Unit Seven - Genetics

Question 1

Definition of the Genetic Chromosome Theory (Mendel)

Answer 1

Genes are inherited by chromosomes

Question 2

Definition of Homozygous (2)

Answer 2

1. Identical Alleles in a Gene (Pure)
2. 2 Recessive Genes (rr) or 2 Dominant Genes (RR)

Question 3

Definition of Punnett Square

Answer 3

Diagram geneticists use to predict possible genetic outcomes when cross/breeding experiment

Question 4

Definition of Law of Dominance (Mendel) (4)

Answer 4

1. When Dominant & Recessive Gene is Present
2. Dominant Expresses Itself & Recessive is Masked
3. Recessive only shows in rr
4. Dominant shows in Rr & RR

Question 5

Definition of Heterozygous (2)

Answer 5

1. Nonidentical Alleles in a Gene (Hybrid)
2. 1 Recessive & 1 Dominant

Question 6

Definition of Genotype

Answer 6

How Genes Look Like (Genetic Makeup)

Question 7

Definition of Phenotype

Answer 7

How Physical Traits Look Like

Question 8

Definition of Pedigree

Answer 8

Family tree that shows how physical/genetic trait/condition is passed down

Question 9

What are the different generations known as in a Pedigree? (3)

Answer 9

1. Parent Generation - P
2. 1st Generation - F1
3. 2nd Generation - F2

Question 10

Definition of Dihybrid Cross (3)

Answer 10

1. Genetic Cross
2. Examines inheritance of two different traits
3. EACH TRAIT HAS 2 ALLELES
   Ex: RrTt x RrTt

Question 11

How do you find the possible allele combinations in a Cross? (2)

Answer 11

1. Each parent can form 4 possible allele combos
2. Distribute the alleles in each trait

Ex: RrBb - RB, Rb, rB, rb

Question 12

What is the probability ratio for dihybrid allele combos in offspring?

Answer 12

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

Question 13

What are the 3 Laws associated with Mendelian Genetics?

Answer 13

1. Law of Dominance
2. Law of Segregation & Recombination
3. Law of Independent Assortment

Question 14

How do you find the probability of traits in an offspring when given traits possessed by both parents?

Answer 14

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

Question 15

Definition of Intermediate Inheritance (3)

Answer 15

1. AKA Incomplete Dominance
2. One allele is partially dominant over the other
3. Offspring’s phenotype is a blend/intermediate of 2 parents’ phenotypes

Question 16

Definition of Codominance

Answer 16

1. Both Alleles are Dominant
2. Both traits show up in the phenotype

Question 17

What do different blood types show up as?

Answer 17

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)

Question 18

Definition of Polygenic Inheritance

Answer 18

Multiple genes are needed to inherit a single trait

Question 19

Definition of Sex - Linked Traits (2)

Answer 19

1. Genes on the X - Chromosome
2. Passed from Mother to Son

Question 20

What is a carrier gene? (3)

Answer 20

1. Only found in XX (mothers)
2. Contains Dominant & Recessive Allele (HᴴHʰ)
3. Mother itself does not have disease but can pass it on to sons (bc dominant and recessive allele cancel out)

Question 21

Why can only mothers pass on X - Linked diseases? (3)

Answer 21

1. Males pass his single X to all of his daughters (Daughters get X from M&D)
2. All daughters will be carriers
3. Sons receive Y chromosome from D (50% gets the from M)

Question 22

Why can males exhibit sex - linked traits more often than females?

Answer 22

1. If the gene is recessive
2. Males need one recessive gene to have sex - linked trait
3. 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

Question 23

What are some examples of sex - linked traits?

Answer 23

1. Hemophilia (Sexlinked Recessive) - Cannot Clot Blood
2. Color Blindness (Sexlinked Recessive) - Cannot See Color
3. Duchenne Muscular Dystrophy (Sexlinked Recessive)

Question 24

What are four types of genes that can be passed down?

Answer 24

1. Autosomal Dominant
2. Autosomal Recessive
3. Sexlinked Recessive
4. Sexlinked Dominant

Question 25

How can you identify what type of gene is passed down on a pedigree? (4)

Answer 25

1. Autosomal Dominant - Male & Female, every generation & lots of receivers
2. Autosomal Recessive - Male & Female, skips generation & limited receivers
3. Sexlinked Recessive - Only Males, skips generation & limited receivers
4. Sexlinked Dominant - Only Males, every generation & lots receivers