MENDELIAN GENETICS & INHERITANCE PATTERNS Flashcards
MENDEL’S LAW
Law of segregation
Law of independent assortment
Law of complete dominance
unit of heredity
Gene
different form of the same gene
Allele
genes that have identical traits (TT)
Homozygous
a trait that always appears
Dominant
a variant that is masked by the presence of a dominant trait but reappears in subsequent generations
Recessive
alleles that have different traits (Tt)
Heterozygous
produced an offspring called the F1 generation (Filial generation).
Parental generation (P-generation)
F1 self-fertilization producing
F2 (Filial 2 generation)
The law of segregation predicts that the phenotypes of the F2 generation will be tall and dwarf in a ratio of?
3:1
An easy way to predict the outcome of simple genetic crosses and self-fertilization experiments
Punnett Square
Punnett square is originally proposed by ___________
Reginald Punnett
Genotypes of a Punnett square
TT, (2) Tt, tt
Two different genes randomly assort their alleles during the
formation of haploid cells.
LAW OF INDEPENDENT ASSORTMENT
Genes of organism
Genotype
Observable trait of organism
Phenotype
The independent assortment has _________ ratio is the expected outcome when heterozygotes for two traits are allowed to self-fertilize.
9 : 3 : 3 : 1 ratio
is a condition in which the
phenotype of a heterozygote is intermediate between the
corresponding homozygous individuals.
Incomplete dominance
The phenomenon in which a heterozygote has greater reproductive success compared with either of the corresponding homozygotes is called
overdominance, or
heterozygote advantage.
Defect in hemoglobin
Sickle anemia
two alleles are both expressed in the heterozygous individual
is called
codominance
relates the behavior of chromosomes to the Mendelian inheritance traits
CHROMOSOME THEORY OF INHERITANCE
When studying human traits, however, researchers cannot control parental crosses. Instead, they must rely on the information contained within family trees, also called
Pedigrees/Pedigrees of Analysis
Follow the well-known mendelian patterns of inheritance.
Single-gene defects (mutations)
Mutations involving single genes follow one of three patterns of inheritance:
Autosomal dominant, Autosomal recessive,
or X-linked.
A single-gene mutation may have many phenotypic effects
Pleiotropy
mutations at several genetic loci may produce the same trait
Genetic Heterogeneity
Disorders of autosomal dominant inheritance are manifested in the heterozygous state, so at least one parent in an index case usually is affected.
Autosomal Dominant inheritance
A ___ reduction in the normal gene product is associated with clinical signs and symptoms.
50%
Proteins
membrane receptors, transport proteins, sturctural proteins
An affected person has at least one affected parent
An affected person has at least a ___ chance of passing the disorder to their children
50%
Disorders of autosomal recessive inheritance are manifested in the homozygous state. They occur when both of the alleles at a given gene locus are mutants.
Autosomal Recessive inheritance
IN Autosomal Recessive inheritance, In many cases, ______are affected by the mutation
enzymes
Linked to mutations in genes on the X chromosome.
The _____________ alleles can be dominant or recessive.
X-linked inheritance
Heterozygous female carriers transmit them only to
sons
An affected male does not transmit the disorder to sons, but
all daughters are carriers.
is an autosomal dominant movement disorder associated with degeneration of the striatum (caudate and putamen).
HUNTINGTON’S DISEASE
Pathogenesis of Huntington’s disease
CAG trinucleotide repeat expansions in a gene located on 4p16.3 that encodes the protein huntingtin.
Gene 4p16.3 code for the protein
Huntingtin
Gene composition of Huntington’s Disease
11-34 CAG
CAG repeat expansion = more CAG =
Glutamine
The HD is characterized by _______________ of all parts of the body
involuntary jerky movements
_________________ movements of the extremities are typical.
death after an average course of about 15 years
writhing movements
The most common skeletal dysplasia
and a major cause of dwarfism.
autosomal dominant disorder resulting from retarded cartilage growth.
ACHONDROPLASIA
The most common skeletal dysplasia
and a major cause of___________.
dwarfism
The most common skeletal dysplasia
and a major cause of dwarfism.
autosomal dominant disorder resulting from retarded
cartilage growth
Defective gene of Achondroplasia
Fibroblast growth factor receptor 3 (FGFR3)
inhibits bone growth
Fibroblast
mutation results in a constitutively active receptor, thereby exaggerating this effect and suppressing growth.
Achondroplasia
Shortened proximal extremities, a trunk of relatively normal length, and an enlarged head with bulging forehead and conspicuous depression of the root of the nose.
Achondroplasia
is a “receptor disease” caused by loss-of-function mutations in the gene encoding the LDL receptor, which is involved in the transport and metabolism of cholesterol.
Familial hypercholesterolemia
Familial hypercholesterolemia is a “receptor disease” caused by loss-of-function mutations in the gene encoding the _____________, which is involved in the transport and metabolism of cholesterol.
LDL receptor
VLDL
ApoC, B-100, ApoE
IDL
B-100, ApoE
LDL
B-100
FAMILIAL HYPERCHOLESTROLEMIA
SYMPTOMS - twofold to threefold elevation of plasma cholesterol
Heterozygotes
fivefold elevation
Homozygous
Cholesterol deposits on skin and tendon sheaths
Xanthoma
Formation of atherosclerosis resulting in coronary artery disease
HYPERTENSION
Defects in the red cell membrane that lead to the formation of spherocytes, nondeformable cells that are highly vulnerable to sequestration and destruction in the spleen.
HEREDITARY SPHEROCYTOSIS
PATHOGENESIS OF HERIDEITARY SPHEROCYTOSIS
Caused by inherited defects
in the membrane skeleton, a network of proteins that stabilizes the lipid bilayer of the red cell.
membrane skeleton a network of proteins that stabilizes the lipid bilayer of the red cell.
membrane skeleton
major membrane skeleton protein.
Spectrin
Mutations that cause hereditary spherocytosis most frequently
involve____,_________,________
ankyrin, band 3, or spectrin.
On smears, spherocytes are
dark red and lack central pallor.
The characteristic features of Hereditary Spherocytosis are
anemia, splenomegaly, and jaundice.
improves the
anemia by removing the major site of red cell destruction.
Splenectomy
Heme consists of a porphyrin ring coordinated with iron and is found mainly in hemoglobin.
PORPHYRIA
Defects in the biosynthesis of heme result in a group of disorders known as
porphyrias
