Bio semester 2 unit 1 test practice

Gene- section of DNA found on a chromosome that codes for a trait

Trait- a characteristic that can be passed onto offspring (inherited)

Allele- alternative forms of a gene; variation of a gene for a trait; ex: gene for the color of pea plants has 2 alleles- G (green) and g (yellow); you have 2 alleles for each trait- one from mom and one from dad Dominant- a trait that covers up another; shown as capital letter; ex: G

Recessive- a trait that can be covered up by another; shown as lowercase letter; ex: g

Genotype - letters that represent the alleles for a trait; ex: Gg

Phenotype- physical trait that corresponds to the genotype; observable characteristic of a trait produced by the genotype; ex: pea plants have green color

Homozygous- purebred; two of the same alleles for a trait; ex: GG or gg

Heterozygous- hybrid; 2 different alleles for a trait; ex: Gg

Carrier- heterozygous for a recessive trait; does not have the trait but can pass it to offspring

Probability- the likelihood of offspring having a particular trait; given as a percentage or ratio

Monohybrid cross- predicts possible genotypes and phenotypes produced from the mating of 2 individuals looking at 1 trait at a time

Dihybrid cross- predicts offspring looking at 2 traits at a time; use the FOIL method to determine the gamete combinations the parents can create; this method shows Mendel’s segregation and independent assortment laws, since each gamete can only have 1 allele for each trait and the alleles for each are independent of each other.

Mendel manipulated pea plants to study the inheritance of their traits

P generation- the parental generation- 2 purebred plants- one dominant and one recessive

F1 generation- first filial generation of offspring from 2 purebred parental groups; all will be heterozygous (appearing like the dominant trait)

F2 generation- second filial generation cross of two heterozygous parents where 3⁄4 of the offspring appear dominant, while 1⁄4 of the offspring appeared recessive; the recessive trait reappeared!

Mendel’s Laws

1. Law of dominance- dominant traits mask (cover up) recessive traits

2. Law of segregation- you can only give your offspring 1 of your 2 alleles when gametes (egg and sperm) are made in meiosis, the alleles are separated; reason you get 1 allele from mom and 1 from dad; two alleles of a gene pair segregate (separate) from each other during meiosis

3. Law of independent assortment- traits are inherited separately, because alleles are lined up randomly during meiosis before they split to make gametes (egg and sperm); genes for different traits are sorted independently from one another when gametes form; the process of meiosis allows for the shuffling of chromosomes and the genetic material they contain; when chromosomes line up a the cell’s equator during meiosis, the order they line up influences the distribution of genetic material into the gametes; This increases genetic variation

Incomplete dominance- when the heterozygous phenotype is in between the 2 homozygous phenotypes (intermediate or blended); no dominant or recessive; neither allele is fully expressed or dominant over the other; ex:snapdragons- flowers can be red (RR), white (rr), or pink (Rr); both phenotypes are partly expressed in the heterozygous, producing a 3rd phenotype in the middle of the two

Codominance- when the heterozygous phenotype is a combination of both homozygous phenotypes; no recessive and one allele is not dominant over the other; ex: plants with red flowers (RR) or white flowers (WW) or red/white striped flowers (RW); both phenotypes are completely expressed in the heterozygous; there are 3 phenotypes with the 3rd expressing both alleles equally; ex: cows can have red hair (RR), white hair (WW), or both red and white hairs (roan) (RW)

Autosomal trait- located on chromosomes 1-22 (just NOT the sex chromosomes- pair 23); do Punnett squares the basic way

Sex-linked trait- located on X or Y chromosomes; X and Y chromosomes do not carry the same genes; males only inherit 1 allele for a trait; XX- female, XY- male; males only have one X and one Y chromosome, so they express all alleles on both chromosomes (even recessive ones); ex: colorblindness and hemophilia A

Pedigree- a chart that shows the inheritance pattern of a trait in a family across generations; circles represent females and squares represent males; shaded means having the trait and unshaded means not having the trait