Inheritance

What did Gregor Mendel discover through his experiments with pea plants?

He completed thousands of experiments which led to the discovery of unlinked genes and complete dominance inheritance.

What is a genotype?

A genotype is the allele combination, consisting of one allele from the sperm and one allele from the egg that created the individual.

What is a phenotype?

A phenotype is the outward expression of characteristics, determined by both genotype and environmental factors.

What is phenotypic plasticity? Provide an example.

Phenotypic plasticity refers to phenotype variations seen under different environmental conditions without changing the genotype. For example, butterflies may change color with temperature, and chameleons change colors.

What is a dominant allele?

A dominant allele has the same effect on phenotype in both homozygous and heterozygous states and masks the effects of recessive alleles.

What is a recessive allele?

A recessive allele affects the phenotype only when present in a homozygous state.

What does homozygous mean?

Homozygous means having two identical alleles of a gene.

What does heterozygous mean?

Heterozygous means having two different alleles of a gene.

In a monohybrid Punnett square, what information should be included?

You should write the gametes and determine the genotypic and phenotypic ratios based on the provided information.

Distinguish between P, F1, and F2 generations.

P generation is the parental generation; F1 generation is the first generation from a P x P cross; F2 generation is the second generation from an F1 x F1 cross.

How many alleles are inherited for each gene in a human?

Humans inherit 2 alleles for each gene.

What are the genotypes for the ABO blood system?

The ABO blood system genotypes are AA, AO, BB, BO, AB, and OO.

Distinguish between codominance and incomplete dominance.

In codominance, both alleles affect the phenotype when present in a heterozygote, such as with AB blood type. In incomplete dominance, alleles blend in the phenotype, such as in four o’clock flowers.

What is a carrier in genetics?

A carrier is someone who is heterozygous for a recessive allele, meaning they do not show the disease but can pass the recessive allele to offspring.

Describe Phenylketonuria (PKU).

PKU is an autosomal recessive condition where the body lacks the enzyme needed to convert phenylalanine to tyrosine, leading to buildup in blood and brain. Generally, both parents are heterozygous, and there is a 25% chance of inheriting the recessive genotype.

What is the genotype of a female and male?

The genotype of a female is XX, whereas that of a male is XY.

What is sex linkage?

Sex linkage refers to genes controlling characteristics that are found on sex chromosomes.

What type of inheritance is most often seen with sex linkage?

X-linked recessive inheritance is most often seen with sex linkage.

How can females be carriers for X-linked disorders, while males cannot?

Females have two X chromosomes, so one normal X can compensate for a mutated one, while males have only one X chromosome and cannot compensate.

Give an example of an X-linked recessive disorder.

Hemophilia is an example of an X-linked recessive disorder.

Explain the inheritance pattern of hemophilia.

Hemophilia is an X-linked recessive condition causing a bleeding disorder due to a mutation in a coagulation factor. More males are affected as they inherit the X from their mother, increasing the chance of inheriting the recessive allele.

What is discrete variation? Provide an example.

Discrete variation consists of distinct phenotypic groups, such as different blood types (Type A, Type B).

What is continuous variation? Provide an example.

Continuous variation shows a wide range of phenotypes that are difficult to group, like human skin color.

Describe polygenic inheritance.

Polygenic inheritance involves a single characteristic being controlled by more than two genes, resulting in continuous variation with a normal distribution curve, such as human skin color.

How is human skin color inherited?

Human skin color is inherited through polygenic inheritance, influenced by multiple genes and the amount of melanin produced.

What type of variation is seen in the phenotypes of skin and wheat color?

Skin and wheat color exhibit continuous variation.

Give an example of polygenic inheritance influenced by environmental factors.

Human height is influenced by genetics (polygenic) and environment (nutrition quality during childhood). Similarly, human skin color can be influenced by genetics and environmental exposure to the sun.

What is a dihybrid cross?

A dihybrid cross involves two unlinked genes (not on the same chromosome) and involves two alleles per gene, producing four gamete combinations.

What does the Law of Independent Assortment state?

The Law of Independent Assortment states that the alleles of one gene separate independently of the alleles of another gene, applicable only to unlinked genes.

What is the phenotypic ratio expected from a dihybrid cross with two heterozygous parents?

The expected phenotypic ratio is 9:3:3:1.

What is a linkage group?

A linkage group consists of genes with loci on the same chromosome that do not follow the Law of Independent Assortment and can be separated through recombination.

Describe the results of a cross between two linked genes.

A cross between two linked genes produces more offspring with parental phenotypes and fewer recombinant phenotypes, which only occur if crossing over happens.