BackgroundThe passage of genetic information is

critical to the reproduction of cells

Genes are segments of DNA representing units of hereditary information

The physical location of a gene on the chromosome is called its locus

Types of ReproductionAsexual reproduction

Single parent cell/organism produces an identical offspring

Except for mutations, the offspring of asexual reproduction are clones of their parents

Sexual reproductionResults in greater variation in genetic material

Two types of cells in humansGametes-haploid cells (n), carry one set of

chromosomes ex. In humans, an egg (1N) and sperm (1N) are reproductive cells that fuse together creating a diploid zygote

Somatic cells (Diploid cells) carry two sets of chromosomes (2n)

In diploid cells, you can pair chromosomes in relation to its size, shape, and banding positions

Karyotyping-arranging chromosomes in relation to number, size, type.

The chromosomes of a pair are called homologous chromosomes

One homologous pair decides your gender

The remaining 22 pairs of chromosomes are called autosomes

Significance of homologous pairs?Their origin! One member of each homologous pair comes

from each parentEx. Human gametes haploid cells- single set of

chrom (23) - Each parent contributes one set of chromosomes

and is a member of each homologous pair.

- Fertilization- Egg+ Sperm Zygote

n n 2n

How are Gametes Formed?Meiosis:

Chromosome number is halved by dividing chromosome members of each homologous pair into different gametes

Goes through two rounds of cell division, produces 4 daughter cells w/ half the chromosome number

Tetrad-four sister chromatids that pair up Chiasmata-crossing over occurs bwtn nonsister chromatids

Mechanisms of genetic variationIndependent assortment

Arrangement of homologous pairs at the metaphase plate in Metaphase I is completely random

Crossing Over Produces recombinant chromosomes which combine

genes inherited from parents

Random Fertilization Random nature of fertilization that adds to genetic

variation

Life CyclesLife cycle- sequence of stages in the

reproductive history of an organismAsexual Life Cycles bacterium by binary

fission

Sexual Life CyclesANIMALS (HUMANS)

Haploid sperm fuses w/ haploid egg diploid zygote

Zygote grows by mitosis to produce a multicelluar organism

Fungi

Plants (some algae)undergo "alternation of generations" where

they exist as haploid organisms (gametophytes) and diploid organisms (sporophytes).

Meiosis/mitosis ComparedProperty Mitosis Meiosis

DNA replication Occurs during interphase before mitosis

Occurs during interphase before mitosis I begins

Number of divisions One, including prophase, metaphase, anaphase, and telophase

Two,Each including PMAT

Synapsis of homo. chromosomes

Does not occur Occurs during prophase I along w/crossing over btwn nonsister chromatids

Number of daughter cells and genetic composition

Two, each diploid (2n) and genetically identical to parent

Four, each haploid (n) containing half as many chromosomes as parent; genetically different from parent and from each other

Role in animal body Enables multicellular adult to arise from zygote; produces cells for growth, repair, and asexual reproduction

produces gametes; reduces number of chromosomes by half and introduces genetic variability among gametes

Mechanisms of genetic variation diagram

Independent Assortment Crossing Over

Vocabulary heredity - the transmission of traits from one generation to the next. variation - offsprings differ somewhat in appearance from parents and siblings. genetics - the scientific study of heredity and hereditary variation. gene pool - the total aggregate of genes in a population at any one time. asexual reproduction - a type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts. clone - a lineage of genetically identical individuals. sexual reproduction - a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents. life cycle - the entire sequence of stages in the life of an organisms, from the adults of one generation to the adults of the next. Somatic cell - any cell in a multicellular organism except a sperm or egg cell. karyotype - a method of organizing the chromosomes of a cell in relation to number, size, and type. homologous chromosomes - chromosome pairs of the same length, centromere position, and staining pattern that possess genes for the same traits at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. sex chromosomes - the pair of chromosomes responsible for determining the sex of an individual. autosome - a chromosome that is not directly involved in determining sex, as opposed to the sex chromosomes. gamete - a haploid egg or sperm cell; gametes unite during sexual reproduction to produce a diploid zygote. haploid cell -a  cell containing only one set of chromosomes (n).

More Vocabularyhaploid cell -a  cell containing only one set of chromosomes (n). fertilization - the union of haploid gametes to produce a diploid zygote. zygote - the diploid product of the union of haploid gametes in conception; a fertilized egg. diploid cell - a cell containing two sets of chromosomes (2n), one set inherited from each parent. meiosis - a two-stage type of cell division in sexually reproducing organisms that results in gametes with half the chromosome number of the original cell. alternation of generations - a life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants. sporophyte - the multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation. gametophyte- the multicellular haploid form in organisms undergoing alternation of generations, which mitotically produces haploid gametes that unite and grow into the sporophyte generation. meiosis I - first division of cells meiosis II - second meiotic division that separates sister chromatids and is virtually identical in mechanism to mitosis. synapsis - the pairing of replicated homologous chromosomes during prophase I of meiosis. tetrad - chiasma - the X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis. crossing over - the reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I.