Name:________________________________
Objectives
– Draw and identify the components of DNA
– Explain how alleles and genes determine our traits.
– Compare and contrast DNA with RNA in structure and function.
– Compare and contrast the various types of RNA in structure and function
– Describe the process of Transcription.
– Describe the process of translation
– Explain how heredity affects gene expression.
Heredity
 Transmission of genetic material from parents to their offspring
 It depends on the segregation and recombination of genetic material
– Segregation: genetic material is cut in half when making sex cells
(sperm, egg)
– Recombination: full amount of genetic material is restored when fertilization occurs
– This system of segregation and recombination creates offspring with new, MIXED DNA which increases variation
 Gregor Mendel crossed ____________________ and observed the changes in 7 traits to better understand how genetics works
 ____________________: the genetic make-up of an organism
 ____________________: the physical appearance of an organism
Cystic Fibrosis
Skin color
Single gene
Multiple genes
Sickle Cell Anemia Single gene affecting multiple traits
The Concept of Genes
 Chromosomes are condensed DNA
 Segments of the DNA encode for certain traits (like nose shape). Those segments are called genes.
 Genes come in flavors called alleles.
Question: Why do you have 2 chromosomes that code for nose shape?

 Two chromosomes with the same genes are called homologous chromosomes
 A pair of homologous chromosomes will have one chromosome from the father and one from the mother
 At a given locus on the chromosome, an allele for a trait will be located
– Example: Say Mom has a button nose and Dad has a big snoot. You will have one allele for a button nose and one allele for a big nose in your pair of homologous chromosomes that code for nose size. (What size your nose is depends on a few other factors we’ll get into later)
Question: Imagine your parents’ noses. Describe what type of allele for nose shape each of them might have given you.
Eye Color Inheritance
• Humans have three eye color genes. Two of these genes are named HERC2 and Gey.
• Each individual has two copies of each gene. These two copies can be the same flavor (allele) or different flavors.
• The HERC2 gene has two flavors - brown and blue. The dominant allele is capitalized B and codes for brown pigment production. Lower-case b codes for blue pigment production, resulting in a blue eye. If there is at least one dominant B, the eye appears brown since brown is darker. Therefore brown is dominant over blue at the HERC2 gene.
• The gey gene also has two flavors - green and blue. In this case, G for green pigment production is dominant over b in the same way.
• The green pigment is dominant over blue and brown is dominant over both blue and green.

Question: What color are they eyes of the person next to you? Which pigments do you think they have genes for?
Gene Linkage
• Sometimes genes located on the same chromosome are said to be linked.
 Linked genes tend to be inherited together because they do not independently assort during meiosis.
 Crossing over occurs between homologues and leads to variation in the offspring.
Gene linkage: Crossing over:
Sex Determination
• Sex Chromosomes- can be homologous XX and non-homologous XY
• Autosomes- 22 homologous pair of non sex chromosomes
• Sex Chromosomes-
– X- XX females only make X eggs
– Y- XY- males make 50% X eggs and 50% Y eggs
DNA (deoxyribonucleic acid)
• Genetic material that is replicated and is passed on to the offspring.

• DNA controls cell activities by influencing the production of protein enzymes or hormones.
– Polypeptides are made in the ribosome which then are put together to make complete proteins
 Hereditary information (DNA) is organized on chromosomes.
 Genes – units of genetic material that codes for a specific trait
 Humans have ~ 23,500 genes.
 DNA is made up of repeating molecules called nucleotides
– PURINES- Adenine (A), Guanine (G)
– PYRIMIDINES- Thymine (T), Cytosine (C)
 Chargaff’s Rule- Adenine must pair with Thymine and Guanine must pair with Cytosine
 The “code” of the chromosome is the SPECIFIC ORDER that bases occur.
A T C G T A T G C G G… o DNA is wrapped tightly around histones and coiled tightly to form chromosomes
Genetic Diversity
 Different arrangements of nucleotides (units of DNA = sugar + phosphate
+ Nitrogen base) provides the key to DIVERSITY among living organisms

Question: Order the following from smallest to largest:
Histone molecule
Nucleotide
Chromosome
Adenine
One base pair
Gene
Question: Do some matching: a.
Nucleic acid b.
Nitrogen base c.
Condensed DNA d.
Encodes a trait e.
Have similar DNA
DNA Replication
1. Chromosome
2. DNA
3. Organisms of the same species
4. Gene
5. Cytosine
Steps
1.
Unwind DNA
2.
Unzip DNA
3.
DNA polymerase recruits and adds complementary bases to make 2 new strands.
Question: So some DNA replicating… Add the appropriate bases…

History of DNA
 Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)
 Rosalind Franklin - X-ray photo of DNA. (1952)
 Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)
 Watson & Crick proposed…
– DNA had specific pairing between the nitrogen bases:
– ADENINE – THYMINE
– CYTOSINE - GUANINE
– DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”
How does DNA become…YOU? PROTEIN SYNTHESIS
1.
Unwind and unzip DNA so you can “read” it’s code
2.
Copy it into a “messenger” that can leave the nucleus
3.
Read the messenger outside of the nucleus
4.
Translate the messenger’s code into a chain of amino acids
5.
Fold the chain of amino acids into a protein
6.
VOILA! That protein has a specific function in YOU now
The same thing restated in scientific terms…
1.
Double-stranded DNA is unwound and unzipped into two single strands of
DNA.
2.
RNA polymerase ________________________ complementary RNA nucleotides to make “messenger RNA” (mRNA). (TRANSCRIPTION)
3.
______________leaves the nucleus and attaches to a ribosome. Other RNA molecules transfer amino acids to the ribosome-mRNA complex. They are called “transfer RNA” or tRNA. As the ribosome moves along the mRNA, amino acids form a chain called a polypeptide ________________.
(TRANSLATION)
4.
Once the ribosome has reached the end of the mRNA code, it lets go and the mRNA is degraded. The polypeptide chain goes to be folded into a protein.
5.
Each proteins’ specific function depends on it’s specific

6.
Each proteins’ specific function depends on it’s specific shape. (Hence why the order of the amino acids is so important).
Question: Label which arrow the appropriate arrows with “translation” and
“transcription”.
Vocabulary:
– Transcription
– Translation
– Polypeptide chain
– Protein
– Amino acid
– DNA
– mRNA
– tRNA
– Ribosome
– Protein synthesis
– Protein folding
– Polypeptide bond
– Nucleotide
– Nitrogen base
– Sugar-phosphate backbone
– Hydrogen bond
– Histone
– Chargaff’s Rule
– Allele
– Gene
– Gene Linkage
– Autosomes
– Sex chromosomes
– Crossing over
– Homologous chromosomes
– Heredity
– Trait
– Double Helix
– Dominant
– Locus/loci