GeneticsBIO.B.2

Protein Synthesis

RNA• Made up of

1. Phosphate2. Ribose (a sugar)3. Four bases

• RNA bases are:– Adenine– Guanine– Cytosine – Uracil (instead of thymine)

• RNA–Single stranded nucleic acid–Forms part of ribosomes–Two types of RNA:

• tRNA (transfer)

• mRNA (messenger)

THE BIG PICTURE• DNA (a gene) provides the instructions to

make a protein.• First, DNA is used to make mRNA in a process

called transcription.• Next, in eukaryotes, mRNA is altered by

removing sections in a process called mRNA processing.

• Then mRNA is used to make a protein in a process called translation.

• Finally, the protein is transported to where it is needed.

The Importance of Proteins

• Each gene controls the making of a protein.

• A gene is section of DNA that gives instructions for a specific protein to be made

• 20 amino acids make up all proteins

• Proteins are required for almost every reaction that occurs in your body!

TRANSCRIPTION

USING DNA TO MAKE mRNA

• RNA polymerase (an enzyme) unzips DNA by breaking the Hydrogen bonds between the bases.

• Only one strand of DNA is transcribed.

• Complementary RNA nucleotides are added to the DNA strand.

DNA RNA A – U G – C T – A C – G

• The start codon is the signal for the place to start transcription.

• Transcription stops at the stop codons.

• The sequence of bases along DNA that is transcribed is a gene.

• The RNA that is made is mRNA.DNALC animation

mRNA PROCESSING

• After mRNA is made, enzymes may cut out pieces of the strand.

• The sections that are removed are called introns.

• The sections that remain are called exons and are put together.

• The finished/mature mRNA strand then leaves the nucleus and is ready for translation.

CODONS

• Codon - three bases in a row that determine the amino acid that is used to make a protein.

mRNA Codon Chart

• Some codons do not represent amino acids, but instead act as stop signals (the end of a protein).

• Note, one amino acid may have more than one codon.

TRANSLATIONFROM mRNA TO PROTEIN

• Begins when a ribosome attaches to a mRNA strand.

• mRNA is used to make a specific protein (or polypeptide).

RIBOSOMES

• The organelle where proteins are made.

• They are made up of 2 subunits with 2 binding sites.

tRNA

• tRNA (transfer RNA) is a strand of nucleotides that has an amino acid attached to it.

• tRNA carries the appropriate amino acid to the mRNA/ribosome complex.

• If mRNA is UGG then the tRNA is ACC.

TRANSLATION• Translation begins with the start

codon.• Each amino acid that is brought in to

the ribosome is attached to the growing amino acid chain (or protein)

• The bond between amino acids is called a peptide bond.

• About 15 amino acids are added per second.

• Translation stops when a stop codon is reached.

• There are no tRNA’s for the stop codons.

• The protein is released to do its job.

Where does the protein go?

• Sometimes the finished protein goes into the rough ER. The rough ER transports it to various places including the plasma membrane, Golgi apparatus, and cytoplasm.

• The Golgi processes and packages proteins. For example, some proteins have sugars attached to them. The remodeled proteins leave the Golgi in vesicles (sacs) to go to other parts of the cell or to leave the cell.

BIOTECHNOLOGY

The future is here!

http://www.photosfan.com/images/indian-girl-with-eight-limbs1.jpg

MUTATIONS

• Mutation - changes in the DNA sequence–Types of mutations:

• Gene mutations - changes within a single gene

• Chromosomal mutations - changes within a whole chromosome (affects multiple genes)

Gene Mutations• Point Mutation - a change in a single

nucleotide (example: changing an A to a C)–Silent mutation – a mutation that produces

a new codon, but does not change the amino acid

–Nonsense mutation – a mutation that produces a stop codon instead of a codon for an amino acid

–Missense mutation – a mutation that produces a new codon, and changes the amino acid

Point Mutations

• NormalAAT TAA TAG GAT TTT AAA

• MutationAAT TAG TAG GAT TTT AAA

The G was used instead of an A.

Examples of Point Mutations

• Silent Mutation– Normal DNA: CCC codes for glycine – Mutated DNA: CCT still codes for glycine

• Nonsense Mutation– Normal DNA: ATA codes for tyrosine – Mutated DNA: ATT codes for a stop codon

• Missense Mutation– Normal DNA: ATA codes for tyrosine – Mutated DNA: TTA codes for asparagine

• Frame-shift Mutation - an insertion or deletion of a nucleotide that causes a different reading frame of codons from the point of the change to the end of the gene

Frame-Shift Mutations

• Normal DNATAC GCA TGG ATT

• Mutated DNA TAT CGC ATG GAT T

T was inserted after the A.

Frameshift example using words:• THE FAT CAT ATE THE RAT

• THE FAT C AT A TE T HE R AT

• TEF ATC ATA TET HER AT• Just like this mutated sentence does not

make sense, frameshift mutations make nonsense proteins that cannot do their jobs correctly.

DELETION of H

Chromosomal Mutations• Deletion – when part or all of a chromosome is

lost• Duplication – when part of a chromosome is

mistakenly repeated• Inversion – when part of a chromosome

becomes oriented in reverse of its normal direction

• Translocation – when one part of a chromosome breaks off and attaches to another nonhomologous (not the partner) chromosome

Chromosomal Mutations

Deletion

Duplication

Inversion

Translocation

When do mutations occur?• During DNA replication, mistakes can be made

when DNA polymerase adds complementary nucleotides.

• If this mutation or mistake happens very early on in a baby’s development, the mutation can affect the entire baby. The rest of the cells will have that same mutation.

• Remember, we all start off as one cell that must make many news cells through mitosis. Every time your cells divide, DNA has to copy itself and mistakes can be made.

• If a one of your skin cells divides right now and a mutation occurs, this is probably not a problem.

• However, if the mutation causes certain genes to change, the new, mutated skin cell can become a cancer cell.

Cause of mutations

• Mutagen – any agent that causes DNA to mutate–UV light–Radiation–Smoking–Many different chemicals

• Mutations gone wild Cats

Gene Regulation• Only some of your genes are being expressed

(used to make protein) at any given time.• Your body needs mechanisms to “turn on” or

“turn off” genes.• Chemicals can act as blocks or starters.• Some cancers are caused by genes being

turned on that should not have been! For example, these genes can be turned on by smoking, which mutates DNA.

Genetic Engineering

Manipulating DNA

Electrophoresis• DNA is cut by restriction enzymes to make fragments.

– Restriction enzymes cut DNA at specific sequences.• Electrophoresis is a technique that separates DNA

fragments (using electricity) in a jello-like slab based on the size of the fragments.

• Smaller fragments are able to travel longer distances more quickly.

• DNA has a negative charge so the fragments will flow toward the positive electrode (opposites attract).

DNA plus restriction enzyme

Mixture of DNA fragments

Gel

Power source

• If you were to compare two samples of the same DNA using the same restriction enzymes, the banding pattern would be the same.

• Different people make different banding patterns.

And why would we do this?• DNA Fingerprinting

– Paternity Tests• Children have a banding that is a combination of

their mom’s and dad’s banding.– Crime solving

• Identify the person who committed a crime (no two people have the same DNA)

– Medical diagnosis• Determine if you have the gene that causes a

disease or disorder.

GMOs

• Genetically modified organism (GMO) – an organism with DNA that has been altered through genetic engineering

• Transgenic - a GMO that has been altered with DNA from another species

Transgenic Bacteria

• Bacteria have had many different genes put into them–Some examples of human genes that

are put into bacteria• Insulin gene• Human growth hormone gene• Clotting factors gene

Transgenic Animals

• Used to study genes and improve the food supply– Mice with human-like immune system

genes.– Livestock with extra copies of growth

hormone genes.– Sheep and pigs that produce human

proteins in their milk.

Transgenic Plants

• Used for food supply and medical supplies–Rice with Vitamin A (beta-carotene)

gene–Genes for herbicide and pesticide

resistance in plants

Cloning

• Producing genetically identical organisms from one original cell.

• We have successfully cloned pigs, cows, mice, sheep, and monkeys.

• The first animal cloned was a sheep named Dolly in 1997.

A donor cell is taken from a sheep’s udder.

Donor Nucleus

The fused cell begins dividing normally.

Embryo

The embryo is placed in the uterus of a foster mother.

Foster Mother

The embryo develops normally into a lamb—Dolly

Cloned Lamb

Egg CellAn egg cell is taken from an adult female sheep.

The nucleus of the egg cell is removed.

These two cells are fused using an electric shock.

Fused Cell

GENETICS

• Genetics – the study of heredity or passing on of genes

• Gene – a sections of DNA that codes for a protein to be made

• Allele – the form that a gene takes (ex. dominant or recessive)

• Homozygous – having the same alleles for a trait• Heterozygous – having different alleles for a trait

• Dominant trait – an allele that is fully expressed in heterozygotes; represented by a capital letter

• Recessive trait – an allele that is not observed in heterozygotes; represented by a lower case letter

• Genotype – the combination of alleles (letters) that an organism has

• Phenotype – the physical trait or visible characteristic determined by the genes

• Polygenic – a trait that is controlled by more than two genes; examples include eye color, height, and skin color

  

 

      

   Link between meiosis and genetics:          

Single Trait Crosses: 

Pedigree:

Incomplete Dominance Crosses: 

Codominance Crosses:

Multiple alleles crosses:

Blood Types

BLOOD TYPES GENOTYPES ANTIGENS

(MARKERS)ANTI-BODIES (FIGHTERS)

RECEIVE FROM? DONATE TO?

TYPE A          

TYPE B          

TYPE AB          

TYPE O          

Blood Type Crosses:

Sex-linked Crosses: