BIOL 1410 The Cell Cycle, Mitosis, Meiosis

LECTURE 4

Nerve cells and muscle cells are an example of what type of cell?

Somatic cells

Ova and sperm are examples of what type of cell?

Gametes (Sex cells)

Somatic cells include all cells of the body except…

Cells undergoing/resulting from meiosis

What are homologous chromosomes?

A pair of chromosomes that are the same size, centromere position, shape, and have genes for the same trait in the same locus. One chromosome is maternal, one chromosome is paternal.

Define gene

Unit of heredity, a region of DNA which contains information for synthesizing a protein

What are different versions of a gene called?

Alleles

23 Xms from an ovum + 23 Xms from a sperm =

46 Xms (diploid/2n somatic cell)

What are autosomal chromosomes?

Chromosome pairs numbered 1-22, contain genes for traits other than biological sex (somatic characteristics)

When does cytokinesis begin?

Anaphase

In what stage does protein/DNA synthesis occur?

Stage S of interphase

In what stage do chromosomes replicate?

Stage S of interphase

What cells do not divide again once mature, and are said to be in the G0 phase?

e.g. Nerve cells, some muscle cells

In what stage does centrosome replication begin?

G1 phase of interphase

What are kinetochores?

Proteins that form on each centromere, site of attachment of spindle microtubules

What is the main purpose of the G2 phase?

Production of enzymes & other proteins needed for cell division, centrosome replication is completed

How is mitosis defined?

Division of nuclear material (chromosomes)

What is cytokinesis?

Division of the cytoplasm

In what phase do chromosomes become individually visible?

Prophase

In what phase do nucleoli disappear and nuclear envelope breaks up?

Prophase

In what phase are kinetochores pulled away from each other, causing the separation of centromeres/sister chromatids?

Anaphase

In what phase do the nucleoli and nuclear envelope reappear?

Telophase

In what phase do microtubules grow out of centrosomes and attach to kinetochores, forming the spindle apparatus?

Prophase

In what phase do replicated chromosomes line up on cell equator?

Metaphase

When does cytokinesis complete?

In or after telophase

What does meiosis produce?

Gametes

Does DNA replication occur between Meiosis I and Meiosis II?

No, it only happens once in the S phase of interphase

What separates as a result of Meiosis I? Meiosis II?

Homologous chromosomes, then sister chromatids

Which Meiosis (I or II) is the reduction division in which chromosome number changes from 2n to n?

Meiosis I

What is new in Prophase I in comparison to Mitosis?

Homologous Xms attach together to form tetrads (4 chromatids in a row, so 2 chromosomes)

What is new in Anaphase I in comparison to Mitosis?

Sister chromatids DON’T separate (They do in Mitosis)

How many chromosomes do new cells have after Meiosis I and cytokinesis?

23 different chromosomes = haploid (n)

Do haploid cells have homologous chromosomes?

No, they only have one copy of each autosomal chromosome (and a single sex chromosome, X or Y) because the cell is HALVED.

23 tetrads line up at the equator in what phase; Metaphase, Metaphase I, or Metaphase II?

Metaphase I

Define the term chromatin

Loose DNA found in the nucleus before division (before it is condensed into chromosomes)