AIII. Inheritance (Mendel’s Law of Inheritance) Flashcards
The question of how hereditary material (?) itself was one of the most baffling problems of biology for many years. Generations of biologists attempted in vain to solve this problem and to answer the question “Why are the offspring of the species undeniably of the species?”.
duplicates
Many though that the chemical basis for heredity lay in the structure of (?). But no one was able to provide evidence showing how it could reproduce itself.
proteins
The answer to the heredity question was finally found in the structure of (?). The unit structure of all living things is the (?).
nucleic acids
cell
Suspended in the nuclei of the cells are (?), which consist largely of proteins and nucleic acids.
chromosomes
Since genes are carried on chromosomes, knowledge of (?) has far-reaching implications for basic genetics, human health, and evolution.
chromosome number and structure
− Alternative forms of the same gene
Alleles
− Alleles for a trait are located at corresponding positions on
homologous chromosomes
– chromosomes that have the same genetic information (genes)
• Homologous chromosomes
• Homologous chromosomes Example:
gene for hair texture exists as two alleles (e.g. one curly code, and one straight code)
− The genes present in the DNA of an organism
Genotype
− The combination of genes
genotype
− It designates the genetic or hereditary make-up of an organism
genotype
− Uses a pair of letters (example: Tt or YY or ss, etc.) to represent genotypes for one particular trait
genotype
− There are always two letters in the (?) as a result of sexual reproduction
genotype
− How the trait physically shows up in the organism
Phenotype
− It is the outward appearance of an organism as the result of gene action
Phenotype
− Examples: Blue eyes, brown fur, striped fruit, yellow flowers, curly hair, etc
phenotypes
− A genetic condition where an individual inherits the same alleles for a particular gene from both parents
Homozygous
− A pair of identical genes
Homozygous
− Represented by two capital or two lowercase letters in the genotype (example: TT or tt)
Homozygous
− Sometimes the word “pure” is used instead of homozygous
Homozygous
− Refers to a pair of genes where one is dominant and one is recessive
Heterozygous
− The paired genes are different or contrasting
Heterozygous
− Having the two alleles at corresponding loci on homologous chromosomes different for one or more loci
Heterozygous
− Represented by one capital letter and one lowercase letter (example: Tt)
Heterozygous
− Can also be referred to as HYBRID
Heterozygous
− One that is manifested, plainly shown and readily perceived by the senses
Morphological Trait
− Example: Y – yellow; y – green
Morphological Trait
Morphological Trait
• Dominant –
• Recessive –
upper case
lower case
– one that can be perceived only by means of special methods that enable differences between molecules to be visualized
• Molecular trait
GENOTYPE PHENOTYPE
Yy Yellow
yy Green
A cross of only one trait
Monohybrid cross
Can be used to show law of dominance and segregation
Monohybrid cross
The character/s being studied in monohybrid cross are governed by two or multiple alleles
single locus
a mating between two individuals with different alleles at one genetic locus of interest
Monohybrid cross
A cross of two traits
Dihybrid cross
Can be used to show law of independent assortment
Dihybrid cross
describes a mating experiment between two organisms that are identically hybrid for two traits
Dihybrid cross
one that is heterozygous, which means that it carries two different alleles at a particular genetic position or locus
hybrid
The mating of two individuals, organisms or strains that have different gene pairs that determine three specific traits or in which three particular characteristics or gene loci are being followed.
Trihybrid cross
Demonstrates that Mendel’s principles apply to inheritance of multiple traits.
Trihybrid cross
− Transmitted on unbroken descent
Autosomal dominant
• 50% mutant gene; Autosomal dominant
− Heterozygote and homozygous recessive
− Between two heterozygotes • Severe conditions are unlikely to be passed on
Autosomal recessive
− Transmitted by a long line of carriers
Autosomal recessive
− ¼ chance
Autosomal recessive
− Common in in-breeding
Autosomal recessive
• Severe conditions are unlikely to be passed on
− Between two heterozygotes
− The chance that both maternal and paternal alleles at one locus are identical by descent
Coefficient of In-breeding
− The proportion of all the individual’s genes are homozygous because of identity by common descent
Coefficient of In-breeding