Genetics Terms

Locus

Gene's specific location on the length of a chromosome (loci is latin for "place")

Haploid

One set of chromosomes (no homologous chromosomes, think gametes and gametophytes)

Diploid

Two sets of chromosomes (2 copies of chromosomes, think somatic cells in eukaryotes)

Autosomes

Chromosomes that are not sex chromosomes

n

Variable used for one set of chromosomes (diploid cell with 23 chromosome per set represented as 2n = 46)

Zygote

fertilized egg

Life Cycle

repeating sequence of stages that an organism goes through from one generation to the next

Sporophyte

The diploid multicellular organism of the Alternation of Generations/Haplodiplontic Life Cycle (seen in plants and some algae)

Spores

haploid cells produced by meiosis of multicellular diploid in haplodiplontic life cycle. Is not a gamete as it undergoes mitosis to create a multicellular haploid organism (gametophyte) instead of combining with other cells.

Gametophyte

A multicellular haploid organism formed by the mitosis of a spore

Meiosis 1

Reductional division (2n turns into 1n). Crossing over occurs and the homologous pairs are separated.

Prophase 1

Most important stage (ONLY stage where crossing over happens in meiosis).

Chiasmata

x formations on the chromosome and can have more than 1; form where crossing over occurred

Metaphase plate

an imaginary line in the middle of the cell where the chromosomes line up for metaphase.

Metaphase 1

Homologous chromosome pairs align at the metaphase plate.

Anaphase 1

Proteins dissolve the bond between homologous chromosomes, separating the homologous chromosomes (sister chromatids are still together)

Meiosis 2

The sister chromatids are separated (looks like mitosis)

Synapsis

process of aligning the two homologs via the synaptonemal complex

Crossing over

The broken strands of corresponding DNA invade the non sister chromatid, and exchange segments

Cohesion of Arms

cohesin proteins hold sister chromatids along their "arms" while chiasmata hold the homologs.

Cohesion of Centromere

Centromere holds sister chromatids together until it is cleaved by enzymes in anaphase 2

Independent Assortment

The idea that the random orientation of the homologous pair in metaphase 1, which determines whether the maternal or paternal chromosome faces a given pole, is determined independently of other chromosomes

Three mechanisms contributing to genetic variation

Independent Assortment of Chromosomes, Crossing Over, Random Fertilization

Diplontic life cycle

A multicellular diploid organism's (dominant stage) germ cells undergo meiosis to form haploid gametes which then combine via fertilization to create a single cell diploid (zygote) which undergoes mitosis to become a multicellular diploid organism.

Haplontic life cycle

A multicellular haploid organism (dominant stage) produces haploid single cell gametes via mitosis, which can undergo fertilization with another haploid single cell gamete to become a single cell diploid (zygote), which undergoes meiosis to form haploid cells, which then undergo mitosis to become a multicellular haploid organism again.

Random Fertilization

Egg can fuse with any sperm (sperm have unique genetic info), further increasing genetic variability/diversity.

True Breeding

Resulting offspring from self pollination always same as parent generation

P Generation (Parental gen)

True Breeding Parents

F1 Generation (First Filial Gen)

"Filial" = "Son" in Latin, 1st generation

F2 Generation

Resulting offspring from self pollinating/crossing F1

Alleles

Alternative versions of a gene that code fro the same trait (i.e. flower color)

The Law of Segregation

The two alleles for a heritable trait split during gamete formation and each goes into a separate gamete

Homozygote

An organism with 2 identical pairs of alleles for a gene, and is considered homozygous for that gene

Heterozygote

An organism with two different alleles for a gene, and is considered heterozygous for that gene.

Phenotype

observable trait of an organism

Genotype

genetic makeup of a trait

Testcross

Breeding an organism with an unknown genotype with a recessive homozygote to determine the unknown genotype

The Law of Independent Assortment

The alleles for each trait separate into gametes independent of each other, and that one allele will not influence the other allele.

Incomplete Dominance

In the case of a heterozygous allele, the phenotype is an intermediate between homozygous dominant and recessive.

Codominance

Both alleles produce functional proteins, making neither "recessive" or "dominant". In heterozygous traits, both alleles are fully expressed.

Pleiotropy

A property of some genes to have multiple phenotypic effects

Epistasis

Expression of gene at one locus affects the expression of another gene at another locus

Polygenic Inheritance

One phenotype influenced by multiple genes at different loci

Quantitative Characters

The tendency for phenotypes influenced by multiple genes to be expressed as a spectrum of phenotypes rather than either/or

Pedigree

A family tree that describes the passing down of a genetic trait over generations.

Dominant Allele

Produces a protein that indirectly expresses a certain characteristic.

Recessive Allele

Produces a non functional protein or no protein at all.

Dominant

overtakes phenotype if allele is heterozygous

Tay-Sachs disease

brain cells cannot metabolize certain lipids, leading to buildup in the brain and leading to death

Inbreeding (Consanguineous mating)

Between organisms with familial ties results in a higher chance of recessive phenotypes.

Multifactorial Disorders

Disorders that are influenced by genetics and environment.

Genetic Counseling

Provides couples with a way to determine the chances that their child will be at risk for a certain disorder they may have a family history for.

Amniocentesis

A test where cells found in the amniotic fluid are cultured and karyotyped (15th to 16th week of pregnancy).

Chorionic villus sampling

A test where a piece of the placenta is analyzed for any disorders (10th to 11th week of pregnancy).

Chromosome Theory of Inheritance

Mendel's theory of genetics is explained by chromosomes.

Wild type

The trait that appears more in the wild.

Mutants

The rarer traits.

X-Y System

The sex of offspring is determined by whether the sperm cell contains an X or Y chromosome.

X-0 System

The sex of offspring is determined by whether the sperm cell contains an X chromosome or no chromosome.

Z-W System

The sex of offspring is determined by whether the egg has a Z or W chromosome.

Haplo-Diploid System

There are no sex chromosomes, females are from fertilized eggs and are therefore diploid, males are from unfertilized eggs and are therefore haploid.

Barr Bodies

Deactivated X chromosome in females, the x chromosome deactivated is determined during embryonic formation randomly.

XIST (X-inactive specific transcript)

A region in one chromosome known as XIST is transcribed to create a Barr body.

Parental Types

Offspring whose phenotype matches the parents.

Recombinant Types

Offspring whose phenotype does not match the parental generation.

Frequency of Recombination

(number of recombinants/total number of offspring) * 100

Degrees of freedom

Total number of phenotypes - 1.

Linkage map

A map that roughly ordered the alleles of a fruit fly.

Repressible operon

Transcription automatic on but can be repressed.

Inducible operon

Transcription automatic off but can be activated.

Allolactose

The inducer in lac operon that deactivates the repressor.

Cyclic Amp (cAMP)

Increases when there is less glucose.

cAMP receptor protein

This protein binds to the lac promoter sites, and they have a high affinity with rna polymerase.

Differential gene expression

Almost all cells in multicellular organism have same genes, look diff because differential gene expression.