10.1

Question 1

what are the two types of chromosome variations?

Answer 1

chromosome rearrangement
changes in chromosome number

Question 2

what are chromosome variations?

Answer 2

permanent chromosomal changes that can be passed down to offspring (if they are in germline cells)

Question 3

what are the four types of chromosome rearrangements?

Answer 3

deletions
duplications
inversions
translocations

Question 4

what is chromosome deletion?

Answer 4

loss of a segment of chromosome

Question 5

how do chromosome deletions happen?

Answer 5

terminal ends breaking off or internal breaking and rejoining at incorrect ends

Question 6

what is the main effect of chromosome deletions?

Answer 6

loss of genetic information

Question 7

how are chromosome deletions detected?

Answer 7

when the chromosomes pair in prophase I, the longer one bunches up to match the shorter one, forming a deletion loop that can be detected during meiosis
OR by molecular methods that detect heterozygosity or gene dosage

Question 8

what happens if a chromosome deletions happens spanning the centromere?

Answer 8

forms an acentric chromosome that will most likely be lost in cell division and may be lethal

Question 9

what is pseudodominance?

Answer 9

expression of alleles that are normally recessive

Question 10

what are the possible consequences of chromosome deletions?

Answer 10

change in gene dosage
pseudo-dominance
acentric chromosomes
haploinsufficiency

Question 11

how does chromosome deletions cause pseudodominance?

Answer 11

it deletes the part of the chromosome with the dominant allele

Question 12

what is haploinsufficiency?

Answer 12

mutant phenotype because gene dosage is too low (requires two copies for normal protein production)

Question 13

what is Cri du chat?

Answer 13

a genetic disorder related to gene dosage and chromosome deletions

Question 14

what is chromosome duplication?

Answer 14

repetition of a chromosome segment

Question 15

what are the simplest form of chromosome duplication?

Answer 15

tandem duplication

Question 16

what affect do chromosome duplications have?

Answer 16

usually not much, but gene dosage changes can cause problems, help evolution

Question 17

what effect do chromosome duplications have on evolution?

Answer 17

provide extra genetic material for new genes and adaptations

Question 18

what are the origins of chromosome duplications?

Answer 18

unequal crossing over of misaligned chromosomes during meiosis (also creates deletions)

Question 19

how are chromosome duplications detected?

Answer 19

when the chromosomes pair in prophase I, the longer one bunches up to match the shorter one, forming a deletion loop that can be detected during meiosis
OR by molecular methods that detect gene dosage

Question 20

what are the evolutionary consequences of chromosome duplications?

Answer 20

both copies may remain the same, alters gene dosage
one coy may become inactive and form a pseudogene and accumulate lots of mutations
one copy may aquire a new function (neofunctionalization)

Question 21

what are the long-term effects of neofunctionalization?

Answer 21

creates new genes and multigene families

Question 22

what effect does gene dosage have?

Answer 22

may affect phenotype
amount of protein created is often proportionate

Question 23

what is an example of gene dosage affecting phenotype?

Answer 23

drosophila eyes (Bar mutant)

Question 24

what are chromosomal inversions?

Answer 24

two breaks on a chromosomes and reinsertion in the opposite orientation

Question 25

what are the types of chromosomal inversions?

Answer 25

pericentric (around centromere)
paracentric (beside centromere)

Question 26

what is the effect of chromosomal inversions on phenotype?

Answer 26

often nothing
sometimes change in position may later expression (genes near chromatic may not be expressed)

Question 27

what happens with chromosomal inversions during crossing over?

Answer 27

if crossing over doesn’t occur - viable
if crossing over occurs OUTSIDE inverted region - viable
if crossing over occurs INSIDE inverted region - some nonviable and reduced recomb frequency

Question 28

why is crossing over in the chromosomal inversion region non-viable?

Answer 28

chromosomes form a dicentric chromatid with a bridge that breaks and gets rid of the acentric chromatid and gets rid of the genes :(

Question 29

what does inversion result in (summarized)?

Answer 29

functional suppression of recombinance and potential loss of fertility

Question 30

what is chromosome translocation?

Answer 30

exchange of segments between non-homologous chromosomes (or to different region on same chromosome

Question 31

what are the two types of chromosome translocation?

Answer 31

reciprocal and non-reciprocal

Question 32

what is a balanced translocation?

Answer 32

a chromosome translocation where no genetic material is lost

Question 33

what are the consequences of chromosome translocation?

Answer 33

may alter expression of genes because of associations or form new gene products

Question 34

what is the philadelphia chromosome?

Answer 34

fused BCR-ABL gene
produces fusion protein that causes chronic muelogenous leukemia