Flashcards in Pedigree/numerical chrom Deck (64)
Loading flashcards...
1
The pedigree (or family history) is ______
a graphical representation of the family tree
2
proband
The affected member through whom a family with a genetic disorder is brought to attention
3
consultand
the person who brings the family to attention (can be affected or unaffected)
4
consanguineous matings
Couples who have >1 known ancestors in common
5
Phenotype:
the observable expression (of a genotype) as a morphological, clinical, cellular, or biochemical trait
6
Genotype:
the set of
alleles that make up his or
her genetic constitution (usually we are talking about a single locus)
7
Two types of structural abnormalities:
Balanced
unbalanced
8
Balanced:
normal complement of chromosomal material
1. Inversions
2. Reciprocal translocations
3. Robertsonian translocations
9
Unbalanced:
abnormal chromosomal content 1. Deletions
2. Duplications
3. Isochromosomes
4. Marker (ring) chromosomes!
10
Structural Rearrangements Require
Double Strand Breaks of the DNA
11
95% of patients with CML have _______
the Philadelphia chromosome and an abnormal chromosome 9
12
Reciprocal Chromosome Translocation Leads to
to Chronic Myelogenous Leukemia
13
Robertsonian translocations can give rise to _________
trimsomy 21
14
Isochromosomes
refers to a chromosome in which one arm is missing and the other arm is duplicated in a mirror-like fashion
15
two models for isochromosomes
1) mis-division through the CEN in meiosis II
2) exchange between one arm of a chromosome and its homolog at the proximal edge of the arm, adjacent to the centromere
16
most common isochromosome is one involving the
long arm of the chrom
17
_____& of the viable offspring of a carrier of isochromosome 21 are abnormal
100
18
Summary of Mechanisms that Lead to Down Syndrome
•meiosis I nondisjunction (maternal) (95% of Down patients) e.g. 47,XY,+21
•Robertsonian translocation (4% of patients) e.g. 46,XX,der(14;21)+21
•Isochromosome (21q21q translocation) e.g. 46,XY,i(21)+21
•Mosaic Down syndrome
phenotype can be milder than typical trisomy 21, but patients exhibit wider variability in phenotypes due to variable portion of trisomy 21 cells in the embryo during development
•Partial trisomy 21
very rare, has only a portion of chromosome 21 duplicated!
19
Aberrant Recombination Events Lead to
Unbalanced
Chromosomal Rearrangements
20
Charcot-Marie-Tooth CMT 1A1
Charcot-Marie-Tooth CMT 1A1
– duplication of the gene for peripheral myelin protein-22, 17p11.2
21
Hereditary neuropathy with liability to pressure palsies
– deletion of the gene encoding peripheral myelin protein-22, 17p11.2
22
Hereditary sensory motor neuropathy - a genomic disorde
1. Charcot-Marie-Tooth CMT 1A1
2. Hereditary neuropathy with liability to pressure palsies
23
Contiguous gene syndromes
1. Velocardiofacial syndrome
cleft palate and septal defects
2. diGeorge syndrome
neural crest, branchial pouches, great vessels
outflow tract defects in the heart
24
Prior to the initiation of meiosis,
cells complete one round of DNA replication
25
Meiosis is a
type of cell division in which diploid germ line cells give rise to haploid gametes.
26
Two key differences between mitosis and meiosis are that
1. paternally- and maternally- derived homologous chromosomes pair at the onset of meiosis (prophase I), whereas the two homologs segregate independently in mitosis;
2. reciprocal recombination events between maternal and paternal sister chromatids generate chiasmata (physical linkages) between homologs.
27
recombination between homologs is rare during ______
mitosis
28
Meiotic prophase I is a critical period during meiosis.
Maternal and paternal homologs of each chromosome become paired or synapsed along their entire lengths, forming structures known as “bivalents”.
This process requires the formation of a proteinaceous structure called the synaptonemal complex. Reciprocal recombination events occurring at this stage generate physical links between homologs. These attachments, or crossovers, are also known as chiasmata.
29
synaptonemal complex, promotes
inter-homolog interactions
30
