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Flashcards in Pedigree/numerical chrom Deck (64)
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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

On average,________, resulting in geneticreassortment between chromosomes.

2-3 crossovers occur on each chromosome,