BIOL 410 Lecture Notes

1-21-20

* Know proteins

* Ploidy: # of sets of chromosomes.

- Diploid: 2, haploid: 1.

* Mitotic Cell Cycle

- Sister chromatids held by cohesion.

- Denovo: from scratch.

• Needs existing strand from RNA polymerase (pol).

- Mitosis starts at prophase. Similar

• Microtubules
Kinetochore
Centromere (Part of chromosome. DNA)

Mitotic spindle Centrosome (protein complex)

- Meiosis starts at prophase I. Not identical cell at end (cytokinesis).

• Homologous chromosomes pair at synaptonemal complex.

- Transcription in nucleus. Translation in cytoplasm.

- ESE: Eukaryotic Splice Enhancer.

• Translation begins with methionine.

,*

Interphase

Mitotic phase (M)

G1

Cytokinesis

S (DNA synthesis)

Mitosis

G2




- G1: most of cell’s life where organelles and proteins are made.

- S: DNA rep. 23 46 pairs of chromosomes.

- G2: prep for mitosis. Make microtubules to pull chromatids apart.

* DNA replication in S phase (linear)

Initiator complex

Duplicated

Bidirectional chromosomes

replication held by cohesion

I II III IV




Origins of replication Licensed origin Sister chromatids

,* Leading strand replication:

- Helicase opens parental DNA. Single Stranded Binding Proteins (SSBP) keeps strands stable

and open. RNA primer attaches to 5’ end (top) made by RNA polymerase (primase). DNA

pol III extends from primer to 3’ with help of “sliding clamp”.

* Lagging strand replication:

- After SSBP is added, RNA primer attaches to 5’ end (bottom). Then, more primers are added

until it reaches the ORI (center). DNA pol III extends from each primer’s 3’ end. DNA pol I

removes any remaining primer and adds more nucleoside triphosphate (3 phosphate group

with 5 – carbon sugar). Finally, DNA ligase seals any nicks that are present.



Sliding clamp

ORI



DNA pol III Primer

5’

3’

Lagging strand also called Okazaki fragment



3’ 5’ – 3’ primer

DNA pol I DNA ligase

Helicase



Primase DNA pol III

, * Mitosis: after interphase, sister chromatids go to prophase for condensation into
heterochromatin. Then, prometaphase nuclear envelope dissolves and attachment of kinetochore
microtubules to centromere occurs. Chromatids align at metaphase from push and pull of
microtubules. Next, cohesion breaks down during anaphase so chromatids can separate.
Telophase decondenses chromosome and nuclear envelope reforms. Ends at cytokinesis.



Interphase Prophase Prometaphase




Centromere Microtubule to kinetochore

Sister chromatids Heterochromatin (next to centromere)



Telophase/Cytokinesis Anaphase Metaphase




* Meiosis makes haploid gametes. Like mitosis except with 2 stages (meiosis I and II). Has 4
pairs instead of 2 pairs of chromatids. Each cell and haploid gamete is unique at the end of their
own division (cytokinesis I and II).