Biology Lecture 14

Complex Inheritance

Single-gene trait

1 gene controls 1 trait

Multiple gene traits

2 or more genes control 1 trait

single-gene

what type of trait is commonly used for practice with Punnett squares (single-gene or multiple gene)

Discrete traits

yes or no, purple or white

continuous traits

range of phenotypes

wild type alleles

most common in the wild population, tends to be the dominant allele

mutant alleles

less common in the wild

autosomal traits

most of our DNA is located on our autosomal chromosomes (autosomes)

sex-linked traits

genes located on a sex chromosome (X or Y)

sex chromosomes

where are sex-linked traits located

since males only have one X chromosomes, there isn’t another one to mask it from the X-linked trait

why are males impacted more often by X-linked traits (XX)? (examples: color blindness and hemophilia)

males

who can be impacted by a Y-linked trait?

sex-influenced traits

autosomal traits with a percentage influenced by sex hormones

karyotype

an image that shows chromosomes arranged by number

IDing chromosomes

what do we use karyotypes for

IDing chromosomes

look at size (length), centrome location, and G bonding patterns (dark/light pattern)

numbers

how are autosomes identified in karyotypes

X or Y

how are sex chromosomes labeled in karyotypes

female

XX

males

XY

pedigree chart

a family tree depicting a genetic trait, an ethical means of studying genetic conditions/diseases

male

what does the square mean in pedigree charts

female

what does a circle mean in pedigree charts

person has the trait

what does a shaded shape mean in pedigree charts

person does not have the phenotype of interest

what does an open shape mean in pedigree charts

look at the ratio of shaded circles vs. squares, if there is a small difference between the two, the trait is autosomal; if the difference is large, the trait is X-linked

how do you determine if a trait is X-linked or autosomal

it is a recessive trait

if a trait is x-linked what is assumed

does the trait skip generations? yes- recessive; no- dominant

if a trait is autosomal, how do you determine if the trait is dominant or recessive