Principle of Genetics, Variation, and Heredity Flashcards
Chapter 4, Pt 2
What are Genetics?
The branch of biology which studies heredity and variation.
What is Heredity?
Heredity is how traits and characteristics are passed down from parents to their offspring through genes.
What are alleles (allelomorphs)?
Alternate forms or variations of a gene. They occupy the same loci on homologous chromosomes and thus govern the same trait
What are Chromosomes?
Thread-like, gene-carrying bodies in the nucleus of a cell.
What is Codominance?
The situation in which two different alleles for a trait are expressed unblended.
e.g. Human ABO blood group
What is Incomplete Dominance?
Incomplete dominance is a type of genetic inheritance where neither of the two alleles is completely dominant over the other. As a result, the offspring displays a blend or intermediate expression of the two
Example of Incomplete Dominance
If one parent has red flowers (with a dominant red allele) and the other has white flowers (with a dominant white allele), the offspring might have pink flowers instead of red or white. The red and white alleles do not completely dominate each other, so the result is a mixture of both.
What is Cross-Pollination?
The mating of two genetically different plants of the same species.
What is a Dominant Allele?
An allele that masks the presence of a recessive allele in the phenotype.
What is a Recessive Allele
An allele that is masked in the phenotype by the presence of a dominant allele.
What is the F1 (filial) Generation
The first offspring.
What is Gene Flow?
The transference of genes from one population to another.
What is a Gene Pool?
The collective phenotype of a population?
What are Genes?
Units of inheritance that usually occur at specific loci on chromosome.
What is Genetic Drift?
Evolution or change in gene pool frequencies, resulting from random chance.
What is Genotype?
The genetic makeup of an individual.
What is phenotype?
The observable or detectable characteristics of an individual organism.
What is a Polygenic Trait?
An inherited trait that is determined by genes at two or more loci .
What is Pleiotropy?
The situation in which a single gene is responsible for a variety of traits.
What is a Punnett Sqaure
A simple graphical method of showing of the potential combination of offspring genotypes that can occur and their probability
What is Purebred?
What is a Regulator Gene?
A gene that can initiate or block the functions of other genes
What is a Sex-Controlled Gene?
A gene that can be inherited by both genders but is usually expressed differently in males and females
What is a Sex-Limited Gene?
A gene that can be inherited by both genders but is usually expressed in only males and females
What is a Sickle-Cell Trait?
A genetically inherited recessive condition in which red blood cells are distorted resulting in severe anemia and related symptoms
What does it mean to be Heterozygous?
A genotype consisting of two different alleles of a gene for a particular trait
What does it mean to be Homologous?
Having the same allele at the same locus on both members of a pair of homologous chromosomes
What is Variation?
The difference which exist between induvial of the same species
What is a Hybrid?
Offspring that are the result if mating between two genetically different kinds of parents.
What is morphological Variation?
The noticeable physical appearance of individuals of the same species
-gives rise to Continuous Variation
What is an example of Continuous Variation
Height, Weight, Heart Rate, Finger Length, Leaf Length
What is Continuous Variation?
Variation that has no limit on the value that can occur within a population.
What is Physiological Variation
The genetic makeup of an individual which differs the organism from others
-Gives rise to -Discontinuous variation
What is Discontinuous Variation?
A characteristic of any species with only a limited number of possible values
What is an example of Discontinuous Variation
-Sex
-Blood Group
-Eye Color
-Ability to taste PTC(phenyl thio carbamide)
-Finger print
What is Genetic Variation?
The measure of the genetic differences that exist within a population
NOTE
Know Gregor Mendal experiments
What are the three parts of the Law of Dominance (First Law of Inheritance?
I) Characters are controlled by discrete units called factors
II) Factors occur in pairs
III) In a dissimilar pair of factors one member of the pair dominates the other
State the Law of Segregation (Second Law of Inheritance)?
The alleles of a gene exist in pairs but when gametes are formed, the members of each pair pass into different gametes. Thus, each gamete contains only one allele of each gene
What is a Dihybrid Cross
A genetic cross between two organisms that are each heterozygous for two traits.
-The typical phenotypic ratio for a dihybrid cross between two heterozygous individuals is 9:3:3:1.
What is the human ABO blood grouping system?
Blood group controlled by the gene I
-The plasma membrane of the red blood cells has sugar polymers that protrude from its surface
Describe the three different alleles of gene I
-I^A: This allele codes for the A antigen on the surface of red blood cells
-I^B: This allele codes for the B antigen on the surface of red blood cells
-i: This allele is recessive and does not produce an antigen on the surface of red blood cells.
Differentiate between Homogametic and Heterogametic
Homogametic contain X chromosomes in all their while Heterogametic produce both X and Y-bearing gametes
Differentiate between X and Y Chromosomes
X chromosomes in humans are much longer than Y chromosomes and also contain more genes
What is X-inactivation?
When one female X chromosome is inactivated to prevent a genetic imbalance
What is Monosomy?
The possession of only single copy of normally paired chromosomes
Examples of sex-linked characteristics
-Red-Green color blindness
Hemophilia
What is the Rhesus factor
A type of proteind foun don the outside of red blood cells’
How role does Rh factor play in Pregnancy?
If the mother is Rh-negative, her immune system treats Rh-positive fetal cells as if they were a foreign body making antibodies against the fetal blood cells.
