Genetics

Front 1

epistasis 1

Back 1

interactions of different genes in which an allele of one gene masks the expression of alleles of another gene.

Front 2

constant expressivity

Back 2

genotype always produces expected phenotype

Front 3

dihybrid phenotypic ratio 2

Back 3

9:3:3:1

Any deviation from this means that the phenotype is the product of the interaction of 2 or more genes.

Front 4

sex limited traits

Back 4

genes that are on autosomes affect a particular character that appears in one sex but not the other

Front 5

crossover frequency

Back 5

frequency of physical exchanges between chromosomes in meiosis for the region between the genes

the farther apart 2 genes are, the greater the crossover frequency

Front 6

variable expressivity

Back 6

genotype doesn't always produce expected phenotype

Front 7

recombination frequency

Back 7

the frequency of recombination of genetic markers in a cross as determined by analyzing the phenotypes of the progeny.

Front 8

expressivity

Back 8

the degree to which a penetrant gene or genotype is phenotypically expressed in an individual.

depends on genotype and environment and may be constant or variable

Front 9

Gene interaction 1

Back 9

progeny that has a phenotype that no parent has

Front 10

parentals

Back 10

progeny showing parental combos of the alleles.

Front 11

hypostatic 1

Back 11

the gene that is being masked in epistasis

Front 12

genetic recombination

Back 12

the process by which recombinants are produced.

Front 13

multiple alleles 2

Back 13

in a population, a gene has many forms of alleles.

A diploid individual only has 2 forms, one on each chromosome.

Front 14

recombinants

Back 14

progeny showing non parental combinations of alleles.

Front 15

recessive epistasis 2

Back 15

a/a B/- and a/a b/b individuals have the same phenotype

the phenotypic ratio is 9:3:4.

Front 16

genetic analysis

Back 16

dissection of the structure and function of genetic material.

progeny from crosses between parents with different genetic characteritics are analysed to see frequency with which different alleles are associated into different combinations.

Front 17

complete dominance 3

Back 17

one allele is dominant to another

the phenotype of the heterozygote is the same as homozygous dominant.

The same phenotype results wether the dominant allele is heterozygous or homozygous.

Front 18

sytenic

Back 18

genes on the same chromosome

don't always assort independently

Front 19

repulsion

Back 19

each homologue has a wild type allele and a recessive mutant allele

also called trans configuration

Front 20

independent assortment

Back 20

assumes genes are on different chromosomes or far away from each other on the same chromosome

Front 21

complete resessiveness: when is it expressed? 2

Back 21

the recessive allele is only phenotypically expressed when the organism is homozygous.

The recessive allele has no effect on the phenotypic outcome of the heterozygote.

Front 22

examples of diseased genes being sex influenced:

Back 22

men: cleft palate, clubfoot, gout.

women: arthritis, lupus, osteroporosis, thyroid disorders

Front 23

coupling

Back 23

2 wild type alleles are on one homologue, and the 2 recessive mutant allels are on the other homologue

also called cis conformation

Front 24

nature vs. nurture

Back 24

social environments affects phenotype.

ex: alcoholism; the genes don't actually make the person an alcoholic, social situations contribute.

Front 25

incomplete dominance 2

Back 25

when one allele is not completely dominant to another allele. The heterozygote's phenotype is in between the two alleles.

It is a mix of the two alleles EX: red and white flowers produce pink.

Front 26

chiasma

Back 26

the place on a homologous pair of chromosomes where the physical exchange is happening.

the site of crossing over

Front 27

duplicate resessive epistasis 3

Back 27

an interaction of two genes to give rise to a specific product.

ex. pea flowers. If the flower is homozygous recessive at either gene loci, it will be white.

Either gene pair produces the same phenotype. THe homozygous recessive alleles mask the dominant alleles of the other gene.

Front 28

phenylketonuria

Back 28

autosomal recessive disorder

can't handle phenylaliine in your diet.

severe mental retardation will occure if there is.

Front 29

phenocopy

Back 29

a phenomenon that occurs when a developing organism is exposed to certain drugs, viruses or chemicals at critical points in development

Front 30

crossing over

Back 30

the process of reciprocal exchange of chromatid segments

involves breakage of two chromatids and rejoining

leads to genetic recombination between linked genes

takes place during prophase I of meiosis

Front 31

how age affects phenotypic expression:

Back 31

not understood how

some phenotypes come out at certain ages

ex:pattern baldness 20-30 yrs
duchenne muscular dystrphy 2-5 yrs

Front 32

pattern baldness

Back 32

gene is dominant in males, and recessive in females.

expression of gene influenced by testosterone.

also shows variable expressivity.

Front 33

Temperature sensitivity:

Back 33

some alleles work at different temps.

ex: himilayan rabbits fur color is dependant on temp.

used in the lab to manipulate genes.

Front 34

chemical environmental disruption:

Back 34

chemicals can effect the phenotype exibited by a genotype.

Phenylketonuria in humans

Front 35

sex influenced traits

Back 35

often on autosomes

may appear in both sexes, but frequency or phenotype is different between sexes

Front 36

codominance 1 + example

Back 36

offspring show phenotype of both parents.

ex: AB blood groups you get a copy of the same allele from each parent, but they differ.

Front 37

examples of phenocopy

Back 37

rubella infection in mom in first 12 weeks

thalidomide for morning sickness caused babies with no arms or legs

not gentic defects, just look as though they are.

Front 38

lethal allele

Back 38

causes death of an organism because of an essential gene.

Front 39

incomplete penetrance

Back 39

less than 100% show phenotypes expected.

Front 40

essential genes

Back 40

when mutated these genes cause death.

Front 41

What ratio is produced by interbreeding of two incomplete dominant individuals? EX: two grey chickens

Back 41

1:2:1

Front 42

linked genes

Back 42

genes that don't assort independently.

belong to a linkage group

Front 43

hla antigens

Back 43

these antigens are codominant, so you will express the tissue typing antigens of both your mother and father.

in the case of a transplant you are most compatible with a sibling.

Front 44

complete penetrance

Back 44

when 100% of individuals are homozygous recessive show that phenotype
100% who are homozygous dominant show that phenotype

and 100% that are heterozygous are alike

Front 45

dominant lethal allele

Back 45

both homozygotes and heterozygotes for that allele will show the lethal phenotype

Front 46

penetrance

Back 46

degree to which a gene expresses itself in a population.

dependant on genotype and the environment.

Front 47

recessive lethal allele

Back 47

only homozygotes for that allele will have the lethal phenotype.