Genes and diseases Lec 2

Phenotypes originate at the

cellular level

The first cells were described by

Robert Hooke in 1665.

The average adult human has

30 trillion cells.

somatic cells

any cells in the body that are not reproductive cells (sperm or egg);

Most body cells are

somatic

Germ cells

rise to haploid gametes

Germ cells give rise to

haploid gametes

Fertilization produces a

diploid zygote

Cells divide and differentiate into

their final cell fates.

How many different type of cells are there

290

Your cells are not

all the same

During gestation, your cells

divide

They all have the same

genome

when cells begin different characteristics depending on which genes are expressed

exome

Expressed

the instructions for a gene are used to create a protein.

cell fate.

As you continue to develop, cells begin to choose a job/identity,

differentiation

when every cell gets a different

Most differentiated cells will never

divide again.

stem cells

Population of cells that continue to divide and replenish damaged body cells.

Cell lineage:

The path (progenitor cell types) a cell takes from egg to final differentiated form

We group cells into four general categories (tissues)

1. Epithelial tissue: linings

2. Neuronal tissue: communication

3. Connective tissue: hold us together

4. Muscle tissue: movement
   

1. Epithelial tissue: linings

• They line the inside of your blood vessels

• They line the outsides of your organs

• They line all your tubes

• They cover the outside of your body

• They line your gut and lungs

2. Neuronal tissue: communication

2. communication
   

• They’re electrically active

• They send out long projections to send signals across the body

3. Connective tissue: hold us together

• They secrete strong elastic fibers

• Or create very strong bones

• Or travel in the circulating fluid carrying oxygen and protecting the body from pathogens

  • (yes, blood is considered a “connective tissue”)

4. Muscle tissue: movemen

• Their structure allows them to contract

• Voluntary: skeletal muscles

• Involuntary: line our digestive system and other organs

Cells of the same type

form tissues,
and tissues form organs

Structure-function relationships:

1. The bumps and pillars and hairs increase the surface area so nutrients can be absorbed faster.

2. The cells that do the absorbing are only one layer thick, and they’re also waterproof and form a barrier to bacteria.

3. The muscles and nerves are arranged to squeeze in waves, moving food in one direction.

Changing the structure

might change the function.

Irritable bowel disease

changes epithelial cell shape and breaks seal between cells

mutations can

also change structure.

What distinguishes an epithelial cell from a muscle cell in the same person?

the exome

Epithelial tissue

These cells are linings. They line the insides and outsides of organs, and form mucous

membranes in the nose and mouth.

muscle tissue

These cells contain proteins that can contract. Some are voluntary and some are involuntary.

Epithelial tissue cells are arranged

single file and each is covered in microscopic little cilia for absorbing nutrients

Connective tissue cells hold

the epithelial cells in the correct shapes, and secure blood vessels to receive the nutrients

Muscle tissue cells help

squeeze digested food along the tube

Nervous tissue cells control the

muscles and carry information about the absorbed nutrients to the brain

Structure influences

function

SAME and DIFFERENT

All cells have the same genome.

Cell types have different exomes.

An inherited mutation will

be present in all cells.

It only affects tissues that require that gene.

A spontaneous mutation

may occur over the course of a lifetime.

• It only affects cell types that arise from that stem cell population.

leukemia (blood cancer) only affects

blood cells

If a zygote inherits a mutation, which cells will have the mutation in their genome?

If a stem/progenitor cell acquires a mutation, which cells will have the mutation in their genome?

In both cases, which cells will exhibit symptoms (phenotype) because of the mutation?

cell diagram.

Explain how specialized cells will have different shapes and internal organelles depending on their job.

cell membrane.

The flexible skin around a cell and its organelles. It has two important properties:

1. It can pinch off to form vesicles, and vesicles can fuse with it

2. It is semipermeable: most chemicals cannot cross the cell membrane unless there

is a protein to transport them.

a. Water can cross the membrane (slowly)

b. Sugars and ion

Nucleus

• Cytoskeleton: Gives the cell shape and helps with movement of materials

Cytoskeleton

The protein “bones” of the cell that support its shape and allow it to move

cytoplasm

The watery substance inside cells

Smooth endoplasmic reticulum

Smooth endoplasmic reticulum (SER) – Makes lipids (fats), helps detoxify harmful substances, and stores calcium.

Rough endoplasmic reticulum

A system of cytoplasmic membranes arranged into maze-like sheets and channels.

Rough ER: Plasma membrane proteins and proteins destined to be secreted are made in here.
- They are shipped to the golgi complex for the next step of their production

golgi bodies

A series of flattened sacs.

- They sort, modify, and package proteins they receive from the rough ER and send them to the membrane or the lysosome.

Lysosome –

Organelles that contain digestive enzymes. They digest old proteins and lipids, and they

also digest food or bacteria the cell brings in from outside.

1. Mitochondria

Organelles that produce energy (ATP) within the cells. They are the reason we must

continually breathe oxygen.

1. Ribosomes

Cytoplasmic particles (made of rRNA and proteins) that read mRNA instructions and

assemble all of the cell’s proteins.

8. Cell membrane

The flexible skin around a cell and its organelles. It has two important properties:

1. It can pinch off to form vesicles, and vesicles can fuse with it

2. It is semipermeable: most chemicals cannot cross the cell membrane unless there

is a protein to transport them.

a. Water can cross the membrane (slowly)

b. Sugars a

Diagram showing different cell types

Cells devote internal space to their

function

This white blood cell

chases and eats bacteria

Lysosomes

Organelles that contain digestive enzymes. They digest old proteins and lipids, and they

also digest food or bacteria the cell brings in from outside.

Pseudopodia

1. Detect and catch bacteria

2. Move the cell around

Muscles are basically

cells full of contractile proteins.

1. how are proteins the most versatile and perform most of the functions in the cell

1. how do DNA contains instructions for building proteins.

Macromolues

• DNA, RNA

• lipids

• carbohydrates

• proteins

• others

DNA

-nucleic acids

- the genome/chromosomes/genetic code

Lipids

Fats and oils: Insoluble in water, store energy (long term)

Phospholipids and cholesterols: make up cell membranes

Carbohydrates:

Sugars, glycogen, starch: energy storage (short term)

Dietary fiber: cellulose from plants (we can’t digest it)

Oligosaccharides: signals on the surface of cells (like AB blood)

Proteins:

Enzymes: build and break down the other molecules (metabolism)

Structure: long fibers for connections and movement

Signaling, Immunity, Shipping and many other functions

other macro molecules

small organic molecules, minerals, and metals

Origin of macromolecules

lactose intolerance (gene to phenotype)

• 1. The DNA change makes a cell unable to make an enzyme called lactase.

  2. Without this enzymes the guts cannot break down lactose sugars into a form we can absorb, so

  lactose lingers in the gut.

  3. Bacteria in the gut eat the lactose instead, causing varying degrees of intestinal discomfort (gas,

  bloating, nausea, diarrhea) when the person eats food containing lactose.

  Some people have a mutation that prevents them from ever being able to make the enzyme. They have

  congenital (inherited) lactose intolerance.

  Others are only lactose intolerant as adults. Many adults stop making the enzyme after breastfeeding is

  done. They have a normal lactase enzyme gene, it’s just not expressed any longer.

Phenotype (or effect of a mutation) ultimately depends on:

1. Which gene is mutated

2. How the mutation changes the protein

3. What the protein does in the cell

4. Which cells/tissues normally make that protein

5. How the cell/tissues’s function changes as a result of the changed protein

6. What that tissue normally does in the body, and how that changes when its cells aren’t working properly

Cells are the basic structural and functional unit

of living systems

Many genetic disorders alter something small at the cellular level

• ❖Often in only a few cell types

• ❖Leads to drastic effects on a tissue and organismal level

A genetic disorder is encoded in the DNA

• ❖…but it alters or breaks function of a protein

• ❖…which then affects the making of, organization and function of other macromolecules in cells

Cells are dynamic structures

❖ Constantly changing shape, reacting to the environment

Structure often reflects function

❖Change the structure or macromolecules, change the function

• How damaged cells would be replaced

• Why all cells have the same genome as the fertilized egg

Why an acquired mutation would only affect a small population of cells

• Explain why cells don’t all look the same;

• cells have outer and inner structures that reflect their function

• Name some examples of structure-function relationships in cells from this lecture

If I give you a new cell type and tell you what its job is, could you predict what organelles it will have inside it?

Somatic cell

Most of the cells in your body have a genome identical to the genome you inherited as a

zygote. (Genome = your personal DNA code), although they vary in structure and function.

Germ cells/

Gametes

Specialized cells that are used in sexual reproduction. Germ or germline cells give rise to

gametes (sperm or egg) cells that carry only half of a genome.

Zygote

A newly fertilized egg

Stem cell

A cell that has the ability to differentiate into one of several related cell types. Mature

differentiated cells do not divide when damaged or dying; stem cell populations replenish

cells in tissues when replacements are needed.

Differentiation and cell fate

The process by which a cell matures into its adult cell type. There are 290 different types

of cells in your body

Cell lineage

The sequence of differentiation steps to produce a mature cell. Example:

Bone marrow stem cell → white blood cell progenitor cell → T-cell (differentiated)

Tissue

A group of cells of the same type that are attached to each other.

Epithelial tissue

These cells are linings. They line the insides and outsides of organs, and form mucous

membranes in the nose and mouth.

Neuronal tissue

These cells use electrical impulses to communicate over long distances

Muscle tissue

These cells contain proteins that can contract. Some are voluntary and some are

involuntary.

Connective tissue

These cells include bones, tendons, ligaments, and blood cells. They all secrete molecules

that maintain tissues around them, and act as a base that other tissues attach to.

Stem cells/progenitor cells are the source

of replacement cells lost to damage or time.

your blood cells are produced from stem

cells inside your bones, in the bone marrow. Why hide the stem cells there? Why not just have the

blood cells keep dividing in the blood to replenish lost cells?

Blood cells in particular are exposed to toxins that we eat and absorb, as well as nasty waste chemicals

produced by our cells. If a cell is old and ready to die, we don’t want that cell to be dividing to replace

itself! Instead, new blood cells come from protected populations hidden away inside bone marrow.

Vesicles

Big bubbles, like transport pods, that transport proteins and other substances throughout

the cell or to the outside. Vesicles can fuse with membranes.