Chromosomes And Chromosomes Abnormality Flashcards
Describe how DNA is packed from strands to chromosome
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
Describe the centromere structure and function
- it is found at the center of chromosomes
- rich in AT sequences
- embedded in heterochromatin
- attachment site for kinetochore microtubule during cell division
Describe telomere structure and function
- 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
Name of short and long arms of chromosomes
- p ( petite arm )
- q arm
How are the arms positioned relative to the centromere
- p arms above
- q arms below
What is non-disjunction and list the 2 types
-it is the abnormal separation of chromosomes during replication / division
1 primary non-disjunction
2 secondary
Describe 1• non-disjunction
- 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
Describe 2• non disjunction
- 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
What is the effect of cross over and synapsid to chromosomes
-the chromosomes will be recombined with new genetic material
Describe the Y chromosome , PAR region , SRY and how it determines sex
- 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
What happens if SRY damaged or copied to X chromosome
- will have XY but be female
- will be XX and male
Describe the X chromosome , what is a Barr body
- 1022 genes essential for normal growth and development
- found in females it is a inactive chromosome highly condensed and heterochromatic
List the 3 Types of chromosomes abnormalities
1 structural
2 autosomal
3 sex / gamete abnormalities
List the 5 types of structural damage to chromosomes
What is chromosome rearrangement
1 deletion 2 inversion 3 translocation 4 duplication 5 ring chromosomes
-structural changes involving part of chromosomes
Describe deletion and duplication damage to chromosomes
- 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 )
Describe inversion and translocation
-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
Describe ring chromosome
2 ways in which inversion can occur
-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
List types of autosomal chromosome abnormalities
List types of sex chromosome abnormalities
1 Down syndrome
2 Cri du chat
3 Edwards
4 Pataus
1 Turners
2 Triple X
3 XYY
4 Kleinfelter
2 ways abnormalities occur in chromosomes
1 structure of chromosomes
2 number Of chromosomes present
What is aneuploidy and polyploidy
- abnormal number of chromosomes in haploid cells ( missing or extra ones ) caused by non disjunction
- cells with more than 2 sets of chromosomes ( homologous )
What is monosomy and trisomy
- individual with missing chromosome from a homologous pair
- individual with 3 chromosomes instead of 2 at a homologous pair
Describe Down syndrome , signs , karotype and cause
- trisomy at chromosome 21 , karotype is 47 ,
- heart defects , characteristics facial features , mental retardation
Describe Edwards syndrome , signs , karotype and cause
- trisomy at chromosome 18 ( low survival rate in kids )
- karotype is 47
- heart defects , mental retardation, microcephaly , hand and feet malformation
Describe Cri du Chat syndrome , signs , karotype and cause
- 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 )
