DNA Structure and Technology

By: Amber Tharpe

DNA Structure

Monomers are nucleotides 3 parts of a nucleotide

Phosphate group Deoxyribose sugar Nitrogen base

4 different bases Cytosine (C) - thymine (T) Adenine (A) - Guanine (G)

DNA Structure

Double helix- shape of 2 chains of DNA in a twisted spiral

2 chains held together by H-bonds between the bases

DNA

Nucleic acid that serves as the “blueprints of life”

Housed in the nucleusDetermines what traits are

inherited from one generation to the next

Leads to the variation in all living things

Base Pairing Rules

A always bonds with T

C always bonds with G

Base Pairing Practice

If one strand of DNA is ACACAC, what is the other strand?

If one strand of DNA is TGAC, what is the other strand?

If one strand of DNA is CTGCTA, what is the other strand?

Replication

DNA has the ability copy itself

An enzyme “unzips” the 2 strands

A single DNA strand serves a template or pattern for making a new strand

Free bases bind based on the base pairing rules

2 identical strands are formed

Replication Terms

Template strand DNA strand that is being copied

Complimentary strand New DNA strand that is formed by

pairing nucleotides to the template strand

DNA polymerases Enzymes that bond nucleotides

together to form complimentary strands

Central Dogma

DNA→ RNA→ ProteinDNA- RNA is transcription

RNA- Protein is translationIn eukaryotes, replication and transcription occurs in the nucleus, while translation occurs in the cytoplasm

RNA

Single-stranded nucleotides with U’s bonding to A’sDNA RNA

sugar deoxyribose

ribose

bases T bonds with A

U bonds with A

strands

Double-stranded

Single-stranded

Transcription

Process of using a strand of template DNA to make a complimentary strand of RNA

RNA polymerasesEnzymes that bond nucleotides together to make a new RNA molecule

Transcription Practice

Transcribe a strand of DNA that is ACACAC.

If a strand of DNA is TGAC, what strand of RNA will it make?

Convert a strand of DNA that is CTGCTA to RNA.

3 Types of RNA

Messenger RNA (mRNA) Code translated to form a protein

Ribosomal RNA (rRNA) Forms part of ribosomes to make

protiens Transfer RNA (tRNA)

Brings amino acids from the cytoplasm to make proteins

Has an anticodon on one end

Transcription

Does not transcribe the whole DNA molecule

Only transcribes the portions of DNA (gene) needed for cell function at that specific time

Translation

The process that converts mRNA into a polypeptide (or protein)

The code for nucleic acids is 4 nucleotides: A,G,C, and T or U

The code for proteins 20 different amino acids

Nucleotides are like letters, while amino acids are like words

Codons

3 nucleotide sequence that codes for a particular amino acid

Considered a triplet code, since 3 nucleotides are used to make each amino acid

Many amino acids are coded for by more than 1 codon

Anticodon Set of 3 nucleotides found on tRNA that

is complimentary to an mRNA codon

Translation

Occurs in the cytoplasm1. mRNA is pulled through the

ribosome exposing one codon at a time to pair with the complimentary tRNA

2. The ribosome forms a peptide bond between the amino acids brought in by the tRNA

3. This process continues as the polypeptide grows and eventually a stop codon is reached

Translation Practice p. 244

If a strand of RNA is ACACAC, what amino acids does this make?

Translate a strand of RNA is UGACUC.

If a strand of DNA is CUGCUA, what amino acids does this make?

Mutation

Change in an organism’s DNA

Can occur in DNA replication or in meiosis

Substitution (point mutation)One nucleotide is substituted for an incorrect one

May alter an amino acid in a protein

Ex: sickle cell anemia

Frameshift Mutation

Frameshift mutation Insertion or deletion of a

nucleotide in DNA Makes an abnormal protein Reading frame is shifted because

DNA is read in a triplet code THE CAT ATE THE RAT Remove the first E What does the sentence say?

Nondisjunction

When chromosomes fail to separate properly in meiosis

Ex. Down Syndrome- 3 copies of chromosome 21

Mutagens

Agents in the environment that can change DNA

Ex: UV light, radiation, chemicals in tobacco products

Often lead to cancer

Biotechnology

The use of organisms or their products to improve human health or food production

Types DNA FingerprintingGenetic EngineeringGenetic Screening

DNA Fingerprinting

Gel electrophoresisUsed for comparing DNA samples

DNA is cut and run through the gel based on electric charge

Smaller fragments move farther than large fragments

The different size fragments make bands on the gel that can be compared

DNA Fingerprinting

UsesPaternity testingForensics

Identifying dead bodiesSolving crimes

Compare DNA left at crime scene to suspects’ DNA

Genetic Engineering

Genes are transferred from 1 organism to another Recombinant DNA

When DNA from 2 different sources are combined

Used in medicine (gene therapy) and agriculture Modify plants to grow larger,

faster, and more disease resistant Use the gene for making insulin to

treat diabetes

Cloning

A normal cell is taken from the organism that is being cloned

An egg cell from an organism of the same species is taken and the nucleus removed

The 2 cells are fused and the embryo is placed in the uterus of a female to develop and be born