Chromosomal Aberrations

Question 1

diploid cells

Answer 1

two homologs (1 maternal + 1 paternal) for each chromosome = 46 total

similar not identical

Question 2

mitosis

Answer 2

separates chromatids (identical halves of a singular chromsome) = two cells w/ 46 chromosomes, 1 chromatid each

Question 3

meiosis

Answer 3

separates homologous chromosomes = 2 cells with 23 chromosomes, 2 chromatids each

cross over exchange b/t homos

2 divisions:
1. reduction = haploid cells w/ 23 chromos
2. equational = gametes

error prone

Question 4

structural abberations causes

Answer 4

1. nonhomologous end joining during double strand break repair
2. unequal crossing-over b/t nonhomologus regions = illegitimate recombination

Question 5

balanced alterations

Answer 5

does NOT change amount of genetic information
-reciprocal translocation so all info still present
-no phenotype

unless rearrangement = new gene product/ new reading frame OR heavily methylated fragment is translocated

Question 6

unbalanced alterations

Answer 6

reduces or increases amount of DNA via
deletion and duplication
-severe phenotype

can occur in meiosis even if carrier is originally balanced

deletions more severe than duplications

Question 7

cri-du-chat

Answer 7

facies: microcephaly, hypertelorism, micrognathia

brain/CNS: severe ID

cardio: heart defects

usually new mutation, specific cry

bascially taking out chromo 5 affects multiple systems

Question 8

di george syndrome

Answer 8

usually new mutation

malformations: congenital heart defect, immunodeficiency, hypothyroidism, mild ID, cleft palate,

deletion of TBX1 gene

Question 9

philadelphia chromosome

Answer 9

specific translocation b/t chromo 9 and 22 = oncogene, dominant gain-of-function mutation

acr-abl kinase = chronic myelogenous leukemia

treat with tyrosine kinase inhibitor

Question 10

robertsonian translocation

Answer 10

chromos exchange entire long and short arms

the short-short arm derivative will dissapear

b/t chromos 13 and 14 most common alteration

Question 11

inversions

Answer 11

inverted chromos = inverted loop during meiosis

recombination in inverted region can generate dicentric and acentric chromos

Question 12

robertsonian translocation in meiosis

Answer 12

3 chromosomes will align (instead of 2 pairs of 2)

separated via 3 diff patterns
1. alternate segregation = normal, balanced gamete
2. two adjacent segregations = unbalanced gamete

Question 13

massive radiation

Answer 13

leads to chronic myelogenous leukemia bc nonhomologous recombination

CBC will show inc WBC count and myeloid cells

assoc with philadelphia chromosome,

Question 14

recurrent pregnancy loss

Answer 14

robertsonian translocation b/t 13 and 14 = unbalanced karyotype, only 45 chromos

parent with 45 chromos > unbalanced offspring

Question 15

cytogenetic analysis

Answer 15

to detect chromosomal aberrations

-stillbirth/neonatal deaths
-fertility problems
-preg w/ advanced maternal age
-cancer or family history

Question 16

inheritance of chromo aberration

Answer 16

-dominant, new mutations (low fitness of carriers)

-multiple abnormalities in affected children w/ dev delay
-spontaneous abortions/multi miscarriages

is possible to have normal and balanced outcomes

Question 17

aberrations in cancer

Answer 17

genome instability hallmark of cancer (hyperdiploid)

cell cycle not stop for DNA repair so cancer resistant to apoptotic signals