Genetics: Chapter 1 &2

DNA Nucleotide is the SMALLEST unit of human genome and it consists of:

1. A Sugar

2. A Phosphate Group

3. A Nitrogenous Base

4 Nitrogenous Bases

1. Adenine

2. Thymine

3. Guanine

4. Cytosine

____ creates the backbones.

Sugar

How many hydrogen bonds pair Cytosine and Guanine?

3 Hydrogen Bonds

How many hydrogen bonds pair Adenine and Thymine?

2 Hydrogen Bonds

How many protein coding genes do humans have?

20,000 genes make proteins

Single Nucleotide Variation (SNV)

At one base there is a difference

• DOES NOT imply how often this variation occurs

Single Nucleotide Polymorphism (SNP)

Does imply that how often the variation occurs

• Observation seen more often than a few individuals (something important at location)

What does 23andMe study?

SNPs (Single Nucleotide Polymorphisms)

Mendelian Trait

A trait caused by a single gene

• Gregor Mendel

Complex Traits

Determined by one or more genes and environmental factors

Do women or men live longer?

On average WOMEN outlive men by about five years

• 73.5 (M) vs 79.3 (W)

What are the top 3 leading causes of death in the U.S?

1. Heart Disease

2. Cancer

3. COVID-19

What is a gene?

Region of DNA that encodes a function

What is the Central Dogma of Biology

1. DNA → RNA = Transcription

2. RNA → Protein = Translation

Where does Transcription take place?

The nucleus

Where does translation take place?

The Cytoplasm

What is the basic unit of chromosome?

The nucleosome

• Composed of HISTONES and DNA

What are some components of the cell nucleus?

1. Euchromatin

2. Heterochromatin

3. Nucleolus

What is Euchromatin?

Lightly packed, enriched in genes

• About 92% of the human genome

• Involved in TRANSCRIPTION

• High GC content

What is Heterochromatin?

Tightly packed, enriched in repetitive, non-coding DNA

• Located in PERINUCLEAR REGION of nucleus

• Very few genes

• High AT content

What is the nucleolus?

Ribosome Biogenesis

• Produces ribosomes

• Gene transcription and gene splicing

What is the largest category of the human genome?

Transcription Factors

• 12% of gene factors

Who named the cell?

Robert Hooke

What is cell theory? List the 3 parts.

1. All living things are made of cells

2. Cells are the basic unit of life

3. All cells come from pre-existing cells

What is used in cell cryopreservation?

Liquid nitrogen

Red Blood Cells

DO NOT contain a nucleus

What is umbilical cord blood good for?

Stem Cells

• High differentiation potential = can be used to replace damaged cells

• if child develops disease in the future

• FDA cleared 80 diseases of the blood and immune to be treated with cord blood

What is the best way to find out if a journal is reliable or not?

Look at its impact factor (number of times used as a citation)

Cells are constructed from four class of macromolecules. List them.

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

What are Carbohydrates?

Sugars and their polymers

• Function: Energy storage, cell identity

What arelipids?

• Fats

• Oils

• Steroids

• Phospholipids

• Triglycerides

What are proteins?

Polymers made from amino acids.

What are nucleic acids?

Polymers of nucleotides

Somatic Cells

All cells in the body except the reproductive cells (germ cells)

• Skin, muscle, liver, blood, nerve cells

• DIPLOID (2n = 46), 23 pairs of chromosomes, one set from each parent

Germ Cell

Sperm and egg cells

• One copy of genome and are HAPLOID (n =23)

• Meeting of sperm and egg = diploid

Self-renewal

Stem cells: diploid cells that divide to give rise differentiated cell, and to other stem cells

• Enable body to grow and repair damages

Plasma Membrane

selectively-permeable phospholipid bilayer forming the boundary of the cells

* outside - hydrophilic, touches body fluid

* inside - hydrophobic, stacked together

* contains proteins penetrating membrane

* more cholesterol, membrane more rigid

• Proteins are embedded in the bilayer w/ carbohydrate molecules on the external surface

All EUKARYOTIC Cells have:

1. Plasma membrane

2. Cytoplasm

3. Membranous organelles

4. Membrane bound nucleus

Animal cells NEVER have a

Cell wall

What is the golgi aparatus?

Stacks ofmembrane-enclosed sacs

• Where sugars are made and linked into starches or joined to lipids or proteines

• Proteins finish folding

Where is the ER (endoplasmic reticulum) found?

In the cytoplasm of eukaryotic cells.

What does the ER do?

Synthesizes and transport gene products

• It helps synthesize, process, and transport proteins and lipids.

• Site of protein synthesis and folding

Rough ER

Protein synthesis begins on the rough ER when messenger RNA attaches to the ribosomes

What does rough ER have?

Ribosomes

Smooth ER

Makes lipids(phospholipids, cholesterol, and steroid hormones)

• Also detoxes

Peroxisome

detoxifies various molecules

G1 Phase

The cell grows larger (making of organelles)

• Synthesize mRNA and proteins required for DNA replication

G0 Phase

Cells are not dividing,but they remain alive and carry out their normal daily functions

• Cells enter G0 from the G1 phase when there is a lack of nutrients, a lack of growth factors, or when the cell reaches full maturity

S Phase

The cell synthesizes a complete copy of its nuclear DNA through DNA replication. It also duplicates the centrosome, which helps separate DNA during cell division.

G2 Phase

The cell continues to grow, synthesizes proteins necessary for chromosome segregation and cell division, and checks for any DNA replication errors or damage before entering the mitotic (M) phase.

Totipotent cell

A cell that can give rise to every cell type

Pluripotent cell

A cell that cannot give rise to every cell type but still has a large number of possible fates

• CANNOT become placenta (extraembryonic membranes)

Multipotent cell

A cell that has only a few developmental choices

Mitochondrion

Two membranes; inner membrane enzyme-studded

• Release energy from nutrients

Signal Transduction

Molecules part of the plasma membrane form pathways to detect signals from outside the cell and transmit them inward

• Later there will be a cell response

• Cancer: due to cells’ failure to recognize or react to signals to cease dividing

Cellular Adhesion

Plasma membrane helps cells attach to certain other cells

• Important in forming tissue

• Cancer: atypical cellular adhesion, enables them to invade healthy tissue

ACE2 Receptors

Spike protein of SARS-CoV-2 target host cells by recognizing ACE2 receptors

• Allows viruses into a cell, expression level determines their functions

Apoptosis

Cell death

• Apoptosis carves out fingers and toes from webbed structures

How many daughter cells in Mitosis?

2 identical daughter cells

• Diploid (2n)

• Asexual division

How many daughter cells in meiosis?

4 genetically unique cells

• Haploid (n)

• Sexual reproduction

flow cytometry

Used to analyze individual cells as they pass through

• Performs cells cycle analysis

• Determines the total DNA content inside each cell using fluorescent DNA-binding dye

G1

2N

S

2N → 4N

G2/M

4N

Cyclins

Regulatory proteins that control the progression of the cell cycle

• Cyclins activate cyclin-dependent kinases (CDKs), which control cell cycle processes through phosphorylation

  • Cyclin-CDK complex turn on the genes that trigger mitosis

  • As mitosis begins enzymes degrade cyclin

• NO CYCLIN: CDK is inactive and S phase factor “off”, and NO DNA replication occurs

DNA Damage checkpoint

Temporarily pauses the cell cycle while special proteins repair damage DNA

• G1/S

Apoptosis checkpoint

Turns on as mitosis begins, survivins accumulate and override signals that tell cells to die so mitosis can occur

• Before mitosis

Spindle Assembly checkpoint

Oversees construction of the spindle and the binding of chromosomes to it

• During mitosis

G1 checkpoints check for

Prevents cell with damage from entering S phase (replication)

1. Cell size

2. Nutrients

3. Growth factors

4. DNA damage

• DNA damge signals activate the tumor suppressor protein p53 which activates CDK-inhibitor

• CDK inhibitor: binds to Cyclin-CDK complex and blocks its enzymatic activity

• Cell pauses in G1

Cancer cells are

clonal descendants from one mutant cell

• Disease of the cell cycle: cells divide uncontrollably (tumors form)

Hormone

Made in a gland and transported in the bloodstream to another part of the body

• Exerts a specific effect

• Controls cell cycle from outside the cell

Growth Factor

Chemical signal the controls cell cycle from outside the cell and acts LOCALLY

• Epidermal Growth Factor (EGF): Stimulate cell division in the skin beneath a scab

Telomeres

Located at the ends of chromosomes

• Repeats of 6-base DNA sequence (TTAGGG)

• Lose 50-200 endmost bases after each cell division

  • After 50 divisions, shortened telomeres signal the cell to stop dividing

Telomerase

Sperm, eggs, bone marrow, and cancer cells produce it

• Prevents shortening of telomeres

Stem cell

Divides by mitosis

• Produces 2 daughter cells or a stem cell, and a progenitor cell (partially specialized)

Progenitor Cell

Do NOT have self-renewal

What are the 3 general sources of human stem cells?

• Embryonic Stem Cells: Created in lab dish using inner cell mass (ICM) of an embryo

• Induced pluripotent stem (iPS) cells: Somatic cells reprogrammed to differentiate into any of several cells types

• Adult stem cell: tissue specific or somatic stem cells

What is a karyotype?

Display of an individual's chromosomes arranged in pairs according to size and structure

Where can DNA be found in a human cell?

Nucleus and Mitochondria

What is liquid-liquid phase separation (LLPS)?

A process in which molecules separate into distinct liquid-like phases.

LLPS was discussed in relation to what disease?

ALS (Amyotrophic Lateral Sclerosis)

• Progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord.

• Paralyzes muscles, and death occurs within 3-5 years after symptoms begin, but some people have lived 10+ years.