HBio Unit 3 Notes:
How do your genes contribute to making you who you are?
I. DNA:
A. Deoxyribonucleic Acid- Molecule that contains heredity information
- 1950 DNA was accepted as the model of heredity
- 1953 Watson and Crick Discovered DNA was in a double helix form “twisted ladder”
B. Structure of DNA
1. Nucleotide
a. Deoxyribose sugar (Side of ladder)
b. Phosphate (Side of ladder)
c. Nitrogens Base – 4 types (Rungs of ladder)
• Adenine
• Thymine
• Guanine
• Cytosine
2. Nucleotides form the double helix (twisted ladder)
a. Order and # of bases makes organisms different
II. Chromosomes:
A. Chromatin- “Long and thin”
- Less coiled DNA in a non-dividing cell
- Can be “unzipped and read” to make a new protein
- Not visible in nucleus
B. Chromosomes
- Coiled up strand of DNA in a dividing cell
- Compact strands line up and move apart- so they don’t tangle
- Visible in cell (no nuclear membrane)
1. Humans = 46
 23 pairs (1 from mom, 1 from dad)
 Bacteria = 1
 Crayfish = 200
2. Karyotype
 Photo of cell’s chromosomes
 Can show number and size of chromosomes and gender
 Cannot show genes
C. Gene
- Section of DNA that gives information to make 1 protein (1 gene = 1 protein)
 Humans:
 3 billion base pairs
 20,000-25,000 genes
 Chromosome #1 = 2968 genes
 Y chromosome = 231 genes
 Human DNA = 99.9% identical
 Not all DNA are genes
 Regulatory sequence “start/stop”
 Non-coding DNA
 Genes work together with the environment to give you traits
III. Cell Type
 Eukaryotic
 Prokaryotic
 Nucleus
 No Nucleus
 Clear membrane:
 DNA
semi-permeable
 In circle
 Chromatin (too big to
anchored to cell
leave nucleus)
membrane
 Nucleolus: Dark
 Plasmid
spots where the
 Tiny, extra circle
nucleotides are made
of DNA (has a
 DNA
few genes)
 In strands consisting
 Can transfer
of genes, regulatory
from 1 cell to
segments, non-coding
another
 Virus
 No Cell!!!
 Very few genes
– not enough to
be considered
living
 DNA/RNA
surrounded in a
protein capsule
1.
IV. DNA Replication
 Enzyme (Helicase) unzips DNA
 One side is copied – Bases are matched up at A-T, C-G other side is copied in loop sections
 Results in 2 identical strands of DNA
V. DNA vs. RNA
DNA
o Deoxyribose sugar
o Thymine
o Double helix
o Housed in the nucleus
o Longer (many genes)
o 1 type
RNA
o
o
o
o
o
o
Ribose sugar
Uracil
Single-stranded
Can go in and out of the nucleus
Shorter (1 gene length)
Different types – mRNA, tRNA
VI. Protein Synthesis
o Definition: Process of making proteins.
o Proteins:
 Building blocks = amino acids (20 different types)
 Order of the amino acids determines the structure and the function of the protein.
 Functions:
 Structural: collagen (cartilage), cell membrane proteins, etc.
 Functional: control chemical reactions (enzymes, hormones, antibodies, etc.)
o Process of making proteins:
 Transcription – copy one gene from the DNA in the form of mRNA, takes place in the
nucleus
 Translation – tRNA brings the amino acid to the mRNA and lines up the amino acids in the
correct order to make a specific protein, takes place on the ribosome.
o Draw out Proteins Synthesis:
Are all mutations bad?
I. Gene Mutations: a random change in the nucleotide sequence of DNA that occurs within a gene
II. Types:
a. Frame shift mutation: gene mutation that shifts the “reading” frame of genetic message by
inserting or deleting a nucleotide
b. Point mutation: gene mutation that affects a single nucleotide usually by substituting one
nucleotide for another.
III. Causes: Inherited, environmental, random.
IV. Effect of gene mutations:
a. Mutations can cause a change in the proteins a cell synthesizes.
b. Mutations can be harmful, beneficial, or have no effect at all.
How do you grow from 1 cell to 10 trillion different cells?
I. Cell cycle
A. Two major parts of the cell cycle:
1. Interphase:
a. Part of the cell cycle where cell does normal cell activities—grows, makes proteins, etc.
b. Also where DNA Replication occurs before mitosis.
2. Cell Division (Mitosis and Cytokinesis)
a. Mitosis: process of cell division that results in 2 genetically identical cells
b. Cytokinesis: actual splitting of the cytoplasm once 2 new nuclei have been made
c. Process:
 DNA replicates in interphase—it’s in the form of chromatin
 DNA coils/condenses into visible chromosomes that are made of sister chromatids
 Nuclear Membrane goes away and spindle fibers form to move the chromosomes
 Chromosomes line up in middle of cell
 Chromatids split
 Cytokinesis Occurs—Cell membrane pinches to make 2 new cells
 Result = 2 genetically identical cells
d. Purpose:
 Growth
 Maintenance
 Repair
 Reproduction of unicellular eukaryotic organisms
II. Cell Differentiation
A. Definition: the process by which stem cells produce specialized cells
B. Cells are different based on which genes are turned on or off
C. Stem cell = cells that have the ability to produce a variety of specialized cells
o Embryonic: stem cells that come from embryos during the first 5 days of development
o Adult/Somatic: partially differentiated cells found in different adult tissues
Is cancer contagious?
What makes a disease contagious?
Why do diseases make you sick?