2 Types of CellsRecall that there are two types of cells in multicellular organismsSomatic cells- all body cells (liver, lungs, etc.) with the exception of sex cells Gametes- sex cells such as egg and sperm which are responsible for passing on our genes

ChromosomesThe somatic cells of each species has a characteristic number of chromosomes per cellChromosome number is not related to complexityA type of fern has 1200Fruit flies have 8Humans have 46

KaryotypesHow did we learn this information about human chromosomes?Karyotypes- pictures of the chromosomes from a somatic cellThis shows normal humans have 46 chromosomes

Human CellsHuman somatic cells are diploid-chromosomes are in pairs (23 pairs for humans=46)

Human gametes, egg and sperm, are haploid-no pairs (only 23 single chromosomes)

Homologous ChromosomesHomologous chromosomes pairs of chromosomes in somatic cells that have the same length and same types of genes In each of our 23 pairsour moms egg contributed one chromosome our dads sperm contributed the other Homologous ChromosomesNote the numbering system for the homologous pairs

Types of ChromosomesThere are two types of chromosomes Autosomes- the chromosomes pairs 1-22 whose DNA codes for characteristics not directly related to the sex of the organismSex chromosomes- the 23rd pair (X, Y) in humans that have genes that directly control the development of sexual characteristicsXX femaleXY male

Cell Division1. Binary fission-cell division in prokaryotes2. Cell Cycle (with Mitosis)-cell division in eukaryotes to form new somatic cells3. Meiosiscell division in eukaryotes to form gametes (egg and sperm)

How Are Gametes Formed? Meiosis--cell division that produces sex cells called gametes from somatic cells in testes and ovaries 1 REPLICATION AND 2 DIVISIONS 46 chromosomes ---------- 23 chromosomes diploid (pairs) MEIOSIS haploid (no pairs)1 somatic (body) cell 4 gametes (sex cells) START END

HAPLOID GAMETE (EGG)23 CHROMOSOMES + =HAPLOID GAMETE (SPERM)23 CHROMOSOMESFIRST DIPLOID SOMATIC CELL OF BABY46 CHROMOSOMES IN PAIRS!!!!

With meiosis cells go from 46 23 chromosomes and the result is: your moms egg (23 chromosomes) + your dads sperm (23 chromosome) first cell of you (46 chromosomes)

WITHOUT MEIOSIS to go from 46 23 chromosomes then it would beyour moms egg (46 chromosomes) + your dads sperm (46 chromosomes) 92 AND NO YOU!!!!!!!!!!

4623232323Spermatogonium in testesSPERM

4623Oogonium in ovariesPolar Bodies(not functional)Egg

23testescellovary cellsperm produced by meiosisfertilizationzygoteova (egg) produced by meiosis but only one develops tomaturity

Cell division continues by the cell cycle (with mitosis), so all the cells willcontain 46 chromosomesearly embryo16

Genetic Diversity in GametesThere is great genetic diversity of the egg and sperm one parent can make due to two processes that occur during meiosisCrossing-over-chromosomes cross and exchange piecesIndependent assortment-chromosomes of each pair are randomly distributed to each egg or spermIndependent assortment and gamete diversity

GeneticsGenetics-study of inherited traitsHeredity-passing of traits from parents to offspring Trait-feature of an organism that can be passed on to offspring ex) hair color, eye color, etc

What Determines Traits?

Genes!Genes-segments of DNA on chromosomesthat code for a protein which produces a traitThere are 1000s of genes on each chromosome Gene Protein Trait

TraitsSome traits are coded for by one gene which codes for one protein causing a trait.i.e. freckles, earlobe attachment, etcprotein

Polygenic traits traits coded for by many genes togetherMore than one gene=more than one protein that causes the trait so complex variation in that traitHand span, height, eye color, etc.Traits

Your Cells Have Two CopiesRecall that your chromosomes are in pairs:Mom contributed one and Dad contributed other of each pair This means each somatic cell has two copies of each chromosome, and therefore, each gene So when we talk about your genes, we must consider BOTH copies you received

AllelesThe same gene can have many versionsAlleles - forms of genes written as lettersF allele codes for freckles f allele codes for no freckles Allele for freckles--FAllele for no frecklesf Position on chromosomes where freckle presence gene is located

FROM FROM MOM DADONE OF YOUR CHROMSOME PAIRSFRECKLE GENE IN ADDITIONTO MANY OTHERS

Genotype vs. PhenotypeGenotype- the genetic makeup of an organism Written as 2 letters-one copy from each parentFF, Ff, or ffPhenotype- the physical traits the organism showsWritten as descriptive wordsFreckles or no freckles

***Phenotype = Genotype + Environment

Genotypes

Homozygous genotype- (purebred) receiving two identical alleles for a particular trait from your parents i.e. Freckle presence gene Alleles F=freckles and f=noneHomozygous: FF or ffHeterozygous genotype (hybrid) receiving two different alleles for a particular trait from your parentsHeterozygous: ________?

Genotypes

Homozygous genotype- (purebred) receiving two identical alleles for a particular trait from your parents i.e. Freckle presence gene Alleles F=freckles and f=noneHomozygous: FF or ffHeterozygous genotype (hybrid) receiving two different alleles for a particular trait from your parentsHeterozygous: ____Ff____?

FFFfff Mom Dad Mom Dad Mom Dad Possibility #1 Possibility #2 Possibility #3

What About the Heterozygous Genotype?FF genotype = ____________ phenotype?ff genotype = _____________phenotype?What about Ff phenotype?As it turns out, the allele coding for freckles, F, dominates over the alleles coding for no freckles, f.The heterozygous genotype, Ff, results in a round phenotype, (freckles)

Dominant allele form of trait that overcomes others and written as a capital letter-i.e. FRecessive alleleform of trait that is hidden in the presence of a dominant one and written as a lower case letter-i.e. f

FFFfff Mom Dad Mom Dad Mom Dad

GenotypeExample PhenotypeHomozygous DominantFrecklesNo frecklesHeterozygous

GenotypeExample PhenotypeHomozygous DominantFFFrecklesHomozygous RecessiveffNo frecklesHeterozygousFfFreckles

So What?How can we use this information on meiosis and genetics?If we know parents genotypes, we can figure out the genotype possibilities of their childrenIt can be used to determine how likely you and your spouse are to have children with freckles, their blood type, or the possibility of passing on a disease to them among other things

Genetics PredictionsTo determine possible genotypes of offspring, we use Punnett squaresPunnett squares -figures used to determine genotype and phenotype probabilities of offspring based on the parents genotypes.For example, if you crossed two heterozygous parents who have freckles, would their kids all have freckles, just some, or none at all? FfParent #2gametesFfParent #1 gametes

Practice

Trait: Number of fingersAlleles: F or f Dominant: F codes for polydactyly so person has more than 5 fingers or toes.

Recessive: f codes for normal five fingers or toes

Use a Punnett square to cross a normal parent with a heterozygous parent. What are their chances of having a child with polydactyly?

GenotypeExample PhenotypeHomozygous DominantFFHomozygous RecessiveFive fingersHeterozygous

Early Ideas - HeredityGregor Mendel was an Austrian monk who decided to run experiments on pea plantsHis data revealed patterns of inheritanceFather of geneticsIt was originally believed a childs traits were the result of blending between parents traitsNothing was known about DNA!

Mendels Pea PlantsWhy did Mendeluse pea plants?1. Peas had several contrasting traits he could observe easily2. He understood their method of reproduction3. They reproduced quickly4. They can self-pollinate

Reproduction in PlantsPlant cells undergo meiosis, just like animals, to create plant gametesPlant sperm =pollen Plant egg = ovule

Reproduction in PlantsPollination Pollen released Pollen fertilizes the ovulesSimilar to fertilization in animals Mendel could control how plants were fertilized because he understood this processPollination Animation

pollen ovum (egg)nucleicombinecell cycle (with mitosis)embryo formedPLANTspermovum(egg)nuclei combinecell cycle (with mitosis)embryoformedANIMAL3

Mendels Experiments Mendel let certain pea plants mate, or crossHe controlled and documented each generations traitsParental generation (P) original group mated First filial generation(F1) offspring of the parental cross Second filial generation (F2) offspring of crossing two F1 plants

Mendels ResultsKey to Mendels understanding was that he looked at the results of each trait individually (i.e. flower color)Mendel realized that blending was NOT happening and there were characteristic patterns of inheritance

Mendels ConclusionsRule #1: Principle of Dominance- one allele can dominate so trait coded by other allele hidden. i.e. R dominates over r when both presentBecause we know this, we represent the round allele with a capital R.

Mendels Conclusions

Law of Segregation- when gametes form, the two copies of our genes are separated so each parent gives only one in their egg or sperm This gave us the idea of meiosis and how gametes are formed!

Pea Parent 1: Pea Parent 2: Rr Rr

R or rR or rgametesgametesmeiosismeiosis

Mendels Conclusions Mendel saw pea plants with round peas and purple flowers, and pea plants with round peas and white flowersMendels Law of Independent Assortment- inheritance of one trait will not affect inheritance of anotherChromosomes and the genes on them most of the time are not tied together so we get a tremendous genetic mixture in a species!Everyone with brown hair does not have blue eyesEveryone who is left handed doesnt have hairy feet

Rules of Genetics

Genetics Rules After MendelRule #1 Principle of DominanceRule #2: Incomplete dominance -some alleles arent completely dominant so they BLEND Rule #3: Codominance -some alleles dominate together so BOTH ARE SEENRule #4: Sex-linked genes -ALL alleles on a males X chromosome (X-linked) are expressed

Complete DominanceRule #1: Some alleles completely dominate over others:B= brown eyesb=blue eyesBb= brown eyes, so B is completely dominant.One allele capital, the other lower case

Incomplete DominanceRule #2: Some alleles DONT COMPLETELY DOMINATE, so they blend:R= red flowersr= white flowersRr = pink flowersOne allele capital, the otherlower case

PINK FLOWERS!!! BLENDING!!!

CodominanceRule #3: Some alleles dominate TOGETHER so they BOTH are shownH = brown hair on horsesH = white hair on horsesHH = both brown and white hairs, so the horse is roan color.Blood types are like this, too.

Antigens-markers on cells Blood type determined by your markers on your red blood cells4 blood group phenotypes:Type A has A antigensType B has B antigensType AB has A and B antigensType O has no antigensBlood Types

Multiple AllelesMultiple alleles- 3 different forms of the gene code for blood types IA, IB, and iAllele IA codes for A antigen IB codes for B antigeni codes for none

Multiple Alleles6 blood group genotypesComplete dominance- IA and IB dominate over iCodominance- IAIB genotype shows BOTH A and B antigensBoth alleles that codominate are written with capital letters!

AntibodiesYour bodys immune systems creates antibodies against anything foreignAntibodies-proteins produced by your immune system to fight off things that look foreignType A--makes anti-B antibodiesType B--makes anti-A antibodiesType AB--makes NO antibodies universal receiverType O--makes anti-A and anti-B antibodies universal donor

Sex-Linked GenesRule #4: sex-linked genes: ALL alleles on a males X chromosome (X-linked) are expressedMale sex chromosomes?_________Female sex chromosomes?_________We also call sex-linked genes by another name, X-linked, because the X chromosome has the majority of the genes

Sex-Linked GenesIn males, EVERY gene on their X chromosome is expressed. The Y doesnt have the same genesIn females this is not the case because they have another copy on their other X chromosome to overcome it Genes: 1000 1000 1000 45

Sex-Linked GenesExamples of sex-linked disorders:ColorblindnessHemophiliaFragile X SyndromeDuchene Muscular Dystrophy Cleft PalateVitamin D Resistant Ricketts3 types of deafnessMale Pattern BaldnessX-linked recessive disorder

Who doesa boy get his Y chromosome from?His X?

Sex-Linked GenesGenes that occur on sex chromosomes are written with Xs and Ys to show this special situation.I.e. red-green colorblindness is a recessive trait. It is found on the X chromosome, not the Y. We write the alleles this way:XC = colorblindnessXC = normalThe slash indicates it is a lower case letter so there is no confusion

4 Sex-Linked Traits:1. Normal Color Vision: A: 29, B: 45, C: --, D: 262. Red-Green Color-Blind: A: 70, B: --, C: 5, D: --3. Red Color-blind: A: 70, B: --, C: 5, D: 64. Green Color-Blind: A: 70, B: --, C: 5, D: 2

Sex-Linked GenesTry to complete this table:

PhenotypesGenotypesNormal MaleColorblind MaleNormal FemaleNormal carrier FemaleColorblind female

Sex-Linked GenesTry to complete this table:

PhenotypesGenotypesNormal Male XCYColorblind Male XCYNormal Female XCXCNormal carrier Female XCXCColorblind female XCXC

Two Types of Mutations

Either type of mutation can involve autosomes (chromosomes 1-22) or sex chromosomes (X & Y)Gene mutation- single genes nucleotide sequence affected, and therefore the protein it codes for is defectiveChromosomal mutation- missing or extra chromosome and ALL of its genes from incorrect chromosome split during meiosis

Gene MutationsThis type of mutation determined by sequencing the DNA from a persons cellsInsertionSubstitutionDeletionInsertionDeletionSubstitution

Chromosomal MutationsThis type of mutation is determined by creating a karyotype, or picture of chromosomes, from a persons cellMonosomyhaving one less chromosome (45)Trisomyhaving an extra chromosome (47)Deletionmissing part of a chromosomeNondisjunction

What is a Karyotype?Karyotype- picture of the chromosomes in a somatic cell46 chromosomes in a normal, human karyotype

What can be determined from looking at a karyotype?1.) Sex of the individualSex chromosomes -either XX (female) or XY (male)Autosomes-all chromosomes except sex chromosomes2.) Chromosomal mutations

What can be determined from looking at THIS karyotype?

What can be determined from looking at THIS karyotype?A trisomy called Klinefelters Syndrome--male

AmniocentesisMethod for obtaining fetal cells to check for defectsThis is a risky procedure and should ONLY be performed on women who:Are in their mid 30s or olderHave had a previous child with a chromosomal defect

Types of Genetic DisordersThere are two types of disorders, depending on what DNA is affectedSex-linked disorders- caused by affected DNA of the sex chromosomes (the 23rd pairX or Y) Autosomal disorders- caused by affected DNA of the autosomes (pairs 1-22)

Sex-Linked DisordersSex-linked disorder disease involving the sex chromosomes or a gene on themRecessive gene on the X chromosome is more likely to be expressed in males because there is no second XAlleles written as XA, Xa or XB, Xb etc.

Sex-Linked Disorders1- Color BlindnessX-linked recessive disorderGene mutation on X chromosome1 of 10 males2- Hemophilia X-linked recessive disorderGene mutation on X chromosome. 1 of 5,000 males Interfere with normal blood clotting

ONLY THE SEX CHROMOSOMESARE INVOLVED

Sex-Linked Disorders3- Klinefelter Syndrome (XXY)1 of 1,000 males. Trisomy- extra X chromosome so chromosomal mutation

Sex-linked Disorders4- Turners Syndrome (XO)1 of 10,000 femalesMonosomy- one of X chromosomes is either missing or inactive so chromosomal mutationHave immature female appearance and lack internal reproductive organs

Autosomal Disorders Autosomal disorder - disease involving the 22 pairs of chromosomes that are NOT sex chromosomes (X,Y) and any genes on themAlleles written as A, a or B, b etc.

AaAaAaaaAaAA

Autosomal Disorders1- Cystic FibrosisRecessive disorderMutated gene on chromosome 17Characterized by excessive, THICK secretion of the mucus in the body

Autosomal Disorders2- Huntington DiseaseDominant disorder Mutated gene on chromosome 4 is responsible. Causes degeneration of neurons producing dementia, and random jerking movements

Autosomal Disorders3- Phenylketonuria (PKU)Recessive disorder Mutated gene on chromosome 12 Mental retardation can result due to lack of ability to breakdown phenylketones4- Sickle-Cell Anemia1 of 12 U.S. African Americans Recessive disorderMutated gene on chromosome 11Blood clots

Autosomal Disorders5- Tay-sachs DiseaseRecessive disorder European Jewish ancestryMutated gene on chromosome 15 Tay-sachsOne Wrong Letter

Autosomal Disorders6- Down Syndrome1 in 1,000 live births Trisomy-extra Chromosome 21 so chromosomal mutation Risk increases with moms ageMild to severe mental retardation

GENETIC DISORDERSAutosomal DisordersChromosomes 1-22Sex-Linked DisordersSex Chromosomes X and Y

Gene Mutations1 gene mutatedon chromosomes 1-22Alleles: A, a or B, b, etc.

ChromosomalMutationsExtra or missing chromosome 1-22shown by karyotypeGene Mutations1 gene mutatedon X chromosomeAlleles: XA, Xa or XB, Xb etc.

ChromosomalMutationsExtra or missing sex chromosomeshown by karyotype

EXAMPLES?

How Do We Know About Our Genes?Human Genome ProjectBegan in 1990; complete 2003Goals:Determine complete sequence of the 3 billion DNA bases in human DNAIdentify all human genes for further biological study

The UnknownGene number, exact locations and functionsGene regulationDNA sequence organizationChromosomal structure and organization

Ethical, Legal and Social IssuesFearsGenetic information used to harm or discriminateDeny access to health insuranceDeny employmentDeny educationDeny loans?Cloning?DNA Databases

CloningCloning -creating many genetically identical cellsfrom one cellCreation of genetically identical organisms

Why Clone Animals?To answer questions of basic BiologyFive genetically identical cloned pigs.For herd improvement. To satisfy our desires (i.e. pet cloning) For pharmaceutical production.

Is Animal Cloning Ethical?The first cloned horse and her surrogate mother/genetic twin.As with many important questions, the answer is beyond the scope of science.

BiotechnologyDolly and surrogate MomGenetically modified rice.Embryonic stem cells and gene therapyBiotechnologyVideo

*Human body cells contain 46 chromosomes, but the gametes contain only 23.At fertilisation, the number is restored to 46.In humans and most other mammals, the ovum mother cell produces four cells by meiosis but only one of these goes on to become a gamete.******