Ch 14: Mendel and the Gene Idea Flashcards
What is a character?
a heritable feature that varies among individuals, such as flower color
What is a trait?
each variant for a character, such as purple or white color for flowers
What is a true-breeding plant?
plants that produce offspring of the same variety when they self-pollinate
What is the process called hybridization?
the mating of two contrasting, true-breeding varieties, ex. a white and purple flower (Mendel)
What is the P generation?
the true-breeding parents
What is the F1 generation?
the hybrid offspring of the P generation
How is the F2 generation produced?
when F1 individuals self-pollinate or cross-pollinate with other F1 hyprides producing the F2 generation
What is the “blending” hypothesis?
in the 1800s, Mendel hypothesized that hereditary characteristics occurred by blending, ex a red and white flower would produce a pink flower
In Mendels experiment, what was the ratio of purple flowers to white plowers?
in the F2 generation there was a ratio of 3:1
What is the first concept in Mendel’s model?
alternative versions of genes account for variations in inherited characters
What is an allele?
alternative versions of a gene which resides at a specific locus on a specific chromosome
What is the second concept in Mendel’s model?
for each character, an organism inherits two alleles, one from each parent
What is the third concept of Mendel’s model?
if the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance, the other, the recessive allele, has no noticeable effect on appearance
What is the fourth concept of Mendel’s model?
the law of segregation
What is the law of segregation?
the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
What does a punnet square show?
possible combinations of alleles
What is a homozygote?
an organism with two identical alleles for a gene, ex AA
What is said to be homozygous?
the gene controlling that character
What is a heterozygote?
an organism with two different alleles for a gene, which are not true-breeding
What is said to be heterozygous?
the gene controlling that character
What is a phenotype?
an organism’s physical appearance
What is a genotype?
an organism’s genetic makeup
How can we determine an organism’s genotype?
by carrying out a testcross
How do we carry out a testcross?
by breeding the mystery individual with a homozygous recessive individual
What does it mean for an offspring to be a monohybrids?
meaning that they were heterozygous for one character
What produces dihybrids?
the crossing (a dihybrid cross) of two true-breeding parents differing in two characters
What is the law of independent assortment?
it states that each pair of alleles segregates independently of any other pair of alleles during gamete formations and this law applies only to genes on different, nonhomologous chromosomes or those far apart on the same chromosome
