DAT Bio Genetics Flashcards
Gene
genetic material on a
chromosome for encoding a trait
Locus
location on chromosome where a
gene is located`
Allele
alternative forms of a gene that
allow for differences such as different hair
or fur colors
Homologous chromosomes
a pair of
chromosomes that contain the same
genetic material
i. Each parent contributes one of the
chromosomes in the pair, thus
allowing for different alleles to be
present for each gene
Law of Segregation
one member of
each chromosome pair migrates to an
opposite pole in anaphase I so that each
gamete is haploid
i. Basically, each gamete is left with one
copy of each allele
Law of Independent Assortment
the
migration of homologues within one pair
of homologous chromosomes does not
influence the migration of homologues of
other homologous pairs
Monohybrid cross
two organisms
with variations at one gene of
interest are crossed
Dihybrid cross
two organisms with
variations at two genes of interest
on different chromosomes are
crossed
Test cross
when the genotype of
an organism expressing the
dominant phenotype is unknown,
the unknown organism is crossed
with a homozygous recessive
organism to determine if the
unknown is homozygous dominant
or heterozygous dominant
Punnett squares
technique that
uses probability rules to determine the
outcomes of either monohybrid or
dihybrid crosses and the subsequent
expected frequencies
Incomplete dominance
blending of
expressions of alleles
For example, a red flower and white
flower are crossed to result in a
unique heterozygous pink offspring
Codominance
both of the inherited
alleles are completely expressed
i. For example, blood types A and B
can show as AB if both are
expressed
Multiple alleles
blood groups have
four possible phenotypes, the
codominant A, B, and O, leading to six
possible genotypes and four possible
phenotypes
AA/AO →
type a
BB/BO →
type b
AB →
codominant AB type
OO →
type O
Epistasis
the process in which one
gene affects the phenotypic
expression of a second gene. A
common example of epistasis is fur
pigmentation in mice → one gene
controls the production of pigment by
either turning on or turning off and the
second gene controls the color or
amount of color deposited in the fur.
Therefore, if the first gene codes for
no pigment, then the second gene has
no effect
Pleiotropy -
when a single
gene has more than one phenotypic
expression
Polygenic inheritance
the interaction
of many genes to shape a single
phenotype with continuous variation
such as height, skin color, or hair color
Linked genes
when two or more
genes reside physically close to one
another on the same chromosome and
therefore cannot separate
independently as they are inherited
together
Sex-linked genes
a type of linked gene
that refers to a single gene residing on a
sex chromosome that is inherited
differently in males and females
Sex-influenced genes
these differ
from sex-linked genes in that the
expression of genes can be influenced
by the sex of the individual carrying the
trait
Penetrance
this concept describes the
probability an organism with a specific
genotype will express a particular
phenotype
