Chapter 17 Flashcards
(10 cards)
Define the following terms:
True-breeding: A lineage of plants that continues to exhibit the same trait after several generations
Self-fertilization: A female gamete is fertilized by a male gamete from the same plant
Cross-fertilization (hybridization): Union of a female gamete and a male gamete from different individuals
Trait: Characteristics of an organism
Genotype: Genetic composition of an individual
Phenotype: characteristics of an organism that are the results of the expression of its gene
Heterozygous: Carries two different alleles
Homozygous: Individual with two identical alleles
Describe monohybrid crosses carried out by Mendel, showing the parents, offspring, traits, and genotype and phenotype ratios.
*Monohybrid cross follows a three-generation pattern where the experimenter follows only 1 trait
*P generation(Parental Generation)
-2 True-breeding parents that are different from each other are cross-fertilized
*F1 generation(First Filial Generation)
-Offspring(monohybrids) of P cross
*F2 generation(Second Filial Generation)
-Offspring that result when F1 plants self-fertilize
Describe the three conclusions demonstrated by the Monohybrid crosses carried out by Mendel, including the definition of related terms
- Dominant vs Recessive:
-The Dominant trait is whichever one is displayed in the F1 generation t
-Recessive variant is not seen in the F1 offspring, but reappears in F2. - Genes and alleles
-Every individual has 2 genes for a trait
-Gene has two variant forms called alleles - Law of Segregation
-The alleles separate from each other, so that each sperm or egg carries only one allele
-Offspring receive one allele from each parent
Describe dihybrid crosses carried out by Mendel, showing the parents, offspring, traits, and genotype and phenotype ratios.
*Dihybrid cross follows a three-generation pattern where the experimenter follows 2 traits in the same organisms:
*P generation
-2 True-breeding parents that are different from each other for two traits are cross-fertilized
- F1 generation
-Offspring of P cross
*F2 generation
-Offspring that result when F1 plants self-fertilize
Describe the conclusion that can be made from Dihybrid crosses carried out by Mendel.
*Law of Independent Assortment:
-9:3:3:1 ratio of F2 hybrids consistent with independent assortment—offspring get new combinations of traits, so the traits are NOT linked(different chromosomes)
*Law of Independent Assortment:
-Alleles of different genes assort independently of each other during gamete formation
-Leads to the potential for new combinations of traits in offspring
*What part of Meiosis explains Independent Assortment?
-Mendel’s law of segregation can be explained by the pairing and segregation of homologous chromosomes
during meiosis.
*Why do some genes NOT follow the Law of Independent Assortment?
-Same chromosome. These linked genes are usually inherited together unless crossing over separates them.
If a trait is Autosomal Dominant, describe what you might see in the pedigree chart.
Autosomal Dominant:
-Trait is dominant and carried on an autosomal chromosome (not a sex chromosome)
*Males vs females:
-Males and females are equally affected
*Affected children with Unaffected parents:
-Affected individual must have at least one affected parent ( no carriers)
*Genotype of unaffected individuals: aa
*Genotypes of affected individuals: AA or Aa
*Why are there no “carriers” of Autosomal Dominant traits?
-Because trait is dominant, only need one allele to show trait
If a trait is Autosomal Recessive, describe what you might see in the pedigree chart.
*Autosomal Recessive:
-Trait is recessive and carried on an autosomal chromosome (not a sex chromosome)
*Males vs females:
-Males and females are equally affected
*Affected children with Unaffected parents:
-Parents can be unaffected carriers who do not show the trait.
*Genotype of unaffected individuals: AA
*Genotypes of affected individuals: aa
*Carriers are what genotype: Aa
If a trait is X-linked recessive, describe what you might see in the pedigree chart.
*X-linked recessive:
-Trait is recessive and carried on the X chromosome
*Males vs females:
-Males are much more affected in a pedigree because they only need one allele to show the trait
*Affected children with Unaffected parents:
-Parents can be unaffected carriers who do not show the trait
*Genotype of unaffected males: X^AY
*Genotype of affected males: X^aY
*Genotype of affected females: X^aX^a
*Genotypes of unaffected females: X^AX^A
*Carriers are what genotype: X^AX^a(only female)
Explain why X-linked recessive traits are inherited differently in males.
Males only have one X chromosome, will show the trait with only one allele (there’s no other
allele to mask the recessive allele
Give examples of how environmental conditions can influence phenotypic expression and define the term ‘norm of reaction.
*For many traits, genetics establish a range
*Norm of reaction is the phenotypic range of a particular genotype that is influenced by the environment
*Where the phenotype ends up is influenced by the environment
*Genetically identical plants grow to different heights in different temperatures
