Bio 230 Genetics

Bio 230 Genetics

The grading for this course: Lecture and Lab

The exams are multiple choice based

The labs start next week – start with basic lab techniques

Kim Curry – open door policy

Chapter 2 – Mitosis and Meiosis

Mitosis – leads to production of two cells each with the same number of chromosomes as the parent cell

Meiosis – leads to production of gametes

Somatic cells have a specific number of chromosomes which present as homologous pairs. Homologous chromosomes are similar but not identical as the alleles may have different versions of the same gene.

Sex-determining chromosomes are usually not homologous yet behave as homologs in meiosis. In females they are the same XX but in males they are different XY. This is displayed in karyotyping. If giving a inhibitor drug during metaphase it stops mitosis at metaphase allowing chromosomes to be organized and karyotyping to occur.

Hemizygous –

Due to the fact that males have XY chromosomes and both chromosomes contains resistive genes this makes males more receptive to disease, which is why males on average live ~5 years less then females.

When sister chromatids are created in the S phase they are identical.

Cell cycle - Eukaryotes, fundamentally the same among eukaryotes conserved throughout evolution and comprised of: interphase and mitosis.

Mitosis is the shortest part of the cell cycle.

G1 phase is to check that no mutations or damage occurred during mitosis.

G0 phase is the final stage for cells and when cells reach this stage they can no longer replicate and divide. Cells can be forced into this phase if G1 detected damage in the daughter cells.

Stem cell research – to grow central nervous system cells and cardiac muscles

Induced pluripotent stem cells – stem cell that is capable of cell renewal (skin cells to IPSC)

Proteins that regulate the cell cycle: Cyclins proteins are regulated by cyclin-dependent kinases (Cdks) enzyme.

The checkpoints are located ate the G1/S, G2/M and M (spindle assembly checkpoint)

The middle of mitosis monitors that chromosomes are correctly attached to the spindle apparatus

If not caught non-disjunction occurs creating a replication of a chromosome

Each checkpoint has specific cyclin proteins that give the ok

Checkpoint proteins detects damage activating the tumor suppressor genes

Tumor suppressor genes will try to: arrest the cell cycle, repair the damage, apotosis (programmed cell death).

The most important tumor suppressor gene is the p53. If this gene is mutated cancer occurs, over half of all cancers contain this mutation.

Meiosis

Meiosis I – reduction division the material and paternal material is separated into two daughter cells. Each daughter cells have two sister chromatids

Meiosis II – The centromere divides and the sister chromatids are separated

At the end of prophase I = pair of the homologues chromosomes

*Do not need to know the sub-stages unless asked

Metaphase I are aligned in a double row (independent assortment) and cross-over (identical but recipical exchange occurs) this increases genetic variation.

The pairing of the at the metaphase plate is completely random (independent assortment = increase genetic variation)

The number of combination for the segregation of homologues chromosomes to daughter cells can be found by the simple formula:

2n where n = the number of homologues present

During fertilization you have to multiple the sperm and the egg together = 64 trillion to get the variability of the offspring (doesn’t include cross-over).

Differences in meiosis in females vs. males

To create a sperm from the spermatogonium takes 64 days

This begins when the male reaches puberty 11 to 13 years old

In early fetal life females meiosis begins and gets to prophase I, at puberty it continues to metaphase I and the genetic material is not shared equally. Creating a secondary oocyte and a polar body. Stalled at metaphase II – ovulation occurs.

If fertilized meiosis will continue (another polar body is formed as well)

The polar bodies will not undergo further division.

The older the female the higher the risk that chromosomal abnormalities will occur. The older the father the higher the chances the offspring will suffer a mutation.

Ehlting

Biotechnology

Recombinant DNA technology – cut and rejoined. Different sources!

• DNA from source 1 and source 2 (organisms)
• Cut out DNA from one organism and combine it with another organism
• Used to make GM food
• Humans manipulate crops

• Traditionally – breeding, selective breeding
• Modern – GMO (past 10-15 years) introducing foreign genes (usually from bacteria)

In order to cut the DNA by using restriction enzymes

• Very predictable
• Recognizes specific DNA sequences -> that’s where they cut
• Very reproducible
• Always cut both sides of DNA

Some restriction enzymes cuts give cohesive end (overhangs) and some give blunt ends

Restriction enzymes come from:

• Bacteria

Bacteria contain restrictive enzymes because if they are attacked by invading virus, the bacteria chops up the viruses DNA. Therefore, it was used for protection.

What goes back to together easier cohesive ends or blunt ends?

• The cohesive ends – Hydrogen bonds already formed
• Palindrome – complimentary to each other, can be read either direction
• DNA ligase – seals the gap between the two organism’s DNA. STABLE CONNECTION

What is a vector?

• Circular DNA

A typical cloning vectors have multiple cloning sites.

Why are multiple restrictive enzymes needed?

• The insert may not have the specific restriction sites
• If a restriction site is in the middle of another one. The middle site must also be cut.

Once sequence has been inserted:

Origin of replication??---------

By using the DNA sequencing primer site, it checks that the DNA has been sequenced correctly.