31: Extensions to mendel/Pedigree analysis

What is the genetic maternal effect? What does it usualy involve?

Genotype of mtoher determined pheynotype of offspring. Neither male parent nor offspring’s genotype affects offspring’s phenotype

Usually inboles components of egg cytoplasm important for development 

When does the paternal genotype become apparent

in f2 because father’s genes contribute to the genotyope of pffspring

Talk through P generation of Dextral (S+S+) male and sinistral (SS) female

Dextral is dominant. All the F1 are heterzygous (S+,S) because the genotype of the motehr determines phenotype of offspring. If self fertilization occurs, then the offspring will be dextral bc the GENOTYPE of the om is S+S, and since S+ is dominant even the offsprung that has SS will still be dextral.

What is genomic imprinting/ What is maternal imprinting vs. paternal imprinting? What does it depend on?

The expression of an allele is determined by the parent from which it was inherited

Maternal Imprinting: The allele inherited from the mother is silences

Paternal impringting: The allele inherited from the father is silences

Imprinting depends on DNA methylation and is a form of epigenetics. Not a change in sequence. Change in expression.

What type of genes can have lots of imprinting 

Developmental genes 

What are the exceptions/extensions to mendel

• sex linked inheritance

• types of dominance

• gene interaction

• sex influenced inheritance

• envrionmental factors

• continuous characteristics

Explsin envrionmental effects and give an example

When the sequence of the protein is affected, not so muhc the gene itself, by envrionmental conditions

Example: Bunnies and temp sensitive alleles. Black pigmentation in rabbits occurs at colder temps in bodies. So bunneis raised in colder conditions will have darker black pigmentation

Explain Continuous Characteristics. What else are they called> What are they influenced by? What do they need to understand them? 

Aka wuantatative charactersitcs. 

Phentoypes experiince conituous variation over a range 

Often involve genes at may loci (polygenic characteristics) basically multiple genes are involved 

May also be influnced by envrionmental factors 

ANalysis may requrie statistical approached to understand patterns of inheritance

What is a reason why human genetics are difficult to understand

Humans are complex organisms, basically opposite of model organisms

What is a pedigree

A way to map inheritance patterns of traits through family history

What is the symbol of unaffected males, unaffected females, and unaffected sex unknowns

Unaffected male: White square

Unaffected female: White circle

Unaffected unknown sex: white diamond

What is the symbol for affected: Males, females, sex unknowns

Male: red square

Female: Red circle

Sex unkown: red diamond

What is the symbol for obligate carrier

Male: White square with red dot

Female: White circle with red dot

Unknown sex: white diamond with red dot

What is the symbol for asymptomatic carrier

Male: white square with vertical line

Female: White circle with verticle line

Unknown sex: White diamond with verticle line

What proband? What is symbol for proband

The first affected family member coming to attention of genetiscists 

Male: red square with p next to it 

Femae: red circle with p next to it 

unknown sex: red diamond with P on and next to it 

What does adoption look like in pedegree

Brackets around the adopted person. Dashed line to adopted parents, solid line to biological parents

What do identical twins look like on pedigree

Triange connecting them to parents with li

hat to nonidentical twins look like

Open triangle connectign to parents

What do unknown twins look like 

Open triangle connecting them to parents with a question mark 

What does incest look like of pedigree

instead of one line between two people indicating relationship, there is 2

what do autosomal recessive traits look line on a pedigree tree

Appear with equal prequency in males and females 

Tend to skip generations (often rises from unaffected parents)

What do autosomal dominant traits look like in pedigree tree

Appear with equal frequency in males and females

Tend to be present in all generations

X linked recessive traits

Appear in higher frequency in males than females

tendency to skip generations

always passed from mother to son, never from father to son

X linked dominant traits 

Appear higher frequency in frmales than males 

does not skip generations 

affected father will produce all affected daughters and no affected sons 

Affected mother will produce ~50% affected sons and daugthers 

Y linked traits

Only apprear in males

Appears in all generations regardless of dominance

What type of pedigrees are more useful for analysis

Pedigrees with more data

What did pedigrees reveal tabout the social organization of a neolthic community

Men stayed on one group when women moved around

absence of half siblings and high number of full siblings = higher fertility, lower mortality, stable conditions

Pedigrees can be cinsturcted from ancient DNA

Twin studeis -concordance revelations. Monozygotic vs dizygotic 

COncordance studies show relative influence of genes and envrionment on traits, very qualatative. Answeres question: does the phenotype result from a combination of genotype and envrionment 

Concordance: is % of twin pairs that share a trait. SO if it is 100% then both twins have the trait 

Monozygotic (identical) share 100% DNA so any difference in phenotype is envrionmental 

Dizygotic (nonidentical) share 50%

If concordance perecent is higher for monozygotic than dizygotic, then trait has genetic component 

What do adoptive twins studies show

Similar characteristics to adopted parents suggests environmental influence

similar characteristics to biological parents suggests genetic influence