Sollars - Human Chromosome Structure/Karyotype

Question 1

Fragile Sites

Answer 1

Non-staining gaps, observed in characteristic sites on several chromosomes.

Question 2

How are fragile sites inherited?

Answer 2

Mendelian codominant fashion

Question 3

When would chromosomes be visible in the classic fashion?

Answer 3

After S-Phase

Question 4

What is the purpose of the centromere?

Answer 4

Attachment of chromosomes to cytoskeleton

Question 5

What 3 things do you need for chromosomes?

Answer 5

Centromere

Telomere

Origin of Replication

Question 6

What are three morphological classifictions of chromosomes?

Answer 6

Metacentric

Submetacentric

Acrocentric

Question 7

Satellite DNA

Answer 7

Any fraction of the DNA that differs sufficiently in its base composition from that of the majority of the DNA fragments to separate as one or more bands distinct from the bands containing the majority of the DNA during centrifugation

Question 8

When does each chromosome have an identical nucleoprotein copy joined by a centromere (sister)?

Answer 8

After S-phase and DNA replication

Question 9

Replication of Origin

Answer 9

Nucleotide sequence at which DNA synthesis begins

Question 10

Type of Chromosome w/a centrally placed centromere =

Type of Chromosome that appears J-shaped at anaphase because the centromere is nearer one end than the other =

Type of Chromosome with a nearly terminal centromere =

Answer 10

Metacentric

Submetacentric

Acrocentric

Question 11

Complex of nucelic acids (DNA/RNA) and proteins (histones/nonhistones) comprising eukaryotic chromosomes

Answer 11

Chromatin

Question 12

What type of chromatin is highly condensed and shows no evidence of active gene expression?

What type contains transcriptionally active DNA and is extended?

Answer 12

Heterochromatin

Euchromatin

Question 13

How many chromosomes does a haploid cell contain?

Answer 13

23

Question 14

What is the structure of mitochondrial chromosomes?

Answer 14

Circular

Question 15

What is the difference between Unique Sequence DNA and Repetitive DNA?

Answer 15

Unique = single copy per haploid genome, low conservation, protein coding, intronic, intergenic

Repetitive DNA = Repeated sequences, >50% of genome

Question 16

Satellite DNA

Answer 16

Any fraction of the DNA that differs substantially in base comp (either A+T rich, or G+C rich); forms bands

Question 17

Short Interspersed Nucleotime Elements (SINES)

and

Long Interspersed Nucleotide Elements (LINES)

Answer 17

SINES: Alu repeats

LINES: L1 (Line-1)

Both are Dispersed Repetitive DNA

Question 18

What are major differences between mitochondrial DNA and Nuclear Genome?

Answer 18

Mitochondrial genome is 10,000x smaller; each cell contains thousands of copies; is highly conserved for coding; and displays maternal inheritance

Nuclear genome is much larger but only contains two copies and displays traditional maternal/paternal inheritance

Question 19

What is the most common cell used for chromosome preparation?

Answer 19

Circulating Lymphocytes

Question 20

What cell cycle would you stop the cell at in order to best study the chromosomes?

Answer 20

Metaphase

Question 21

Define each number for the following gene:

10p23

Answer 21

10(chromosome) p(arm) 2(region) 3(band)

Hint: Remeber C.A.R.B

Question 22

What type of study is treatment with trypsin following by staining with Wright’s (Giemsa)?

What is characteristic of this study?

Answer 22

G-banding

Characteristic, and reproducible patterns of light and dark bands

Question 23

What type of study features fluorescent dye binding to A-T rich regions preferentially?

Answer 23

Q-banding

Question 24

What technique freezes cells earlier in their cycle, and is useful in detecting subtl structural abnormalities?

Answer 24

High-resolution banding (prophase or metaphase banding)

Question 25

What is the difference between R and G bands?

Answer 25

R = early replication, light bands, genes are mostly concentrated here G = A-T rich dark bands, few expressed genes, rich in L1 sequences

Question 26

What type of band is light, G-C rich, contains expressed genes, and is rich in Alu?

Answer 26

R-band

Question 27

What type of band is A-T rich, has few expressed genes, and is rich in L1 repeated sequences?

Answer 27

G-bands

Question 28

Fluorescent *in situ* Hybridization (FISH) Commonly used for what?

Answer 28

Analysis method to us a labeled, **chromosome specific** DNA segment to hybridized with metaphase, prophase, or interphase chromosomes and visualize under a fluorescent microscope Conformation of Down's syndrome

Question 29

Spectral Karyotyping (SKY)

Answer 29

Using multiple fluorescent probes specific for each chromosome to generate specific colors along most of its length. Greatly incrased accuracy and efficiency of detecting abnormalities.

Question 30

Comparative Genomic Hybridization (CGH)

Answer 30

DNA from test source is labeled with a green gluoropore and control normal DNA is labeled with red fluorophores. Two mixed, hybridized to normal chromosomes. Deletions or additions will alter the green:red ratio. **Widely used in cancer genetics.**