Chromosomes and Cell Division

Ch. 3

What are the contents of chromosomes?

DNA and Histone Proteins

Sister chromatids

2 identical arms of chromosome

When does DNA replication occur during the cell cycle?

during S phase

Centromere

where chromatids connect

What is contained within a centromere?

100kb + repetitive DNA

What part of the chromosome controls movement during cell division?

centromere

What are the two chromosome arms?

Short arm (p)

Long arm (q)

Centromere location can differ along the chromosome arms. What is it called when the centromere is located centrally?

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A. Acrocentric

B. Metacentric

C. Submetacentric

B. Metacentric

Centromere location can differ along the chromosome arms. What is it called when the centromere is located intermediately?

\
A. Acrocentric

B. Metacentric

C. Submetacentric

C. Submetacentric

Centromere location can differ along the chromosome arms. What is it called when the centromere is located terminally?

\
A. Acrocentric

B. Metacentric

C. Submetacentric

A. Acrocentric

Telomere

ends of chromosome, made of repetitive sequence of non-coding DNA (TTAGGG)

What is the function of the telomere?

maintains structural integrity

Telomerase

enzyme that adds nucleotides to the 5’ end of telomeres

A normal cell nucleus contains how many autosome pairs and how many sex chromosome pairs?

22 autosome pairs

1 sex chromosome pair

Homologs

member of pair of chromosome

Diploid, 46 chromosomes

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A. Gametes (ova and sperm)

B. Somatic cells

B. Somatic cells

Haploid, 23 chromosomes

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A. Gametes (ova and sperm)

B. Somatic cells

A. Gametes (ova and sperm)

Phytohemagglutinin

stimulates T cell division

Colchicine

inhibits mitotic spindle formation

Trypsin

digests proteins on chromosomes so DNA is available

Giemsa

DNA binding dye that binds to phosphate groups

Euchromatin

light stain that expresses gene activity

Heterochromatin

dark stain that shows genetically inactive region

Idiogram

shows idealized banding pattern where chromosomes are counted and bands compared

How do you read chromosome nomenclature, 15q2.5?

Chromosome 15

Arm q

Region 2

Band 5

What are DNA probes labeled with?

labeled with fluorochrome

Fluorescent microscope can be used to visualize what?

to visualize chromosomes

What are examples of FISH (Fluorescent In-situ Hybridization) probes?

Telomeric probes

Centromeric probes

Chromosome-specific unique-sequence probes

What do telomeric probes bind to?

binds to telomere DNA; fluoresces yellow

What do centromeric probes bind to?

bind to repetitive DNA

Centromeric probes can be used to make what type of diagnosis?

aneuploidy diagnosis (missing or extra chromosome)

Chromosome-specific unique-sequence probes are specific for what?

specific for a single locus

What can chromosome-specific unique-sequence probes be used to identify?

used to identify deletions and duplications

Why would you use a cocktail of probes to “paint the entire chromosome”?

to help identify translocations and complex rearrangements

What are the stages of the cell cycle?

Interphase

G1

S Stage

G2

Mitosis

What period of the cell cycle is described below?

* Period between mitoses (M)
* 16-24 hr in rapidly dividing cells

\
A. Interphase

B. G1

C. S Stage

D. G2

E. Mitosis

A. Interphase

What period of the cell cycle is described below?

* Chromosomes thin and extend
* Two paths:
* G0: Noncycle
* S: synthesis

\
A. Interphase

B. G1

C. S Stage

D. G2

E. Mitosis

B. G1

What happens during G0, noncyclic stage, of G1 cell cycle stage?

Cells have stopped dividing

Arrest cycle (i.e. neurons)

What happens during S, synthesis, of G1 cell cycle stage?

Replication of chromatin (2 chromatids (X shape))

What period of the cell cycle is described below?

* Homologous pairs replicate together
* X Chromosomes (female) have one that lags behind
* Lagging becomes the barr body

\
A. Interphase

B. G1

C. S Stage

D. G2

E. Mitosis

C. S Stage

What period of the cell cycle is described below?

* Chromosomes condense
* Prepare for next mitotic phase
* Rapid cell growth
* Relatively short

\
A. Interphase

B. G1

C. S Stage

D. G2

E. Mitosis

D. G2

What period of the cell cycle is described below?

* Somatic cell division
* Nucleus divides

\
A. Interphase

B. G1

C. S Stage

D. G2

E. Mitosis

E. Mitosis

What are the phases of mitosis?

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

What phase of mitosis is described below?

* Chromosomes condense
* Mitotic spindle begins to form

\
A. Anaphase

B. Cytokinesis

C. Metaphase

D. Prophase

E. Telophase

D. Prophase

During what phase of mitosis does the centriole form?

forms during prophase

What does the centriole form?

forms the area where the mitotic spindle forms

How many centrioles are present in a single cell?

2 form in a single cell

What phase of mitosis is described below?

* Chromosomes are in most condensed form
* Chromosomes align on equatorial plate
* Each chromosome attaches to the centriole via microtubule forming mature spindle

A. Anaphase

B. Cytokinesis

C. Metaphase

D. Prophase

E. Telophase

C. Metaphase

What phase of mitosis is described below?

* Centromere divides longitudinally.
* Daughter chromatids separate to opposite poles.

\
A. Anaphase

B. Cytokinesis

C. Metaphase

D. Prophase

E. Telophase

A. Anaphase

What phase of mitosis is described below?

* Chromatids are completely separated.
* Enveloped in a new nuclear membrane.

\
A. Anaphase

B. Cytokinesis

C. Metaphase

D. Prophase

E. Telophase

E. Telophase

What phase of mitosis is described below?

* Cell envelope separates
* 2 new daughter cells are formed and each daughter cell has diploid chromosome complement.

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A. Anaphase

B. Cytokinesis

C. Metaphase

D. Prophase

E. Telophase

B. Cytokinesis

Mitosis generates what?

generates 2 identical diploid cells

Meiosis generates what?

generates 4 nonidentical haploid cells

Meiosis is unique to cells where?

cells in the germline

Gamete

haploid cell produced by the parents which will fuse together to form offspring (sperm and egg/ova)

Sperm

male gametes

Egg or Ova

female gametes

Fertilization

union of egg and sperm

What are the two parts of meiosis?

Meiosis I and Meiosis II

What type of division occurs in meiosis I?

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A. Equatorial Division

B. Reduction Division

B. Reduction Division

What type of division occurs in meiosis II?

\
A. Equatorial Division

B. Reduction Division

A. Equatorial Division

What happens during Prophase I of Meiosis I?

homologous chromosomes eventually align

What are the 5 steps of Prophase I?

Leptotene

Zygotene

Pachytene

Diplotene

Diakinesis

Place the steps of Prophase I in order.

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Leptotene

Diakinesis

Diplotene

Pachytene

Zygotene

Leptotene

Zygotene

Pachytene

Diplotene

Diakinesis

During which step of Prophase I does the following happen?

* Chromosomes start to condense

\
A. Leptotene

B. Zygotene

C. Pachytene

D. Diplotene

E. Diakinesis

A. Leptotene

During which step of Prophase I does the following happen?

* Synapsis
* Synaptonemal complexes form

\
A. Leptotene

B. Zygotene

C. Pachytene

D. Diplotene

E. Diakinesis

B. Zygotene

What happens during Synapsis?

homologous chromosomes align opposite each other

When does synapsis NOT occur?

in mitosis

What do the synaptonemal complexes hold together?

hold together chromosomes

During which step of Prophase I does the following happen?

* Homologous chromosomes are tightly coiled
* Crossing over occurs

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A. Leptotene

B. Zygotene

C. Pachytene

D. Diplotene

E. Diakinesis

C. Pachytene

What occurs during crossing over of chromosomes?

Exchange of homologous segments between chromatids

During which step of Prophase I does the following happen?

* Chromosomes begin to separate
* Chiasmata forms

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A. Leptotene

B. Zygotene

C. Pachytene

D. Diplotene

E. Diakinesis

D. Diplotene

What is the chiasmata?

where chromosomes remain attached at crossing over points

During which step of Prophase I does the following happen?

* Separation of homologous pairs.
* Bivalents begin to move towards the equatorial plane

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A. Leptotene

B. Zygotene

C. Pachytene

D. Diplotene

E. Diakinesis

E. Diakinesis

Pseudoautosomal Region

tip of chromosome with homology (XY)

What happens during Metaphase I of Meiosis I?

The nuclear membrane disappears

Homologous pairs align on equatorial plane and attached to mitotic spindle

What happens during Anaphase I of Meiosis I?

Homologous chromosomes are pulled apart

Sister chromatids remain attached

What happens during Telophase I of Meiosis I?

Chromosomes reach the opposite sides of cell

Nuclear envelope begins to form

What occurs during Meiosis II?

each chromosomes (pair of chromatids) alight and split

What are the consequences of meiosis?

Halves the diploid number of chromosomes.

Generates diversity

How do we increase diversity during Meiosis I?

independent assortment (Mendel’s 3rd Law)

When does crossing over (gene shuffling) occur?

during prophase I

What occurs during crossing over?

DNA is exchanged, maternal and paternal, so that when meiosis is complete, each daughter cell has unique chromosomes

What is the process of Oogenesis?

Primordial germ cells (3 months) → Oogonia → 1º oocytes → 2º oocytes

Dictyotene

maturation arrest of all oocytes

During what cycle does ovulation occur?

\
A. Meiosis I

B. Meiosis II

A. Meiosis I

During what cycle can fertilization occur?

\
A. Meiosis I

B. Meiosis II

B. Meiosis II

Polar body

daughter cell from division

Long Dictyotene results from what?

‘Wear and Tear’

Damaged spindle formation

Lack of repair mechanisms

Approximately, how many times per year does spermatogenesis occur?

25 times/year

What is the process of spermatogenesis?

Spermatogonia → primary spermatocyte → secondary spermatocyte

Between what two stages of Meiosis I are primary oocytes and primary spermatocytes found?

between metaphase I and anaphase I

Between what two stages of Meiosis are secondary oocytes and secondary spermatocytes found?

between Telophase I and Metaphase II

Between what two stages of Meiosis II are large eggs, polar bodies, and spermatids of equal size found?

at anaphase II

What numerical abnormality is described below?

* Loss or gain of 1+ chromosome

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A. Aneuploidy

B. Monosomy

C. Polyploidy

D. Tetrasomy

E. Trisomy

A. Aneuploidy

What numerical abnormality is described below?

* Loss of a single chromosome

\

A. Aneuploidy

B. Monosomy

C. Polyploidy

D. Tetrasomy

E. Trisomy

B. Monosomy

What numerical abnormality is described below?

* Gain of a single chromosome

\

A. Aneuploidy

B. Monosomy

C. Polyploidy

D. Tetrasomy

E. Trisomy

E. Trisomy

What numerical abnormality is described below?

* Gain of 2 chromosomes

\

A. Aneuploidy

B. Monosomy

C. Polyploidy

D. Tetrasomy

E. Trisomy

D. Tetrasomy

What numerical abnormality is described below?

* Gain of an entire haploid copy

\

A. Aneuploidy

B. Monosomy

C. Polyploidy

D. Tetrasomy

E. Trisomy

C. Polyploidy

What forms of Trisomy survive to term?

\
A. Extra sex chromosome

B. Trisomy 13

C. Trisomy 16

D. Trisomy 18

E. Trisomy 21

A. Extra sex chromosome

B. Trisomy 13

D. Trisomy 18

E. Trisomy 21