Law of Segregation and Interaction

Heredity

transfer of genetic material from parents to their offspring, only possible through reproduction.

Gametogenesis

formation of reproductive cells or gametes

Oogenesis, Spermatogenesis

Kinds of Gametogenesis

Fertilization

process of the union of sperm and egg cell to form a zygote, which develops a new individual.

Mitosis

division of somatic (body) cells; serves the function of cell duplication, with each cell inheriting a complete diploid (2n) set of chromosomes.

Meiosis

cell division in gametes (sex cells) resulting in a reduction to a haploid (n) set of chromosome.

spermatogenesis

produces spermatozoa within the testes.

Oogenesis

produces eggs in the ovary.

CHROMOSOMES

Literally means “colored bodies;” they are contained in the nucleus and are visible under the microscope as dark-staining, rod-like or rounded bodies.

Chromatins

Threadlike Bodies

Walther Flemming

Chromatins

Heinrich Wilhelm Gottfried von Walfeyer Hartz

Chromosomes

Chromatin

DNA and chromosomeproteins

Chromosomes

carriers of the hereditary material.

Walther Stanborough Sutton

Discovered that chromosomes are the carriers of hereditary material

Karyotype

The entire chromosome complement of an individual organism or cell, as seen during mitotic metaphase.

Autosomes

chromosomes that contain genes for anything that does not relate to sex determination.

sex chromosomes

determine the sex of the individual.

homologouschromosomes.

Chromosome pairs in diploid organisms

Chromosomes

made up of tightly-coiled strands of DNA

DNA

complex molecule composed of deoxyribose, phosphoric acid, and four bases.

Loci

Individual genes are located in a fixed position on the strands of DNA.

Gene

section of DNA that code for one protein. It is made up of a specific functional sequence of nucleotides, which code for specific proteins.

Allele

different versions of a gene.

Law of Segregation

Mendel's 1st Law of Heredity

Law of independent assortment

Mendel's 2nd Law of Heredity

Law of Dominance

Mendel's 3rd Law of Heredity

Dominant Allele

determines the organism’s appearace

recessive allelle

fails to be expressed phenotypically

Chance and probability

Segregation and recombination are governed by chance; occurrence of combinations are predicted according to probability.

Structural genes

directly responsible for the synthesis of certain biochemical products during cell metabolism

Regulator Genes

serve to control the function of other genes; control I terms of quantity, quality, timing of activity

Additive Gene Effect

when phenotypic effect of one gene adds to the phenotype of its own allelle or other genes in the phenotype

Non-additive Gene Effect

phenotypic expression of one gene does not add to the phenotypic expression of the other; classified as dominance or epistasis

Dominance

one gene blocks out, covers, masks or conceals the expression of its allelle when paired together in body cells

Complete, Incomplete/Co-dominance, Overdominance

Types of Dominance

Epistasis

interaction between genes at 2 or more loci

Linkage

presence in the same chromosome of two non-allelic genes affecting two trait

Backcross(ing)

method used to test the linkage of genes; double heterozygous (PpBb) is mated to a homozygous recessive for both pairs of genes (ppbb). (wherein: P =polled, p=horned,B=black,b=red)

crossing-over

there is an exchange of parts of homologous chromosomes during meiosis prior to the formation of gametes.

Recombinants

new gene combinations

Sex-Related Traits

– traits whose expressions are related to sex – either sex-linked, sex-influenced, or sex-limited

Sex-linked, Sex-influenced, Sex-limited

Sex-Related Traits

Sex-linked

influenced by genes situated on the sex chromosomes; associated with loci on the X (mammals) or Z (birds) chromosomes

Sex-influenced

-Controlled by autosomal loci, or carried in autosomes- But: their expression in the heterozygote depends on the sex

Sex-limited

- Have a phenotypic expression that is limited to only one sex- Commercially the most important

Multiple Alleles

a series of more than 2 genes, which can occupy a particular locus on a chromosome. Instead of only 2 alternative alleles, there may be many alleles at one locus; large number of genotypes is possible

Pleiotrophy

• A single allele influences more than one distinct trait• May occur more often since one gene is likely to affect more than one metabolic process during development• It is the major cause of genetic correlations

Intersex

an animal that has the phenotypic characteristics of both sexes but cannot function as either sex

Variable Expressivity

Genotype of a trait is expressed to a greater or lesser degree in phenotype

Incomplete Penetrance

• A genotype is not always expressed in the phenotype

Extranuclear (cytoplasmic) inheritance

Genes/DNA do not come from chromosomes (e.g. plasmids, mitochondria); rare in animals

Maternal Influence

influences the characteristics of offsprings• Part of the total environment

Lethal Genes

Alleles that cause an organism to die

Genetic recombination

reason fullsiblings made from egg and sperm cells fromthe same two parents can look very differentfrom one another.