Genetics Study Guide Flashcards
Who is the father of modern genetics? What did he study?
Gregor Mendel. Mendel studied inheritance patterns in pea plants. He discovered the basic principles of heredity, including the concepts of dominant and recessive traits, and formulated the Law of Segregation and Law of Independent Assortment, which form the foundation of modern genetics.
Genotype
The genetic makeup of an organism, representing the combination of alleles it inherits from its parents (e.g., AA, Aa, aa) and describing the alleles it carries for a given trait.
Allele
Different versions of a gene that can exist at a specific locus (location on a chromosome). For example, a gene for flower color may have an allele for red (R) or white (r).
Gene
A segment of DNA that encodes information for a particular trait. Each gene can have different versions (alleles).
Homozygous
An organism that has two identical alleles for a particular gene (e.g., AA or aa).
Heterozygous
An organism that has two different alleles for a particular gene (e.g., Aa).
Hybrid
The offspring resulting from the cross of two different genetic traits or different species. In genetics, it refers to the offspring of parents with different alleles for a particular trait (e.g., hybrid pea plant).
Phenotype
The physical expression or observable traits of an organism, determined by its genotype and environmental factors (e.g., purple flowers or tall height).
Law of Segregation
Mendel’s principle that states during the formation of gametes (egg and sperm), the two alleles for a gene segregate (separate), so each gamete carries only one allele for each gene.
Law of Independent Assortment
Mendel’s principle that states genes for different traits assort independently of each other during gamete formation, provided the genes are located on different chromosomes.
P Generation
The parental generation in a genetic cross.
F1 Generation
The first filial generation, offspring of the P generation.
F2 Generation
The second filial generation, offspring of the F1 generation, typically used in Mendelian experiments.
Polygenic Inheritance
A type of inheritance where multiple genes contribute to a single trait (e.g., skin color, height). This results in a wide range of phenotypes.
Test Cross
A breeding experiment used to determine the genotype of an organism with a dominant phenotype. The organism in question is crossed with a homozygous recessive individual, and the offspring’s phenotypes are analyzed to infer the unknown genotype.
Example of Homozygous Dominant
AA
(Both alleles are dominant for a trait, such as the gene for purple flower color in pea plants.)
Example of Heterozygous
Aa
(One dominant allele and one recessive allele. For example, in pea plants, a hybrid plant with one allele for purple flowers and one for white flowers.)
Example of Homozygous Recessive
aa
(Both alleles are recessive for a trait, such as the gene for white flower color in pea plants, where two recessive alleles are needed for the white phenotype.)
How many alleles are donated from each parent to their offspring for a particular trait?
Each parent will donate one allele to their offspring, resulting in possible genotypes like AA, Aa, or aa for the offspring.
A Punnett square shows the actual or probable results from a genetic cross?
A Punnett square shows the probable results from a genetic cross.
If you cross homozygous dominant yellow seeds with homozygous recessive green seeds all of your offspring will be what color and why?
Yellow:
The homozygous dominant yellow seeds (YY) have two dominant alleles for yellow color.
The homozygous recessive green seeds (yy) have two recessive alleles for green color.
When you perform the cross, each parent will donate one allele:
The YY parent will donate a Y allele (since both alleles are dominant).
The yy parent will donate a y allele (since both alleles are recessive).
The resulting offspring will all have the genotype Yy, meaning they have one dominant yellow allele (Y) and one recessive green allele (y).
Since yellow is dominant over green, the Y allele will mask the effect of the y allele, and all of the offspring will have yellow seeds.
The allele for yellow seeds is dominant over green seeds. If you cross a yellow and green seed plant and you get 48 yellow and 53 green, what are the genotypes of the parents?
A 1:1 ratio suggests that one parent is heterozygous (Yy) and the other parent is homozygous recessive (yy).
In flies red eyes are recessive to the wild type. If you have two wild type flies and they produce a fly with red eyes, what are the genotypes of the parents?
The genotypes of the parents must both be Rr (heterozygous wild type).
Red eyes (r) are recessive.
Wild type eyes (R) are dominant over red eyes.
For a fly to have red eyes (rr), it must inherit two recessive alleles (one from each parent).
In Hamsters Black fur is dominant to brown. If you cross a brown hamster with a black hamster, who had a parent that was brown, what are the chances of having a black hamster?
There is a 50% chance (2 out of 4) that the offspring will inherit the Bb genotype (black fur).
There is a 50% chance (2 out of 4) that the offspring will inherit the bb genotype (brown fur).
A brown hamster must have the genotype bb (homozygous recessive), as it can only pass on the b allele.
The black hamster with a brown parent must be heterozygous (Bb), because the black hamster inherited the b allele from the brown parent.