Chapter 5 - Mendelian Genetics - Patterns of Inheritance (+Ch6) Flashcards
law of dominance
when an organism is hybrid for a pair of contrasting traits, it will show only the dominant trait
true breeding organisms
AKA purebred; homozygous for a certain trait; will always pass this trait onto offspring
What is the purpose of a monohybrid cross?
a cross designed to study the inheritance of only one trait
law of segregation
factors that appear in pairs are separated from each other during gamete formation and recombined at fertilization; cells receive 2 alleles for each gene
genotype
combination of alleles (letters); e.g. YY, Yy
phenotype
physical expression of a gene in words; e.g. yellow seeds, purple flowers
homozygous
2 of the same allele (e.g. YY, yy)
heterozygous
2 different alleles (e.g. Yy)
contrasting traits
one or the other is expressed; there is no in between
Difference between the P, F1 and F2 generations
P gen - parents
F1 gen - offspring
F2 gen - offspring of F1 gen cross
incomplete dominance
when 2 alleles are equally dominant; the heterozygous condition results in the blending of traits (e.g. red and white snapdragons creating pink)
codominance
when 2 alleles are equally dominant; the heterozygous condition shows both traits equally (e.g. roan cows)
What is a pedigree?
A diagram of an individual’s ancestors used in human genetics to analyze the Mendelian inheritance of a certain trait
autosomal inheritance
inheritance of alleles located on autosomal (non-sex) chromosomes
Chromosome 1-22 are also known as…
Autosomes
Difference between monohybrid and dihybrid
Monohybrid is a cross between 2 different true breeding plants that differ in only ONE characteristic (eg, purple flower x white flower); a dihybrid cross involves TWO characteristics/heterozygous alleles (eg, yellow wrinkled x green smooth)
Discontinuous variation
The expression of one gene has no effect in the expression of another gene; trait is either expressed or it isn’t
Continuous variation
The expression of one gene is affected by the expression of another gene; can be additive allele (have partial influence) or negate expression entirely; expression of a characteristic is the sum of the expression of all alleles involved
During which stage of meiosis do homologous chromosomes separate?
Anaphase I
Define point mutation and list the different types
A change in one or a few nucleotides of DNA; e.g. base-pair substitution, insertion, deletion
What is a nucleotide?
Each section of DNA composed of phosphate, sugar and base
Describe sickle cell anemia.
- change in one nucleotide in hemoglobin gene
- recessive disorder
- blood cells distorted and don’t flow properly
