Biology Unit 7

gene

segment of DNA that codes for a specific protein, influencing traits

trait

characteristic determined by gene

alleles

different versions of gene

dominant allele

allele that expresses trait even if only 1 copy is present

recessive allele

allele that only shows it’s trait if 2 copies are present

genotype

genetic makeup of an individual

phenotype

physical expression of a trait

homozygous dominant (BB)

2 dominant alleles, shows dominant trait

homozygous recessive (bb)

2 recessive alleles, shows recessive trait

heterozygous (Bb)

1 dominant & 1 recessive allele, expresses dominant trait

somatic cells

body cells (ex. skin, muscle); not involved in reproduction

diploid cells (2n)

cells with 2 sets of chromosomes (one from each parent); found in somatic cells

meiosis

cell division that creates gametes (sex cells) with half the chromosome number

gametes

reproductive cells (sperm & egg) with half the genetic material

haploid cells (n)

cells with one set of chromosomes (ex. gametes)

sex cells

another term of gametes (sperm & egg)

autosomal chromosome

chromosome not involved in determining sex

sex chromosome

chromosome that determine biological sex (XX=female, XY=male)

homologous chromosomes

pair of chromosomes (one from each parent) that have the same genes but may have different alleles

tetrad

a group of 4 chromatids formed when homologous chromosomes pair up during meiosis

law of independent assortment

genes for different traits are inherited separately unless linked

law of segregation

each parent passes only 1 allele for a trait to their offspring

crossing over

exchange of genetic material between homologous chromosomes during meiosis, increasing genetic diversity

purebred (homozygous)

organism with 2 identical alleles for a trait (ex. BB or Bb)

hybrid (heterozygous)

organism with 2 different alleles for a trait (ex. Bb)

P-generation

parent generation in a genetic cross

F1 generation

first generation of offspring from the P-generation

F2 generation

second generation of offspring, produced by crossing F1 individuals

monohybrid cross

genetic cross involving 1 trait (ex. Bb x Bb)

dihybrid cross

genetic cross involving 2 traits (ex. RrYy x RrYy)

incomplete dominance

type of inheritance where heterozygous phenotype is an blend of 2 parent traits, rather than 1 being dominant (RW)

codominance

type of inheritance where both alleles in a heterozygous genotype are fully expressed, without blending (Blood type AB)

sex-linked gene

gene located on sex chromosome, often leading traits that are more common in 1 sex