BIOLOGY UNIT 5 TEST STUDY GUIDECell division enables:

Repair / ReplacementGrowthReproduction

ASEXUAL REPRODUCTION SEXUAL REPRODUCTION

HOW IT WORKS

Single cell or group of cellseach duplicates its genetic

material& then splits into TWO

genetically identical cells

Genetic material from each of two parents combines,

producing offspring that differ genetically from either parent

PARENT Single cell or group of cellsTwo distinct parents

joining of sex cells

OFFSPRING TWO new cells or new groups of cells

Typically multicelluar

GENETIC MATERIALAll offspring’s genetic material is

inherited from ONE parentNew combinations of parent’s

genetic material

IDENTITYOffspring are genetically

identical to one another & to their parent

Offspring are genetically unique from one another & parents

TYPE OF ORGANISMSingle-celled & some

multicellular organisms, conditionally

Multicellular organisms & some unicellular organisms

SPECIAL CASESSea stars can regrow into 2

whole new individuals; Geraniums grown from leaf

cutting

NONE

Understand progress of genetic material during cell cycle Genetic material as mass of very long thin fibers Chromatin fibers condense into compact structures

Label Cell Cycle

Metabolic processes of Interphase Cell increases its supply of proteins Cell increases the number of many of its organelles (like mitochondria & ribosomes) Cell grows in size – Cytoplasm & Cell membrane

INTERPHASE

G1 S G2

FUNCTIONS

Cellular contents, excluding the

chromosomes, are duplicated

Each of the (46, if a human) is duplicated

by the cell

The cell cycle double checks the duplicated

chromosomes for errors, making repairs

as needed; Cell prepares to divide

Starting point : GAP 1

GAP 2

SYNTHESIS

MITOSIS

INTERPHASE

PHASES OF MITOSIS

G2 of Interphase : Cell has duplicated its DNA Individual chromosomes can’t be visualized

o Still loosely packed chromatin fibers Nucleolus present

o Still producing ribosomes

Prophase : In nucleus, chromatin fibers have condensed

o Nucleolus begins to disappear Each chromosome consists of pair of sister

chromatids joined at centromere In cytoplasm, mitotic spindle forms from aster

Prometaphase : Nuclear envelope breaks down Chromatids attach to microtubules @ kinetochore Kinetochore & nonkinetochore microtubules of spindle

starts tugging chromosomes toward center of cell

Metaphase : Chromosomes all gather in plane across middle of

cell – metaphase plate Mitotic spindle is fully formed

o All chromosomes are attached to kinetochore microtubules, with centromeres lined up about halfway between poles of spindle

Anaphase :

Sister chromatids suddenly separate from their partnerso Each chromatid = daughter chromosome

Proteins @ centromeres help move daughter chromosomes along kinetochore microtubules toward poles

o Kinetochore microtubules shorten Nonkinetochore microtubules grow longer & push poles apart

Telophase : Begins when chromosomes reach poles of spindle Processes that occurred in prophase are reversed

o Spindle disappearso Two nuclear envelopes reform

One around each set of dtr chromosomes

o Chromosomes uncoil & lengtheno Nucleoli reappear

Mitosis is completeCytokinesis :

Divides cytoplasm into two daughter cellso Each with nucleus

Understand difference between cytokinesis in animal cells & plant cellAnimals: First sign is appearance of indentation around middle of cell

Caused by contraction of ring of microfilaments just under cell membrane Pinches parent cell in two

Plants: Disk containing cell wall material = cell plate forms inside cell Cell plate grows outward Eventually divides cell in two, each cell bounded by its own continuous membrane & own cell

well

Distinguish between homologous chromosomes & sister chromatidsHomologous chromosomes: MATCHING PAIR of chromosomes, one from MOTHER + one from FATHER

EACH Carries same sequence of genes controlling same inherited characteristicso Carry slightly different version of same gene; humans have 23

Sister chromatids: DUPLICATED COPIES of single chromosome, attached to each other Both chromatids contain exactly same forms of each gene

Define karyotype = display of 46 chromosomes of an individual

Understand composition of sex chromosomes = 23rd pair of chromosomes, two forms X & Y Male mammals: XY Female mammals: XX Only small parts of X & Y are homologous

DIPLOID HAPLOIDCells that contain TWO homologous sets of

chromosomesCells that contain SINGLE set of chromosomes

2n2n = 46 in humans

nn = 23 in humans

Almost all human cells Only egg & sperm or gametesProduced following fertilization, sustained through

mitosisProduced through process of meiosis

Know steps of HUMAN LIFE CYCLEHUMAN ADULTS (2n=46) thru Meiosis Egg (n=23) / Sperm (n=23) Fertilization (fusion of sperm & egg, 2n=46) Diploid zygote (2n=46) thru MitosisEarly embryo (2n=46 for each cell) Juvenile (2n=46) thru differentiation & growth … … HUMAN ADULTS

MEIOSIS I

Interphase : Cell duplicates DNA

o Each chromosome then consists of TWO identical sister chromatids

Prophase I : Proteins cause homologous chromosomes to actually

stick together along their lengtho Paired chromosomes = FOUR chromatids = tetrads

Tetrads attach to spindle Sister chromatids in tetrads exchange some genetic material

o 2n = 6, in this example

Metaphase I : Tetrads move to middle of cell Tetrads line up across spindle

Anaphase I : Homologous chromosomes separate as they migrate to

opposite poles of spindleo Sister chromatids migrate togethero Each chromosomes is made of TWO copieso There are only TWO chromosomes, each with

TWO copies

Telophase I : Chromosomes arrive at poles

o Each pole has HAPLOID daughter nucleus b/c has only ONE set of chromosomes

o Each chromosomes consists of TWO sister chromatids

Cytokinesis I : Forms TWO HAPLOID daughter cells

o Chromosomes in each daughter cell are still duplicated

MEIOSIS II

Prophase II : In each HAPLOID daughter cell, spindle forms

o Spindle attaches to centromereso Spindle moves individual chromosomes to

middle of cell

Metaphase II :

Chromosomes line up in middle of cell with kinetochore microtubules attached to each sister chromatid

Anaphase II : Sister chromatids separate &

move to opposite poles

Telophase II : Chromatids are now considered individual

chromosomeso Chromatids arrive at poles

Cytokinesis II : Splits cells one more time Meiosis is complete FOUR HAPLOID daughter cells result