Take out a blank sheet of paper On the paper write :

1. your name (first and last)

2. The date today 5/7)

3. The letter of the correct answer to the following question

1. A parent homozygous for Type B blood marries a person with Type AB blood. What is the probability they will have a child with type A blood?

A.0% C. 50%

B. 25%. D. 100%.

Multiple AllelesMultiple Alleles Often each allele has its own effect and Often each allele has its own effect and

the alleles are considered the alleles are considered codominantcodominant..Human ABO Blood typeHuman ABO Blood type

Type Type AA individuals only galactosamine individuals only galactosamine Type Type BB individuals add only galactose individuals add only galactose Type Type ABAB individuals add both sugars individuals add both sugars Type Type O O individuals add neither sugarindividuals add neither sugar

Rh Blood GroupRh Blood Group Rh cell surface markerRh cell surface marker

EpistasisEpistasis

EpistasisEpistasis - Interaction between - Interaction between products of two genes where one gene products of two genes where one gene modifies the other gene’s phenotypic modifies the other gene’s phenotypic expression.expression.Emerson - To produce pigment, a Emerson - To produce pigment, a Zea Zea

maysmays plant must possess at least one plant must possess at least one functional copy of each enzyme gene.functional copy of each enzyme gene.

EpistasisEpistasis

Sex LinkageSex Linkage A trait determined by a gene on the A trait determined by a gene on the

sex chromosome is said to be sex-sex chromosome is said to be sex-linked.linked.– In In DrosophilaDrosophila, sex is determined by the , sex is determined by the

number of copies of the x chromosome.number of copies of the x chromosome.

Heterozygous for red eye color

Eye color gene is carried on the X chromosome

X R X r

What alleles will the sperm have?

What alleles will the eggs have?

X R

Y

X R X R X R X r

X R Y X r Y

Offspring phenotypes

All females have red eyes

½ of the males have white eyes and ½ the males have red eyes

Mutations in Human Mutations in Human HeredityHeredity Mutations are accidental changes in Mutations are accidental changes in

genes.genes.– Rare, random, and usually result in Rare, random, and usually result in

recessive alleles.recessive alleles. Pedigrees used to study heredity.Pedigrees used to study heredity.

– Hemophilia Hemophilia - Inherited condition where - Inherited condition where blood is slow to clot or does not clot at all.blood is slow to clot or does not clot at all.

Only expressed when individual has no copies of Only expressed when individual has no copies of the normal allele.the normal allele.

Royal Hempohilia - Sex-linkedRoyal Hempohilia - Sex-linked

Sickle-Cell AnemiaSickle-Cell Anemia

Sickle-Cell Anemia is a recessive Sickle-Cell Anemia is a recessive inherited disorder in which inherited disorder in which afflicted individuals have afflicted individuals have defective hemoglobin, and thus defective hemoglobin, and thus are unable to properly transport are unable to properly transport oxygen to tissues.oxygen to tissues.

Heterozygotes usually appear normal.Heterozygotes usually appear normal. Homozygotes have Sickle-Cell, but are Homozygotes have Sickle-Cell, but are

resistant to malaria.resistant to malaria.Copyright © McGraw-Hill Companies Permission required for reproduction or display

Other DisordersOther Disorders

Tay-SachsTay-Sachs– Incurable heredity disorder which causes Incurable heredity disorder which causes

brain to deteriorates.brain to deteriorates. Nonfunctional form of hexosaminidas A enzyme.Nonfunctional form of hexosaminidas A enzyme.

Huntington’s DiseaseHuntington’s Disease– Inherited condition caused by dominant Inherited condition caused by dominant

allele causing progressive brain allele causing progressive brain deterioration.deterioration.

Symptoms usually develop late in life.Symptoms usually develop late in life.

Genetic Counseling Genetic Counseling and Therapyand Therapy Process of identifying parents at Process of identifying parents at

risk of producing children with risk of producing children with genetic defects and assessing genetic defects and assessing genetic state of early embryos.genetic state of early embryos.– AmniocentesisAmniocentesis– UltrasoundUltrasound– Chorionic Villi SamplingChorionic Villi Sampling

Pedigree AnalysisPedigree Analysis

Mendel’s laws allow us to analyze the genetic Mendel’s laws allow us to analyze the genetic information in family records (information in family records (pedigreespedigrees))

From this we can determine the nature of alleles From this we can determine the nature of alleles that control traits. From this we can:that control traits. From this we can:deduce whether the trait is dominant or deduce whether the trait is dominant or

recessiverecessivededuce whether the trait is sex linked deduce whether the trait is sex linked deduce the genotypes of members of the family deduce the genotypes of members of the family predict the phenotypes of future offspringpredict the phenotypes of future offspringdeduce the genotypes of parents from their deduce the genotypes of parents from their

offspring phenotypesoffspring phenotypes

In a pedigree, each individual In a pedigree, each individual is represented by a symbolis represented by a symbol

The shape, color, and The shape, color, and location of the symbol carry location of the symbol carry information about the sex information about the sex and phenotype of the and phenotype of the individualindividual

In a pedigree, each individual In a pedigree, each individual is represented by a symbolis represented by a symbol

The shape, color, and The shape, color, and location of the symbol carry location of the symbol carry information about the sex information about the sex and phenotype of the and phenotype of the individualindividual

A dominant allele has a different pattern of A dominant allele has a different pattern of inheritance:inheritance:

A dominant allele has a different pattern of A dominant allele has a different pattern of inheritance:inheritance:

Trait A dominantA a A a

Only a a for recessive trait expression so both parents have to have a recessive allele

Enzymes serve as a catalyst for chemical reactions by lowering the activation energy.

Enzymes also function to control the rate of a reaction.

The laws of thermodynamics dictate that a reaction will not proceed spontaneously unless the molecules that result from the reaction, the products, have lower energy than the molecules that began the reaction, the reactants.

Products: less energy content Products: more energy content

An Energy Diagram of a Reaction: a Plot of State Versus Energy

A plot of the free energy of the reaction vs the course of the reaction:

Original energy state of the reactants

Final energy state of the products (exergonic)

A reaction is a change of state of matter

Energy

Course of the reaction

A-BC-D

A~BC~D

A-CB-D

EA activation energy

G

Spontaneous: ClarificationSpontaneous reactions do NOT just go forward immediately to produce products. This is because the reactants must overcome an activation energy, EA.

Enzymes are protein catalysts that enormously speed up reactions. They often have an “-ase” ending to their name.

e.g., hexokinase, catalase, peptidase, mutase

They are not themselves changed (except for a brief period of time) and are the same before and after a reaction.Enzymes:1.Lower the activation energy: this is the MOST

important characteristic2.Do not add or remove energy from a reaction3.Do not change the equilibrium for a reaction4.Are reused over and over

Enzymes

Enzyme Function

DNA – the heredity DNA – the heredity materialmaterial

Very early it was discovered chromosomes are composed of proteins and DNA. But it took several experiments to conclusively determine specifically which substance made up genes.

Griffith ExperimentDocumented movement of genes from one organism to another (transformation 1928).

– Avery Experiment (1944)Avery Experiment (1944) Removed almost all protein from Removed almost all protein from

bacteria, and found no reduction bacteria, and found no reduction in transforming activity.in transforming activity.

– Hershey-Chase (1952)Hershey-Chase (1952) Used radioactive isotopes to label Used radioactive isotopes to label

DNA and protein. Found genes DNA and protein. Found genes used to specify new generations used to specify new generations of viruses were made of DNAof viruses were made of DNA..

DNA - genetic DNA - genetic materialmaterial Eukaryotes

– DNA located in the nucleus

membrane bound

organelle

Prokaryotes– DNA located in the

nucleoid. No membrane surrounded organelle

Discovering DNA Discovering DNA StructureStructure

DNA made up of nucleotides.DNA made up of nucleotides.– Central sugar, phosphate group, and an Central sugar, phosphate group, and an

organic base.organic base. Purines - Large basesPurines - Large bases

– Adenine and GuanineAdenine and Guanine Pyrimidines - Small basesPyrimidines - Small bases

– Cytosine and ThymineCytosine and Thymine

Nucleotide BaseNucleotide Base

DNA – 4 nucleotide DNA – 4 nucleotide basesbases

4 base nucleotides4 base nucleotidesChargaff’s RuleChargaff’s RuleA =T and G=CA =T and G=C

Discovering DNA StructureDiscovering DNA Structure

Watson Watson and and Crick Crick 1953 1953

&( Wilkins) &( Wilkins) deduced deduced structurstructure of DNA e of DNA as a as a double double helix.helix.

Base Base pairs pairs linkedlinked

5 ‘ end

3 ‘ end

5 ‘ end

3 ‘ end

Double Helix structureDouble Helix structure

two stands of nucleotides

Outer part of the ladder is the sugar-phosphate backbone

Anti-parallel allows for H-bonds between complementary base pairs

H- bonds between base H- bonds between base pairspairs

3 H-bonds 3 H-bonds

Packaging Packaging DNA in the DNA in the nucleusnucleus

DNA ReplicationDNA Replication

Weak hydrogen bonds between base Weak hydrogen bonds between base pairs hold DNA strands together.pairs hold DNA strands together.

Each chain in the helix is a Each chain in the helix is a complimentary mirror image of the complimentary mirror image of the other.other.– Double helix unzips and undergoes Double helix unzips and undergoes

semi-conservative replication.semi-conservative replication. Confirmed by Meselson-Stahl Experiment.Confirmed by Meselson-Stahl Experiment.

Bi-directional Bi-directional replicationreplication

Proofreading by DNA Proofreading by DNA polymerase IIIpolymerase III

Producing proteins from genes is known as gene expression– DNA - RNA - Protein

Gene Expression - Use of information in DNA to direct production of particular proteins.

– Transcription - mRNA molecule is synthesized from gene

within DNA.– Translation - mRNA used to direct protein

production.

Genes to ProteinsGenes to Proteins

DNA vs RNADNA vs RNA

TranscriptionTranscription The RNA copy of a gene used to The RNA copy of a gene used to

produce a protein is called messenger produce a protein is called messenger RNA RNA (mRNA).(mRNA). Essence of gene expression is reading Essence of gene expression is reading

information encoded within DNA and information encoded within DNA and directing protein production.directing protein production.– Each gene is read from a fixed promoter Each gene is read from a fixed promoter

site where RNA polymerase binds to DNA.site where RNA polymerase binds to DNA.– RNA polymerase moves down DNA in RNA polymerase moves down DNA in

three-nucleotide steps (three-nucleotide steps (CodonsCodons).).– Each codon corresponds to a particular Each codon corresponds to a particular

amino acid.amino acid. 64 possible codons64 possible codons

Transcription Transcription Uracil replaces Uracil replaces thyminethymineProduction of mRNA (messenger RNA)Production of mRNA (messenger RNA)

Is all of the DNA Is all of the DNA expressed?expressed?

Codons – triplet codeCodons – triplet code

Translation – Translation – mRNA >> mRNA >> polypeptidepolypeptide

Translation – the Translation – the ribosomeribosome

Translation – the Translation – the ribosomeribosome

Overview of translationOverview of translation