II. RNA

-Ribonucleic Acid-Function – makes proteins

A. Differences between RNA and DNA

-- DNA RNA-- 2 strands 1 strand-- deoxyribose ribose sugar-- thymine uracil

B. 3 types of RNA

1. Messenger RNA (mRNA) - straight strand

- transmit information from nucleus to ribosomes on how to make protein

2. Transfer RNA (tRNA) - folded strand - 20 types – each type is an amino acid

- brings amino acid to ribosome to make protein 3. Ribosomal RNA (rRNA) - globular (round) - makes ribosomes

C. Transcription• The making of RNA from DNA• Done in the nucleus • Uses RNA polymerase instead of DNA

helicase to break H-bonds between DNA strands. RNA polymerase attaches to a section of DNA called a promoter. Will stop transcribing when a termination signal is reached.

DNA strand

C – G

T – A

A – T

T – A

T – A

G – C

A - T

mRNA

C

U

A

U

U

G

A

G

A

U

A

A

C

U

mRNA

•Introns – sections of DNA that will not be read (“junk DNA”)•Exons – sections of DNA that will be read•mRNA goes from nucleus to cytoplasm to ribosomes to make proteins.

D. Factors that damage DNA

• Excessive body heat (fever)• Radiation (UV and X-rays)• Chemicals (carcinogens)

**** errors do occur but rarely – about 1 per billion nucleotides**** DNA is constantly trying to repair itself, has proofreading enzymes

III. Protein Synthesis the making of proteins using information coded from

DNA and carried out by RNA.

• A. Amino Acids - basic building blocks of proteins

- 20 different ones - joined together by peptide bonds - carried by tRNA

• B. Codon – 3 bases in a row within a mRNA strand that call for a specific anticodon that codes for a specific amino acid. *** AUGAUG is the universal start codon for all

organisms.

C. Translation Translation – process of making proteins by using mRNA

A U G G C G U A G G C U

U A C C G C A U C C G A

tRNA

Start alanine stop alanine amino acids

mRNA

occurs in ribosomes

codon

anticodon

Human Genome Project

• 15 year project with scientist all over the world. Mapped out the sequence and location of all traits (genes) on all chromosomes of a human.

• Humans have 3,200,000,000 base pairs per sex cell. (It would take about 10yrs. to read each base.)

Transcription/translation Model

Review

1. What are the 3 types of RNA. 2. Give 3 differences between RNA and DNA.3. The process of making more DNA is called ________ while

the making of RNA is __________.4. How does a cell know it is making RNA from DNA

instead of making more DNA from DNA ?5. Change the following DNA strand into mRNA T-T-A-A-G-C-G-A-T-C6. RNA is used in the making of ___________.7. There are 20 different kinds of this type of RNA.

Review

1. Change the following DNA strand into mRNA. A-T-C-G-C-G-T-T-A-G-C-T

2. Assemble the protein from the mRNA sequence from your answer to #1.

IV. Mutations - change in DNA - germ cell mutations – mutations

in sex cells – affect offspring - somatic cell mutations – occur in body cells . Ex. Skin cancer, leukemia• A. Chromosome Mutations 1. Deletion – piece of chromosome breaks off. Ex. Fragile X syndrome 2. Inversion – piece breaks off and reattaches upside down. A A B C C B

3. translocation – inversion with a non homologous chromosome. Piece breaks off and attaches to different # chromosome upside down.

A

B

C

D

A

B

21

A

B

C

D

A

B

C

D

D

C

19

4. Nondisjunction- when chromosome pairs fail to separate so there are multiple copies. Ex. Down Syndome Ex. 21st chromosome

B. Gene Mutations - occur within a specific gene or

piece of a gene 1. Point mutation – substitution,

addition, or deletion of a nitrogen base. Ex. Sickle cell anemia

-- frameshift mutation - type of point mutation that involves the addition or deletion of a nitrogen base.

• Ex. ATTCGCGGT• ATTTCGCGGT• ATCGCGGT -- additions and deletions have a

greater effect than substitutions.