Biology - Gr.11 🧬 (UNIT 1: GENETICS)

LESSON #1: 1. Intro to cell and cell theory 2. The cell parts + functions 3. Types of Asexual Reproduction 4,5. Mitosis & Cell cycle 6. Cancer and its causes

1. INTRO TO THE CELL + CELL THEORY

• cell theory

• Prokaryotic + Eukaryotic cells

What is genetics?

scientific study of heredity and variation

What is the cell theory?

1. The cell is the smallest living unit in all organisms
2. All living things are made of cells
3. All cells come from other pre-existing cells

Q. What is the difference b/n prokaryotic and eukaryotic cells?

Prokaryotic:

• simple & small

• ✅ cell membrane: cytoplasm, DNA/RNA, ribosomes

• ✘ membrane bound organelles: nucleus, nuclear membrane

  ex. bacteria

Eukaryotic:

• comple & large

• DNA condensed inside the nuclear membrane

• ✅ membrane organelles: mitochondria, chloroplasts, lysosomes

  ex. protists, plants, fungi

Prokaryotes have.../don't have...

✓ DNA
✓ Ribosomes
✓ Cell membrane
x nucleus
x Membrane bound organelles (mitochondria & chloroplasts)

Eukaryotes have.../don't have...

✓ DNA
✓ Ribosomes
✓ Cell membrane
✓ nucleus
✓ Membrane bound organelles (mitochondria & chloroplasts)

What are somatic cells?:

Somatic cells are all the cells in the body that are not reproductive cells, or germ cells. (creds: google)

2. THE CELL: Parts and their functions

• nucleus

• nucleoplasm

• nucleolus

• nuclear membrane

• RER

• SER

• Ribosomes

• vacuoles

• chloroplasts

• cell wall

• plasma membrane

• mitochondria

• golgi vesicles

• golgi apparatus

Nucleus

controls the cell (+ cell reproeduction & contains DNA)

Nucleousplasm

where genetic info is found: several enzymes are present that help w/ synthesis of DNA and RNA (stores lipids and carbohydrates)

Nucleuolus

center of ribosomes synthesis and production of certain proteins

image: eukaryote

Nuclear membrane

double membrane that encloses the cell nucleus

Rough endoplasmic reticulum (RER)

synthesizes and transports proteins. Rough = presence of ribosomes on the surface

Smooth endoplasmic reticulum (SER)

metabolizes several chemicals and synthesizes lipids, phospolipids and steroids

Ribosomes

makes proteins

Vacuoles

LARGE in the plant cell, contains/stores water (maintains cell rigidity + acts like a storage)

Chloroplast

performs photosynthesis (6CO2 + 6H2O → C6H12O6 + 6O2) in plant cells

Cell wall

additional cell protection for plant cells (gives shape + protects from external forces)

Mitochondria

performs cellular respiration (contains its own DNA)

Plasma membrane (aka cell membrane)

• semi-permeable

• controls what enters and leaves the cell (ex. complex proteins)

Cytoplasm

holds dissolved materials

Golgi vesicles

transports molecules prodcued by other organelles

Golgi apparatus

stores and transports proteins and lipids

Lysosome

membrane-bound organelle that contains digestive enzymes

Q. What is the difference b/n animal and plant cell?

Animal:

• no cell wall or chloroplast

• prescence of lysosomes

• one or more small vacuoles

Plant:

• has cell wall and chloroplast

• no lysosomes

• LARGE vacuole (bigger than nucleus)

3. ASEXUAL REPRODUCTION

Budding, Vegetative Reproduction, Parthenogensis, Fragmentation

What is asexual reproduction?

a type of reproduction that does not require two gametes

Budding:

formation of a new identical organism from a bud (ex. hydra)

Vegetative reproduction:

formation of a new plant (clone) from stolen (ex. strawberry), tuber (potato), rhizome (ex. in mint plant)

Parthonogensis

fertilization of an egg w/o the prescence of a male (sperm)

Fragmentation

Production of new individual when the parental organism divides into pieces (each piece produces a clone)

Binary Fission

→ bacteria and protists divide asexually by a process called ‘binary fission’ while eukaryotic cells use the process of mitosis

What is sexual reproduction?

when a sperm from a male parent fertilizes an egg from a female parent to produce offspring

4. THE CELL CYCLE

• Interphase + DNA replication

• Mitosis

• Cytokinesis

THREE reasons for cell division:

• growth, repair, replace

Q. Why do cells divide?

Cells need to divide because if they get bigger, they won’t be able to divide. Process of diffusion would be slower and the cell would not be able to get nutrients, remove waste and die.

The Cell cycle THREE stages:

1. Interphase
2. Mitosis
3. Cytokinesis

1. Interphase:

- most of the cell is interphase (90 %)
- chromosomes are copied (so each new cell has a full set of DNA)

• Phase G1: (Growth)

• First part of interphase

• Cellular contents in the cell are duplicated

• Phase S: (Synthesis)

• DNA synthesis and replication (future cells obtain similar copies of DNA and associated proteins)

• 46 chromosomes are duplicated by the cell

• Phase G2: (Growth + Preperation)

• Replication or duplication of centrioles

• Preparing for division

What is G0?

cell cycle arrest, which occurs if there’s an error

How many chromosomes do humans have?

46 chromosomes

Sister chromatid:

identical copy of a chromosome which remains attached until anaphase

Sex chromosome:

type of a chromosome that determines sex (X + X = female) (X+Y = male)

Chromatin:

DNA is unravelled (messy) in interphase

Chromosome:

DNA is coiled and condensed (organized) in mitosis

→ double-stranded chromatid

Genome:

a complete set of DNA in an organism

Gene:

segment of DNA that codes for a trait

Allele:

a specific form of gene

→ recessive or dominant (the line thingys that appear on the chromosomes during prophase (l) )

Centromere:

holds two chromatids together in a pair of chromosomes

Centriole:

protein bodies in the cytoplasm that form & organize spindle fibres

Spindle fibres:

attaches to the centromere to pull sister chromatids apart

2. Mitosis:

- purpose: separate replicated DNA into two identical cells
- 4 phases (PMAT)

- nucleus divides

Prophase:

- the double stranded chromosome becomes visible, the nuclear membrane disappears and spindle fibres form between the two poles of the cell & each centromere

Metaphase:

- the chromosomes move into an imaginary line across the centre of the cell

Anaphase:

- the centromere splits and sister chromatids separate which are now called 'daughter chromosomes'. They are now pulled to opposite sides of the cell

Telophase:

- one complete set of daughter chromosomes which unwind to form chromatin and the nuclear membrane appears

3. Cytokinesis

- In plant cells: golgi vesicles will fuse to form an equatorial plate which will fuse and separate the cell into two

- In animal cells: the "cell membrane" pinches off the centre (cleavage furrow)

- cytoplasm divides

- results in two daughter cells

Q. How is cytokinesis different in animal vs plant cells?

In animal cells, a cleavage furrow (where the cell pinches off from the middle)

In plant cells, an equatorial plate will form (small pieces of cells attach togther on the equator of the cell to form a new cell wall, thus seperating the two new cells

Q. Why is mitosis important?

1. Growth

2. Repair of damaged tissue

3. Regeneration (replacing dead cells)

In unicellular organisms (paramecia), mitotic division _______ the size of the population (reproduction)

INCREASES

In multicellular organisms the ____ and the _____ depends on mitotic cell division

GROWTH & REPAIR

How long does it take for skin cells to complete their processes?

14-20 days

How long does it take for brain cells?

20-50 years

6. CANCER AND ITS CAUSES

• Hallmarks of cancer

What is cancer?

uncontrolled cell growth

What is apoptosis?

when a cell kills itself (self-destruct) when something is wrong in its development

Tumour:

a mass of cells that continue to grow and divide without any obvious function in the body

Metastatic cells:

cells that break away and start a tumour elsewhere in the body

Causes of cancer:

Mutations and Carcinogens

Mutations:

random changes in the DNA, results in the cell dividing uncontrollably

Carcinogens:

Environmental factors that can cause cancers (ex. tobacco smoke, radiation, UV rays)

Hallmarks of Cancer

• Insensitivity to anti-growth signals

• Evading the immune system

• Genomic instability

• Sustained angiogenesis

• Tumour promoting inflammation

Give a desc of three hallmarks of cancer

Evading the immune system:

• white blood cells are responsible for killing cancer cells, but cancer cells are able to hide. Similar to an ‘invisible cloak’. They can trick the white blood cells

Sustained angiogenesis:

• tumour collecting blood flow (leading and causing growth). New blood cells are formed and allows the tumour to receive oxygen and nutrients

Genomic instability:

• In heredity cancers, it’s mutations in the DNA which affects how certain cells divide

Q. What’s the difference b/n somatic and cancer cells?

Cancer cells are uncontrolled cell growth and somatic cells are normal cells besides germ and sex cells. Cancer cells metastasize (travels to different parts, they CANNOT self-destruct (apoptosis)

Q. What are three ways to treat cancer?

• Chemotherapy

• Radiation

• Surgery

Ways to avoid having cancer:

- Lifestyle choices
- avoiding smoking
- eating healthy
- wearing sunscreen

7. DNA AND GENETIC MATERIAL

• DNA

• Hershey-Chase experiment

• 3 components of DNA structure (nucleotide): Sugar (pentose), phosphate group, Nitrogenous Bases (4 types)

• Theory: Erwin Chargaff, Rosalind Franklin, Watson & Crick

What does the acronym DNA mean?

Deoxyribonucleic acid

Q. What is the Hershey-Chase experiment?

Experiment description: Phage dyed w/ radioactive dye. DNA core and protein coat. One phage used sulfur for the protein coat and the other used phosphate (only found in DNA). Phosphate was able to enter the bacteria proving that…

→ proved that genetic info is carried in DNA and NOT in proteins

Q. What are the THREE components of the structure of DNA (nucleotide)?

1. Sugar (deoxyribose-pentose) - pentose, shaped with five sides

2. Phosphate group

3. Nitrogenous base (4 different one)

What are the FOUR nitrogenous bases? How many rings?

Purines (double ring):

• Adenine (A)

• Guanine (G)

Pyrimidines (single ring):

• Thymine (T)

• Cytosine (C)

What are the complementary bases?

A-T = 2 hydrogen bonds , C-G = 3 hydrogen bonds

Q. What is Erwin Chargaff’s theory?

→ the amount of A&T were similar and true for C&G (ratios are equal)

→ 30% C-G

→ 70% A-T

Q. What is Rosalind Franklin’s theory?

→ used x-ray crystallography to determine that the structure of DNA is in the form of a double helix (photo 51)

Q. What is Watson & Crick’s theory?

→ used existing date (Franklin’s) to determine 2 strands lined up in opposite directions (double helix, backbone)

• strand: formed from sugar, phosphates, nitrogenous bases. The bases are held by hydrogen bonds

8. SEXUAL REPRODUCTION - MEIOSIS

• Diploid vs Haploid

• Chromosomes: 46 in human somatic cells

• Gametes (sex cells, sperm & egg): 23 chromosomes

• Zygote: fertilized egg

• Autosomes: chromosomes that are not linked to determining the sex of an individual

• Karyotypes

• Meiosis (l)

  • Prophase (l)

  • Metaphase (l)

  • Anaphase (l)

  • Telophase (l)

• Meiosis (ll)

  • Prophase (ll)

  • Metaphase (ll)

  • Anaphase (ll)

  • Telophase (ll)

• Cytokinesis

• Errors during Mitosis

  → nondisjunction

  → trisomy

  → triploid

• Gametogenesis + Spermatogenesis

What is meiosis?

→ production of sex cells (gametes) such as sperm and the ovum that are genetically different

→ Human somatic cells contain: 46 chromosomes

→ Gametes contain: 23 chromosomes

Q. What’s the difference between Diploid vs Haploid?

• Diploid: 2n

(2 sets of chromosomes, Mother & Father)

• Haploid: n

(1 set of chromosomes, genetically different)

Each sperm cell and egg cell contains:

• 22 autosomes

• 1 sex chromosome (either X or Y)

What are autosomes?

any chromosome other than sex chromosomes

What is a karyotype?

a visual representation of homologous pairs of chromosomes

What are the THREE purposes of Meiosis?

• Reduction of # of chromosomes so that fertilization can regenerate the regular # of chromosomes

• 23 chromosomes from mother & 23 from father

• Chromosomes that are similar in shape, length and arrangement of genes are called ‘homologous chromosomes’

PART 1 - Chromatin Replication (interphase ‘S’ phase)

• producing an exact copy of all the chromatin in the original nucleus to produce enough chromatin for 4 copies ( 4 gametes)

PART 2 - Meiosis

• chromatin copies are split twice and randomly distributed to form 4 completely different haploid nuclei

Prophase (l)

• exchange of genetic material occurs between the maternal and paternal chromosomes (synapsis)

  → causing variation

Metaphase (l)

• the paternal and maternal chromosomes from the original nucleus are randomly distributed to form 2 new nuclei

• the homologous pairs line up side by side in the middle of the cell

• spindle fibers connect to the centromeres

• they are called ‘tetrads’

  →random assortment

Anaphase (l)

• homologous pairs are pulled to opposite poles of the cell

Telophase (l)

• the chromosomes are at opposite sides and form two clusters

• it will divide to develop two daughter cells (23 chromosomes in each)