Chapter 9 Flashcards
Dwarfism is caused by a dominant mutation. Individuals who are homozygous for the dominant mutation die before birth. Two individuals, both with dwarfism, marry and wish to have children.
D- dwarfism gene
What are the genotypes of the parents?
Male: Dd
Female: Dd
Dwarfism is caused by a dominant mutation. Individuals who are homozygous for the dominant mutation die before birth. Two individuals, both with dwarfism, marry and wish to have children.
D- dwarfism gene
What is the probability of the (living) offspring expressing dwarfism?
2/3 or 66.66% chance
Dwarfism is caused by a dominant mutation. Individuals who are homozygous for the dominant mutation die before birth. Two individuals, both with dwarfism, marry and wish to have children.
D- dwarfism gene
What is the probability of the offspring expressing a normal phenotype?
1/3 or 33.33% chance
How would you represent alleles for A, B, and O blood types?
Dominant alleles: _________ or ________
Recessive allele: ________
Dominant alleles: ____IA_____ or ____IB____
Recessive allele: ____i____
What is the mode of inheritance (or inheritance pattern) for blood type?
The mode of inheritance for blood type is autosomal codominant because while time O blood is recessive, type A and B are equally dominant, and if both are present, both will be expressed.
Imagine that you are a genetic counselor, and a couple planning to start a family is seeking your assistance.
John is currently married to Laura. He was also married to Carol, and he and his first wife (Carol) had a child with albinism. John’s parents and Laura’s parents also do not have albinism.
What is the probability that John and Laura will have a baby with albinism. (it will be helpful to draw a pedigree)
The probability is 1/6.
Define and distinguish between self-fertilization, cross-fertilization, purebred organisms, hybrids, the P generation, the F1 generation, and the F2 generation.
self-fertilization: when the plant (or other organism) is able to fuse its gametes (fertilization) with only its own gametes, so it has both female sex-cells and male sex cells (both eggs and sperm)
cross-fertilization: when the plant’s (or other organism’s) gamete(s) fuse with those of another plant (or other organism) so that the offspring has half of its genes from one parent and the other half of its genes from the other parent.
purebred organisms: organisms that have been bred w/ their siblings for at least 10 generations and each now has homologous chromosomes that are exactly the same
hybrids: the offspring of purebreds or the offspring of the offspring of purebreds
P generation: the purebred parents of hybrids
F1 generation: the offspring of the purebred parents and have half of each of their parents genes, meaning that they are all heterozygotes, so we are able to tell which allele is dominant based on their phenotype. F stands for filial, which is Latin for a male or female child
F2 generation: the offspring of two F1 organisms (through either self-fertilization or cross-fertilization since they’re all the same) that allows us to see whether 2 genes travel together or whether you can see them separately as well (Mendel’s law of independent assortment). The genotypic ratio of the F2 offspring is 1:2:1 (PP: Pp: pp) and the phenotypic ration of the F2 offspring is 3:1 (purple-dominant: white-recessive). the F stands for filial, which is Latin for a male or female child
Define and distinguish between the following pairs of terms: heterozygous versus homozygous, dominant allele versus recessive allele, genotype versus phenotype, and
phenotypic ratio versus genotypic ratio.
heterozygous vs. homozygous: a heterozygous genotype means that an organism has a recessive and a dominant copy of the gene while a homozygous genotype means that an organism has two identical copies of the gene (whether it’s HOM dominant or HOM recessive)
Dominant allele vs. recessive allele: the dominant allele is the allele that will be expressed when there are two alleles of the same gene, while the recessive allele will only be expressed if there are two copies of the recessive allele. If there is a dominant allele and a recessive allele, the recessive allele will not be expressed in the organism’s phenotype
Genotype vs. phenotype: the genotype is the combination of alleles, or versions of genes, that an organism possess while the phenotype is the physical traits or characteristics that the organism expresses, so the genotype will not always be the same as the phenotype and it is not always possible to tell the genotype from the phenotype
Phenotypic ratio vs. genotypic ratio: the phenotypic ratio is the ratio of the phenotypes of all the possible offspring while the genotypic ratio is the ratio of the genotypes of all the possible offspring
Define the law of segregation and explain how it applies to reproduction.
The law of segregation states that there is a 50-50 chance of a gamete receiving one of the two alleles of a gene after homologous chromosomes split. This relates to reproduction because this means that there’s an equal chance of an egg being fertilized by a gamete with one allele as there is with the other, which means there is a 50-50 chance that the offspring will receive one of those alleles.
Define Mendel’s law of independent assortment and explain how it applies to a dihybrid cross.
Mendel’s law of independent assortment says that a gamete does not have a greater chance of receiving one allele of one gene than it does to receive one allele from another gene because if the alleles are on different chromosomes (not linked xsms), then the alleles travel independent of one another. This means that if you have blue eyes, it does not mean that you also have to have blonde hair, hair color and eye color genes have nothing to do with each other. This law applies to a dihybrid cross because just because an offspring receives one allele does not mean that it must also receive a certain allele of a different gene; in a dihybrid cross, you can have any combination of gametes with any combination of alleles from different genes so one combination of alleles of different genes in the offspring occurs randomly because the alleles from different genes in the gametes sort randomly and independently.
