Unit Seven - Genetics Flashcards
Definition of the Genetic Chromosome Theory (Mendel)
Genes are inherited by chromosomes
Definition of Homozygous (2)
- Identical Alleles in a Gene (Pure)
- 2 Recessive Genes (rr) or 2 Dominant Genes (RR)
Definition of Punnett Square
Diagram geneticists use to predict possible genetic outcomes when cross/breeding experiment
Definition of Law of Dominance (Mendel) (4)
- When Dominant & Recessive Gene is Present
- Dominant Expresses Itself & Recessive is Masked
- Recessive only shows in rr
- Dominant shows in Rr & RR
Definition of Heterozygous (2)
- Nonidentical Alleles in a Gene (Hybrid)
- 1 Recessive & 1 Dominant
Definition of Genotype
How Genes Look Like (Genetic Makeup)
Definition of Phenotype
How Physical Traits Look Like
Definition of Pedigree
Family tree that shows how physical/genetic trait/condition is passed down
What are the different generations known as in a Pedigree? (3)
- Parent Generation - P
- 1st Generation - F1
- 2nd Generation - F2
Definition of Dihybrid Cross (3)
- Genetic Cross
- Examines inheritance of two different traits
- EACH TRAIT HAS 2 ALLELES
Ex: RrTt x RrTt
How do you find the possible allele combinations in a Cross? (2)
- Each parent can form 4 possible allele combos
- Distribute the alleles in each trait
Ex: RrBb - RB, Rb, rB, rb
What is the probability ratio for dihybrid allele combos in offspring?
9:3:3:1
2. 4x4 Punnett Square
5. Or 2x2 Punnett Square for each trait, and record the probability for each trait and multiply the fraction
What are the 3 Laws associated with Mendelian Genetics?
- Law of Dominance
- Law of Segregation & Recombination
- Law of Independent Assortment
How do you find the probability of traits in an offspring when given traits possessed by both parents?
1st Option - 4x4 Punnett Square
a. One Side for Mother’s 4 Possible Allelic Combos (RT, Rt, rT, rt)
b. Other Side for Father’s 4 Possible Allelic Combos
c. Fill in boxes through multiplication to find Allelic Combos in offspring
d. Find probability for each of the four phenotypes as a fraction out of 16
(Round & Tall - 9/16, Round & Short - 3/16, Wrinkled & Tall - 3/16, Wrinkled & Short - 1/16)
2nd Option - 2 2x2 Punnett Square
a. One Side for Mother’s 2 Alleles in Trait (Ex: R & r)
b. Other Side for Father’s 2 Alleles in Same Trait (Ex: r & r)
c. Fill in boxes through multiplication to find Allelic Combos in offspring
d. Repeat for Other Punnett Square for the Other Trait
e. Find Probability of Recessive & Dominant Trait in each square
f. Multiply fractions together from both squares
g. 4 Products are Probabilities for Phenotypes
Definition of Intermediate Inheritance (3)
- AKA Incomplete Dominance
- One allele is partially dominant over the other
- Offspring’s phenotype is a blend/intermediate of 2 parents’ phenotypes
Definition of Codominance
- Both Alleles are Dominant
- Both traits show up in the phenotype
What do different blood types show up as?
Type A - IᴬIᴬ or Iᴬi (AA or AO)
Type B - IᴮIᴮ pr Iᴮi (BB or BO)
Type AB - IᴬIᴮ (AB - codominant)
Type O - ii (OO - recessive)
Definition of Polygenic Inheritance
Multiple genes are needed to inherit a single trait
Definition of Sex - Linked Traits (2)
- Genes on the X - Chromosome
- Passed from Mother to Son
What is a carrier gene? (3)
- Only found in XX (mothers)
- Contains Dominant & Recessive Allele (HᴴHʰ)
- Mother itself does not have disease but can pass it on to sons (bc dominant and recessive allele cancel out)
Why can only mothers pass on X - Linked diseases? (3)
- Males pass his single X to all of his daughters (Daughters get X from M&D)
- All daughters will be carriers
- Sons receive Y chromosome from D (50% gets the from M)
Why can males exhibit sex - linked traits more often than females?
- If the gene is recessive
- Males need one recessive gene to have sex - linked trait
- Females need two recessive genes to exhibit trait, because if one of the X is recessive (affected), the other X (dominant) can compensate and cancel out the disease
What are some examples of sex - linked traits?
- Hemophilia (Sexlinked Recessive) - Cannot Clot Blood
- Color Blindness (Sexlinked Recessive) - Cannot See Color
- Duchenne Muscular Dystrophy (Sexlinked Recessive)
What are four types of genes that can be passed down?
- Autosomal Dominant
- Autosomal Recessive
- Sexlinked Recessive
- Sexlinked Dominant
How can you identify what type of gene is passed down on a pedigree? (4)
- Autosomal Dominant - Male & Female, every generation & lots of receivers
- Autosomal Recessive - Male & Female, skips generation & limited receivers
- Sexlinked Recessive - Only Males, skips generation & limited receivers
- Sexlinked Dominant - Only Males, every generation & lots receivers
