Genetics Flashcards
Mendel’s Early work
P -> Parental
F1 -> First Filial (Offspring of Parental generation)
F2 -> Second Filial (Offspring of F1)
He crossed a white and a purple flower, their offspring (F1) were 100% purple. He let F1 self-pollinate and their offspring (F2) were 75% purple and 25% white (3:1)
He concluded that purple was a dominant trait and white was recessive.
What’s Independent Assortment?
When genes separate independently during the formation of gametes. Leads to variation
Explain Dominant/Recessive Alleles
A dominant allele masks the appearance of another and a recessive alleles only appears when both alleles are recessive
Explain Heterozygous, Homozygous, Purebreds and Hybrids
Heterozygous (Hybrid) -> Organisms that have two different alleles
Homozygous (Purebreds) -> Organisms that have a pair of identical alleles
Genotype VS. Phenotype
Genotype -> Genetic make-up of an organism (TT,Tt,tt)
Phenotype -> An organisms appearance (blue eyes)
Explain Codominace and give an example
A condition in which both alleles contribute to the phenotype of an organisms
Ex. Erminette Chicken, (Black + White Alleles)
Explain Incomplete Dominance and give an example
A case in which one allele is not completly dominant over another allele. The heterozygous offspring are a blend of the parents phenotypes
Ex. Pink Flower (Red Flower + White Flower)
Multiple Alleles
A gene that has more than two alleles
Ex. human blood types
Polygenic Traits
A trait that is controlled by two or more GENES
Ex. Skin tone
What is a Punnett Square for?
The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment
In which situations do 3:1 and 9:3:3:1 ratios apply?
9: 3:3:1 -> Dihybrid Crosses (BbEe × BbEe)
3: 1 -> Monohybrid Cosses (Rw x Rw)
Karyotype
A picture of the full set of human chromosomes
Autosomes -> First 22 pairs
Sex Chromosomes -> 23rd pair (XX or XY)
What is Non-disjunction and how does it cause conditions such as Down’s, Kleinefelter’s and Turner Syndome
Non-Disjunction -> The failure of homologous chromosomes or sister chromatids to separate properly during cell division
Turners (Females, Karyotype 45) -> causes a female to inherit only one “X” chromosome from her parents
Kleinefelters (Males, Karyotype 47) -> causes a male to inherit two “X” chromosomes along with a “Y”
Downs -> Trisomy on Pair 21
Describe Autosomal Chromosome Disorders
- Happens in one of the first 22 chromosomes
Recessive -> must inherit both alleles to show disorder
ex. Albinism, Cystic Fibrosis
Dominant -> Only need to show one
Ex. Huntingtons
Sex - Linkage
Sex- linked Disorders are liked to sex- linked genes, which are any genes on the X and Y chromosomes
ALL SEX LINKED DISORDERS ARE X-LINKED
Why are males more effected by sex linked disorders?
Because women have two chances to inherit the dominant allele meanwhile men have half the chance of getting the dominant allele
Examples of Sex linked Disorders
Red/Green Colour Blindness, Hemophilia
What do squares and circles symbolize in a pedigree and what does it mean when they’re shaded vs when they aren’t
Female = circle Male = square
Shaded means they’re affected with the disorder in question and unshaded means they aren’t
