BIOLOGY 151 Lecture Notes - Lecture 22: Sister Chromatids, Spindle Apparatus, Homologous Chromosome

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1 Apr 2016

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Homologous chromosomes- they have alleles for same genes at speciic loci. (unatached) Sister chromaids of duplicated chromosomes have same alleles for each gene. (2 atached chromaids) G1 is the longest phase of the cell cycle. Mitosis- in reverse order -cytokinesis, telophase, anaphase, metaphase, pro-metaphase, prophase. Start of with homologous chromosomes- s phase 2 homologous chromosomes each with two sister chromaids. And the chromaids are connected at the centromere. Mitosis is the soring process so that all the daughter cells get the right chromosomes. Mitoic spindle spindle ibers with anchors on both sides of the cell that are formed at the end of g2 right before mitosis starts. Prophase- chromosomes have already replicated, to produce 12 chromaids, joined as six pairs of sister chromaids. Chromaids condense into highly compacted structures that are readily visible by light microscopy. Prometaphase- mitoic spindle completely formed during this phase, centrosomes move apart and demarcate the two poles. Kinetochores- the center of the pair of chromsomes.

Related Questions

31.????? interphase A. cytoplasm divided between the two daughter cells

32.????? chromosomenumber B. final phase of mitosis; daughter nuclei form

33.????? chromatid C. sum total of chromosomes in all cells of a given

type

34.????? cytokinesis D. chromosomes condense and mitotic spindle

begins to form

35.????? metaphase E. chromosomes line up at spindle equator

36.????? alleles F. sister chromatids separate, move to opposite

spindle poles now

37.????? prophase G. none between meiosis I and II

38.????? telophase H. half of a chromosome in prophase

39. ????? anaphase I. different molecular forms of the same gene

Matching

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1) A tissue in a mouse contains two types of cells: one that divides rapidly and one that divides more slowly. The most likely difference between these two cell types is that the slow-dividing cell type spends more time in phase

G1, G2, G3, M, or S

2) In meiosis II

a- four genetically identical cells are generated

b- sister chromatids are separated

c- DNA replication occurs

d- crossing over occurs

e- both a and b

3) The four haploid nuclei found at the end of meiosis differ from one another in their exact genetic composition. Some of this difference is the result of?

a- cytokinesis

b- replication of DNA during the S phase

c- separation of sister chromatids at anaphase II

d- spindle formation

e- crossing over during prophase I

4) Which of the following does not occur during mitotic prometaphase?

a- disappearance of the nuclear envelope

b- initial movement of chromosomes towards the equatorial plate

c- adhesion of chromatids at the centromere

d- pairing of homologous chromosomes

e- disappearance of the nuclei

Match the term with its correct definition or explanation.

Chromatin

Homologous Chromosomes

Sister chromatids

Diploid

Interphase

S Phase

Synapsis

Crossing Over

Cell Plate

Cleavage Furrow

A. The exchange of genetic material between homologous chromosomes during meiosis I.

B. The pairing or tight association of homologous chromosomes in meiosis I. Results in the formation of a tetrad.

C. Non-identical copies of the same chromosome. Present in all diploid cells, even before replication. These chromosomes are the same length and contain genes for the same characteristics, but may have different alleles for each gene. D.

The period of the cell cycle that includes G1, S phase, and G2. E. A structure that develops during cytokinesis in plants.

F. Condensed chromosomes.

G. An invagination that develops during cytokinesis in animal cells.

H. When an organism has two copies of every chromosome (2n).

I. Two identical copies of a chromosome. These are only present after DNA replication.

J. The phase of the cell cycle when DNA is replicated.

BIOLOGY 151 Lecture Notes - Lecture 22: Sister Chromatids, Spindle Apparatus, Homologous Chromosome

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