Chapter 10-test 2

Question 1

Chromosome condensation reaches a

Answer 1

maximum at metaphase

Question 2

Fluorescent in situ hybridization

Answer 2

• uses molecular probes to detect a target sequence; sequences may be gene-specific
• labeled w/ compounds that emit fluorescent light

Question 3

Multiple genes can be contained in

Answer 3

each chromosome band. 1 human band: 1milli-10milli

Question 4

euchromatin

Answer 4

Regions that contain actively expressed genes and are less condensed. lightly stained regions.

Question 5

heterochromatin

Answer 5

Regions that contain many fewer expressed genes and are tightly condensed. darkly stained regions.

Question 6

Nondisjunction

Answer 6

failure of chromosomes and sister chromatids to properly separate
•abnormalities in chromosome #
• abnormalities affect phenotype in animals, less in plants

Question 7

number of chromosomes in a nucleus for males and

females of a species?

Answer 7

the same

Question 8

euploid number

Answer 8

number of complete sets (e.g., n, 2n, 3n)

Question 9

aneuploid

Answer 9

If cells have a # of chromosomes that aren’t euploid. (one or more extra or missing chromosomes) cause: chromosome nondisjunction.

Question 10

result of nondisjunction in germ-line cells

Answer 10

aneuploid gametes that can produce aneuploid zygotes

Question 11

nondisjunction in meiosis I means

Answer 11

failure of homologs to separate; the gametes are n + 1 or n - 1

Question 12

Fusion of these gametes with normal (n) gametes produces

Answer 12

trisomic (2n + 1) or monosomic (2n - 1) offspring

Question 13

Among the four gametes produced by meiosis

Answer 13

only two will be affected. ( 2 will be normal (n) and the other 2 will be n + 1 and n - 1)

Question 14

Blakeslee and Belling (1913) studied aneuploidy in the jimson weed (Datura stramonium; 2n = 24)

Answer 14

identified 12 phenotypically distinct lines

Question 15

gene dosage

Answer 15

of copies of a gene; aneuploidy alters dosage of all genes on affected chromosome

Question 16

Changes in gene dosage lead to an

Answer 16

imbalance of gene products

Question 17

Most animals are highly sensitive to

in contrast,

Answer 17

• changes in gene dosage

- plants tolerate gene dosage changes more readily

Question 18

Changes to chromosome structure

Answer 18

caused by chromosome breakage or other events. may lead to loss or gain of chromosome segments or partial deletion or duplication

Question 19

chromosome break point

Answer 19

When a chromosome breaks, both DNA strands are severed.broken chromosome ends can stick to each other, to other broken ends, or termini of intact chromosomes

Question 20

terminal deletion

Answer 20

Detachment of all or part of one chromosome arm.broken fragment contains a telomere and additional genetic material.

Question 21

acentric

Answer 21

lacks centromere. If a broken chromosome fragment is acentric, it may be lost during cell division

Question 22

interstitial deletion

Answer 22

loss of an internal portion of a chromosome, and results from two chromosome breaks
• observed in many organisms, including humans

Question 23

unequal crossover

results in

Answer 23

takes place between two homologs

partial duplication on one homolog and partial deletion on the other

Question 24

partial duplication heterozygote

Answer 24

organism with one normal and one duplication homolog

Question 25

partial deletion heterozygote

Answer 25

organism with one normal and one deleted homolog

Question 26

Unequal crossover does not occur often

Answer 26

occurs when regions of homologs misalign

Question 27

Microdeletions and microduplications

Answer 27

are much smaller and not easily detected with banding analysis. instead use FISH.

Question 28

Sometimes chromosome breakage leads to

Answer 28

reattachment of the wrong broken ends

Question 29

chromosome inversion

Answer 29

Reattachment in the wrong orientation

Question 30

chromosome translocation (Translocation heterozygotes) if no

Answer 30

reattachment to a nonhomologous chromosome - critical genes are mutated, and dose-sensitive genes remain in balance, there may be no phenotypic conseq. - may experience semisterility due to segregation abnormalities

Question 31

meiotic complications may affect

Answer 31

chromosome segregation and fertility

Question 32

paracentric inversion

Answer 32

the centromere is outside of the inverted region

Question 33

pericentric inversion

Answer 33

the centromere is within the inverted region

Question 34

Inversion heterozygotes

Answer 34

have one normal and one inverted homolog

Question 35

probability of crossover within inversion loop depends on

Answer 35

size of inversion loop

Question 36

crossover in inversion loop results:

Answer 36

2 viable gametes (normal chromosome) | 2 nonviable gametes (inversion chromosome)

Question 37

Nonreciprocal (unbalanced) translocations

Answer 37

piece of one chromosome is translocated to a nonhomolog and there's no reciprocal event

Question 38

Reciprocal balanced translocations

Answer 38

pieces of two nonhomologs switch places

Question 39

Robertsonian translocations or chromosome fusion

Answer 39

fusion of two nonhomologous chromosomes

Question 40

Chromatin organization is important for

Answer 40

- proper function and distribution of chromosomes in cell division - plays an important role in regulation of gene expression in eukaryotic cells

Question 41

eukaryotic chromosomes could not fit

Answer 41

in nucleus without compaction. Each chromosome is approx half DNA and half protein

Question 42

histone proteins

Answer 42

About half of the proteins are histone proteins, small basic proteins that tightly bind DNA

Question 43

nonhistone proteins

Answer 43

remaining proteins. diverse and perform diff tasks in the nucleus

Question 44

how many histone proteins in chromatin?

Answer 44

5 (H1, H2A, H2B, H3, and H4)

Question 45

Nucleosome core particles

Answer 45

contains two molecules each of the four histones H2A, H2B, H3, and H4 (octomer)

Question 46

nucleosome

Answer 46

DNA ~146 bp long (core DNA) wraps around each octamer

Question 47

Nucleosome Assembly

Answer 47

- H2A and H2B assemble into dimers; H3 and H4 also form dimers - Two H3-H4 dimers form a tetramer, then two H2A-H2B dimers associate with it to form octamer - wrapping of DNA around the octamer=1st level of dna condensation, compacts dna sevenfold.

Question 48

10-nm fiber

Answer 48

Electron micrographs of chromatin in its least condensed state. “beads-on-a-string” morphology (“beads” are nucleosomes)

Question 49

linker DNA

Answer 49

variable-length “string” between nucleosomes

Question 50

30-nm fiber

Answer 50

in vitro conditions. forms when the 10-nm fiber coils into solenoid structure, w/ 6-8 nucleosomes per turn and histone H1 stabilizing solenoid

Question 51

When lysines in histone tails are neutralized | by methylation, gene expression

Answer 51

increases, because chromatin becomes less compact

Question 52

30 nm fiber turns into

Answer 52

300 nm fiber, turns on axis, forms 700 nm fiber.

Question 53

Aneuploidy can cause phenotypes associated with

Answer 53

increase/decrease of gene expression, defects in gene formation.

Question 54

chromosome 13, 18, 21

Answer 54

only trisomies seen in humans. humans are sensitive to gene dosage changes. (only a region of chromosome 21 causes down syndrome)

Question 55

DSCAM

Answer 55

s associated with formation of heart and nervous system

Question 56

How can a translocation or an inversion have phenotypic consequences for a cell ?

Answer 56

It can place a gene under control of a new enhancer