Genetics 2026

allele

copies of genes

Phenotype

refers to the appearance of an organism

Genotype

refers to its genetic makeup

Mendel’s law of segregation

copies of genes segregate away from each other during reproduction to produce gametes ( sperm and egg, pollen, and ovules, etc) with only one allele of each gene

Gametes

Haploid reproductive cells in organisms that unite during sexual reproduction to form a new diploid individual

Homozygote

individual with two identical alleles of a given gene is said to be homozygous for that gene and is called a homozygote

heterozygote

An individual with two different alleles of a given gene is said to be heterozygous for that gene and is called a heterozygote

what does pure breeding mean?

organisms that consistently produce offspring with the same phenotype, observable traits, as the parents when self-pollinated or mated with others of the same type. They are homozygous

What does the “/” mean in genotypes?

/ Separates two versions or alleles of a gene

Alleles are present on homologous chromosomes

What is a monohybrid cross

A monohybrid cross involves mating two parents that are heterozygous (hybrid) for a single trait, meaning

each parent carries one dominant and one recessive allele(𝐴𝑎 ×𝐴𝑎). This cross, often illustrated on a Punnett Square, analyzes the inheritance of a single gene locus to predict the genotype (1:2:1 ratio) and phenotype (3:1 ratio) of offspring

genome

all the genes you possess—controls traits as diverse as a cleft chin; balding as you age; your hair, eye, and skin color; and even your susceptibility to certain diseases.”

self fertilization/ selfing

Both egg and pollen which contain sperm, come from the same plant, often the same flower

To ____ two plants, Mendel removed the stamens from the flowers of one plant (to prevent selfing), and then he brushed pollen from the other plant onto the pistils of the first plant

cross-fertilize (cross)

discrete trait

an inherited trait that exhibits an either/ or status ( that is purple vs white flowers)

continuous trait

An inherited trait that is controlled by many different genes and sometimes also by environmental factors. The characteristics associated with quantitative traits, such as human height, can be measured and assigned a numeric value.

Matings within such ____ lines produce offspring carrying specific parental characteristics that remain constant from generation to generation. These lines are also called inbred because they have been mated only to each other for many generations.”

pure-breeding (or true-breeding)

inbred

describes individuals or a population of organisms produced by matings of close genetic relatives: inbreeding results in homozygosity

hybrids

offspring of genetically dissimilar parents: often used as a synonym for heterozygotes

reciprocal crosses

crosses performed in two directions, with the characteristics of traits in the males and females reversed relative to the other, thereby controlling whether a particular character is transmitted by the male or female gamete.

testcross

cross of an individual with an ambiguous genotype with a homozygous recessive individual

__ helps establish the genotype behind the dominant phenotype

testcross

Product Rule

The probability of two independent events occurring toether is the product of their individual probalities

Sum rule

The probability of either of two mutually exclusive events occurring is the sum of their individual probabilities

parental (P) generation

individuals whose progeny in subsequent generations will be studied for specific traits

gene

a specific segment of DNA in a discrete region of a chromsome that serves as a unit of function by encoding a particular RNA or protein.

autosomes

all chromsomes except X and Y

Sex chromosomes

unpaired X and Y

Karyotype

a description of chromsome number and metaphase morphology for a given species