topic 1: mendelian inheritance Flashcards
children do not inherit particular physical traits, but rather
genes
what is heredity?
the transmission of traits from one generation to the next
what is variation?
the differences in appearance between offsprings and their parents
what are the 2 laws of inheritance discovered by Gregor Mendel?
- law of segregation
- law of independent assortment
what are some advantages of using pea plants for genetic study?
- many different characteristics and traits
- mating of plants can be controlled
- each pea plant has sperm and egg producing organs
- cross pollination
what are sperm-producing organs and egg-producing organs known as?
stamens - (sperm-producing)
carpels - (egg-producing)
what is the difference between characteristics and traits?
characteristics - distinct heritable features (ex: flower color)
traits - characteristic variants (ex: purple or white flower)
what is cross-pollination?
fertilization between different plants
(can be achieved by dusting one plant with pollen from another)
what are true-breeding varieties?
- homozygotes
- plants that produce offspring of the same variants only when they self-pollinate
what is hybridization?
mating 2 CONTRASTING true-breeding plant varieties
(ex: white and purple flowered pea plants)
if all F1 plants had purple flowers after mating true-breeding white and purple flowered plants, what conclusion does that give?
purple flowers are dominant, while white flowers are recessive
if all F1 plants had purple flowers after mating true-breeding white and purple flowered plants, what is the ratio of purple to white flowers in the F2 generation?
3:1
what is meant by homozygous?
an organism with 2 identical alleles for a character for a gene controlling that character
(ex: AA or aa; true-breeding)
what is meant by heterozygous?
an organism with 2 different alleles for a character for a gene controlling that character
(ex: Aa; hybrid)
what is the difference between phenotype and genotype?
phenotype - the physical appearance of an organism
genotype - the genetic make up of an organism
what are dominant and recessive alleles?
dominant alleles - the ones expressed in the phenotype
recessive alleles - not expressed in the phenotype when combined with a dominant allele
what are the 4 related concepts explaining the 3:1 inheritance pattern Mendel observed in F2 offspring?
1 - alternative versions of genes (alleles) account for variation in inherited characteristics
2 - an organism inherits 2 alleles for each characteristic
3 - if the 2 alleles differ at a locus, then the dominant allele determines the phenotype of an organism while the recessive allele has no noticeable feature
4 - the law of segregation
what does the law of segregation state?
segregation of alleles corresponds to the separation of homologous chromosomes to different gametes during meiosis
what is a Punnett square used for?
a diagram that predicts the results of a genetic cross between individuals of known genetic makeup
how can we tell the genotype of an individual with the dominant phenotype?
by carrying out a testcross
how is a testcross carried?
by breeding the unknown genotype individual with a homozygous recessive individual
if the offspring displays the recessive phenotype in a testcross, then the unknown parent must be?
heterozygous
what are monohybrids?
organisms that are heterozygous for ONE character
Mendel derived the law of segregation through the inheritance pattern of?
monohybrids