Goal 3DNA, Protein Synthesis, Genetics, Biotechnology

and Evolution

3.01 DNA, RNA and Protein Synthesis

DNA is the code of life. It contains the information on how to make proteins.

Structure of DNA DNA (deoxyribonucleic

acid)forms a double-helix shape

Consists of a sugar (deoxyribose), a phosphate, and a nitrogenous base

Bases – Adenine-Thymine– Guanine-Cytosine(complementary base

pairing)

Nucleotide –building blocks of DNA

A nucleotide is made up of a phosphate group, nitrogen base (A,T,G,C) and sugar.

Hydrogen Bonds

Weak hydrogen bonds attach the two strands of the DNA molecule.

DNA replication Copying of genetic

material before mitosis and meiosis

3 steps– 1) DNA unzips at

hydrogen bonds– 2) free nitrogenous

bases join up to newly opened bases

– 3) sugar-phosphate “backbone” rebuilt

The Code

Every three nitrogen bases is the code for one amino acid.

An error in a nitrogen base is called a mutation.

RNA

Ribonucleic AcidSingle strand.Uracil instead of

thymine.Ribose instead of

deoxyribose.

Types of RNA

Messenger RNA – carries DNA code from nucleus to ribosome

(why can’t DNA leave the nucleus?)Transfer RNA - carries amino acids

from the cytoplasm to the ribosomeRibosomal RNA – what the ribosome is

made of

Protein Synthesis

Two Steps

Transcription – copying DNA code onto the mRNA

Translation – making protein in the ribosome

Protein Synthesis

Transcription – DNA unwinds and

unzipsmRNA nucleotides

match up to the complimentary DNA nucleotide

Single strand of mRNA is made with the DNA code

Protein Synthesis

mRNA leaves the nucleus and carries the code to the ribosome

Protein Synthesis

Translation –mRNA lines up in the ribosomemRNA triplet codes (codons)match up with

tRNA triplet codes (anticodons)

Protein Synthesis

Translation continuedAmino acids are put in correct sequence.Peptide bond forms between amino acids.Polypeptide folds into protein.

Protein

Reading and interpreting an mRNA codon chart

Find each codon (3 base sequence) from the mRNA

Use chart to find the correct amino acid that it codes for

Gene Regulation

All cells of an organism have the same DNA.

What type of cell develops depends on which genes get turned on or off.

This is why a multicellular organism is able to differentiate into many types of cells. For example: skin cells, muscle cells, bone cells.

Gene Regulation

Cells respond to their environment by producing different types and amount of protein.

Examples:1. You get cut and your skin cells need to

make proteins to repair your skin.2. Cancer may result when your cells make

too many cells (protein).3. Diabetes may result if your pancreatic

cells don’t make enough insulin (protein).

3.02 Cell Division

2 Types of cell division:

1. Mitosis – involved in growth, repair and asexual reproduction

2. Meiosis – involved in the production of gametes

Examples of asexual reproduction

Binary fission

Asexual reproduction

Budding inHydra.

Asexual Reproduction

Cutting of a plant

Mitosis

Occurs in all body cells Results in 2 new genetically identical

daughter cells Maintains the chromosome number Chromosomes DOUBLE then SPLITExample: humans 46 92 46

Stages of Mitosis

1. DNA (chromosomes) replicate

2. Spindle forms, nuclear membrane disappears

3. Chromosomes line up along the equator

4. Spindle fibers shorten, bringing chromosomes towards poles

5. Cytoplasm divides

Replicated chromosme

Replicated chromosome is actually two identical chromosomes attached at the centromere

Meiosis

Occurs only in the sex organs (testes and ovaries)

Results in 4 gametes (sex cells) Reduces the chromosome number in

half (for sexual reproduction) Chromosomes DOUBLE SPLITSPLITExample: human 46924623

Stages of Meiosis

1. DNA replicates2. Chromosomes line

up along the equator

3. Replicated pairs split

4. Chromosomes line up again

5. Centromere splits

Sources of variation

Crossing over (only occurs during meiosis).

Sources of Variation

RandomAssortmentOf chromosomes

Sources of Variation

Gene mutation

Nondisjunction

Fertilization

3.03 Patterns of Inheritance Gregor Mendel Father of genetics Austrian Monk First noticed

inheritance of traits Studied heredity in

pea plants, and noted statistics included within monohybrid/dihybrid crosses

Mendel’s Experiments

Results of Mendel’s crosses with pea plants.

He studied seven different traits.

Genetic Vocabulary

Dominant- allele which masks the phenotype of other alleles

Recessive – allele that will not be expressed if dominant allele is present

Genetic Vocabulary

Heterozygous (hybrid) – the

genes in the

gene pair are

differentHomozygous (pure) – the genes are the same

Genetic Vocabulary

Geneotype – The actual genes of an organism

Phenotype – What an organism actually looks like.

Genetic Vocabulary

Parental generation

F1 Generation

F2 Generation

Law of Segregation

During meiosis, the gene pair splits and each gamete only has one member of each

pair of genes.

Law of Independent Assortment

During meiosis, the genes in each gene pair move into the gametes independently of each other. Notice you can still get a 3:1 ratio between yellow and green or round and smooth.

Genotype and Phenotype

A change in the environment also can affect the phenotype. Although we often think of flamingos as being pink, pinkness is not encoded into their genotype. The food they eat makes their phenotype white or pink

Test Cross

Mate unknown with a pure recessive.B – black guinea pigb – white guinea pigBlack guinea pig – BB or Bb?

BB x bb Bb x bbResult: only black Result: blackoffspring and white pigs

Incomplete Dominance

Blending of two traits.

Incomplete Punnett Square

Co-dominance

Co-dominant alleles result in the expression of both traits. Examples: roan shorthorn cattle of AB blood

Pedigrees Tools used by

scientists to trace inherited genes through a family tree

Squares= male Circle=female Filled=affected Half filled = carrier Empty=not affected

Polygenic Traits Traits which are

coded for by more than one allele.

Usually results in a blending of traits (ex: eye color, skin color, hair color)

Polygenic – Skin color

Human Genetics

Examples of single gene, autosomal inheritance patterns:

Sickle Cell AnemiaCystic FibrosisHuntington’s Disease

Sickle Cell Anemia

RecessivePredominantly in

people of African/African- American descent.

Hybrid individuals are resistant to malaria

Symptoms: tired, pain in joints

Cystic Fibrosis

RecessivePredominantly in

caucasiansSymptoms: mucous

clogs lungs and other organs, individuals usually don’t live past 20 years old

Huntington’s Disease

DominantSymptoms: Abnormal

body movements,gradual deterioration

or loss of intellectual abilities (dementia),

behavior problems

Blood Types

A and B are co-dominant.

O is recessive.

Punnett Square - Blood

Sex Linked Traits

Trait is more likely to be inherited by males

Gene for these traits are found on the X chromosome, but not the Y because it is so short

Recessive

Sex Linked Traits

Hemophilia Defective gene

prevents the normal formation of the proteins for clotting (platelets)

Symptoms: uncontrollable bleeding when cut

Sex Linked Traits

Colorblindness

Unable to distinguish between certain colors. For example – red/green color blindness

Karyotypes

What sex is this individual?

Karyotypes

What disease does this individual have?

3.04 Biotechnology

Human Genome Project

Scientists have uncovered the entire human DNA code.

Information useful in screening for diseases, gene therapy and developing drugs.

Gene Therapy

Inserting corrected gene into person who has a defective gene.

Still in the experimental stages.

Gel electrophoresis

DNA fragments separate according to size

Gel Electrophoresis

Also called DNA fingerprinting. Used in crime scene investigations.

Used to determine how closely related organisms are.

Transgenic Organisms

Having DNA from another species

Example: a cow or pig has a human gene

Used to make human insulin by inserting human gene in bacteria

Firefly DNA inserted into tobacco plant

Transgenic Cow

A Dutch biotechnology company called Pharming has genetically engineered cows, outfitting females with a human gene that causes them to express high levels of the protein human lactoferrin in their milk

Transgenic Bacteria

Biotechnology

Ethical issues and implications:

Stem Cell Research

More controversy

Genetically modified food (sometimes called Franken Food)

Will it harm us?Will it harm the

environment?Is it the future?

3.05 Evolution

Abiogenesis – Life can come from

non lifeExamples: flies from

meatMice from ragsFrogs and insects

from mud

Biogenesis

Francesco Redi used flies, meat and screens to disprove abiogenesis.

Biogenesis

Louis Pasteur used specially made flasks and broth to prove biogenesis

Theory of Natural Selection

Charles Darwin

Naturalist on the British Ship the HMS Beagle

The Voyage

Galapagos

Iguanas and Tortoises

Finches and Boobies

Early earth

Hypothesis that the first organisms to evolve were

ANAEROBIC &HETEROTROPHIC &PROKARYOTIC

Early Earth - Experiments

Experiment:Sparks (lightning)Gasses (volcanoes)Water droplets (rain)Heat (geothermal)NO OXYGEN

1 week = amino acids

Evolution of eukaryotic cells

Evolution of aerobic and photosynthetic organisms

1. Prokaryotic anaerobic heterotrophic organisms

2. Prokaryotic autotrophs started to produce oxygen and change the ancient atmosphere

3. Eventually enough oxygen was present in the atmosphere to promote the evolution of aerobic organisms

Evidence for Evolution

Fossils

Biochemicalsimilarities

Shared anatomicalstructures

Patterns in the fossil record

What can they tell us?

The most primitive organisms are the oldest.

The most advanced organisms are the youngest.

Fossilization

Relative Dating

Finding the age by comparing the fossil to the rocks or fossils near by.

Fossilization

Absolute

Dating

Using

radioactive isotopes to

determine age.

Biochemical similarities

Similar Structures

Similarembryologicaldevelopment canshow closeevolutionaryrelationships.

Similar Structures

Four different mammal limbs have the same basic bone structure.

Mechanisms of Evolution

Variation (provides material)

Geographic Isolation

Environment (selection pressures)

Peppered Moth

Variation provides material for natural selection.

Geographic Isolation

Examples: Kaibab squirrel (top) and the Albert squirrel (bottom) from the Grand Canyon

Galapagos finches

Australia’s marsupials

Natural SelectionRecent Examples

Resistance to Pesticides