Exam 1: Lecture 10

Question 1

why can’t cavendish bananas evolve disease resistance?

Answer 1

they are triploid and hence all sterile. 3 copies of genome present and cannot go through meiosis correctly and produce fertile seeds. Therefore they are genetically identical bc they are propagated by conventional vegetative reproduction. Very predicatle and lack of variability means virtually no way to identify variance in genes that would be resistant to fungus/disease to manipulate them. Need to identify genes to GMO.

Question 2

cavendish bananas are triploid and sterile. why?

Answer 2

cross btwn two individuals and unreduced gamete from one indiv that crossed with normal indiv (normal genomic state) so when you make a cross, get 2 copies from 1 species genome and only 1 copy from other. Species close enough related that chromosomes pair together during meiosis and leads to 3 copies of each chromosome and don’t know how to separate going through meiosis to produce nonfcnal gametes (uneven genome copy number)

Question 3

why are cavendish bananas more robust than parents

Answer 3

have more genetic information (triploid)

Question 4

what is chromosome morphology

Answer 4

position of the centromere on the chromosome:

• metacentric
• submetacentric
• acrocentric
• telocentric

Question 5

the satellite at metaphase contains

Answer 5

the nucleolar organizer region (NOR) around which the nucleolus forms. NOR contains tandem repeats of genes encoding ribosomal RNA

Question 6

the NOR can be detected by

Answer 6

silver staining (dark spots) and is useful landmark for chromosome identification

Question 7

karyotyping

Answer 7

• chromosomes prepared from actively dividing cells
• halted in metaphase (w/ colchicine)
• chromosome arranged by size

Question 8

banding: g bands

Answer 8

giemsa stain, trypsin digestion, metaphase chromosomes; 400-600 bands

Question 9

banding: q bands

Answer 9

quinacrine stain; A/T rich regions

Question 10

banding: c bands

Answer 10

reveals centromeric heterochromatin (around centromere) useful for if region near centromere is deleted/missing

Question 11

banding: r bands

Answer 11

regions rich in cytosine-guanine base pairs

Question 12

chromosome painting

Answer 12

fluorescent tags a piece of DNA that is complementary to various parts of the genome.

Question 13

types of chromosome mutations: aneuploidy

Answer 13

loss or gain of individual chromosomes (1 or a few chromosomes) ex trisomy down’s syndrome

Question 14

types of chromosome mutations: polyploidy

Answer 14

loss or gain of entire sets of chromosomes/genomes ex cavendish bananas

Question 15

polyploid cells and organisms are those containing more than

Answer 15

2 complete paired (homologous) sets of chromosomes

Question 16

aneuploidy is common in

Answer 16

cancer

Question 17

what is a tandem repeat

Answer 17

duplication follows right after

Question 18

chromosome mutations consist of

Answer 18

chromosome rearrangements, aneuploids, and polyploids

Question 19

what is an ex of chromosome rearrangement

Answer 19

duplications

Question 20

what is an ex of aneuploidy

Answer 20

trisomy

Question 21

what is an ex of polyploidy

Answer 21

autotriploids

Question 22

2n = 6

Answer 22

chromosome arrangement

Question 23

2n + 1 = 7

Answer 23

aneuploidy

Question 24

3n = 9

Answer 24

polyploidy

Question 25

what are the 4 types of chromosomal rearrangements

Answer 25

1. duplication
2. deletion
3. inversion
4. translocation

Question 26

chromosomal rearrangements often happen as:

Answer 26

a consequence of mispairing of repeated regions of the genome

Question 27

chromosome rearrangements alter

Answer 27

chromosome structure

Question 28

what happens in chromosome duplication

Answer 28

a segment of the chromosome is duplicated

Question 29

what happens in a chromosome deletion

Answer 29

a segment of the chromosome is deleted

Question 30

what happens in a chromosome inversion

Answer 30

a segment of the chromosome is turned 180 ex DEF is FED (seq is just flipped around)

Question 31

what happens in a chromosome translocation

Answer 31

segment of a chromosome moves from one chromosome to a nonhomologous chromosome or to another place on the same chromosome

Question 32

what happens during prophase I when there is an indiv heterozygous for a duplication?

Answer 32

need to pair chromatids together and duplicated region has no partner on the homolog so forms a loop structure and this looped region is prone to damage w/ loss/gain of material

Question 33

why is dosage sensitivity important in duplication

Answer 33

most genes important for development need to be present in the right dosage. duplication leads to inappropriate over expression/alteration in rations and subsequent disrupted development

Question 34

why are large deletions easily detected

Answer 34

during pairing, normal chromosome loops out (during prophase I)

Question 35

what are the effects of deletions

Answer 35

• imbalances in gene product
• pseudodominance (expression of recessive genes)
• haploinsufficiency (1 functional copy not enough to preserve normal fcn)