Biology - 4.1-4.3 (mitosis and meiosis)

heredity

heredity

the passing of traits from parents to offspring

genetics

the branch of biology dealing with heredity and the variation of inherited characteristics

deoxyribonucleic acid (DNA)

a molecule that carries genetic information in cells

chromosome

thread-like structures located inside the nucleus of cells made of proteins and DNA that are organized into genes

gene

a segment of a DNA molecule that codes for a particular trait; found at a specific location on a chromosome

locus

the location of a gene on a chromosome

polyploid

having more than two sets of chromosomes; many plants are polyploids

asexual reproduction

the production of offspring from a single parent; the genetic makeup of the offspring is identical to that of the parent

sexual reproduction

the production of offspring from the fusion of two sex cells (usually from two different parents); the genetic makeup of the offspring is different from that of either parent

fragmentation

a method of asexual reproduction in which a piece or body fragment of the parent organism develops into a mature individual

mitosis

the process by which a eukaryotic cell divides the genetic material in its nucleus into two new identical nuclei

interphase

the portion of the cell cycle between mitotic divisions when the genetic material (in the form of chromatin) is duplicated

interphase: G1 - gap 1 (3)

• growth phase

• make more proteins

• make more organelles

interphase: S - synthesis (1)

• DNA replication

interphase: G2 - gap 2 (1)

• preparation for mitosis (formation of spindle fibers)

Interphase: G0 - gap 0 (1)

• somes cells step out of growing to carry out their function(s)

chromatin

the tangled strands of DNA and protein within a eukaryotic nucleus

chromatid

one of two identical halves of a chromosome that has been replicated in preparation for cell division

sister chromatid

identical copies of a single chromosome that remains attached to the original chromosome at the centromere

centromere

constricted region of linear chromosomes that help to keep chromosomes properly aligned during cell division

centriole

structure that forms spindle fibres

spindle fibres

collections of microtubules that move chromosomes during cell divison

mitosis: prophase (6)

• condensation of chromatin (chromosomes have already been duplicated)

• observe duplicated chromosomes

• nuclear membrane disappears

• nucleolus disappears

• centrioles (duplicated in interphase) move towards opposite poles

• centrioles start forming spindle fibres

mitosis: metaphase (4)

• spindle fibres attach to centromeres

• duplicated chromosomes line up at the equatorial plate

• spindle fibres from both centrosomes are attached to EACH duplicated chromosome—one per sister chromatid

• nuclear membrane has disappeared

mitosis: anaphase (3)

• centromeres split apart

• spindle fibres shorten to split apart the sister chromatids

• one complete set of chromosomes is pulled

  towards each pole of the cell

mitosis: telophase (3)

• each set of chromosomes have reached the poles of the cell

• chromosomes begin to unwind

• THIS IS THE END OF MITOSIS (genetic material is split)

mitosis: cytokinesis (5)

separation of the cytoplasm and formation of two new cells

• spindle fibres break down and disappear

• nucleolus reappears

• the nuclear membrane is reformed

• animal cells – cleavage furrow

• plant cells – cell plate formed from centre of cell to already formed cell wall.

cloning

the process of producing one individual that is genetically identical to another, using a single cell or tissue

biotechnology

the use and modification of organisms for applications in engineering, industry, and medicine

genetically modified organism

an organism in which the genetic material has been altered using genetic engineering techniques

cloning endangered species

Captive breeding programs can be used to help save endangered species. Unfortunately, many species from Ontario and around the world are extremely difficult to breed in captivity. Cloning provides an alternative.

gamete

a sex cell; includes sperm cells in males and egg cells in females

fertilization

the formation of a zygote by the joining together, or fusion, of two gametes

zygote

a cell produced by the fusion of two gametes

homologous chromosomes

matching pairs of chromosomes similar in size and carrying information for the same genes

meiosis

a two-stage cell division in which the resulting daughter cells have half the number of chromosomes as the parent cell; results in the formation of gametes or spores

meiosis I

diploid - 2 chromosomes, 2 copies of each

meiosis II

haploid - 2 chromosomes, 1 copy of each

meiosis I: prophase I (6)

• Chromosomes start to shorten and thicken

• The nuclear membrane begins to dissolve

• The centrioles separate and move to opposite poles of the cell

• Spindle fibres form

• Chromosomes start to come together in homologous pairs forming a tetrad

• Crossing over – the exchange of chromosome segments between homologous pairs during synapsis (resulting in an exchange of information between non-sister chromatids)

meiosis I: metaphase I (1)

• Tetrads migrate toward the centre and align their centromeres across the middle of the cell

meiosis I: anaphase I (2)

• Homologous chromosomes move to the opposite poles of the cell

• Reduction Division occurs... Only one chromosome from each homologous pair

  will be found in each new daughter cell

meiosis 1: telophase I (1)

• Nuclear membranes begin to form around the chromosomes at each end of the

  cell and the cell begins to divide

meiosis II: prophase II (2)

• Nuclear membrane dissolves

• Spindle fibers begin to form

meiosis II: metaphase II (2)

• Arrangement of the sister chromatids at the midline of the cell

• Spindle fibers attach at the centromeres

meiosis II: anaphase II (2)

• Sister chromatids separate toward opposite poles of the cell

• Nuclear membrane begins to form around the chromosomes

meiosis II: telophase II (1)

• Second nuclear division is complete

Meiosis: cytokinesis

• seperation of the cytoplasm

tetrad

a pair of homologous chromosomes each with two sister chromatids

synapsis

the physical pairing of homologous chromosomes during prophase I of meiosis

crossing over

the exchange of chromosome segments between homologous pairs during synapsis

random assortment

During meiosis I, homologous chromosomes pair up during prophase I and metaphase I. Th ey are then separated from each other during anaphase I. Each daughter cell is now haploid, having received only one chromosome from each pair. When this happens, the chromosomes in each pair are assorted independently. In other words, a daughter cell can receive either chromosome of each homologous pair—this is called random assortment

gametogenesis

the production of gametes (sex cells) in animals

spermatogenesis

the production of mature sperm cells

oogenesis

the production of mature egg cells

karyotype

the chromosomes of an individual that have been sorted and arranged according to size and type

sex chromosomes

chromosomes that differ in males and females of the same species

sex determination

the combination of sex chromosomes determines the sex of the offspring

autosomes

non-sex chromosomes