Unit 4 - Biology 5b

Lecture 16 - Viral Life

The next 6 are the steps of viruses

Describe the process of HIVspreading among cells

HIV is +ssRNA

1. HIV fuses to a host cell's surface

2. HIV RNA, reverse transcriptase, integrase, and other viral proteins enter the host

3. Viral DNA is formed by reverse transcription turning ssRNA into dsDNA

4. Viral DNA is transported across nucleus and integrated into host DNA

5. New viral RNA is used as the genome to make more viral proteins using hosts mechanisms

6. New viral RNA and proteins move to cell surface and new imature HIV forms

7. The virus matures when protease releases proteins that form mature HIV

What are persistent viruses, and what are the 2 types?

Viruses that are not completely cleared from the host

1. Latent - Remain hidden or dormant and can infect later on

2. Chronic - Symptoms are recurrent

RNA World Hypothesis

Nucleotide pool starts joining nucleotides together and makes a pool of even larger ones, then they start folding to make ribozymes which are enzymes made of RNA allowing them to copy themselves

Lecture 17 - Asexual Reproduction

What is reproduction and what are the two types?

Organisms making new organisms

1. Asexual - Don't produce gametes

2. Sexual - Produce gametes (sperm/egg, pollen/ovules)

What is genetic variation?

A property of populations produced by mutations

What are the 3 types of asexual reproduction?

1. Budding

2. Fragmentation

3. Binary Fission

Describe the 6 steps of binary fission

1. DNA uncoils

2. Duplication

3. Separation of duplicated chromosomes

4. FtsZ protein forms Z ring, causing new growth of a cell wall

5. Cell wall is fully formed

6. Cells split into identical daughter cells

What is Natural Selection?

Differential reproduction of organisms based on heritable traits

- + or - direction (good traits integrate, bad ones are weeded out)

- Agent of selection is the environment

What conditions must be met for natural selection to work?

1. Traits must have a genetic basis (if you lose your arm, it won't be passed down)

2. Existing genetic variation

What is artificial selection?

Organisms act as the agents of selection instead of the environment

What is the Lenski experiment? (watch the full video)

Used to determine mutation rate of ecoli, and observe how mutations are carried on throughout lineages

One family evolved the ability to metabolize citrate

Lecture 18 - Sexual Reproduction

What are gametes?

Haploid sex cells

What is isogamy?

Population with equal-sized gametes

What is anisogamy?

Population with different-sized gametes

What is biological sex determined by?

Gamete size - Larger gamete = Female, Smaller gamete = Male (requires anisogamy)

Why do populations tend to shift towards anisogamy?

Smaller gametes tend to be mass produced and increase the rates of reproduction

Resource Allocation

Distribution of resources among competing uses. Usually comes with trade-offs.

What are hermaphrodites?

Make both male and female gametes

What is diacious?

Make one kind of gamete

Flowering plants

Produce pollen (male) and ovule (female); hermaphrodites

Describe sexual reproduction in Chlamydomonas green algae

1. Mature cells are haploid and have a single cup-shaped chloroplast

2. In response to stress, cells turn into gametes

3. Gametes of different mating type (+ and - because isogamous) fuse to form diploid zygotes

4. Zygotes make durable coat to protect cell from stress

5. After dormant period, meiosis produces 4 haploid individuals which mature

Note: Sexual reproduction for these only occur if there is stress, if not then asexual reproduction

Lecture 19 - Human fertility and pregnancy

Describe the ovarian cycle

1. Proliferative phase: Days 1 to 14 (follicular). Menstruation days 1 to 4: thin endometrium, estrogen level increased, multiple follicles develop. Ovulation on day 14

2. Secretory phase: Day 15 to 28 (luteal): corpus luteum secretes progesterone, endometrium thickens, decrease in estrogen and progesterone. Menses day 28

This cycle is almost never 28 days exactly, meaning those days are just estimates

What does GnRH do?

stimulates release of FSH and LH, causing a triple peak of these two hormones and estrogen that starts ovulation

Describe the fertile window

4-5 days each cycle

around 4 days before ovulation, up to 1 day after

Multiple ways to test for this:

- Basal body temp (although it only tells you that you already ovulated)

- Previous cycle data

- Cervical mucous

-Urine LH tests

How do LH strips work?

Every day has a mark because LH is always in the body, but the strip is not positive until both marks are similar color. Once they are, it means that GnRH let out the pulses of FSH and LH and ovulation is imminent.

Describe the oocyte life cycle

1. Oocytes get more and more mature until peak of LH and FSH

2. Mature oocyte is released and leaves behind corpus luteus

3. Fertilization: sperm meets egge and there's around a 50% chance of pregnancy

4. Cells divide until blastocyst implants in uterus, increasing hcg hormone (this is also when conception is)

- The highest chance of pregnancy is about 2 days before ovulation

How long is pregnancy?

Around 40 weeks (again, not exactly)

- Split into 3 trimesters

1. Trimester 1 is weeks 1-13 is when miscarriage is most common

2. Trimester 2 is weeks 14-27

3. Trimester 3 is weeks 28-37

-Full term is anywhere between weeks 38-42 and is when the baby can be delivered

Lecture 20 - The story of domestication

Why is incest bad?

increase the risk of a child inheriting a disease or bad allele from the parents

What is inbreeding?

Mating of related individuals

What are the 3 things you need to observe adaptive evolutionary change?

1. Existing genetic variation (a population)

2. Time and reproduction (you can't observe it with just one being; it's an emergent feature)

3. Differential reproductive rates correlated with heritable traits

What is domestication?

An organism is acquired from the wild and selectively bred in captivity (ants, beetles and termites with fungi)

Describe the main points in the history of agriculture

Neolithic - Humans domesticated plants

Paleolithic - Crop rotation (humans discovered mutualisms between plants)

1700's - Selective breeding of sheep and other animals

1800's - More advanced machinery because of electricity

What type of relationship is a virus?

Parasitic (+/-)

Adhesion

Virus binds to the host cell

Insertion of genetic material

Genetic material enters the cell itself (doesn't necessarily integrate its DNA into the host genome)

Synthesis of viral proteins

Uses host organelles to make viral proteins

Replication of genetic material

Replication of the DNA or RNA of the virus

Assembly of viral particles

Putting together the virus structure

Release (two different ways)

1. Lysis - Host explodes

2. Budding - host cell survives but viral packages bud offof cells

What is a virus?

A protein capsid with genetic material

What is the trade-off between virulence and lethality?

Typicall the more a virus can spread (virulence), the less lethal it is and vice versa.

What are the two ways that viruses store genes and express them?

1. DNA - Single strand and double strand (usually copied in nucleus)

2. RNA - +single strand (mRNA), - single strand (complement of mRNA) and double strand (all of these usually copied in cytoplasm).

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