Heredity Flashcards
Heredity
To determine the probablity of two or more independent events occurring together multiply the probabilities of each separate event
gene
genetic material on a chromosome for a trait
allele
variance of genes such as different color
homologous chromosomes
a pair of chromosomes that contains same genetic material (gene for gene). Each parents contributed 1 of the chromosomes in the pair
law of segregation
one member of each chromosome pair migrates to an opposite pole so that each gamete is haploid (aka each gamete has only one copy of each allele. Occurs i anaphase 1
Law of independent assortment
Independant assortment of alleles. migration of homologues within one pair of homologous chromosomes does not influence the migration of homologues of other homologous pairs
What is similar between law of segregation and law of independent assortment?
1) both pertain to meiosis
2) both contribute to genetic variety
What is different between law of segregation and law of independent assortment?
The difference is that law of segregation is
basically “when we form gametes we separate our allele copies so gametes are haploid” and law of independent assortment says “the separation of each pair of chromosomes is completely independent from the separation of any other pair -they each separate at random, outcome of one doesn’t affect others”
Test crosses
Monohybrid crosses test one gene, Dihybrid test two. Crosses have P, F1, and F2 generations
Incomplete Dominance
Blending of expressions of alleles
Ex: pink flower from a red parents and white parent
Codominance
both inherited alleles are completely expressed
Ex: Blood
Multiple alleles
Blood groups have 3 possible alleles, the codominant A and B and the O, leading to 4 possible genotypes: AO (A type), BO (B type), AB (codominant AB type), OO (O type)
phenotype
the set of observable characteristics determined by genotype
genotype
the genetic constitution of an individual organism
Epistasis
one gene affects phenotypic expression of 2nd gene
Ex: Pigmentation (one gene controls (turn on/off) the production of pigment, and 2nd gene controls color or amount). If 1st gene codes for no pigment => 2nd gene has no effect
Pleiotropy
single gene has more than 1 phenotype expression
Ex:gene in pea plants that expressed seed texture also influences phenotype of starch metabolism and water uptake
Ex: sickle cell anemia leads to different health conditions
Polygenic inheritance
the interaction of many genes to shape a single phenotype with continuous variation (height, skin, color))
Linked genes
two or more genes that reside on the same chromosomes and thus cannot separate independently bc they are physically connected (inherited together)
Linkage map
B-V is 18%, A-V is 12%, and B-A is 6% => B——A————V
Linked genes exhibit recombination about ____% of the time
18%. This means that is bv and BV are linked, we will see the recombinate Bv or bV 18% of the time
Sex linked
refers to when a single gene resides on sex chromosome; when male (XY) receives an X from mother, whether it is dominant or recessive will be expressed because there is no copy on the Y chromosome
sex-influenced
an be influenced by sex of individual carrying trait (e.g. Bb female not bald, Bb male is)
Penetrance
probability an organism with a specific genotype will express a particular phenotype
expressivity
term describing the variation of phenotype for a specific genotype
X-inactivation
during embryonic development in female mammals, one of two X chromosomes does not uncoil into chromatin. Barr body is dark and coiled compact body chromosome that is not expressed, making the genes on the other X chromosome expressed. Either one can be inactivated; genes in a female will not be expressed similarly, so all cells in a female mammal not necessarily functionally identical
Example of X-inactivity?
calico cats (always female)
hemophilia
cannot form blood clot
nondisjuncton
failure of one or more chromosome pairs or chromatids to separate during mitosis.
When can nondisjuntion happen?
1) Mitosis -failure of two chromatids of a single chromosome during anaphase
2) meiosis -homologous chromosomes to separate during Meiosis I (anaphase 1) or sister chromatids to separate during Meiosis II (anaphase 2); result in trisomy or monosomy; ex Down syndrome
What is a resulting disorder when nondisjunction happens?
trisomy or monosomy; ex Down syndrome
Mosaicism
in cells that undergo nondisjunction in mitosis during embryonic development; fraction of body cells have extra or missing chromosome
Polyploidy
all chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of chromosomes. Common in plants
