GENETICS is the branch of biology that deals

GENETICS is the branch of biology that deals with inheritance.

Do you see any characteristics that these children share with their parents or their brothers and sisters?

DNA is the genetic material that is passed from generation to generation. Cells -> Nucleus –> Chromosomes –> Gene –> Trait BIGGEST----------------- smallest

WATSON and CRICK described the DNA molecule as a DOUBLE HELIX – two strands joined together and twisted around one another. DNA molecules are very long. Each DNA is made up of thousands of units called NUCLEOTIDES.

• Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring. Each nucleotide has three parts: sugar, phosphate, nitrogenous base

There are four different nitrogenous bases found in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).

The four nitrogenous bases of DNA nucleotides bond together in only one way: DNA -> DNA (A) pairs with (T), (C) pairs with (G). Air goes in Tires Gas goes in Cars

A T G C C G T A T C G A A T C G

Hydrogen bonds hold the two strands together between the bases.

DNA REPLICATION – When DNA copies itself

DNA Replication

The DNA controls cellular activities by providing instructions for PROTEIN SYNTHESIS.

DNA ->m. RNA A -> U T -> A C <-> G

MESSENGER RNA (m. RNA) carries the DNA code to the ribosome for protein synthesis. m. RNA is formed by copying DNA as a pattern or TEMPLATE in a process called TRANSCRIPTION.

PRACTICE TRANSCRIPTION If the DNA code reads : AGCTGTACA Then the m. RNA strand would read : UCGACAUGU REMEMBER: when you transcribe DNA code to RNA code, use U in place of T.

TRANSFER RNA (t. RNA) carries amino acids to the ribosomes for protein synthesis

The placement of the amino acids in the correct order in a protein depends upon the reading of the m. RNA strand. This process is called TRANSLATION. Click here to see it in action And see it again here

m. RNA molecules are read three bases at a time. Each three base sequence is called a CODON.

Each CODON represents one of the 20 amino acids, or START or STOP.

In SUMMARY: PROTEIN SYNTHESIS requires two steps: TRANSCRIPTION (DNA m. RNA) and TRANSLATION (m. RNA polypeptide)

What polypeptide would be formed from this DNA strand? ? TACTTCAAAATC AUGAAGUUUUAG met-lys-phe

Any change in the sequence of nucleotides in a DNA molecule is a GENE MUTATION. The mutation may result in changes that affect the structure and function of the protein made by that gene. A single mutation of the hemoglobin gene causes sickle cell anemia.

POINT MUTATION A single base change in the DNA sequence. The effect of the mutation varies from no effect at all to a mutation that can cause a serious disease. A mutation that affects the third position of the m. RNA codon has the least effect on the production of a particular protein.

FRAME SHIFT MUTATION A single base is either added to or deleted from the DNA sequence. The mutation affects every codon after the location of the mutation. Very serious effects. Causes a completely different amino acid chain to be produced.

Although mutations occur spontaneously, the rate of mutation can be increased by exposure to MUTAGENIC AGENTS. X rays, ultraviolet rays, radioactive substances, and cosmic rays are mutagenic agents. Mutagenic chemicals include formaldehyde, benzene, and asbestos fibers.

Mutations may be transmitted to the next generation ONLY if they are present in the gametes. Mutations in body cells may be passed on to new cells of the individual as a result of mitosis, but will NOT be transmitted to the offspring.

RESTRICTION ENZYMES are used to cut apart DNA molecules so they can be spliced together.

GEL ELECTROPHORESIS – “DNA fingerprinting” Uses RESTRICTION ENZYMES to cut DNA into pieces Then SORTS OUT the DNA by SIZE. You can COMPARE the banding patterns produced by the DNA piles to determine the relationships between specimens.