DNA and Modern Genetics

Chapter 5

Chapter 5Section 1

NOTESPage 135

DeoxyriboNucleic Acid

• DNA is a molecule that stores information that a cell needs to function, grow, & divide.

• Proteins are large molecules that are made up of chains of amino acids.– Do most of the work of the cell and make up much of the structure

of a cell – 20 different amino acids combine to make up thousands of

different proteins.

• DNA provides the code, or set of rules, for making proteins.

**How do DNA and proteins work together??

Nucleotide Bases

• DNA is a double-stranded spiral, much like a twisted ladder.

• It is made up of four nucleotides:– adenine (A), – thymine (T), – cytosine (C), and – guanine (G). – Adenine pairs with thymine & cytosine pairs

with guanine

• Genes are made up of a sequence of bases at a particular location on the DNA

DeoxyriboNucleic Acid• Before a cell divides, its entire DNA is copied in a process call replication.• DNA separates into 2 strands. – Each strand is used as a

template to produce a copy of the other strand

• Nucleotides in the area match up with the bases left & form 2 new strands

RiboNucleic Acid

• RNA, ribonucleic acid, is involved in making proteins. • 3 types of RNA

– Messenger RNA (mRNA): carries the information from DNA to a ribosome.

– Ribosomal RNA (rRNA): forms the ribosome with other proteins.

– Transfer RNA (tRNA): carries an amino acid and matches up to a complementary mRNA at the ribosome.

Transcription and Translation

• Transcription: the process of transferring information from DNA to RNA. – RNA base pairs: cytosine pairs with guanine &

adenine pairs with uracil.

• Transcription VS. Replication– Only 1 strand of DNA is transcribed, producing a

single strand of RNA– After transcription, RNA is released– Many copies of RNA can be made from the same gene

• Translation: the assembly of amino acids in their proper sequence according to the mRNA template.

Chapter 5Section 2

NOTESPage # 144

DeoxyriboNucleic Acid• 46 chromosomes contain 6 billion base pairs of DNA. • 99.9% of DNA in the cells of two different humans is the

same. • 0.1% variation in DNA makes a unique person. • Errors can occur when DNA is copied. – Any change in DNA is called a mutation. This

mutation can have • no effect: each cell has 2 sets of DNA, even if one is

mutated, the other may work fine• minor effect: could affect physical appearance• major effect: can cause genetic disorder

– A genetic disorder is a disease or condition that results from mutations that affect the normal functioning of a cell.

Pedigree: a diagram of family relationships that shows two or more generations

Chapter 5Section 3

NOTESPage # 150

What can we use DNA for?• Selective breeding: process of selecting and breeding

parent organisms to pass on particular traits to the offspring– People are not changing DNA, but causing certain alleles to

become more common in a particular breed.» **How does selective breeding affect

the DNA of a species?

• Genetic Engineering: process in which a sequence of DNA of another organism is first isolated, then inserted into the DNA of another organism, changing that organisms DNA– Example: plants, organic foods

**What is one major difference between changing offspring through selective breeding and genetic engineering?

• DNA Technology: DNA identification helps police establish if a criminal is guilty. Specialists can compare DNA evidence from a crime scene with DNA from a suspect to determine if the person was at the scene.

• Cloning is a technique that uses technology to make copies of DNA. Cloning has been used in bacteria to make proteins and drugs to fight disease. – In 1996, scientists successfully cloned the first

mammal, a sheep named Dolly. All of her DNA came from a single body cell. Dolly lived for 6 years.

**Why might the practice of cloning raise concerns about its future use?