Mendelian Genetics and Inheritance Patterns

Law of Independent Assortment

Explains how traits are inherited independently.

Father of Genetics

Gregor Mendel is known as the 'Father of Genetics'.

Dominant allele

Expressed when only one copy is present.

Fundamental unit of heredity

Gene is the fundamental unit of heredity.

Codominance

In codominance, the heterozygous phenotype shows both traits equally.

Alternative forms of a gene

Alleles are alternative forms of a gene.

Incomplete dominance

A red flower crossed with a white flower produces pink flowers.

Observable traits

The observable traits of an organism are referred to as its phenotype.

X chromosome

Carries most sex-linked traits.

Homozygous

If an organism has two identical alleles for a trait, it is homozygous.

X-linked recessive traits

Males are more likely to express X-linked recessive traits because they have only one X chromosome.

Law of Segregation

States that alleles separate during gamete formation.

Punnett square

Used to predict genetic outcomes.

Monohybrid cross

Examines one trait.

Expected phenotypic ratio for a heterozygous monohybrid cross

Is 3:1.

Dihybrid cross

Involves two genes.

Expected phenotypic ratio for a heterozygous dihybrid cross

Is 9:3:3:1.

Main source of genetic variation

Is mutation.

Gene recombination

Occurs during meiosis.

Down syndrome

Is caused by chromosomal abnormalities.

Gene flow

Refers to genetic exchange between populations.

Environmental factor affecting phenotype

Temperature is an environmental factor affecting phenotype.

Genetic counseling

Is based on Mendelian principles.

Chromosomal variation involving loss of a segment

Is deletion.

Chromosomal variation resulting in an extra copy

Is duplication.

Chromosomal variation involving rearrangement

Is translocation.

Down syndrome

A genetic disorder caused by the presence of an extra chromosome 21.

Crossing over

A process that results in a new combination of alleles during meiosis.

Mendel's work

Laid the foundation for modern genetics.

Homozygous

An organism with two identical alleles for a trait.

Phenotype

The observable characteristics of an organism.

Alleles

Different versions of a gene.

Incomplete dominance

A genetic situation in which one allele does not completely dominate another allele, resulting in a new phenotype.

Codominance

A genetic scenario where both alleles are equally expressed in the phenotype.

Genotypic ratio of F2 generation in incomplete dominance

1:2:1.

Expected phenotypic ratio when crossing two pink snapdragon flowers (Rr)

1 red : 2 pink : 1 white.

Probability of getting a red-flowered offspring

50% when a heterozygous pink flower is crossed with a red flower.

Percentage of offspring that will be pink when two heterozygous pink flowers (Rr) are crossed

50%.

Example of incomplete dominance

Red and white snapdragon flowers producing pink offspring.

Phenotype of an Rr individual in snapdragons

Pink.

Mendelian principles

Basic rules of inheritance established by Gregor Mendel.

Trisomy 21

Another term for Down syndrome, characterized by the presence of an extra 21st chromosome.

Law of Independent Assortment

Mendel's principle that states alleles for different traits are distributed to sex cells (& gametes) independently of one another.

Temperature's effect on genetic expression

Can influence the phenotype of certain traits.

Blood type AB

An example of codominance in humans where both A and B alleles are expressed.

Intermediate phenotype in incomplete dominance

The heterozygous phenotype is a blend of the dominant and recessive phenotypes.

Genetic exchange between populations

Occurs when alleles are shared between different groups, contributing to genetic diversity.

Mutation

A change in the DNA sequence that can lead to different traits.

X-linked inheritance

Traits that are determined by genes located on the X chromosome.

F1 generation

The first filial generation, which is the result of a cross between two parental organisms.

Expected offspring from a pink and white flower cross

50% pink and 50% white.

Alleles separate during gamete formation

A principle of Mendel's law of segregation.

Complete dominance

One allele is completely dominant over the other.

Incomplete dominance

The heterozygous phenotype is an intermediate of both alleles.

Codominance

Both alleles are expressed equally in the heterozygote.

Recessive allele

The recessive allele is not expressed.

Eye color

An example of a trait influenced by multiple alleles.

Blood type AB

A blood type resulting from the genotype IAIB.

Skin color

An example of a polygenic trait influenced by multiple genes.

Hair type

An example of a trait that can show multiple phenotypes.

Genotype for blood type AB

IAIB.

Genotype for type O blood

ii.

Phenotypic ratio of offspring from heterozygous codominant individuals

1:2:1.

Possible blood types of offspring from IAIA and IBi parents

A, B, and AB.

Probability of type O child from IAi and IBi parents

25%.

Blood type A

Has only A antigens.

Blood type B

Has only B antigens.

Blood type AB

Has both A and B antigens.

Inheritance pattern of red and white spotted petals

Codominance.

Third phenotype distinct from both parents

Polygenic inheritance.

Blood type AB donation

Can donate to any blood type.

Statement about incomplete dominance and codominance

Incomplete dominance shows a blended trait, codominance shows both traits distinctly.

Outcome of codominance in flower color

The flower would have both red and white patches.

Parents' blood types for a child with blood type AB

Cannot be AB and O.

Percentage of white offspring from roan cattle

25%.

Heterozygous genotype in codominance

Both alleles being equally expressed.

Phenotype

The observable characteristics of an organism resulting from the interaction of its genotype with the environment.

Heterozygous phenotype

An intermediate of the two alleles.

Blood type AB

A blood type characterized by the presence of both A and B antigens.

IAIB

The genotype for blood type AB.

Lethal allele

An allele that causes death when homozygous.

Dominant lethal allele

An allele that is always dominant and can cause death before reproductive age.

Recessive lethal allele

An allele that is only lethal in homozygous individuals.

Multiple alleles

A gene that has more than two allelic forms.

Universal recipient

A person with blood type AB who can receive blood from any type.

Survival ratio for recessive lethal allele

Typically 2:1 when heterozygous carriers are crossed.

Sickle-cell anemia

An example of a disease caused by a lethal allele.

Huntington's disease

An example of a dominant lethal allele.

Polydactyly

An example of a lethal allele.

Pedigree chart

A diagram used to show the genetic relationships among a group of individuals.

Type O blood

A blood type characterized by the absence of A and B antigens.

Genotype for blood type O

ii.

Possible genotypes for type B blood

IBIB and IBi.

Possible blood types of parents for a child with blood type AB

A and B.

Expected survival ratio for a cross between two heterozygous carriers of a recessive lethal allele

2:1.

Flower phenotype in codominance

The flower would have both red and white patches.

Blood type characteristics

Type A and B can be present in the same individual.

Example of a trait controlled by multiple alleles

Blood type.

Inheritance of lethal alleles

They are passed down through dominant inheritance.

Probability of inheriting a lethal allele from a heterozygous parent

25%.