GN 301 Module 5: Basics of Mendelian Genetics and Pedigrees

gene

segment of DNA

allele

form of a gene

locus/loci

where on the chromosome the gene is located

Phenotype

appearance of an individual regarding a specific traits

genotype

alleles present in an individual for a trait

homozygous

same alleles for the same trait

heterozygous

different alleles for the same trait

dominant

only one allele is required for the trait to be expressed

recessive

two of the same alleles are required for the trait to be expressed

Mendel’s Law of Random Segregation

alleles segregate randomly into gametes; when the gametes are formed, each allele of one parent segregates randomly into the gametes, so that half of the parent’s gametes carry each allele

AA x AA results in

AA

aa x aa results in

aa

Aa x aa results in

Aa or aa

Aa x Aa results in

AA, aa, or Aa

◻️

male

⚪

female

🔶

sex unknown

Individuals with a specific trait are shaded:

◼️⚫, etc

shape with a question mark in it

phenotype unknown

shape crossed out

deceased

two shapes connected by a bar

marriage bar

a bar connected overhead of two shapes

sibling bar

an arrow pointing to a shape

progeny (the individual the pedigree was made for)

two shapes connected by slanted bars

fraternal twins

two shapes connected by slanted bars with a line in the middle

identical twins

double bars between shapes

consanguineous union (related individuals marry)

shape with a number inside of it

\# of siblings with the same phenotype and gender

Looking at a pedigree, how do you know if a trait is dominant or recessive?

IF DOMINANT:

* you might see two people with a trait have a kid without the trait, indicating they are heterozygous dominant
* you might see two people with a trait have kids and grandkids always have the trait until it is “wiped out” by double recessives in one marriage

IF RECESSIVE:

* you might see a trait skip generations