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BMS2042 DEFINITIONS
NEWLY FORMATTED DOCUMENT
Law of Segregation When an organism makes gametes, each
gamete receives only one gene copy, which
is selected randomly
The alleles for one gene sort into gametes
Law of Independent independently of the alleles of another
Assortment
gene
- produces 3:1 ratio
Reveals how one trait is transmitted from
generation to generation
Monohybrid cross - mating true-breeding individuals
- 3:1
Used to determine whether an organism with
a dominant phenotype is homozygous or
heterozygous.
Test Cross
- An unknown dominant crossed with a
known homozygous recessive
- If the result is all dominant offspring; homozygous
- If the result is 1:1; heterozygous
A cross between individuals that have
different alleles for the same gene.
Dihybrid Cross P = homozygous dominant x
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homozygous recessive F1 =
heterozygous dominant
F2 = 9:3:3:1
- Loss of function
- Males and female equally affected
Autosomal Recessive - Skips generations: affected people are
inheritance normally born to non- affected parents
- After the birth of one affected child, each
subsequent child has a 25% chance of being
affected
- Males and females equally affected
Autosomal Dominant - Affected individuals in multiple generations
inheritance - Transmission by both sexes are equal
- Affected children born to affected parents
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Designed to test the role of parental sex on a
given inheritance pattern.
- Crossing a male with the trait with a female
Reciprocal Cross without the trait, and then in another cross,
crossing a male without the trait with a
female with the trait
- Discovery of sex-linked traits
- White eyed flies
This is supported by:
Chromosomal Theory - Behaviour of chromosomes at meiosis
- Sex linked genes
- One X chromosome in each cell is randomly
inactivated early in the embryonic
development of females (mosaics)
X-Chromosome - This ensures that females will produce X-
Inactivation linked gene products in quantities roughly
similar to those produces in males: dosage
compensation
- If a women carries a recessive mutation
in a gene in the X chromosome, she can
still express symptoms due to X-
inactivation, depending which one get
inactivated
- Mostly males affected
- Transmitted through female carriers;
no male to male transmission
- Affected males are usually born to
X-linked Recessive unaffected parents (female carriers)
inheritance - Females may be affected if the father is
affected and the mother is a carriers, or
occasionally as a result of non-random x-
BMS2042 DEFINITIONS
NEWLY FORMATTED DOCUMENT
Law of Segregation When an organism makes gametes, each
gamete receives only one gene copy, which
is selected randomly
The alleles for one gene sort into gametes
Law of Independent independently of the alleles of another
Assortment
gene
- produces 3:1 ratio
Reveals how one trait is transmitted from
generation to generation
Monohybrid cross - mating true-breeding individuals
- 3:1
Used to determine whether an organism with
a dominant phenotype is homozygous or
heterozygous.
Test Cross
- An unknown dominant crossed with a
known homozygous recessive
- If the result is all dominant offspring; homozygous
- If the result is 1:1; heterozygous
A cross between individuals that have
different alleles for the same gene.
Dihybrid Cross P = homozygous dominant x
,2|Page
homozygous recessive F1 =
heterozygous dominant
F2 = 9:3:3:1
- Loss of function
- Males and female equally affected
Autosomal Recessive - Skips generations: affected people are
inheritance normally born to non- affected parents
- After the birth of one affected child, each
subsequent child has a 25% chance of being
affected
- Males and females equally affected
Autosomal Dominant - Affected individuals in multiple generations
inheritance - Transmission by both sexes are equal
- Affected children born to affected parents
, 3|Page
Designed to test the role of parental sex on a
given inheritance pattern.
- Crossing a male with the trait with a female
Reciprocal Cross without the trait, and then in another cross,
crossing a male without the trait with a
female with the trait
- Discovery of sex-linked traits
- White eyed flies
This is supported by:
Chromosomal Theory - Behaviour of chromosomes at meiosis
- Sex linked genes
- One X chromosome in each cell is randomly
inactivated early in the embryonic
development of females (mosaics)
X-Chromosome - This ensures that females will produce X-
Inactivation linked gene products in quantities roughly
similar to those produces in males: dosage
compensation
- If a women carries a recessive mutation
in a gene in the X chromosome, she can
still express symptoms due to X-
inactivation, depending which one get
inactivated
- Mostly males affected
- Transmitted through female carriers;
no male to male transmission
- Affected males are usually born to
X-linked Recessive unaffected parents (female carriers)
inheritance - Females may be affected if the father is
affected and the mother is a carriers, or
occasionally as a result of non-random x-
