11
Q

What happens if SRY damaged or copied to X chromosome

A
  • will have XY but be female

- will be XX and male

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12
Q

Describe the X chromosome , what is a Barr body

A
  • 1022 genes essential for normal growth and development

- found in females it is a inactive chromosome highly condensed and heterochromatic

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13
Q

List the 3 Types of chromosomes abnormalities

A

1 structural
2 autosomal
3 sex / gamete abnormalities

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14
Q

List the 5 types of structural damage to chromosomes

What is chromosome rearrangement

A 
1 deletion 
2 inversion 
3 translocation 
4 duplication 
5 ring chromosomes

-structural changes involving part of chromosomes

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15
Q

Describe deletion and duplication damage to chromosomes

A
  • part of chromosome deleted and individual has one copy instead of 2 ( missing genes cause disorders )
  • section of chromosome copied and individual now has 3 copies ( extra genes cause disorders/ partial trisomy )
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16
Q

Describe inversion and translocation

A

-2 breaks occur in the chromosome segment and the broken part is flipped over
( no loss of gain but breaks can cause disorders )

-part of chromosome removed due to 2 breaks and exchanged with other non homologous chromosome

17
Q

Describe ring chromosome

2 ways in which inversion can occur

A

-p and q ends break of ( or maybe they won’t ) and the chromosome attached to itself
( problematic in cell division )

1 pericentral - centromere involved
2 paracentral - centromere not involved

18
Q

List types of autosomal chromosome abnormalities

List types of sex chromosome abnormalities

A

1 Down syndrome
2 Cri du chat
3 Edwards
4 Pataus

1 Turners
2 Triple X
3 XYY
4 Kleinfelter

19
Q

2 ways abnormalities occur in chromosomes

A

1 structure of chromosomes

2 number Of chromosomes present

20
Q

What is aneuploidy and polyploidy

A
  • abnormal number of chromosomes in haploid cells ( missing or extra ones ) caused by non disjunction
  • cells with more than 2 sets of chromosomes ( homologous )
21
Q

What is monosomy and trisomy

A
  • individual with missing chromosome from a homologous pair

- individual with 3 chromosomes instead of 2 at a homologous pair

22
Q

Describe Down syndrome , signs , karotype and cause

A
  • trisomy at chromosome 21 , karotype is 47 ,

- heart defects , characteristics facial features , mental retardation

23
Q

Describe Edwards syndrome , signs , karotype and cause

A
  • trisomy at chromosome 18 ( low survival rate in kids )
  • karotype is 47
  • heart defects , mental retardation, microcephaly , hand and feet malformation
24
Q

Describe Cri du Chat syndrome , signs , karotype and cause

A
  • Deletion at 5p11
  • heart defects , microcephaly , unusual facial expression , microcephaly , nervous system and larynx defects causes characteristics meow sound
  • hypotonia ( weak muscle tone )
  • micrognathia ( smaller lower jaw )
  • strabismus ( cross eyed , eyes don’t face same direction )
25
Q

Describe XYY characteristics and treatment

A
  • male , tall stature , low IQ , verbal

- no treatment

26
Q

Describe XXX characteristics and treatment

A
  • triple X
  • female , normal appearance, mental retardation , irregular mensural cycle

-special education

27
Q

Describe XYX characteristics and treatment

A
  • kleinfelter syndrome
  • male , sterile , underdeveloped sex organs ,mental retardation ,tall statue , slightly feminized physique , breast development , small testis

-hormone treatment , special education

28
Q

Describe XO characteristics and treatment

A
  • turners syndrome
  • female , short stature , webbed neck , sterile , no mensural cycle , underdeveloped organs , constriction of aorta

-hormones , special education

BioChemistry (15 decks)

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