Review of eukaryotic chromosomes, mitosis, and meiosis

1
Chapter 2

• Review of eukaryotic chromosomes, mitosis, and
  meiosis

2
Euk chromosomes

• You should familiarize yourself with mitosis,
  meiosis and the cell cycle. If you are confused
  about the material, make sure that you review the
  subject matter first and then come and ask
  questions.

3
Euk chromosomes

• Euk characteristics
• Typically multiple linear chromosomes
• Species has characteristic number of chromosomes
• Complexity is not correlated with chromosome
  number.
• Euks may be haploid or diploidwhat does this
  mean?

4
Euk chromosomes
Fig. 1.11
5
Euk chromosomes

• Euk characteristics
• Generally, animals are diploid.
• Fungi are typically haploid.
• What are
• Homologous chromosomes
• Nonhomologous chromosomes
• Sex chromosomes
• autosomes

6
Euk chromosomes

• Euk characteristics
• Chromosomes that an organism possesses differ in
  size and appearance
• Chromosome may be named for the placement of the
  centromere (do you remember this structure?)
• Metacentric chromosome
• Submetacentric chromosome
• Acrocentric chromosome
• Telocentric chromosome

7
Euk chromosomes
Fig. 1.12
8
Euk chromosomes

• Euk characteristics
• Karyotypecomplete set of metaphase chromosomes
  in a cell (FIG. 1.13)
• Used to determine if individual has chromosomal
  abnormalities
• Autosomes are numbered 1-22 (1 is largest)
• X and Y (sex) chromosomes are not numbered
• Chromosomes are grouped together based on
  characteristicsletter categories
• Banding patterns (staining) and size help to
  identify the chromosomes

9
Euk chromosomes

• Euk characteristics
• Chromosome nomenclature
• Important so that genes or markers can be
  referred to on a chromosome
• Use metaphase chromosomes
• Each has 2 arms separated by ceontromere
• Long arm q
• Short arm p

10
Euk chromosomes

• Euk characteristics
• Chromosome nomenclature
• Regions are assigned on each arm and designated
  with a number begin numbering at the centromere
• Subregions have a decimal point (regions within
  the regions
• Cystic fibrosis located on 7q31.2-31.3
• BRCA1 located at 7q21

11
Euk Reproduction

• Briefly what are mitosis and meiosis?
• What cell types undergo these processes and why?
• Do all eukaryotic cells undergo both mitosis and
  meiosis?
• Why do sexually reproducing organisms alternate
  between a diploid and haploid state?
• Animal life cycle

12
Euk Reproduction
Fig. 1.14
13
Mitosis

• Interphase
• G1
• S
• G2
• Mitosis and cytokinesis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis (cleavage furrow vs. cell plate)

14
Euk Reproduction

• Review nomenclature for the chromosomes

15
Mitosis
Mitosis animation
Fig. 1.15
16
Mitosis-cytokinesis
Fig. 1.19
17
Meiosis

• Must start with a 2N cellwhy?
• What is the end result of meiosis?
• Are the cells different from the parental cells?
• In animal cells, what does type of cells does
  meiosis produce?

18
Meiosis

• Interphasemust be a 2N cell!!
• DNA replication before Meiosis I but NOT meiosis
  II
• Meiosis I and II and cytokinesis
• Prophase I and II
• Metaphase I and II
• Anaphase I and II
• Telophase I and II
• Cytokinesis (cleavage furrow vs. cell plate)

19
Meiosis
Fig. 1.20
20
Meiosis

• Meiosis I
• Prophase I
• Synapsis, chaisma, crossing over
• Metaphase I
• Homologous pairs line up at the equator
• Anaphase I
• Homologous chromosomes separate and migrate to
  opposite poles
• Telophase I
• 2 nuclei result each with 1 copy of each
  chromosome with its sister chromatid
• Cytokinesis

21
Meiosis

• Meiosis Ilike mitosis
• Prophase II
• Metaphase II
• Chromosomes align single-file
• Anaphase II
• Sister chromatids separate and move to opposite
  poles
• Telophase II
• 4 haploid nuclei arise each has one copy of each
  type of chromosome
• Cytokinesis

22
Meiosis

• How are mitosis and meiosis different?
• Cells that are generated
• Number of chromosomes
• Differences in stages

23
Meiosis

• How is genetic diversity generated in meiosis?
• Independent assortment of chromosomes
• Number of combinations of chromosomes in a gamete
  is 2n-1 (or 2n).
• Random fertilization
• Possible chrm arrangements in maternal chrm X
  possible chrm arrangements in paternal chrm
• Crossing over

24
Meiosisgenetic diversity
Fig. 1.23
25
Meiosisgenetic diversity
Fig. 1.24