1. Molecular Basis of Heredity

2. DNA
Instructions are inherited (passed) from parent to offspring in the form of a genetic code known as genes
DNA: Molecules that carry the genetic code.
The code is used to make PROTEINS
The proteins become cell parts and carry out most functions of the cell.

3. DNA Molecule Genes are made up of molecules of DNA:
“Deoxyribonucleic acid”
Found in nucleus.
Controls manufacture of enzymes, proteins
Made up of repeating subunits known as nucleotide subunits.

4. The nucleotide is made of 3 “parts”}
1. Phosphate group
A sugar, called “deoxyribose”
Nitrogenous base (the “rungs of the ladder”)
(“sides” of the ladder)

5. The double helix

6. Nucleotides - DNA Nitrogenous base:
Adenine “A” (always pairs with “T”)
Thymine “T” (always pairs with “A”)
Guanine “G” (always pairs with “C”)
Cytosine “C” (always pairs with “G”)
Forms the “rung” of the ladder

8. DNA Replication
During reproduction DNA makes exact copies of itself called REPLICATION.
Occurs in nucleus during both mitosis and meiosis.
DNA polymerase (an enzyme!) causes the two strands (sides) to “unzip”: the bonds between the base pairs break
TEMPLATE: Each side serves as a pattern or template. Each base pair will attract the complementary nucleotide A—T or G—C

10. The two DNA strands will be identical

11. Genetic Code Genetic Code: Heredity information
--depends upon the order of the nucleotides in the DNA molecule.
--determines which type of protein is made
Gene: the sequence of nucleotides that make the protein
Triplet codes: group of three nucleotides that is specific to each amino acid.
also known as a CODON

13. RNA and Protein Synthesis
DNA provides the instruction to make proteins
But DNA is too large to pass through the nuclear membrane (double strand too BIG) How will it get the instructions out of the nucleus?
RNA!
RNA exists as a single strand which is small enough to pass through nuclear membrane

14. Messenger “mRNA” is made in the nucleus
They serve as “messengers” from DNA to the ribosome.
RNA base pairing:
Cytosine—Guanine C—G Adenine—Uracil A—U (not T!!)
Really important!!

15. RNA- Ribonucleic acid DNA RNA Sugar: deoxyribose Sugar: ribose
Nitrogen bases: adenine, thymine, cytosine, guanine
Nitrogen bases: adenine, cytosine, guanine and uracil instead of thymine
Double-stranded
Single-stranded
Only one kind of DNA
Three kinds:
messenger RNA (mRNA),
ribosomal RNA (rRNA),
transfer RNA (tRNA)

16. Ribosomal RNA makes up the major portion of the Ribosome (the site of protein synthesis) Location: cytoplasm!
Transfer RNA transfers amino acids to the ribosome during protein synthesis

17. Protein Synthesis DNA mRNA Protein
transcription
translation
DNA mRNA Protein
(nucleus)
(cytoplasm)
The order of the bases in the DNA specifies the order of bases in the mRNA, and The order of bases in the mRNA specifies the order of amino acids in a protein.

19. Transcription
RNA polymerase (an enzyme!) binds to the DNA and separates the DNA strands
One strand of the DNA acts as a template from which nucleotides are assembled into a strand of mRNA.
This strand is complementary to the DNA, except that uracil binds to adenine not thymine!
(BTW, what happens to the other strand of DNA?)

20. Protein Synthesis REMEMBER: The RNA is only single stranded!
The mRNA may now pass through the nuclear membrane into the cell and over to the ribosome

22. Translation
During translation, the mRNA transported to the cytoplasm is "de-coded" or "translated" to produce the correct order of amino acids in a protein
Nucleotides on mRNA are read "three at a time" (3= codon) by the ribosome
The mRNA will bind with tRNA at the codons

23. Translation
tRNA = transfer RNA; small RNA molecules that carry a specific amino acid at one end and an anticodon region that recognizes and binds to the codon (mRNA) at the other end. The tRNA.
The codon of the mRNA determines what amino acid is added to a protein chain.
The process continues, chaining the amino acids together until the “stop” codon is reached

24. Codon – anti codon
Lysine
Methionine
Anti-codon
codon

26. Changing Chromosome Structure
Translocation: transfer of one section of a chromosome
Addition: a portion of one chromosome is attached to another chromosome
Deletion: a portion of a chromosome is taken away from a chromosome
Inversion: a portion of a chromosome breaks off and then becomes reattached to the same chromosome in an inverted (upside down) fashion