Cytogenetics

Question 1

of chromosomes in human

Answer 1

46; 23 pairs; 22 pairs of autosomes (1-22 largest-smallest) and 1 pair of sex chromosomes

Question 2

karyotype

Answer 2

3 elements: total # of chromosomes, sex chromosomes, any abnormalities; can refer to chromosome status - how many? which sex chromosomes? any abnormalities? can refer to pic of ind’s actual chromosomes

Question 3

male w down syndrome

Answer 3

47 (extra chromosome 21) chromosomes, XY

Question 4

female w turner syndrome

Answer 4

45 (missing X chromosome), X

Question 5

male missing one chromosome 6

Answer 5

45, XY, -6

Question 6

g banding

Answer 6

gives each chromosome arm unique combination of black, white, and grey bands; allows for detection of chromosome rearrangements; grow cells in culture and halt mitosis in metaphase when chrs are densest and easiest to see under a microscope

Question 7

fluorescence in situ hybridization (FISH)

Answer 7

relies on the fact that complementary seqs bind to each other

Question 8

probes

Answer 8

single stranded DNA mols that have been labelled w fluorescent molecule used by hybridization techniques

Question 9

metaphase spread

Answer 9

when cells and nuclei burst and chromosomes spill out after dropping culture onto glass slides

Question 10

aneuploidy

Answer 10

not having the “standard” # of chromosomes for your species (having wild type # of chromosomes = euploid)

Question 11

polyploidy

Answer 11

having one or more extra full sets of chromosomes (ex: triploidy = having 3 full sets) occurs in 10% of spontaneous abortion in humans

Question 12

aneusomy

Answer 12

increase or decrease in the # of a specific chromosomes (not entire sets as in polyploidy)

Question 13

nullisomy

Answer 13

no copies of a specific chromosome

Question 14

monosomy

Answer 14

1 copy of a specific chromosome (di, tri, tetra)

Question 15

partial aneusomies

Answer 15

deletion and duplications that include a portion of a chromosome

Question 16

chromosome nondisjunctions

Answer 16

leads to aneusomies; can happen as somatic mutation during mitosis - present in only a subset of the ind’s cells; mosaicism; increases w age (reduced ability to recombine during prometaphase I)

Question 17

mosaicism

Answer 17

all people are mosaics because all people have somatic mutations

Question 18

trisomy 21

Answer 18

only trisomy that produces viable offspring; other trisomies are usually lethal; in other organisms trisomies are viable (ex: Jimson weed)

Question 19

polyploidy in plants

Answer 19

common; strawberries are hexaploid; commercially desirable: larger cells larger fruits, veggies, leaves; usually sterile w poorly developed seeds which makes them easier to eat

Question 20

autopolyploidy

Answer 20

all chromosomes are from the same species; results from wholesale nondisjunction of all chromosomes or failure of the cell to split; 3 specific mechanisms*; sterility bc of unbalanced gametes

Question 21

allopolyploidy

Answer 21

ind inherits chromosomes from 2 different species (species must be similar enough to each other for sperm and egg to be compatible); results from hybridization of gametes from 2 diff species

Question 22

early mitotic nondisjunction

Answer 22

creates diploid cells that can undergo meiosis

Question 23

euploid

Answer 23

having wild type # of chromosomes; non of us are completely euploid

Question 24

centromere deletion

Answer 24

chromosome will be post during next cell division; transposable elements can cause deletions*

Question 25

pseudodominance

Answer 25

ind loses dominant allele phenotypic characteristics reflects presence of recessive allele as only allele present

Question 26

haploinsufficiency

Answer 26

one copy of gene is lost and causes abnormal phenotype bc one working copy of the gene cannot make enough of the protein

Question 27

using deletions to map genes responsible for diseases

Answer 27

people w deletions in specific area = some have disease some don’t both narrow down location of disease causing mutation

Question 28

displaced duplication

Answer 28

not side by side

Question 29

reverse duplication

Answer 29

inverted duplication

Question 30

duplication & new genes

Answer 30

possible for mutation to affect duplicate w/o harming org

Question 31

insertion (nonreciprocal translocations)

Answer 31

piece of one chromosome is broken out and inserted into another chromosome

Question 32

reciprocal translocations

Answer 32

2 chromosomes break and exchange pieces

Question 33

balanced reciprocal translocation

Answer 33

no DNA lost; possible to have normal phenotype; can produce unbalanced gametes

Question 34

unbalanced reciprocal translocation

Answer 34

DNA lost; possible but less likely to have normal phenotype

Question 35

position effect

Answer 35

some genes expressed in specific order = moving one away from cluster may silence it; translocation can move normally active gene close to heterochromatic region = silencing the gene

Question 36

Robertsonian translocations

Answer 36

result from fusion of 2 acrocentric chromosomes (13, 14, 15, 21); single chromosome; do not usually produce abnormal phenotypes* (so many copies of rRNA gene in acrocentric chrs you can afford to lose some); can result in trisomies bc cell recognizes RT as single chr

Question 37

Rob(14q;21q)

Answer 37

one of the more common causes of down syndrome

Question 38

pericentric

Answer 38

if inversion breakpoints lie on either side of centromere

Question 39

paracentric

Answer 39

if both breakpoints lie w/i same chromosome arm

Question 40

transposable elements

Answer 40

can cause inversions (balanced vs. unbalanced)

Question 41

inversion

Answer 41

segment of chromosome is turned 180 degrees; balanced vs. unbalanced; position effects

Question 42

inversion loop

Answer 42

in heterozygotes homologous chromosomes must form inversion loop during meiosis so all regions of chromosome can align properly

Question 43

heterozygous pericentric inversion

Answer 43

result in reciprocal duplications/deletions*

Question 44

ring chromosomes

Answer 44

lose material from both p and q arm then form a ring