DAT Heredity cheat sheet Flashcards
A basic unit or sequence of genetic material
that encodes a trait
gene
A gene’s location within a genome
locus
Normal version of an allele
wild type
A variant form of a gene
allele
An allele with an altered DNA sequence
affecting a gene’s phenotype
mutant
The alleles an individual carries (e.g., Aa)
genotype
A pair of
chromosomes (1 maternal, 1 paternal) that
contain the same genes in the same locations
homologous chromosomes
Having only one copy of a gene
instead of two
hemizygous
Carrying a copy of the recessive
allele on one of the homologous chromosomes
and a copy of the dominant allele on the other
chromosome (e.g., Aa)
heterozygous
Carrying the same alleles on each
homologous chromosome
homozygous
pairs of alleles are separated when gametes are formed
segregation
Pairs of alleles will be sorted
independently of one another
when gametes are formed
independent assortment
One dominant allele masks
effect of recessive allele
principle of dominance
gametes combine to form zygotes with two copies of each gene
fertilisation
During anaphase I, homologous chromosomes segregate,
resulting in haploid gametes that
contain only one allele per gene
law of segregation
The lining up & separation of one
pair of homologous chromosomes
does not influence that of a
different pair of homologous
chromosomes
the law of independent assortment
A genetic cross between a homozygous recessive
individual and an individual in question to determine the latter’s
genotype for a given trait
test cross
- Monohybrid cross tests
a single gene
dihybrid cross tests
two
different genes
simultaneously
P1
parental
f1
first generation of offspring
f2
second generation of offspring
show all possible allelic
combinations of gametes in a cross between two individuals with known genotpyes
Punnett square
One gene affects
the phenotypic expression
of an independently
inherited gene
epistasis
More
than two typical alleles
exist for a gene
multiple alleles
Many genes
interact to shape a single phenotype,
often with continuous variation (height)
polygenic inheritance
Single gene controls for the
expression of multiple phenotypic traits (e.g., a
single gene controls a plant’s height, color, and
texture)
Pleiotropy:
There is a
blending of alleles, producing a
unique heterozygous phenotype
incomplete dominance
both alleles are
completely expressed
codominance
reside on a sex chromosome
Sex-linked genes
can be affected by the sex of the individual
carrying the trait
sex influenced genes
uses recombination frequency to show the relative
positions of genes on a chromosome
linkage map
The closer together the genes are, the less likely
they are to be
separated by recombination
reside close together on a chromosome,
linked genes
During embryonic
development in female mammals, one of
the two X chromosomes is inactivated,
x-inactivation
a highly condensed chromosome
barr body
The proportion of individuals
with a specific genotype will express the
corresponding phenotype
penetrance
The variation of a phenotype
for a specific genotype
expressivity
The occurrence of an abnormal number
(extra/missing) of chromosomes
aneuploidy
what often causes aneuploidy
nondisjunction
Having three copies of
chromosome 21 instead of the normal two copies
trisomy 21 (downs)
The failure of chromosomes or chromatids to
separate during Mitosis/Meiosis;
nondisjunction
arrests mitosis by interfering with mitotic spindle formation;
Colchicine
what can colchicine prevent cells from doing
replicating
stimulate normal growth;
protooncogenes
mutated protooncogenes can become what
oncogenes, cancer casuing
make proteins that help control cell growth;
tumor suppressor genes
A chromosome
segment is
rearranged in
the reverse of
its original
orientation
inversion
A chromosome
segment is
missing or
deleted
deletion
A chromosome
segment is moved
to another; it can be
reciprocal or
nonreciprocal
(substitution)
trasnlocatin
A chromosome
segment is
repeated on the
same
chromosome
duplication
Changes in chromosome number or structure
Chromosomal aberrations:
A single copy
of the mutated gene is enough to
express the condition
Autosomal dominant:
Two copies of
the mutated gene must be present to
express the condition
autosomal recessive
A single copy of
the mutation of a gene on the X
chromosome is enough to cause the
condition in both males & females
X-linked dominant:
Two copies of the
mutated gene on the X chromosomes
causes the condition in females; one
copy will cause the condition in males
x linked recessive
Genes located on the Y
chromosome cause the
condition/trait
y linked
cannot be recessive
autosomal dominant
cannot be dominant
autosomal recessive
100% incidence of affected daughters from an
affected father suggests
x linked dominance
100% incidence of affected sons from an
affected mother suggests
x linked recessive
