GENETICS EXAM 2 (aLLeles interactions)

•Genes are the physical units of heredity

the physical units of heredity

chromosomes are

long molecules of doubl- stranded DNA

genes are on what

chromosomes

2 copies of each sexually reproducing chromosome (2 copies of each gene)

diploid

alleles are

alternative forms of a gene

each gene may have?

multiple alleles in a population

alleles encode what type of gene product

different version

each diploid individual can be homozygous, which means

2 gene copies are same allele

A1 AND A1

each diploid individual can be heterozygous , which means

2 gene copies are different alleles

genotype

the genetic makeup of an organism

• allele combination, what allele combination do you have

phenotype

the observable traits of an organism

• what you see

• natural selection acts on the phenotype which is determined by the underlying genotype

evolution

one phenotype is favored, the frequencies of alleles associated with each phenotype change across generations

wild type

the allele that occurs most frequently in the population

• normal allele

mutant allele

any alleles whose DNA sequence differs from the wild type allele

• diff in DNA sequence

• encodes diff RNA OR PROTEIN

GENE INTERACTION

genes and alleles interact to influence phenotype

dominance

relationship between 2 alleles of the same gene

complete dominance

phenotype of only one allele is visible in a heterozygote

in dominant alleles the phenotype is observed in

the homozygous and heterozygous genotypes

in recessive alleles the phenotype is observed in

only when HOMOzygous

phenotypes are a consequence of

the activities of the protein products produced by the alleles of a gene

dominance is determined by the

activity of protein products of the alleles

gene dosage

key to determining dominance

more copies of a gene there are, more gene product will be produced when that gene is expressed

haplosufficient

in diploids , genes only require a single copy for a normal level of function

a gene is haplosufficient when

the person is carrying one functional allele and one non-functional allele (heterozygotes) , they will display the wild type phenotype (WILD TYPE ALLELE IS DOM)

a gene is haploinsufficient when

a perosn is carrying one functional allele and one non- functional allele (heterzygotes), they will display the mutant phenotype (MUTANT PHENOTYPE IS DOMINANT)

mutant alleles can be; loss of function

complete loss of a functional gene product

mutant alleles can be; gain- of- function

acquires a new function

loss of function mutations; null mutaiton

lethal when homozygous

loss of function mutations; leaky mutation

results in a partial loss of function due to decreased gene product

dominant negative mutations

multimeric proteins, composted of 2 or more polypeptides join together to form a functional protein

• have a spoiler effect on the protein as a whole (one bad apple spoils the whole bunch)

gain of function mutations; hypermorphic

mutations produce more gene product than normal

gain of function mutation- neomorphic

gene product with novel function not found in the wild type

incomplete dominance

heterozygous people display phenotypes intermediate to either homozygous phenotype po

• HETERO ARE INTERMEDIATE

codominance

heterozygotes with different phenotype than that of either homozygote

NOT PHENOTYPE

OWN THING NOT INTERMEDIATES

ABO ALLELES; IA ,IB AND i

IA AND IB- ARE COMPLETELY DOM OVER THE i allele

• CODOMINANT WITH EACHOTHER

type A

pressense of one antigen on the blood cell surface

type B

the presence of a different antigen

type AB people

have both antigens

type O

people have neither

wild type C allele

full coat of color

completely dom over all the others

c ch

dilute phenotype, called chinchilla

• incompletely dominant over c h

c h

called himalayan, little pigment on the body but full color on the extremities

c

fully recessive null , white phenotype

lethal mutations

single- gene mutations that cause death that are inherited as alleles