Genetics

Meiosis

Cell division that produces reproductive cells (egg/sperm) in sexually reproducing organisms

Meiosis 1

Homologous chromosomes separate

Meiosis 2

sister chromatids separate

end result of meiosis

4 haploid daughter cells- all genetically different; produces sex cells

genetic variation

Heritable variations in a population

Gametes

sex cells formed by meiosis

Tetrad

structure containing 4 chromatids when they combine that forms during prophase 1 of meiosis 1

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate; during anaphase 1 or 2

sister chromatids

Replicated forms of a chromosome joined together by the centromere

chromosomal mutation

A change in the chromosome structure, resulting in new gene combinations.

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during prophase 1 of meiosis 1.

Recombination

a combining of genes or characters different from what they were in the parents

Homologous chromosomes

Chromosomes that have the same structure and code for the same trait (1 from mom and 1 from dad)

Haploid cell (n)

A cell containing only one set of chromosomes (n).

Diploid cell (2n)

Somatic cells that have 2 chromosomes

Gene

A segment of DNA on a chromosome that codes for a specific trait

Mitosis

A process in which cells duplicate for asexual reproduction

Daughter cells in meiosis and mitosis

2- mitosis, 4- meiosis

# of chromosomes in mitosis/meiosis

46- mitosis, 23- meiosis

inversion mutation

A mutation involving a piece of a chromosome that breaks off and reattaches in reverse orientation.

Translocation mutation

mutation in which one part of one chromosome breaks off and attaches to another

Genotype

genetic makeup of an organism (ex: Bb)

Phenotype

An organism's physical appearance, or visible traits (ex: Brown eyes)

Allele

Different forms of a gene (ex: blue and brown eyes)

Dominant Trait

Describes a trait that covers over, or dominates, another form of that trait.

Recessive Trait

Masked by the dominant trait; a trait that is apparent only when two recessive alleles for the same characteristic are inherited

Gregor Mendel

Father of genetics

Homozygous

Having two of the same alleles for a particular gene (ex: AA or aa)

Heterozygous

An organism that has two different alleles for a trait (ex: Aa)

Punnett Square

diagram showing the possible gene combinations that might result from a genetic cross

Monohybrid Cross

a cross in which only ONE characteristic is tracked

Dihybrid Cross

Cross or mating between organisms involving TWO pairs of traits

Trait

A characteristic that an organism can pass on to its offspring through its genes.

F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

Offspring resulting from interbreeding of the hybrid F1 generation.

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a BLENDING of the traits. (ex: red + white = pink)

Codominance

A condition in which both alleles for a gene are fully expressed resulting in BOTH being shown. (ex: red + white = red/white spots)

sex-linked traits

Traits controlled by genes located on sex chromosomes.

Principle of Independent
Assortment

•genes can separate independently during the formation of gametes
-If there are 2 different alleles of one gene on one chromosome, then each allele could end up in each daughter cell
-inheritance of one trait has no effect on another

Mendel’s Law of Segregation

-2 alleles coding for the same trait separate or segregate during gamete formation
-pass down 1 allele of each gene only

Gene Linkage

Genes located on the same chromosome