1

DNA and GenesBiology: Chapter 11

2

DNA• Deoxyribonucleic Acid (____________)• The genetic material

• Contains the “_______________” for an organism• Instructions for an organism’s ____________

• Nucleic Acid-______________ (chain) of _______________• Very long molecule• A single strand is ~5 feet long• If all uncoiled, your DNA would reach from the Earth to the Sun• 600+ times!

• DNA is _______________to leave the nucleus through the pores

3

DNA, Genes, and Chromosomes• DNA=__________________ material• _____________=segment of DNA that codes for a specific _________• Chromosome=tightly wound strand of _________________________

4

Structure of Nucleotides• A nucleotide is a subunit of DNA (a ____________)• 3 parts:• A Sugar (____________________)• A phosphate group• A nitrogenous base (Adenine (__), Thymine (___), Cytosine (___), or Guanine (___)

• All organisms have these same 4 bases• Bases come in 2 forms• ____________: Adenine and Guanine• Pure as Gold

• _______________: Cytosine, Uracil (to be discussed later) and Thymine• Py Cut

5

Structure of DNA•DNA is a string of nucleotides• The structure was discovered by

____________________using X-Ray technology

6

Watson and Crick• James Watson and Francis Crick (1953)• “Used” Frankin’s work to come up with the 3-D structure of DNA

• DNA resembles a twisted ladder or twisted zipper• Called a ____________________• Nucleotides are held together by ___________________________

7

Nucleotide Sequences• The sequence of nucleotides determines the make-up of the

organism• The sequence of nucleotides on a strand of DNA is called a

______________• A gene is a segment of DNA that is a code for a __________________

8

DNA Replication• DNA must constantly __________• New copy is used during cell division and production of sperm and egg

(mitosis and meiosis-to be discussed later)• Simplified Process• An enzyme called ______________breaks the hydrogen bonds between

nucleotides• This “_____________” the strand

• Another enzyme called ___________________adds a complementary nucleotide

9

10

Complementary Base Pairing

• ____ bonds to ____ (apple tree)• ____ bonds to ____ (car garage)

•Practice: What would be the complementary strand for the following?• A T G C T G• ______________

11

RNA• Also a __________________(polymer of nucleic acids)• Very similar to DNA• 3 parts:• A sugar (________________)• A phosphate group• A nitrogenous base (Adenine (__), Cytosine (__), Guanine (__), and Uracil (__)

• Uracil replaces _______________• Bonds to Adenine

• 3 types of RNA• Messenger RNA (_____)-Brings instructions from DNA to cytoplasm

(_____________)• Ribosomal RNA (_____)-Binds to mRNA and assembles amino acids in correct order • Transfer RNA (______)-Carries amino acids to the ribosome

12

Transcription• DNA double helix __________• _________________(A, U, G, C) bond to the complementary base•mRNA strand ________________•mRNA leaves the __________and travels to the _________, where it

binds to a _______________• __________ within the ribosome binds to the mRNA and “________” the code

13

Amino Acids• “The language of proteins uses an alphabet of amino acids.”• There are _____ common amino acids• The sequence of nucleotides determines the sequence of

_______________• ___ bases code for ____ amino acid• This group of 3 bases is called a ___________• Example: UUU = phenylalanine

• Several codons code for the same amino acid• Example UUU and UUC both code for phenylalanine

• Some codons are not codes for amino acids, but instructions to start or stop transcription.• _____________=Start codon (Methionine)• _________, ________, and ______________=Stop codons

14

15

Translation• Translating _______ into a sequence of amino acids to form a _______• Amino acids dissolved in the cytoplasm are brought to the ribosome by

__________• tRNA contains a sequence of 3 amino acids called an ______________• The anticodon is complementary to a codon.

• Example: AUG is a start codon and codes for the amino acid Methionine • Methionine will be attached to a tRNA molecule that has the anticodon UAC

• As the amino acids attach to the mRNA strand, the tRNA releases and returns to the cytoplasm to pick up another amino acid• __________bonds are formed between the amino acids, forming a

protein

16

Protein structure•The sequence of amino acids determines the protein’s _______________•Proteins always form in the same 3-D shape• These proteins become _________and ___________ structures.

•Central Dogma of Biology• __________________________• This occurs in all organisms• It also explain how you get your traits• You get some DNA from mom, some from dad, and this DNA

determines the proteins and, therefore, all of the traits you have.

17

When things go wrong•_____________-Change in DNA sequence•Can be caused by many different things• Errors in DNA replication or transcription• Errors in cell division• External factors (____________)• Radiation (sun or tanning)• Smoking• Alcohol• Asbestos • Many more

18

Results of Mutations•Most mutation are _________•Can result in cell division going out of control• Leads to a mass of cells, called a ______________• This is how ______________happens.

•Some mutations are ___________•Minor change, or the cell catches it and fixes or destroys it

before • In rare cases, mutations are ____________•Give the organism something it did not previously have• These are what __________________________acts on.

19

Point Mutations•Change in a ___________________in DNA•Alters the amino acid, and therefore the ________________

of the protein

20

Frameshift Mutations•Shifts the _____________________by one base•Unlike point mutations, __________________ after the

mutation are altered, and this drastically changes the protein shape.

21

Chromosomal Mutations•Change to the _________________of a chromosome• Part of the chromosome may break off, or fold incorrectly

22

Repairing DNA•Mutation sometimes occur and are able to be fixed•Certain enzymes are able to “_____________” DNA to

ensure that all is well• Can replace incorrect nucleotides, or instruct the cell to destroy

the DNA containing the errors•This process is not perfect, but usually works well•Best course of action is avoiding mutagens as much as

possible.