Complex Genetics: Extensions to Mendel Flashcards
3 ways complex genetics is different than Mendelian genetics
- More than 2 alleles are possible
- Dominance amount can be variable
- Sex chromosomes alter rates
Probabilities can still be calculated using complex genetics it’s just….
the interpretation is different
Explain what an allele is
An allele is one of a pair of genes that appear at a particular location on a particular chromosome and control the same characteristic, such as blood type or colorblindness.
ASK ABBY
What are 5 different types of dominance used in complex genetics
co-dominance, incomplete dominance, epistasis, sex-linked, polygenetic
Does dominance affect the transmission of alleles?? aka HOW punnet squares are formed??
NO
Complete dominance
Hybrid resembles one of the two parents, depending on which was the dominant trait. All of mendel’s traits show complete dominance
Example-you have dominant R for a white mouse and r for a black mouse. When mixed together if you get Rr it’s going to be white. The mouse fully resembles only ONE of two parents
Incomplete dominance
Hybrid resembles neither parent
Ex. So let’s say AA-equals red and aa-equals white cross breed with each other and you get 100% Aa’s which are Pink. That’s incomplete dominance.
Codominance
Hybrid shows traits from both parents
Codominance Example
Hybrid shows traits from both parents
Example:
Let’s say A controls those with A sugar and B is for B sugar. If you cross these two you’ll have an individual with both A AND B. COOOOODOMINANCE WOOOO
There are six different genotypes that produce four blood types
I^A I^A A
I^A i
I^B I^B B
I^B i
I^A I^B AB
ii O
Why do we care about blood types?
Because successful blood transfusions can only be made with matching blood types. The reason being is the body automatically makes antibodies for the sugars that are NOT present on their own red blood cells
Polygenetic
two or more genes control a single phenotype
Polygenetic Example
two or more genes control a single phenotype.
There’s this picture of an example. There are purple and white flowers. And for the flower to be purple it not only has to have a capital A, but a capital B as well to exhibit the color purple, OTHERWISE KNOWN AS, a single phenotype.
Complementary Polygenetics
Basically what happens is for a particular phenotype to be expressed the enzymes like AA or Aa or some other letters have to be working, along with another enzyme, it’s partner, BB or Bb or some other letter in order to code for a particular phenotype. If the A’s aren’t working there’s no pigment. If the B’s aren’t working there’s no pigment. It doesn’t matter WHAT order. If one doesn’t work NEITHER DOES THE OTHER. AND you need at least one dominant allele of both genes in order for the pigment to work. That’s why I said AA or Aa, not aa. That results in a non-functional enzyme.
Sex-linked traits
traits associated with X and Y chromosomes
Would a woman ever have a trait on a Y chromosome?
No, because women have two XX’s they never deal with Y’s in general
What’s the most prominent pattern of inheritance in sex-linked traits?
X-linked recessive
why would X-linked dominant traits be more common in women?
Because if their father had a trait it automatically gets passed onto his offspring because he only has one X to contribute which is the contaminated one
X-linked recessive traits are more common in?
MORE COMMON IN MEN
X-linked dominant traits are more common in?
MORE COMMON IN WOMEN
Epistasis
An allele at one gene masking the effects of another gene
A gene modifies another gene or multiple other genes
Recessive Epistasis
Epistatic gene must be homozygous recessive to mask the other gene Example: Genotype ee masks the effect of all B genotypes
Dominant Epistasis
Epistatic gene can be homozygous dominant or heterozygous to mask the other gene
Example:
An interaction between non-allelic genes that results in the masking of expression of a phenotype is
epistasis
