DNA in the CellDNA in the Cell

Inside the nucleus are chromosomes, which house DNAChromosome made from proteins + histones. Coils DNA so it can fit into a cellEach chromosome consists of identical halves called chromatidsCenter of the chromosome is called the centromere

Number & Types of Number & Types of ChromosomesChromosomes

Sex chromosomes determine the sex of an organismSex chromosomes determine the sex of an organismXX = femaleXX = femaleXY = Male XY = Male All other chromosomes are called autosomesAll other chromosomes are called autosomes

Homologous ChromosomesHomologous ChromosomesEach organism gets two copies of each autosome; 1 from mom and 1 from Each organism gets two copies of each autosome; 1 from mom and 1 from dad (46 total chromosomes; 23 pairs in humans)dad (46 total chromosomes; 23 pairs in humans)

Each 2 paired chromosomes are called homologous chromosomesEach 2 paired chromosomes are called homologous chromosomes

Homologous chromosomes carry genes for the same traitsHomologous chromosomes carry genes for the same traits

Homologous ChromosomesHomologous Chromosomes

How Many Chromosomes?

CARP- 104

ELEPHANT-56

KANGAROO-12

PINEAPPLE-50

SHRIMP-92

ADDER’S TONGUE FERN-1200

Diploid & Haploid CellsDiploid & Haploid Cells

Diploid Cells Diploid Cells Cells with 2 copies of each chromosome Cells with 2 copies of each chromosomeHaploid Cells Haploid Cells Cells with 1 copy of each chromosome Cells with 1 copy of each chromosomeMost cells in the body are diploidMost cells in the body are diploidSex cells (sperm & egg) are haploidSex cells (sperm & egg) are haploid

Diploid & Haploid CellsDiploid & Haploid Cells

Why Do Cells Divide?Why Do Cells Divide?

1.1. Get too big (take in more nutrients than they can metabolize)Get too big (take in more nutrients than they can metabolize)2.2. Death/ Need replacementDeath/ Need replacement3.3. Surface to volume ratio; too much volume, not enough surfaceSurface to volume ratio; too much volume, not enough surface

When do cells divide?When do cells divide?Depends on the type of cell (days, weeks, months, some never divide) Depends on the type of cell (days, weeks, months, some never divide) Cell Cycle Cell Cycle Cells will grow, replicate, and die Cells will grow, replicate, and die

Cell Division in ProkaryotesCell Division in Prokaryotes

Prokaryote Prokaryote unicellular bacteria with no nucleus unicellular bacteria with no nucleus

Binary Fission Binary Fission DNA is replicated, cell doubles in size DNA is replicated, cell doubles in size and splitsand splits

Stages of Cell Cycle in Stages of Cell Cycle in EukaryotesEukaryotes

Interphase Interphase Growth Phase Growth Phase

G1 G1 Cell growth Cell growth

S S Synthesis/ Replication of DNA Synthesis/ Replication of DNA

G2 -> Final growthG2 -> Final growth

Mitosis Mitosis DNA, which has DNA, which has

been replicated (remember last unit?) been replicated (remember last unit?)

needs to be distributed equally needs to be distributed equally

to each new cellto each new cell

Stages of MitosisStages of Mitosis

ProphaseProphase

Chromatin condenses (chromosomes) & nucleus disappearsChromatin condenses (chromosomes) & nucleus disappears

Spindle fibers (microtubules) form & move chromosomesSpindle fibers (microtubules) form & move chromosomes

MetaphaseMetaphase

Spindles align chromosomes in the middle of the cellSpindles align chromosomes in the middle of the cell

AnaphaseAnaphase

Centromeres divide and sister chromatids splitCentromeres divide and sister chromatids split

Chromatids move toward opposite polesChromatids move toward opposite poles

TelophaseTelophase

Chromosomes arrive at opposite ends of cellChromosomes arrive at opposite ends of cell

Nucleus reappearsNucleus reappears

Spindle disappearsSpindle disappears

Cell splits (cytokinesis)Cell splits (cytokinesis)

Stages of MitosisStages of Mitosis

CytokinesisCytokinesis

Animal Cell cleavage furrow pinches one cell into 2 cells

Plant Cell cell plate makes new cell wall; cell splits

Mitosis AnimationMitosis Animation

Additional Mitosis Additional Mitosis VocabularyVocabulary

G0 Phase Cell is neither growing or dividing

Centrioles Create Ropes that pull chromosomes around the cell (make

spindle fibers)

Difference Between Plant Difference Between Plant Cell & Animal Cell MitosisCell & Animal Cell Mitosis

•Plant cells are surrounded by a tough outer case Plant cells are surrounded by a tough outer case called a cell wallcalled a cell wall•Animal cells are surrounded by a soft outer case Animal cells are surrounded by a soft outer case called a cell membranecalled a cell membrane•The first 3 stages of mitosis in plant and animal cells The first 3 stages of mitosis in plant and animal cells are the sameare the same

TelophaseTelophase

Animal Cell Animal Cell Formation of a cleavage furrow Formation of a cleavage furrow

Plant Cell Plant Cell Formation of cell plate Formation of cell plate

Meiosis VocabularyMeiosis Vocabulary

•Diploid Cells cells with 2 of each type of chromosome (1 from mom and 1 from dad)

•n= number of pairs of chromosomes

•Diploid Cells = 2n

•Zygote = fertilized egg

•Gametes= haploid sex cells

•Fertilization= union of egg and sperm

•Sexual Reproduction Parents generate specialized sex cells

MeiosisMeiosis

Getting from diploid to haploid cells: Meiosis

Where does it occur in humans?

Males Testes

Females Ovaries

Meiosis OverviewMeiosis Overview

Meiosis IMeiosis I

Diploid cells splits into 2 haploid cellsDiploid cells splits into 2 haploid cells

Meiosis IIMeiosis II

2 haploid daughter cells undergo mitosis2 haploid daughter cells undergo mitosis

Forms 4 haploid sex cellsForms 4 haploid sex cells

Same as mitosisSame as mitosis

Meiosis IMeiosis I

Prophase IProphase I

Homologous chromosomes pair together (called synapsis)Homologous chromosomes pair together (called synapsis)

Each homologous pair of chromosomes is called a tetradEach homologous pair of chromosomes is called a tetrad

Some chromatids break off and attach to adjacent homologous chromatids Some chromatids break off and attach to adjacent homologous chromatids (crossing over)(crossing over)

Crossing Over creates new genetic combinationsCrossing Over creates new genetic combinations

Metaphase IMetaphase I

Homologous chromosomes line up in the middle of the cellHomologous chromosomes line up in the middle of the cell

Anaphase IAnaphase I

Homologous CHROMOSOMES move to opposite poles of the cellHomologous CHROMOSOMES move to opposite poles of the cell

Random separation of homologous chromosomes is called Independent Random separation of homologous chromosomes is called Independent AssortmentAssortment

Telophase ITelophase I

Chromosomes reach opposite poles of the cellChromosomes reach opposite poles of the cell

Cytokinesis beginsCytokinesis begins

Meiosis IMeiosis I

Meiosis IIMeiosis II

2 haploid cells go through the process of mitosis & cell 2 haploid cells go through the process of mitosis & cell divisiondivision

End result of meiosis II is 4 haploid cellsEnd result of meiosis II is 4 haploid cells

Gamete FormationGamete Formation

In males meiosis creates 4 sperm cells (called In males meiosis creates 4 sperm cells (called spermatids)spermatids)

In females the cytoplasm is unevenly divided so that In females the cytoplasm is unevenly divided so that only 1 big cell is formed, along with 3 other polar only 1 big cell is formed, along with 3 other polar bodiesbodies

Meiosis IIMeiosis II

Meiosis AnimationMeiosis Animation

Meiosis Animation