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What is a gene?
A physical unit of heredity composed of a DNA sequence that encodes a protein or a functional molecule.
Define allele.
Alternative forms of a gene.
What does it mean for an allele to be dominant?
Only one copy is needed for the phenotype to be expressed.
What is a recessive allele?
Two copies are needed for the phenotype to be expressed.
What is a genotype?
The genetic composition of an organism.
What is the phenotype?
Observable traits of an organism.
Who was Gregor Mendel?
A geneticist in the 19th century known for his experiments with pea plants.
What was the blending hypothesis?
The idea that offspring have a mixture of their parents' traits, like blending paint colors.
What is a monohybrid cross?
A genetic cross between two individuals focusing on one trait.
What ratio results from a monohybrid cross of heterozygous parents (Bb x Bb)?
1:2:1 genotype ratio; 3:1 phenotype ratio.
What is the Law of Segregation?
Mendel's first law stating that every organism carries a pair of alleles for each trait, which separate during gamete formation.
What does a test cross determine?
The genotype of a phenotypically dominant organism.
What is a dihybrid cross?
A cross between individuals that examines two traits.
What is the Law of Independent Assortment?
Mendel's second law stating that alleles of one gene segregate independently of alleles of another gene during gamete formation.
Define codominance.
A situation where both alleles contribute equally and separately to the phenotype of the organism.
What are polygenic traits?
Traits influenced by two or more genes.
What does the term 'epistasis' refer to?
Interactions between genes where the expression of one gene affects the expression of another gene.
What is pleiotropy?
A single gene influences multiple traits.
What is a Barr body?
An inactivated X chromosome in a female cell.
What results from nondisjunction during meiosis?
Aneuploidy, which is an abnormal number of chromosomes.
What is the difference between dominant and recessive alleles?
Dominant alleles express their traits with one copy; recessive alleles require two copies for expression.
What is the significance of the SRY gene?
It is located on the Y chromosome and determines male sex in humans.
What happens during X inactivation?
One of the X chromosomes in females is randomly inactivated to balance gene expression.
What are translocations in chromosomes?
A segment of one chromosome moves to another chromosome, which can lead to disorders.
What are aneuploidy conditions?
Abnormalities in chromosome number, such as trisomy 21 (Down syndrome).
What can cause Huntington's disease?
It is an autosomal dominant disorder that results from a single gene mutation.
What do pedigrees show?
They illustrate the genetic relationships or patterns of inheritance between family members.
What is genetic linkage?
Genes on the same chromosome are linked and do not assort independently.
How does crossing over affect linkage?
Crossover can occur between genes that are further apart on the same chromosome, creating recombinant gametes.
What is the purpose of linkage maps?
To show the relative distances between genes based on crossover frequency.
