Ch4: Modification of Mendelian Ratios

Extranuclear inheritance

DNA within organelles (outside of nucleus) can also affect an organism’s phenotype

• mtDNA (organelle heredity)

  • maternal effect

what is considered a wild type allele

the most frequent allele in a population

loss of function mutation results in ________

null allele

drosophila genetics

short name (1-3 letters) to label mutations based on what the mutation looks like

vg = vestigal wings

incomplete dominance results in __________

intermediate phenotype

offsprings traits look like mix of parents traits

red + white = pink

codominance

both alleles are fully expressed

bombay phenotype

rare genetic condition where a person genetically has blood type A, B, or AB but appears as type O in blood tests bc they lack the H antigen where A & B attach to.

lethal alleles

• recessive lethal → you need 2 copies to die (aa).

• dominant lethal → just 1 copy is enough (Aa or AA).

epigenesis

step by step development with multiple genes

epistasis

when one gene hides/changes the effect of another

• bombay phenotype

Recessive Epistasis

• aa masks B/

• (9:3:4)

Dominant Epistasis

A/ masks B or bb

• (12:3:1)

duplicate recessive epistasis/ complimentary gene interaction

one dominant of both genes to show phenotype

if either aa or bb, its masked ]

• (9:7)

Duplicate Dominant epistasis

either A or B gives the same result

• aa + bb

• (15:1)

novel phenotypes

two genes interacting creates new traits that arent seen in either parent

complementation analysis

used to figure out if two mutations are in the same gene or dif genes by :

• cross them → look at F1 generation

  • If F1 looks different the mutations are in dif genes = complementation

  • if F1 looks the same as parents, the mutations are in the same gene = no complementation

pleiotropy

one gene affects many traits

men are ____ because they have one copy of each sex gene

hemizygous

crisscross inheritance

x linked trait is passed from homozygous mom to her sons, then again to daughter then to son

• color blindness

• duchenne muscular dystrophy

penetrance

how many ppl show the mutation phenotype?

expressivity

how strong is the mutation in each person ?

Position Effect

where a gene is located on a chromosome can affect whether or how much its expressed

• if gene moves near heterochromatin is might get turned off

types of conditional mutations

1. Temperature effects phenotype

   • gene can be expressed in a certain environment (not mutation)

   • siamese cats w/ darker fur in cooler areas

2. Temperature-sensitive mutations

   • permissive condition = gene functions in lower temp

   • restrictive condition = gene stops working at high temp

   • Flies w/ no eyes if developed in above 30C

genetic anticipation

when a genetic disease gets worse and starts earlier in each new generation

• grandpa = 60 , mom starts at 40, you at 20

heteroplasmy

cell has a mix of normal and mutated mitochondrial DNA

if a trait is controlled by _______ its biparental , and if the trait is controlled by chloroplast / mtDNA its __________.

nuclear genes ; maternal

whats inside mtDNA in humans ?

• 16,569 base pairs

• 13 proteins for aerobic respiration

• 22 tRNAs to delivery building blocks for proteins

• 2 rRNAs to build proteins

Bicoid (bcd) gene

mother’s genotype helps the embryo of flies know where the head should form ; if mom is homozygous recessive for bcd, embryo wont have a head, heterozygous = head