Genetics MSU Peebles Test 1

Methemoglobinemia (met-H)

blue gene
autosomal recessive gene

Polygene concept

multiple genes affect one trait

Pleiotropism Concept

multiple traits affect one gene

Epiloia (tuberous sclerosis)

dominantly inherited congenital
adenoma sebaceum
benign tumor-like malformations in nervous system, heart, and kidneys
epilepsy
mental retardation

Penetrance

% of individuals that show a particular phenotype to any degree among those capable of showing it

affected by modifier genes, epistatic genes, or suppressor genes or by modifying effects of environment

Expressivity

the degree of effect produced by a penetrant genotype.
a trait, although penetrant, may be quite variable in its expression

Mendels 2nd Law

Independent Assortment

either allele of 1 gene pair can enter a gamete with either allele of any other gene pair and all possible combinations are produced in equal proportions

Gene Interaction

pertains to the relationships between alleles belonging to different gene pairs

Sorrel

horse w/ base color or red with no black or dilution gene

Palomino

sorrel/chestnut that received 1 copy of creme dilution gene from 1 parent

pale cream to golden to chocolate and white mane and tail

Cremello

sorrel/chestnut that received 1 cope of creme dilution gene from each parent

pink skin, blue eyes, cream to white coat/ white mane and tail

Bay

black horse with bay gene (restricts black mane, tail, and legs)

no dilution gene

Buckskin

bay horse with 1 copy of creme dilution gene from 1 parent

very pale to gold to dark smutty and black points

Perlino

bay with 1 copy of creme genes from each parent

pink skin, blue eyes, cream to white coat and dark mane and tail

Black

black horse with no bay gene

Smoky Black

black horse with 1 copy of creme dilution gene from 1 parent

Smoky Cream

black horse with 1 copy of creme dilution gene from each parent

pink skin, blue eyes, orange or red cast to entire coat

Gene Interaction

the expression of a gene will sometimes modify the expression of another gene

Mendel

father of genetics
1856-64 conducted garden pea experiment

Who discovered Mendels work in 1900 after it was duplicated?

Hugo de Vries
Car Correns
Erich von Tschermak

William Bateson

gave England 1st news of Mendel
May 8, 1900

Garden Pea

Plsum Sativum

annual
well defined characteristics
easily grown and crossed

Tetrad

the quadruple of group of chromatids that is formed by the association of split homologous chromosomes during meiosis

gene (biological)

a section of DNA that determines the amino acid sequence of a polypeptide

gene (mendelian)

the unit of inheritance. that inherited unit located on chromosomes which determines a biological characteristic.
a unit of function and mutation

Locus

a fixed position on a chromosome that is occupied by a given gene or one of its alleles

Allele

one contrasting form of a gene
located on homologous chromosomes

Homologous Chromosomes

chromosomes in pairs at meiotic prophase
similar in size, shape, and centromere location
contain alleles for same gene
NOT IDENTICAL

Backcross

a cross between an F1 heterozygote and 1 of the P1 parents

Mendels 1st Law

Allelic Segregation
alleles of each gene segregate at the time of meiosis (gamete formation) so that half the gametes carry one allele and half carry the other

Testcross

a cross between a genetically unknown individual and homozygous recessive individual (testcross parent)

Semi-Dominant lethality Examples

creeper chicken syndrome
familial hyper-cholesterolemia (FH) in humans
osteoperosis

Dominant Lethality Examples

epiloia in humans
whenever lethal allele is expressed, the individual dies (no cross needed)

Recessive Lethality Examples

cystic fibrosis
amaurotic idiocy (Tay-Sachs)

F1 generation

always heterozygous

F2 generation

produced by cross two F1's

P generation

homozygous for contrasting genes

probability of getting one specific combination of alleles in a gamete

1/2^n

number of different F1 gametes

2^n

number of different F2 genotypes

3^n

number of different F2 phenotypes

2^n

Brachyphalangy

semidominant lethality

Dihybrid

(AaBb)
2^n --> 4

Trihybrid

(AaBbCc)
2^n -->8

(FH) homozygous dominant (FF)

normal plasma LDL levels
normal number of receptors

(FH) heterozygous (Ff)

2x normal plasma LDL levels
1/2 normal number of receptors

(FH) homozygous recessive (ff)

6x normal plasma LDL levels
lacking normal receptors

Genes present in human genome

20-25K

Autosomes

non-sex chromosomes (22 pairs)

Chromosome pairs present in human kayotype

22

What kind of dominance is present at the organism level of sickle cell anemia>

complete dominance

What kind of dominance is present at the cellular level of sickle cell anemia?

semi-dominance

What kind of dominance is present at the molecular level of sickle cell anemia?

co-dominance

Co-Dominance

a form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive.

Blood Types