Lecture 9 - Chromosomal Abnormalities

Question 1

What are the three types of chromosome mutations

Answer 1

rearrangements, aneuploids, polyploids

Question 2

What do chromosome rearrangements do generally

Answer 2

alter the structure of chromosomes

Question 3

What are the 4 types of chromosome rearrangements

Answer 3

duplications, deletions, inversions, translocations

Question 4

What is the definition of an aneuploid

Answer 4

they have an altered number of chromosomes in terms of being added or deleted

Question 5

What is the definition of a polyploid

Answer 5

one or more complete sets of chromosomes are added or deleted

Question 6

What is the definition of duplications and what are the two types

Answer 6

segment of a chromosome is duplicated
Tandem duplications
Displaced duplications

Question 7

What is the definition of a tandem duplication

Answer 7

duplicated regions are adjacent to the original section

Question 8

What is the definition of a displaced duplication

Answer 8

duplicated region is elsewhere in the genome

Question 9

What is the outcome of homozygous duplications during replication

Answer 9

not a problem during replication

Question 10

What is the outcome of heterozygous duplications during replication

Answer 10

chromosomes are not the same length, the duplicated chromosome has to form an inversion loop so regions can line up

Question 11

Define unbalanced gene dosage

Answer 11

if genes are duplicated it can lead to a greater production of those gene products which can affect phenotype

Question 12

What percentage of human genome contains segmental duplications

Answer 12

4%

Question 13

Explain the role of duplication in evolution

Answer 13

• existing copies of a gene are not free to vary if encoding something essential
• if that gene gets duplicated extra copies can undergo mutation and change
• over time extra copy might acquire enough mutations to assume new function to organism

Question 14

Define a deletion

Answer 14

segment of chromosome is deleted

Question 15

What are the effects of heterozygous chromosomes concerning a deletion during replication

Answer 15

the longer wild type chromosome must form an inversion loop to line up with the chromosome with a deletion

Question 16

What are the effects of a homozygous deletion

Answer 16

It is lethal in the homozygous due to loss of essential genes

Question 17

Define haploinsufficient and what type of chromosomal rearrangement is it associated with

Answer 17

Associated with deletions when a single copy of a gene is not sufficient to produce a wile type phenotype

Question 18

Define inversions and what are the two types

Answer 18

when chromosome segment gets inverted
paracentric inversions
Pericentric inversions

Question 19

What are paracentric inversions

Answer 19

inversions do not span the centromere

Question 20

what are pericentric inversions

Answer 20

inversions do span the centromere

Question 21

What are the effects of inversion on phenotype

Answer 21

typically profound effect

can disrupt gene or gene order

Question 22

Does a homozygous individual for a particular inversion have problems in meiosis

Answer 22

no problems

Question 23

Does a heterozygous individual for a particular inversion have problems in meiosis

Answer 23

Yes needs a 4 strand inversion loop

Question 24

What are the results in the gametes of a heterozygous paracentric person where the chromosomes have crossed over in the inversion loop

Answer 24

1 non-recombinant gamete with no inversion
2 recombinant short nonviable gametes
1 non-recombinant gamete with paracentric inversion

Question 25

What are the results in the gametes of a heterozygous pericentric person where the chromosomes have crossed over in the inversion loop

Answer 25

1 non recombinant gamete with no inversion 2 recombinant long nonviable gametes 1 non recombinant gamete with pericentric inversion

Question 26

What is distinguishable between paracentric and pericentric inversions during crossing over in meiosis

Answer 26

Paracentric inversion leads to formation of a dicentric chromatid and an acentric chromatid

Question 27

What is the definition of a dicentric chromatid

Answer 27

has two centromeres

Question 28

What is the definition of an acentric chromatid

Answer 28

lacks a centromere

Question 29

What is the definition of a translocation

Answer 29

movement of genetic material between non homologous chromosomes or within the same chromosome

Question 30

What are the effects of translocations

Answer 30

link genes that were originally located on different chromosomes can disrupt gene sequences

Question 31

Define robertsonian translocation and what is the overall result on the genome

Answer 31

deletion associated with translation where two long arms are joined together and two short arms are joined and lost Overall result is a reduction in chromosome number by 1

Question 32

Can aneuploidy happen in meiosis or mitosis

Answer 32

both

Question 33

can aneuploidy happen in meiosis I or II

Answer 33

both

Question 34

What are the 3 specific ways that aneuploidy can happen

Answer 34

1. centromere gets deleted 2. small chromosome lost in robertsonian translocation 3. nondisjunction and failure of homologous chromosomes or sister chromatids to separate

Question 35

What are the 4 types of aneuploidy and what is the math that goes with them

Answer 35

nullisomy 2n-2 Monosomy 2n-1 trisomy 2n+1 tetrasomy 2n+2

Question 36

What are the rates of aneuploidy in human pregnancy

Answer 36

30% of conceptions aborted and 50 % of those due to aneuploidy

Question 37

What causes trisomy 21

Answer 37

nondisjunction in oogenisis

Question 38

Primary down syndrome is what

Answer 38

not heritable resulting from spontaneous nondisjunction in oogenisis

Question 39

What is maternal age linked to increased rates of down syndrome

Answer 39

oocytes suspended in diplotene for a long period of time start to have cohesin in spindle structure break down leading to nondisjunction of chromosomes.

Question 40

What is the definition of familial down syndrome

Answer 40

Parents who are carriers of chromosomes which have undergone robertsonian translocation Long arm of 21 and 14 join together Gametes can segregate 6 different ways, 3 of which will cause a live birth , 1 of those ways leads to down syndrome`

Question 41

What are the two types of polyploidy

Answer 41

autopolyploidy and allopolyploidy

Question 42

Define autopolyploidy

Answer 42

ploidy event that derives from a single species caused by accidents in mitosis or meiosis

Question 43

Define allopolyploidy

Answer 43

arises from hybridization between two species where one species carries chromosome sets from two or more species

Question 44

What ploidy are allopolyploidy hybrids

Answer 44

diploid

Question 45

Cell volume is correlated to what

Answer 45

nuclear volume