MOLECULAR GENETICS

CHAPTER 10 and 13

The Blue People of Troublesome Creek

Analysis Questions for The Blue People of Troublesome Creek

1. What physical TRAIT did Martin Fugate and his wife pass on to their many generations of offspring?

2. What physical VARIATION of this trait did Martin Fugate and his wife pass on to their many generations of offspring?

3. Why did this condition occur?

4. What role did genes play in both the appearance of the trait and the passing on of the trait?

5. Based on this reading and your responses to the above questions, how might you begin to define the term “genetics”?

6. Based on this reading and your responses to the above questions, how might you begin to define the term “trait”?

7. Based on this reading and your responses to the above questions, describe the relationship between enzymes (proteins) and traits.

CENTRAL DOGMA OF MOLECULAR

BIOLOGY

On the road to discovery of DNA…. Hershey and Chase 1952

› worked with viruses that infect bacteria called bacteriophages and E. Coli bacteria

› Found DNA, not protein, is the hereditary molecule.

Chargaff 1947› For all organisms, adenine = thymine and

cytosine = guanine

Wilkins and Rosalind Franklin, early 1950’s studied the structure of DNA crystals using X-

rays. Found double helix with equal subunits

Watson and Crick, 1953 Used Chargaff's base data and Franklin’s X-ray

diffraction data to construct a model of DNA.

DNA

• Deoxyribonucleic acid• A large polymer used to

carry the genetic code of all living organisms

DNA is found packed in the nucleus of eukaryotic organisms; it is found in the cytoplasm of prokaryotic organisms

DNA is packed together and wrapped around special proteins called HISTONES

DNA bound protein is called CHROMATIN

When chromatin condenses (gets thicker) it forms CHROMOSOMES

Gene DNA Chromatin Chromosomes

DNA structure Double Helix - twisted ladder

Made of monomers called nucleotides

Nucleotides are composed of:› Deoxyribose: 5 carbon sugar

(side of helix) › Phosphate group (side of helix)› Purine and Pyrimidine Base

(steps ladder)› Hydrogen bonds hold sides

together

Nucleotide

Nitrogenous Bases Two types:

› Purines (two rings) larger bases

› Pyrimidines (one ring) smaller bases

Purines (2 RINGS)› Adenine and

Guanine Pyrimidines (1 RING)

› Thymine and Cytosine

PurinesAdenine Guanine

PyrimidinesCytosine Thymine

Phosphate group Deoxyribose

Chargaff’s rules: Base pairing rule is A-T and G-C Thymine is replaced by Uracil in RNA Bases are bonded to each other by weak

hydrogen bondsDiscovered because of the relative percent of each base; (notice that A-T is similar and C-G are similar) there was complementary base pairing of a purine with a pyrimidineThe paired bases can occur in any order, giving an overwhelming diversity of sequences http://www.dnatube.com/video/1358/Structure-of-DNA-explained-in-detail

DNA REPLICATION Making a complete copy of an

entire length of DNA Occurs in S phase of cell cycle

for both Mitosis and Meiosis Occurs in the nucleus of the

cell Complimentary sides are formed due to nitrogenous

base pairing joined by hydrogen bond

Semi Conservative Model

Explains process of replication

1 original DNA serves as template (guide) for making another DNA side

Replication will work in opposite directions on both sides at same time

an enzyme called helicase “unzips” the DNA to create a replicating bubble.Single stranded binding proteins keep 2 sides apart and stableAnother enzyme, DNA polymerase, moves along the bases on each side and connects complementary nucleotides.

How Does Replication Start?

Anti Parallel Strand DNA runs in opposite directions It is read in a 5 3 direction

› 5’Carbon of Deoxyribose has phosphate attached to it

› 1’ Carbon of sugar has nitrogen base attached to it

› 3’ Carbon of sugar has an open bond (connector site for next nucleotide)

Leading vs. Lagging Strand

in replication forkLeading

Runs in a continuous 5’ 3’ direction as it opens

Lagging Doesn’t run in 5’

3’ direction Slower, works

backward making Okazaki fragment

• http://www.dnatube.com/video/2335/Video-for-DNA-Replication• http://www.dnatube.com/video/335/Animated-DNA-Replication

How does DNA get the genetic code out of the

nucleus???

Transcription and

Translation with RNA

RNA Ribonucleic acid Single-stranded Sugar is ribose Thymine is replaced by URACIL

Differences between DNA & RNA DNA

Structure: › Double stranded

Sugar› Deoxyribose

Bases:› Adenine› Guanine› Cytosine› Thymine

RNA Structure:

› Single stranded Sugar

› Ribose Bases:

› Adenine› Guanine› Cytosine› Uracil

Transcription- how RNA is madeOccurs in Nucleus

Makes a disposable copy of DNA, just in form of RNA RNA polymerase temporarily separates the strands of a small section of the DNA molecule exposing some of the bases of the DNA molecule.Along one strand, the RNA polymerase binds complementary RNA nucleotides to the exposed DNA bases.As the RNA polymerase moves along, it makes a strand of messenger RNA (mRNA). It carries DNA’s message out of the nucleus and into the cytoplasm.

Types of RNA:1) Messenger RNA (mRNA)

o carries information from DNA to ribosome

2) Ribosomal RNA (rRNA)o Combines with proteins that

makes up ribosomes

3) Transfer RNA (tRNA)o Carries amino acids to

ribosome

PROTEIN SYNTHESISTRANSCRIPTION – the synthesis of RNA

under the direction of DNA

TRANSLATION – the actual synthesis of a protein, which occurs under the direction of

mRNA

http://www.dnatube.com/video/3450/DNA-Transcription

http://www.dnatube.com/video/5763/DNA-Transcription-animation

Codons

a sequence of 3 nitrogen bases on mRNA that code for 1 amino acid, it’s a triplet code; Universal with all life.

61 of 64 codons code for 20 amino acids on earth

Codons match up with anticodons to create a protein

The Genetic CodeThe Genetic CodeThe Messenger RNA Genetic Code

First LetterSecond Letter

UU C A G

Third Letter

UCAGUCAGUCAG

UCAG

C

A

G

Phenylalanine (UUU)

Phenylalanine (UUC)

Leucine (UUA)

Leucine (UUG)

Leucine (CUU)

Leucine (CUC)

Leucine (CUA)

Leucine (CUG)

Isoleucine (AUU)

Isoleucine (AUC)

Isoleucine (AUA)

Methionine;Start (AUG)

Valine (GUU)

Valine (GUC)

Valine (GUA)

Valine (GUG)

Serine (UCU)

Serine (UCC)

Serine (UCA)

Serine (UCG)

Proline (CCU)

Proline (CCC)

Proline (CCA)

Proline (CCG)

Threonine (ACU)

Threonine (ACC)

Threonine (ACA)

Threonine (ACG)

Alanine (GCU)

Alanine (GCC)

Alanine (GCA)

Alanine (GCG)

Tyrosine (UAU)

Tyrosine (UAC)

Stop (UAA)

Stop (UAG)

Histadine (CAU)

Histadine (CAC)

Glutamine (CAA)

Glutamine (CAG)

Asparagine (AAU)

Asparagine (AAC)

Lysine (AAA)

Lysine (AAG)

Aspartate (GAU)

Aspartate (GAC)

Glutamate (GAA)Glutamate (GAG)

Cysteine (UGU)

Cysteine (UGC)

Stop (UGA)

Tryptophan (UGG)

Arginine (CGU)

Arginine (CGC)

Arginine (CGA)

Arginine (CGG)

Serine (AGU)

Serine (AGC)

Arginine (AGA)Arginine (AGG)

Glycine (GGU)

Glycine (GGC)Glycine (GGC)

Glycine (GGA)

Glycine (GGG)

Translation Occurs in cytoplasm mRNA combines with a ribosome

mRNA carries the codon tRNA carries the anticodon which

pairs up with the codon These amino acid links form a

protein

SO:

Say the mRNA strand reads:› mRNA (codon) AUG–GAC–CAG-UGA› tRNA (anticodon) UAC-CUG-GUC-ACU

tRNA would bring the amino acids: Methionine-Aspartic acid-Glutamine-

stop

http://www.dnatube.com/video/4195/Translation http://www.dnatube.com/video/5934/Basic-explanation-of-

mRNA-Translation

TRANSCRIPTION AND TRANSLATION

http://www.dnatube.com/video/28981/What-is-Transcription-and-Translation

MUTATION Change in nucleotide

sequence of DNA or mRNA that code for a protein

Caused by mutagens (physical or chemical interactions that change the nucleotide sequence of DNA)

2 types of mutations Point

mutations› Single nucleotide mutates and affects a single codon

Reading Frameshift› Alter codon

sequence› Insertion: adding

nucleotides to the sequence

› Deletion: taking out nucleotides from the sequence

A new form of manipulation that biologists created where they can engineer a set of genetic changes directly into an organisms DNA

GENETIC ENGINEERING

Computers and other devices used to help in performing science

DNA gene cloning is an example

BIOTECHNOLOGY

POLYMERASE CHAIN REACTION

Requires no organism in the production of new DNA molecules

Turns a single molecule of DNA into a large, identical DNA molecules

Used in forensics

Recombinant DNA Major focus of genetic engineering

The sequence of nucleotides in the gene being manipulated are

read Desired gene is cut from

surrounding genes DNA from 2 different sources is

joined into one molecule (hybrid)http://www.dnatube.com/video/193/Contruction-of-Recombinant-DNA

Plasmids molecules of DNA found in

bacteria separate from the bacterial chromosome.

small (a few thousand base pairs) and circular

usually carry only one or a few genes

TRANSFORMATION Genetic alteration of a cell that is

caused from directly taking in DNA from outside the cell membrane.

It can occur naturally in some species of bacteria, but it can also be effected by artificial means in other cells

http://www.dnatube.com/video/202/Understanding-Bacterial-Transformation

DNA FingerprintingPattern of bands made up of specific fragments from an individuals DNA

Restriction enzymes can cut the DNA at specific sites with “sticky ends”

DNA Ligase can join DNA at specific sites

The DNA created artificially is called recombinant DNA

Creates a DNA fingerprint Different DNA samples are exposed to

the SAME restriction enzyme creating RFLP (fragments of different lengths of DNA)

Those fragments are loaded into agarose gel and electric currents are used

RFLP’s will separate according to length/size of the fragments which create a unique fingerprint

Gel Electrophoresis

Transgenic Organisms

Recombined DNA from 2 different organisms to make 1 organism that has traits from BOTH parents.

These traits will then be carried on to offspring

Human Genome Project

Began 1990 ended in 2003 Mapped out entire DNA

genome nucleotide sequences for all humans as a species

Contains approximately 40,000 different genes

What is DNA technology used for?

Gene therapy Pharmaceuticals

Criminal Forensics Environmental

Clean-up Agriculture Livestock