I. (Mendelian Genetics, Dominance Relationships, Multiple Allelism, Lethal Alleles, Modifier Genes) Flashcards
Who is the Father of Genetics?
Gregor Mendel
What serves as the basis of the study of inheritance?
Gregor Mendel’s Experiment on Pisum sativum, the garden pea.
He had a good choice of which experimental organism to use because garden peas are easy to grow and only need 1 season. He used true-breeding (homozygous) plants and chose varieties that differed in only one trait (monohybrid cross).
___ is the fundamental physical and functional unit of heredity that carries information from generation to generation. It is a segment of DNA that makes possible transcriptions.
Gene
The existence of a gene can be confirmed by ____ ____ and it occupies a specific ____ ____.
allelic variants; chromosomal locus
What is another term for Gene?
Mendelian Factor
In molecular terms, a gene is a nucleotide sequence in DNA that specifies a ____ or ____.
polypeptide; RNA
What gives rise to species and individual variation?
Alterations in a gene’s sequence.
____ is the basic unit of biological information; a specific segment of DNA in a discrete region of a chromosome that serves as a unit of function by encoding a particular RNA or protein.
Gene
____ is a position on a chromosome where a gene is located.
Locus
An ____ is any 2 or more related genes of a trait.
Allele or Allelemorph
A ____ ____ expresses its effect over another allele; it masks the recessive allele in the heterozygous organism.
Dominant Allele
A ____ ____ is masked in a heterozygous individual by the presence of a dominant allele.
Recessive Allele
____ is the visible appearance.
Phenotype
____ is the genetic constitution.
Genotype
_____ _____ are crossing a male with one trait with a female having the other trait (from a pair of contrasting traits).
Reciprocal Crosses
____ is also referred to as self-pollination. It is the crossing of individuals from the same generation.
Selfing
____ is the observable heritable feature.
Character
____ is a variant for a character.
Trait
The ____ is the parental generation; where the 1st individuals crossed.
P
The ____ generation is the 1st filial generation offspring; the offspring of P.
F1
____ generation is the 2nd filial generation offspring; the offspring of F1.
F2
The ____ states that an individual organism possesses two alleles encoding a trait and that these two alleles separate in equal proportions when gametes are formed.
Law of Segregation
____ is a cross between 2 individuals involving 1 character.
Monohybrid Cross
A ____ _____ is used to present the gametes of the parents and the genotypes and phenotypes of the offspring.
Punnett Square
The _____ states that the genes encoding different characters assort independently when gametes are formed.
Law of Independent Assortment
Differentiate the Law of Segregation from the Law of Independent Assortment.
Law of Segregation - Allele pairs separate and each goes into a different gamete.
Law of Independent Assortment - Alleles from one locus segregate into gametes independently of those from another locus.
____ is a cross between 2 individuals involving 2 characters (e.g. seed shape and seed color).
Dihybrid Cross
____ is a genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the latter.
Test Cross
A ____ is a cross or a breeding experiment between two organisms that differ in one characteristic or trait.
Monohybrid Test Cross
A ____ is a genetic cross between two individuals that differ or are hybrid in two traits or characters.
Dihybrid Test Cross
The ____ or ____ can also be used as a more orderly way of showing the gametes that a particular genotype can generate.
Forked-Line Method; Branch Diagram
What formula should be used to determine the number of gamete types formed by an individual?
2n, where n represents the number of heterozygous characters.
In _____, for a specific character, there is a dominant allele that when present, the dominant trait is always expressed.
Complete Dominance
In _____, one copy of the gene is enough for the individual to be affected; both males and females are affected with equal frequency.
Autosomal Dominant Inheritance
What are some examples of conditions inherited in this manner (autosomal dominance)? (4)
- Huntington’s Disease
- Achondroplasia (Short-limbed Dwarfism)
- Polycystic Kidney Disease
- Polydactyly
In ____, it takes 2 copies of the gene for the trait to be expressed, both males and females are affected with equal frequency.
Autosomal Recessive Inheritance
What are some examples of conditions inherited in this manner (autosomal recessive)? (4)
- Cystic Fibrosis
- Tay-Sachs
- Hemochromatosis
- Phenylketonuria (PKU)
In ____, there is a dominant allele and a recessive allele but the dominant one cannot completely mask the effect of the recessive allele such that heterozygotes come out with a blended phenotype. Both parental phenotypes are not seen. Instead, there is a new phenotype that results from the mixing of the parental genes.
Incomplete Dominance or Partial Dominance
In ____, both alleles involved are equally dominant. Both parental phenotypes can be seen simultaneously expressed in the same offspring.
Codominance
If the coat color of the parents is blended, it can represent _____.
Incomplete/Partial Dominance
If the individual coat colors of the parents are both visible, it is _____.
Codominance
In ____, the heterozygote has a more extreme phenotype than that of either of his parents.
Overdominance
Why is overdominance also referred to as heterozygote advantage?
The heterozygous individuals have a higher fitness than the homozygous individuals.
What is it called when a character is controlled by three or more alleles for a gene?
Multiple Allelism
A ____ is a rare blood type that lacks A, B, and H antigens in the red cells and has anti-H antibodies in the serum.
Bombay Phenotype Blood
A Bombay phenotype often results from ____.
Consanguineous Mating; parents are blood relatives (e.g. first cousins).
Whenever inbreeding occurs, the proportion of rare homozygotes ____ in frequency.
increases
____ are alleles that cause an organism to die only when present in homozygous condition, where the gene involved must have been an essential gene.
Lethal Alleles
____ is the case where no individual of a certain genotype attains the age of reproduction.
Complete Lethality
Such lethal genes that handicap but do not destroy their possessor are called ____.
Subvital/Sublethal/Semi-lethal Genes
Instead of mutations altering the phenotypes of the
organisms, a ____ could cause death.
Mutant Allele
When an essential gene is mutated, it can result in a ____.
Lethal Phenotype
Are most lethal genes dominant or recessive?
Recessive
In humans, recessive lethal genes are present in individuals with ___, ____, and ____. (3)
Tay-Sachs, Cystic Fibrosis, and Sickle Cell Anemia
____ is due to the deficiency of hexosaminidase A, resulting in the inability to break down specific membrane lipids. It progressively destroys nerve cells (neurons) in the brain and spinal cord.
Tay-Sachs Disease
What are some of the symptoms of Tay-Sachs?
Infants: slow development, weak muscles, lost motor skills (e.g. turning over, sitting, crawling), developed an exaggerated startled reaction to loud noises.
Children: experience seizures, vision and hearing loss, intellectual disability, paralysis, and cherry-red spot (eye abnormality).
____ refers to the cause of the sickling of all red blood cells.
Sickle Cell Anemia
____ refers to if the mutation is caused by a dominant lethal allele, the heterozygote for the allele will then show the lethal phenotype; whose lethal effects occur in heterozygous individuals.
Dominant Lethal Genes
____ is a dominant progressive disorder that affects the brain’s basal ganglia (includes voluntary and involuntary motor control, procedural learning, eye movements, and cognitive, emotional functions).
Huntington’s Disease
____ are those whose effects are exerted only under certain environmental conditions; can be expressed due to specific circumstances (e.g. temperature).
Conditional Lethal Genes
____ is a sex-linked, inherited condition that results from a deficiency in an enzyme called glucose-6-phosphate dehydrogenase (G6PD).
Favism
____ are genes that kill some individuals in a population, but not all of them; environmental factors and other genes may help prevent the detrimental effects of these genes.
Semi-lethal/Sublethal Genes
____ is a hereditary disease caused by deficiencies in clotting factors, which results in impaired blood clotting and coagulation.
Hemophilia
____ are genes that do not mask the effects of another gene. Instead, they can modify the expression of a second gene.
Modifier Genes
When two genotypes produce the same phenotype due to different environments, each one is called the _____ of the other, because they differ genotypically.
Phenocopy
