Bell WorkGCCTTA1. What would be the DNA compliment of the

section of DNA above?a. CGGAATb. CGGUUTc. ATTCCGd. TAAGGC

Question1. Which of the following is NOT true about DNA replication?a.It occurs during interphaseb.The new DNA is identical to the original DNAc.It is semi-conservatived.The sequence of the nucleotides is changed

Question2. DNA contains genetic information on its ___.a.Hydrogen bondsb.Deoxyribose sugarc.Nucleotide sequenced.Phosphate bonds

Question3. Which of the following is true about the relationship between DNA, genes, and chromosomes?a.Chromosomes and proteins make up genes and genes make up DNAb.Chromosomes are made up of DNA and protein. Genes are sections of DNA on a chromosomec.Genes and proteins make up DNA. The sequence of genes and proteins make up a chromosome.d.Proteins make up chromosomes and DNA. DNA and chromosomes make up genes.

Notes

• Proteins control all the processes of the cell– DNA controls the production of every protein• To be made correctly, 3 processes must occur

– 1. DNA replication– 2. transcription– 3. tanslation

• If the nucleotide sequence changes, then the information that it carries will change

Notes

• DNA– Made of nucleotides • 3 parts of a nucleotide

– Sugar (deoxyribose)– phosphate group – nitrogen bases (complimentary pairs: A-T, C-G)

– 1953: Crick and Watson• Discovered that DNA was made of two nucleotide

chains joined at the nitrogen bases by hydrogen bonds.• Discovered that it was a twisted helix

Notes

• The more closely the DNA sequences are between two organisms, the more similar they are.

DNA

• Chromosomes are made of proteins and DNA• Genes are the sections of DNA that provide

information about specific traits.

Notes:

Replication, Transcription and Translationallow an organism to express its inherited genes.

DNA Replication

• DNA replication– The process by which DNA copies itself– Takes place during interphase– An exact replica of the DNA is made

Step 1 of DNA Replication

• An enzyme breaks the hydrogen bonds between the nitrogen bases causing the DNA to “unzip”, exposing the nitrogen bases

Step 2 of DNA Replication

• Nucleotides that are floating around in the cell (free nucleotides) pair with the exposed nitrogen bases– This type of replication is called “semi-

conservative” since the new molecules of DNA will have one side of the original DNA and the other side will be formed new from free nucleotides.

Step 3 of DNA Replication

• The sugar and phosphate parts of the free nucleotides bond together to form a complete strand that will make up the new side of the DNA molecule

• The original strand bonds to the new strand

Step 4 of DNA Replication

• The result is two molecules of DNA that are identical since the base pairs have to join their complimenting nitrogen base

Transcription and Translation

• RNA– Consist of the sugar ribose, instead of the

deoxyribose sugar of DNA– Pairs A to U instead of A to T– Single strand instead of double strand– 3 types: messenger RNA (mRNA), transfer RNA

(tRNA) and ribosomal RNA

Why RNA is needed

• Proteins are made on the ribosomes in the cell, but the DNA (instructions) are located in the nucleus

• Information from the DNA must be sent to the ribosomes…..TRANSCRIPTION

Transcription

• Transcription– A process that copies the instructions in the DNA

onto a strand of mRNA

Notes: Steps in Transcription

• Step 1– DNA unzips like it did in replication– Free RNA nucleotides pair with the nitrogen bases– Adenine (A) pairs with uracil (U)– Cytosine (C) still pairs with guanine (G)

Notes: Steps in Transcription

• Step 2– Base pairing finishes– mRNA breaks away from the DNA strand– 2 DNA strands zip back together– The mRNA goes out of the nucleus and into the

cytoplasm of the cell

Notes: mRNA

• Codons– Nitrogen bases in the mRNA also forms groups of

three bases called codons– The code for an amino acid• 64 different combinations of 3 bases are possible.– These combinations make up the codes for the

twenty different amino acids» Combinations of the 20 amino acids make up

proteins in all organisms

Notes: Translation

• Translation– The process that builds proteins– Takes place after the ribosomes attach to the

mRNA– The mRNA attaches to the rRNA and “reads” the

sequence 3 bases at a time

Notes

• Transfer RNA – (tRNA) is used to carry amino acids to the

ribosome– Has a three nucleotide sequence called an

anticodon– Anticodons form base pairs with the codons of the

mRNA

Notes: Translation

• tRNA carries a specific amino acid that was determined by the anticodon sequence

• A bond forms between the two amino acids.• The tRNA is released

Notes: Translation continued

• Process repeats itself over and over and a chain of amino acids is built

• When the rRNA reads a special stop codon, translation stops and the chain is released into the cytoplasm

• The polypeptide may then be used in cellular processes OR it may bond with other polypeptides to form proteins

Notes

• Proteins

Notes

• Proteins

Notes

• Proteins

Notes

• Proteins