fHelpful videos (if you’re a visual learner)
● Chapter 6:
○ https://www.youtube.com/watch?v=Hio0Hys_UaU
Chapter 4: Gene Interaction
● Types of Epistasis (alternate phenotypes resulting from gene interaction)
○ Complementary gene interaction (9:7 ratio)- genes work together (remember
what complementary means)
example: Allele C and P both code for purple and white flowers. Dominant C and P (C_P_)
code for purple flowers, if there is recessivity for either c or p, or both, the flowers will be white
○ Duplicate gene interaction (15:1 ratio)- ) genes are in redundant system
(remember duplicate means “copy”)
i. P and R code for purple (dom.) or white (rec.) flowers. PpRr x PpRr is a
redundant system, meaning it only needs 1 dominant allele to make
purple show up. (P_R_, P_rr, ppR_ all code for purple, as they all have
one dominant allele)
ii. pprr is white
○ Dominant gene interaction (9:6:1 ratio)- where there are 3 phenotypes
i. Both alleles are dominant or heterozygous (A_B_) 9
ii. One allele is dominant, the other is recessive (A_bb or aaB_) 6
iii. Both alleles are recessive (aabb) 1
○ Recessive epistasis (9:3:4 ratio)- There are two genes, and the recessive allele of
one of them can mask the other
● SWGene B makes eumelanin an d Gene E distributes eumelanin. They both have to be
dominant to show up
i. B_E_ means that eumelanin is made and distributed (black Lab) 9
ii. bb_E means that eumelanin is not made even if eumelanin can be
distributed (chocolate Lab since eu. couldn’t fully distribute) 3
iii. B_ee means that eumelanin is being made but not distributed (yellow
Lab)
iv. bbee means no eumelanin and no eu. distribution (makes pheomelanin
instead, which makes Labradors yellow)
○ Dominant epistasis (12:3:1 ratio)- Two genes are present and the dominant
allele of one blocks the other
i. Two alleles, W and Y (W codes for white, Y codes for yellow if W isn’t
dominant, and yy codes for green if W isn’t dominant)
ii. The allele W cancels out Y’s effects, whether Y is dominant or recessive
iii. W_Y and W_yy both are white 12
iv. wwY_ is yellow 3
v. wwyy is green 1
○ Dominant suppression (13:3 ratio)- dominant allele of one gene suppresses the
expression of the other gene
i. L= blue, ll= white, D=suppresses blue
ii. L_D_ is white, because even though the allele for blue (L) is present, D
suppresses it
iii. llD_ is white
iv. lldd is white
, v. L_dd is blue because of the presence of L and no big D
COMPLEMENTATION
- Mutants are marked with (-) and they fail to complement one another
- Regular crosses are marked with a (+)
- We are looking for complementation groups
- If two letters/numbers meet at a (+), they can’t be in the same complementation group
Group 1- A, C, E, H
Group 2- B,D,F
Group 3- G
Chapter 5: Genetic linkage & mapping in Eukaryotes
● Foundational theories in genetics
○ Theory of heredity
■ Genes are carried on chromosomes
○ Genes are composed of nucleotides, recombination can occur
○ Evolutionary theory
● Mutation and recombination generates the raw genetic diversity on which evolution
depends
● Sexual reproduction and recombination operates to increase diversity between
generations
● Syntenic genes- genes located on the same chromosome
● Genetic linkage produces a distinctive pattern of gamete genotypes that can be
quantified and analyzed to map the locations of genes on chromosomes
● Homologous recombination= crossing over in prophase 1 of meiosis, reciprocal process
○ Homologous chromosomes that do not undergo crossing over retain all the
same alleles they had when they were transmitted
● Sexually reproducing organisms-
○ recombination chromosomes contain a combination of alleles initially carried by
the different parents of the organism in which recombination is occurring
● Syntenic genes located far apart and genes located on separate chromosomes
● Chapter 6:
○ https://www.youtube.com/watch?v=Hio0Hys_UaU
Chapter 4: Gene Interaction
● Types of Epistasis (alternate phenotypes resulting from gene interaction)
○ Complementary gene interaction (9:7 ratio)- genes work together (remember
what complementary means)
example: Allele C and P both code for purple and white flowers. Dominant C and P (C_P_)
code for purple flowers, if there is recessivity for either c or p, or both, the flowers will be white
○ Duplicate gene interaction (15:1 ratio)- ) genes are in redundant system
(remember duplicate means “copy”)
i. P and R code for purple (dom.) or white (rec.) flowers. PpRr x PpRr is a
redundant system, meaning it only needs 1 dominant allele to make
purple show up. (P_R_, P_rr, ppR_ all code for purple, as they all have
one dominant allele)
ii. pprr is white
○ Dominant gene interaction (9:6:1 ratio)- where there are 3 phenotypes
i. Both alleles are dominant or heterozygous (A_B_) 9
ii. One allele is dominant, the other is recessive (A_bb or aaB_) 6
iii. Both alleles are recessive (aabb) 1
○ Recessive epistasis (9:3:4 ratio)- There are two genes, and the recessive allele of
one of them can mask the other
● SWGene B makes eumelanin an d Gene E distributes eumelanin. They both have to be
dominant to show up
i. B_E_ means that eumelanin is made and distributed (black Lab) 9
ii. bb_E means that eumelanin is not made even if eumelanin can be
distributed (chocolate Lab since eu. couldn’t fully distribute) 3
iii. B_ee means that eumelanin is being made but not distributed (yellow
Lab)
iv. bbee means no eumelanin and no eu. distribution (makes pheomelanin
instead, which makes Labradors yellow)
○ Dominant epistasis (12:3:1 ratio)- Two genes are present and the dominant
allele of one blocks the other
i. Two alleles, W and Y (W codes for white, Y codes for yellow if W isn’t
dominant, and yy codes for green if W isn’t dominant)
ii. The allele W cancels out Y’s effects, whether Y is dominant or recessive
iii. W_Y and W_yy both are white 12
iv. wwY_ is yellow 3
v. wwyy is green 1
○ Dominant suppression (13:3 ratio)- dominant allele of one gene suppresses the
expression of the other gene
i. L= blue, ll= white, D=suppresses blue
ii. L_D_ is white, because even though the allele for blue (L) is present, D
suppresses it
iii. llD_ is white
iv. lldd is white
, v. L_dd is blue because of the presence of L and no big D
COMPLEMENTATION
- Mutants are marked with (-) and they fail to complement one another
- Regular crosses are marked with a (+)
- We are looking for complementation groups
- If two letters/numbers meet at a (+), they can’t be in the same complementation group
Group 1- A, C, E, H
Group 2- B,D,F
Group 3- G
Chapter 5: Genetic linkage & mapping in Eukaryotes
● Foundational theories in genetics
○ Theory of heredity
■ Genes are carried on chromosomes
○ Genes are composed of nucleotides, recombination can occur
○ Evolutionary theory
● Mutation and recombination generates the raw genetic diversity on which evolution
depends
● Sexual reproduction and recombination operates to increase diversity between
generations
● Syntenic genes- genes located on the same chromosome
● Genetic linkage produces a distinctive pattern of gamete genotypes that can be
quantified and analyzed to map the locations of genes on chromosomes
● Homologous recombination= crossing over in prophase 1 of meiosis, reciprocal process
○ Homologous chromosomes that do not undergo crossing over retain all the
same alleles they had when they were transmitted
● Sexually reproducing organisms-
○ recombination chromosomes contain a combination of alleles initially carried by
the different parents of the organism in which recombination is occurring
● Syntenic genes located far apart and genes located on separate chromosomes
