42 terms

Genetics Vocab

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Allele
An alternative form of a gene
Crossing over
Exchange of genetic material between non-sister chromatids from homologous chromosome during prophase I of meiosis; results in new allele combinations
Diploid
Containing two complete sets of chromosomes, one from each parent.
Dominant
Describes a trait that covers over, or dominates, another form of that trait
Egg
Haploid female sex cell produced by meiosis
Fertilization
Fusion of male and female gametes to form a zygote
Gamete
Male and female sex cells, sperm and eggs
Genetic recombination
Major source of genetic variation among organisms caused by re-assortment or crossing over during meiosis
Genetics
Branch of biology that studies heredity
Genotype
Combination of genes in an organism
Haploid
Having a single set of unpaired chromosomes
Heredity
Passing on of characteristics from parents to offspring
Heterozygous
An organism that has two different alleles for a trait
Homologous chromosome
Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.
Homozygous
An organism that has two identical alleles for a trait
Dihybrid cross
A cross between individuals that have different alleles for the same gene
Monohybrid cross
A cross between individuals that involves one pair of contrasting traits
Law of Independent Assortment
Mendelian principal stating that genes for different traits are inherited independently of each other

When does it occur?
-During Meiosis both alleles segregate away from each other
Law of Segregation
1) Each cell has 2 alleles per trait variation of a gene because chromosomes exist as homologous pairs
2) every parent gives its offspring one allele per trait because of the homologous split
Meiosis
Cell division that produces reproductive cells in sexually reproducing organisms
Nondisjunction
Failure of homologous chromosomes to separate properly during meiosis; results in gametes with too many or too few chromosomes
Phenotype
Outward appearance of an organism, regardless of its genes
Pollination
Transfer of male pollen grains to the pistil of a flower
Recessive
Trait of an organism that can be masked by the dominant form of a trait
Sexual Reproduction
Pattern of reproduction that involves the production of subsequent fusion of haploid cells
Sperm
Haploid male sex cells produced by meiosis
Trait
Characteristic that is inherited; can be either dominant or recessive
Zygote
Diploid cell formed when a sperm fertilizes an egg
Principle of dominance
Mendel's second conclusion, which states that some alleles are dominant and others are recessive
Segregation
Separation of alleles during gamete formation
Probability
Likelihood that a particular event will occur
Incomplete dominance
A situation in which one allele is not completely dominant over another allele (hair type, PTC taste)
Complete dominance
a relationship in which one allele is completely dominant over another (blood type)
Co-dominance
Situation in which both alleles of a gene contribute to the phenotype of the organism
Multiple alleles
A gene that has more than two alleles (ex. blood type)
Polygenic traits
Traits controlled by two or more genes (ex. skin color, hair color)
Sex-linked gene (X-linked traits)
Gene located on a sex chromosome, X-linked traits (color blindness, hemophilia)
Pedigree
A chart that shows the presence or absence of a trait according to the relationships within a family across several generations
Pleiotropy
A single gene having multiple effects on an individuals phenotype
Generations of genetics
P Generation
Parental generation, the first two individuals that mate in a genetic cross

F1 Generation
The first generation of offspring obtained from an experimental cross of two organisms

F2 Generation
Offspring of the F1 generation
Gregor Mendel
- Why pea plants?
- Steps in his experiment
- Mendel's major conclusions
Why pea plants?
- Easily observable, only 7 traits, he could manipulate the traits, grow fast
- could control mating

Mendel's major conclusions:
-recessive, dominant, incomplete dominance, co dominance
- law of segregation
- law of independent assortment
Punnett Square
A chart that shows all the possible combinations of alleles that can result from a genetic cross