21 DNA Biology and Technology

Question 1

What must DNA Do?

Answer 1

1. Replicate to be passed on to the next generation
2. Store information
3. Undergo mutations to provide genetic diversity

Question 2

DNA Structure

Answer 2

• Double-stranded helix
• Composed of repeating nucleotides (made of pentose sugar, a phosphate and a nitrogenous base)
• Sugars and phosphates make up the “sides of the ladder” while the nitrogenous bases make up the “rungs of the ladder”
• Nitrogenous bases have complementary pairing of: adenine (A) pairs with thymine (T), guanine (G) pairs with cytosine (C)

Question 3

Replication of DNA

Answer 3

Two strands of DNA ‘unzip’ by breaking hydrogen bonds between base paris.

Complementary nucleotides are added to each open strand by enzyme DNA polymerase.

Each new double-helix is made of one new strand and one old strand (semi-conservative replication)

The sequence of base pairs forms genes, which make each individual unique.

Question 4

DNA Replication Errors

Answer 4

If an error occurs in replication (wrong base inserted), repair enzymes may be able to fix the problem and correct he base pair sequence.

But IF NOT, this is a mutation, or a permanent chang ein base pair sequencing.

Mutations change both genotypes and phenotypes, and introduce variability in the genome (some good, some bad!)

Question 5

RNA Structure and Function

Answer 5

• Single-stranded
• Composed of repeating nucleotides
• Sugar-Phosphate backbone similar to DNA
• Nitrogenous bases are Edenine, Cytosine, Guanine and Uracil (U replaces Thymine)

Question 6

4 Types of RNA

Answer 6

1. RIBOSOMAL (rRNA): joins with proteins to form ribosomes
2. MESSENGER (mRNA): carries genetic coded information from SNA in the nyucleus out to the ribosomes, codes for proteins
3. TRANSFER (tRNA): transfers amono acids to ribosome where they are strung together to form a protein - one tRNA for each amino acid
4. SMALL (sRNA): several types do various jobs - splice mRNA, modify rRNA, prepare mRNA for degradation

Question 7

Comparing DNA to RNA

Answer 7

• SIMILARITIES

Both are nucleic acids

Both are made of nucleotides

Both have sugar-phosphate backbones

Both are found in the nucleus

• DIFFERENCES

DNA is double-stranded helix, while RNA is single stranded and straight

DNA has Thymine, RNA has Uracil

RNA is found both in the cytoplasm as well as the nucleus, while DNA is onlly in the nucleus (EXCEPT MITOCHONDRIAL DNA)

Question 8

2 Steps to Gene Expression

Answer 8

1. TRANSCRIPTION: DNA Code is “read” to make mRNA in the cell nucleus
2. TRANSLATION: mRNA code is read to make a protein at ribosomes, in the cytoplasm

Question 9

The Genetic Code

Answer 9

• Uses only the 4 bases (A,U,G and C) to code for amino acids during translation
• Every 3 bases on the mRNA is called a codon that codes for a particulat amino acid
• Same code exists in nealy all lving things

Question 10

Proteins

(A review)

Answer 10

Composed of subunits of amino acids linked together

Sequence of different amino acids determines the shape (and therefore function) of the protein

Synthesized at ribosomes

Important for diverse functions in the body uncluding hormones, enzymes and transport (hemoglobin, actin, myosin, insulin, etc)

Question 11

Transcription

Answer 11

mRNA is made from DNA template in the nucleus during transcription

mRNA is processed before leaving the nucleus

mRNA moves outside the nucleus to the ribosomes, to be “read”

Every 3 bases on the mRNA is a codon, that codes for a particular amino acid during translation

PROCESSING OF mRNA AFTER TRANSCRIPTION: One end of the RNA is capped, introns removed, Poly-A tail is added.

Question 12

Translation

Answer 12

Sequence of nucleotides (A,U,G,C) in mRNA translated into sequence of amono acids in protein.

1. INITIATION: mRNA binds to the small ribosomal subunit, then the large ribosomal subunit associates with it
2. ELONGATION: Polypeptide begins and lengthens. tRNA picks up an amino acid, tRNA has an anticodon that is complementary to the codon on the mRNA, tRNA anticodon binds to the codon and drops off an amino acid at the growing polypeptide
3. TERMINATION: a stop codon on the mRNA causes the ribosome to fall off the mRNA

Question 13

Regulation of Gene Expression

Answer 13

Each and every cell of an organism contains all of its genes

Cells differ as to which genes are expressed (e.g. muscle and nerve cells differ in which proteins ar emanufactured there and become active in each)

Gene expression in each type of cell is controlled in five primary ways.

Question 14

Regulation of Gene Expression

Answer 14

1. Pre-ranscriptional control (nucleus): DNA must be available for transcription (decondense, or uncoil)
2. Transcriptional control (nucleus) Transcription factors start the process of forming mRNA
3. Post-Transcriptional Control (nucleus): mRNA processing (removal of mRNA introns, etc.)
4. Translational control (cytoplalsm): Differential ability of mRNA to bind to ribosomes
5. Post-translational control(cytoplasm): Changes to the newly-made protein make it functional (phosphorylation)

Question 15

The Human Genome Project

Answer 15

The “genome” consists of all human DNa, which has about 3 billion bases and 20,500 genes (in every autosomal cell). It is not yet know what every gene actually does.

Most of the human genome was sequenced by 2003

There are many polymorphisms or small regions of DNA that very among individuals

Genome size is not correlated with the number of genes or complexity of the organism.

Question 16

The Next Steps in the HGP

Answer 16

• Functional genomics: Understanding what 20,500 genes do and understanding what the 95% of our DNA that does not code for protein does.
• Comparative genomics: Help understand how species have evolved, comparing genomes may help identify base dsequence that cause human illness (95-98% of our genes identical to chimps, 85% simillar to a mouse) and help in our understanding of gene regulation.

Question 17

Can we modify a person’s genome?

Answer 17

Gene Therapy: insertion of genetic material (genes) into human cells to treat a disorder

• Ex Vivo Therapy: cells are removed, genetically altered and then returned to the patient
• In Vivo Therapy: a gene is directly inserted into an individual through a vector (e.g. viruses) or directly injected to replace mutated genes or to restore normal controls over gene activity

BEEN MOST SUCCESSFUL IN TREATING CANCER.

Question 18

Genetic Engineering

Answer 18

Altering DNA in bacteria, viruses, plants and animal cells through recombinant DNA technology

Question 19

Recombinant DNA

Answer 19

contains DNA from 2 or more different sources

Question 20

Transgenic Organisms

Answer 20

Organisms that have a foregn gene from a different species inserted into their DNA

Question 21

Biotechnology

Answer 21

Using natural biological systems to creeate a product or to achieve a result desired by humans.

Question 22

DNA Technology

Answer 22

1. Gene cloning through recombinant DNA
2. Polymerase chain reaction (PCR)
3. DNA Fingerprinting
4. Biotechnology products from bacteria, plants and animals

Question 23

Gene Cloning

Answer 23

1. Cut out a specific segment of DNA from one organism. Then insert it into the DNA of a completely different organism using a vector.
2. Asexually reproduce that new organism having the ‘combined’ DNA, and use it to make large amounts of substance the transferred DNA codes for

BACTERIA MAKES HUMAN INSULIN!!!

Question 24

Polymerase Chain Reaction

PCR

Answer 24

Used to clone small pieces of DNA

Important for amplifying DNA for analyses such as DNA Finger-Printing

Question 25

DNA Fingerprinting

Answer 25

Frangments are separated by their charge/size ratio

Results ina distinctive patterns for each individual

Used to establish paternity, identify a body, or a person who was at a crime scene

Question 26

Geneticall enfineered products: Transfenic bacteria can produce non-bacterial substances

Answer 26

Uses:

• Insulin
• HGH
• clotting factor VIII
• Tissue plasminogen activator 9t-PA)
• Hepatitis B vaccine
• Bioremediation: cleaning up the environment such as oil degrading bacteria

Question 27

Biotechnology Products: Transgenic Plants

Answer 27

• IMPORTANT USES:

1. Produce human proteins in their seeds such as hormones, clotting factors and antibodies
2. Plants resistant to hebicides
3. Plants resistant to insects
4. Plants resistant to frost

CORN, SOYBEANS AND COTTON PLANTS ARE COMMONLY GENETICALLY ALTERED

92% OF SOYBEANS AND 80% OF THE CORN PLANTED IN THE US HAVE BEEN GENETICALLY ‘ENGINEERED” CALLED GMO.

Question 28

Health Focus:

Ecological concern about genetically altered crops

Answer 28

• Resistance incrasing in the target pest
• Exchange of genetic material between the transgenic plant and a related species
• Concern about the impact of genetically altered crops on non-target scpecies

Question 29

Biotechnology Products:

Transgenic Animals

Answer 29

• Gene is inserted into the egg that when gertilized will develop into a trangenic animal.

CURRENT USES:

1. Gene pharming: production of pharmaceuticals in the milk of farm animals
2. Larger animals: includes fish, cows, pigs, rabbits and sheet
3. Mouse models: the use of mice for various gene studies
4. Xenotransplantation: pigs can express human antigens on their organs, making it easier to transplant them into humans.