Genetics Unit Test #1 Flashcards
Dominant allele
- Functional protein
- Masks other alleles
Textbook: the form of a trait that always appears when a individual has an allele for it
Recessive allele
- Allele makes a malfunctioning protein
- If it’s paired with a dominant allele, it will be masked by the dominant allele
Textbook: the form of a trait that only appears when an individual has two alleles for it
P
Parents
(P generation):
Textbook: in breeding, the organisms initially crossed and are typically true breeding
F1
First generation
(F1 generation)
the offspring of a cross of the P generation
F2
Second generation
(F2 generation)
Textbook: the offspring of a cross between the F1 generation
Homozygous
Textbook: an organism that has two identical alleles of a gene
= SAME alleles
(e.g. homozygous dominant, homozygous recessive)
- An organism is homozygous when it is true-breeding or pure-breeding
Heterozygous
Textbook: an organism that has two different alleles of a gene
= DIFFERENT alleles
(e.g. an uppercase and a lowercase letter)
Phenotype
Textbook: the physical and physiological traits of an organism
- Description of an organism’s trait
- The “physical”
- Two organisms can have the SAME phenotype, but a different genotype
–WHY?? EXPLAIN!!!
Genotype
Textbook: the combination of alleles for any given trait, or the organism’s entire genetic make-up
- Description of an organism’s genetic makeup
Mendel’s Law of Segregation
Textbook: traits are determined by pairs of alleles that segregate during meiosis so that each gamete receives one allele.
During meiosis, alleles segregate
- Homologous chromosomes separate
Each allele for a trait is packaged into a separate gamete
HAPPENS IN:
Metaphase 1
This law states that the two alleles of a pair segregate or separate during gamete formation such that a gamete receives only one of the two factors. for example heterozygous organism of F1 generation produces two types of gametes i.e. T and t.
Mendel’s Law of Independent Assortment
(2nd law of heredity)
Textbook: during gamete formation, the two alleles for one gene segregate or assort independently of the alleles for other genes.
Different loci (genes) separate into gametes independently
- Non-homologous chromosomes align independently
- Classes of gametes produced in equal amounts (YR = Yr = yR = yr)
- Only true for genes on separate chromosomes or on the same chromosome but so far apart that crossing over happens frequently
Mendel’s law of independent assortment vs Mendel’s law of segregation
The law of segregation states that every individual possesses two alleles and only one allele is passed on to the offspring.
The law of independent assortment states that the inheritance of one pair of genes is independent of inheritance of another pair.
Mendel’s Law of Segregation – apply to monohydrid and dihybrid crosses
Monohybrid cross:
- Pairs of alleles for one trait segregate during meiosis (metaphase I) so that the offspring only receives one of the two alleles of that gene.
Dihybrid cross:
- Two pairs of alleles (for two traits) segregate during meiosis (metaphase I) so that the offspring only receives one of the two alleles for both genes.
Mendel’s Law of Independent Assortment – apply to monohydrid and dihybrid crosses
Dihybrid cross:
- In a dihybrid cross, during gamete formation, the alleles for one gene assort independently from the alleles for the second gene.
Monohybrid:
- Does not apply because there is no second trait to assort independently from
Gametes
*a reproductive cell of an animal or plant
Alleles
*Two different versions of a gene
Monohybrid cross
Textbook: a cross of two individuals that differ by one trait
*A monohybrid cross is a cross between two organisms involving ONE trait.
Dihybrid cross
Textbook: A cross of two individuals that differ in two traits due to two different genes.
*A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.
*experiments following the inheritance of 2 different characters (e.g. seed color AND shape)–dihybrid cross
