Inheritance Flashcards
(71 cards)
What is a gene?
A gene is a unit of inheritance.
Genes are segments of DNA that determine specific traits.
What are alleles?
Alleles are different forms of the same gene.
Each allele can result in different traits.
Where do alleles occupy on chromosomes?
Alleles occupy the same relative positions/gene loci on a pair of homologous chromosomes.
This is crucial for genetic inheritance.
What does a dominant allele do?
A dominant allele expresses itself and gives the same phenotype in both homozygous and heterozygous conditions.
Dominant alleles mask the effects of recessive alleles.
How does a recessive allele express itself?
A recessive allele only expresses itself in the phenotype in the homozygous condition.
This means two copies of the recessive allele must be present.
What is codominance?
Codominance is a condition where both alleles express themselves equally in the phenotype.
Example: IA and IB alleles in blood group.
Define homozygous.
Homozygous refers to an organism that has identical alleles for a particular phenotype/trait.
This results in a consistent expression of that trait.
Fill in the blank: A _______ allele refers to an allele that expresses itself in both homozygous and heterozygous conditions.
[dominant]
Fill in the blank: A _______ allele only expresses itself in the phenotype in the homozygous condition.
[recessive]
True or False: Codominance results in one allele being dominant over another.
False.
In codominance, both alleles are expressed equally.
True or False: Homozygous organisms have different alleles for a specific trait.
False.
Homozygous organisms have identical alleles for a trait.
What does heterozygous refer to?
An organism that has different alleles for a particular phenotype/trait.
Heterozygous organisms have two different versions of a gene.
Define phenotype.
The expressed trait in an organism, such as observable features like eye colour and height.
Phenotype is the result of the interaction between genotype and the environment.
What is genotype?
The genetic make-up of an organism.
Genotype refers to the specific alleles an organism possesses.
What is the expected phenotypic ratio when both parents are heterozygous?
3:1
This ratio is typically observed in a monohybrid cross of heterozygous parents.
What are the terms used to describe the generations in genetic crosses?
F1 generation and F2 generation.
F1 refers to the first filial generation, while F2 refers to the second filial generation.
What is the genotype of the parents in the genetic diagram provided?
Tt x Tt
This indicates that both parents are heterozygous for the trait.
Fill in the blank: To obtain an expected ratio of 3:1 in the offspring generation, both parents must be _______.
heterozygous
What is required to obtain an expected ratio of 1:1 in the offspring generation?
One parent must be heterozygous while the other is homozygous recessive
This is known as a test cross.
How can a test cross help determine if a genotype is homozygous dominant or heterozygous dominant?
By crossing with a homozygous recessive. Offspring will show all traits if homozygous dominant, or a 1:1 ratio if heterozygous dominant.
Why do observed ratios often differ from expected ratios?
Due to random fusion of nuclei of gametes and small sample size
Smaller numbers of progeny can lead to significant variations in ratios.
What is co-dominance?
A condition where both alleles in a heterozygote are fully expressed
An example is blood group AB, which expresses both antigens.
What are multiple alleles?
Genes that exist in more than two types of alleles
An example is the ABO blood group system.
What are the three alleles that control blood group?
- I_A
- I_B
- I_O
