Mechanisms of Evolution: Mechanisms of Evolution: Overview and Cell DivisionOverview and Cell Division

Anthropology 101Anthropology 101

Hybrid CourseHybrid Course

Introduction to GeneticsIntroduction to Genetics

Genetics is the study of genes and the ways whereby Genetics is the study of genes and the ways whereby they determine the traits of an organismthey determine the traits of an organism

We cover the following concepts and principles of We cover the following concepts and principles of evolution based on genetics: evolution based on genetics:

Biological GeneticsBiological Genetics Chromosomes and GenesChromosomes and Genes Mitosis and MeiosisMitosis and Meiosis Population GeneticsPopulation Genetics Molecular BiologyMolecular Biology

Key Concepts in Evolution: Natural Key Concepts in Evolution: Natural SelectionSelection

SpeciesSpecies: A group of life forms (plants and : A group of life forms (plants and animals) that can reproduce fertile offspring animals) that can reproduce fertile offspring among themselvesamong themselves

EvolutionEvolution: Change through time of biological : Change through time of biological speciesspecies

Natural selectionNatural selection: Evolutionary change based : Evolutionary change based on differential reproduction of the species on differential reproduction of the species within an environmentwithin an environment

Key Concepts in Evolutionary Key Concepts in Evolutionary Thought: MutationThought: Mutation

Heredity:Heredity: the transmission of all biological traits the transmission of all biological traits (inherited characteristic) from generation to (inherited characteristic) from generation to generationgeneration

ChromosomeChromosome: Body in the nucleus of the cell that : Body in the nucleus of the cell that contains the hereditary material: DNA and proteincontains the hereditary material: DNA and protein

GenesGenes: A chromosomal segment with a specific : A chromosomal segment with a specific functionfunction

MutationMutation: Alteration of genetic material giving rise : Alteration of genetic material giving rise to new life formsto new life forms

Structure of Cell: DiagramStructure of Cell: Diagram To understand how To understand how

genetics works, we genetics works, we must start with the must start with the cellcell

The next The next discussion follows discussion follows this diagram of a this diagram of a cell and its cell and its componentscomponents

Cell Structure: DescriptionCell Structure: Description CellCell: Smallest unit of the organism : Smallest unit of the organism

considered to be aliveconsidered to be alive NucleusNucleus: Center of the cell, which : Center of the cell, which

contains genetic material contains genetic material (chromosomes, comprising the genes)(chromosomes, comprising the genes)

Nuclear MembraneNuclear Membrane: Membrane : Membrane enclosing the nucleusenclosing the nucleus

CytoplasmCytoplasm: Jellylike material that : Jellylike material that make up the rest of the cellmake up the rest of the cell

Plasma MembranePlasma Membrane: The membrane : The membrane that keeps the cell in shape and allows that keeps the cell in shape and allows entry and exit of certain material.entry and exit of certain material.

The diagram to the left show other The diagram to the left show other specialized parts: nerve cell, white specialized parts: nerve cell, white blood cell, spermblood cell, sperm

Cells: Other PartsCells: Other Parts

Proteins: Proteins: The organic molecules that maintain The organic molecules that maintain the cells’ functionsthe cells’ functions

Organelles: Organelles: functional parts within cytoplasmfunctional parts within cytoplasm RibosomesRibosomes: organelles important to protein : organelles important to protein

synthesis, as we will seesynthesis, as we will see Mitochondria:Mitochondria: organelles responsible for organelles responsible for

energy production; They have their own DNA energy production; They have their own DNA whose regular mutations enable relative dating whose regular mutations enable relative dating within a species, human in this casewithin a species, human in this case

Concepts of GeneticsConcepts of Genetics

Trait: Trait: Any inborn feature of a living organismAny inborn feature of a living organism Each organism contains a pair of Each organism contains a pair of genesgenes for each trait for each trait Each Each genegene may have two or more may have two or more alleles (variants)alleles (variants) Monogenic Trait: Monogenic Trait: a trait coded by one gene for each a trait coded by one gene for each

trait (e.g., phenylthiocarbamide [PTC] taster vs. trait (e.g., phenylthiocarbamide [PTC] taster vs. nontaster of the bitterness of Brussels sprouts);nontaster of the bitterness of Brussels sprouts);

Mendelian Trait: Mendelian Trait: This is a synonym forThis is a synonym for Monogenic Monogenic traittrait

Polygenic: Polygenic: a trait coded by more than one gene (e.g. a trait coded by more than one gene (e.g. skin color, eye color)skin color, eye color)

Genes and ChromosomesGenes and Chromosomes

In the cell nucleus is genetic material which In the cell nucleus is genetic material which determines our traits. determines our traits.

ChromosomesChromosomes are long strands of are long strands of moleculesmolecules and and protein; they come in pairsprotein; they come in pairs

Humans have 23 pairs of chromosomes, or 46 in allHumans have 23 pairs of chromosomes, or 46 in all GenesGenes are units within chromosomes are units within chromosomes Also in pairs, they occur in specific location, or Also in pairs, they occur in specific location, or lociloci, ,

of the chromosomesof the chromosomes Each variant of a trait is determined by an Each variant of a trait is determined by an alleleallele of a of a

genegene

Genetic Composition: GenotypeGenetic Composition: Genotype

GenotypeGenotype: Alleles of a gene possessed by an : Alleles of a gene possessed by an organismorganism

HomozygousHomozygous: Having two of the same allele : Having two of the same allele in a gene pairin a gene pair

HeterozygousHeterozygous: Having two different alleles in : Having two different alleles in a gene paira gene pair

Genetic Appearance: PhenotypeGenetic Appearance: Phenotype

PhenotypePhenotype: Observable characteristics of an : Observable characteristics of an organismorganism

DominantDominant: Allele of a pair that is expressed in the : Allele of a pair that is expressed in the phenotype (e.g. PTC taster)phenotype (e.g. PTC taster)

RecessiveRecessive: Allele of a pair that is expressed only : Allele of a pair that is expressed only when homozygous (e.g. PTC nontaster, Blood Type when homozygous (e.g. PTC nontaster, Blood Type O)O)

CodominantCodominant: Both alleles of a pair are expressed in : Both alleles of a pair are expressed in the phenotype (e.g., Blood Type A and B)the phenotype (e.g., Blood Type A and B)

Or four o’clock flowers: red, white—and pinkOr four o’clock flowers: red, white—and pink

Cell DivisionCell Division

Cell division is a constant process in all living forms.Cell division is a constant process in all living forms. There are two types of cell division: There are two types of cell division: Mitosis: Mitosis: The division of The division of somatic somatic or body cellsor body cells Meiosis: Meiosis: The division of The division of gametes gametes or sex cells: or sex cells: sperm sperm

in the males of any species and in the males of any species and ovum ovum (plural (plural ovaova) or ) or egg in the females of any speciesegg in the females of any species

The next sections explain how these two types of The next sections explain how these two types of cells divide. Refer to the diagram in the next panelcells divide. Refer to the diagram in the next panel

Mitosis: First PhasesMitosis: First Phases

In theIn the interphase interphase, the cell is “at rest” between one division and the next, the cell is “at rest” between one division and the next In the In the prophaseprophase, the chromosome double, from 46 (23 pairs) , the chromosome double, from 46 (23 pairs)

chromosomes to 92 (46 pairs)chromosomes to 92 (46 pairs) They appear to “thicken” as each chromosome replicates itself.They appear to “thicken” as each chromosome replicates itself. The chromosomes are attached to each other at the center, forming an x; The chromosomes are attached to each other at the center, forming an x;

these are known as these are known as centromerescentromeres

Mitosis: Middle PhasesMitosis: Middle Phases

In the In the prometaphase prometaphase the nucleus dissolves, the chromosomes line the nucleus dissolves, the chromosomes line up in the center, up in the center, centriolescentrioles form at the opposite end of the cells, and form at the opposite end of the cells, and spindle spindle fibersfibers (fibrils or microtubules) form between the (fibrils or microtubules) form between the centromerescentromeres of the chromosomes and the of the chromosomes and the centriolescentrioles (top diagram) (top diagram)

In the In the metaphase, metaphase, the chromosomes are lined up and the centrioles the chromosomes are lined up and the centrioles prepare to pull each new pair of chromosomes toward them using prepare to pull each new pair of chromosomes toward them using the spindle fibers)the spindle fibers)

Mitosis: End PhasesMitosis: End Phases In the In the anaphase,anaphase, the fibrils the fibrils

anchored by the centrioles anchored by the centrioles pull the chromosomes pull the chromosomes toward the center of each toward the center of each new cellnew cell

In the In the telophase, telophase, the fibrils the fibrils and the centrioles dissolve and the centrioles dissolve and the wall forms between and the wall forms between the two new cellsthe two new cells

In In cytokinesiscytokinesis, the walls are , the walls are completely formed and the completely formed and the two new cells are in two new cells are in interphase.interphase.

Meiosis: Introduction and TermsMeiosis: Introduction and Terms

Meiosis Meiosis refers to cell division of a fertilized egg in refers to cell division of a fertilized egg in the reproductive process.the reproductive process.

GametesGametes: sex cells: sex cells SpermSperm: male sex cells: male sex cells OvumOvum: female sex cells: female sex cells Each gamete (sex cell)Each gamete (sex cell) Contains half the normal number of chromosomes in Contains half the normal number of chromosomes in

cellscells Contains 23 chromosomes in humansContains 23 chromosomes in humans

Meiosis: Fertilization of an Meiosis: Fertilization of an OvumOvum

First, the sperm has fertilizes an First, the sperm has fertilizes an ovum (above left)ovum (above left)

Three million sperms enter the Three million sperms enter the vagina; only one ultimately enters the vagina; only one ultimately enters the ovum, roughly a third of the way ovum, roughly a third of the way down the Fallopian tubedown the Fallopian tube

The fertilized ovum (now a The fertilized ovum (now a zygotezygote) is ) is then implanted in the uterusthen implanted in the uterus

The rapid process of The rapid process of meiosis meiosis begins begins therethere

Of course, some couples don’t get it Of course, some couples don’t get it quite right (below left)quite right (below left)

Meiosis I: Beginning PhasesMeiosis I: Beginning Phases

In the prophase stage, the doubled chromosomes cross over, so some of the In the prophase stage, the doubled chromosomes cross over, so some of the genes on one chromosome moves over to the other chromosome—and vice genes on one chromosome moves over to the other chromosome—and vice versaversa

Otherwise, the process is the same as mitosisOtherwise, the process is the same as mitosis The prometaphase follow the same process as in mitosis: the chromosomes The prometaphase follow the same process as in mitosis: the chromosomes

line up and the spindle fibers and centrioles are now in position. line up and the spindle fibers and centrioles are now in position.

Meiosis II: Early Middle PhasesMeiosis II: Early Middle Phases

The first metaphase continues as mitosis; the chromosomes The first metaphase continues as mitosis; the chromosomes have been doubled and now line up.have been doubled and now line up.

The anaphase continues as in mitosis; the chromosomes are The anaphase continues as in mitosis; the chromosomes are pulled apart by the spindle fibers and the centriolespulled apart by the spindle fibers and the centrioles

The telophase continues as in mitosis; the chromosomes are The telophase continues as in mitosis; the chromosomes are centered in the daughter cells and a new wall forms.centered in the daughter cells and a new wall forms.

Meiosis III: Late Middle PhasesMeiosis III: Late Middle Phases

In the interphase 2, the chromosomes remain lined up and the nucleus has In the interphase 2, the chromosomes remain lined up and the nucleus has not formednot formed

In metaphase 2, there is only a pair of chromosomes in each cell; they In metaphase 2, there is only a pair of chromosomes in each cell; they remain lined up and the spindle fibers and the centrioles go into positionremain lined up and the spindle fibers and the centrioles go into position

In anaphase 2, the chromosomes (now numbering 23 as In anaphase 2, the chromosomes (now numbering 23 as haploidshaploids) are ) are pulled apart. pulled apart.

Meiosis IV: Final PhasesMeiosis IV: Final Phases

In telophase 2, a wall forms between each of the cells and the In telophase 2, a wall forms between each of the cells and the nuclei start to formnuclei start to form

In cytokinesis or interphase, the daughter cells remain with In cytokinesis or interphase, the daughter cells remain with one pair of chromosomes. one pair of chromosomes.

On fertilization, the sperm will contribute half the On fertilization, the sperm will contribute half the chromosomes and the ovum contributes half to the offspringchromosomes and the ovum contributes half to the offspring

End of Meiosis; Beginning of Mitosis: End of Meiosis; Beginning of Mitosis: Fertilization of an OvumFertilization of an Ovum

When the couple copulates, the sperm When the couple copulates, the sperm fertilizes the egg (upper left)fertilizes the egg (upper left)

In so doing, each parent contributes In so doing, each parent contributes exactly half of the chromosomes of exactly half of the chromosomes of the offspring cellthe offspring cell

Three million sperms enter the Three million sperms enter the vagina; only one ultimately enters the vagina; only one ultimately enters the ovum, roughly a third of the way ovum, roughly a third of the way down the Fallopian tubedown the Fallopian tube

The fertilized ovum (now a The fertilized ovum (now a zygotezygote) is ) is then implanted in the uterusthen implanted in the uterus

The rapid process of The rapid process of mitosis of the mitosis of the zygote zygote begins therebegins there

Of course, some couples don’t get it Of course, some couples don’t get it quite right (lower left) quite right (lower left)