Biology Test 5 Notes Genetics

Who was Gregor Mendel?

An Austrian monk who formulated the foundational principles of genetics through experiments with pea plants.

What did Mendel determine about traits?

Traits are inherited as discrete units, known as genes.

What are the generations documented by Mendel in his experiments?

Parent Generation (P), F1 Generation (offspring of P), and F2 Generation (offspring of F1).

What was the ratio of recessive traits in the F2 generation?

Recessive traits reappeared in a ratio of approximately 3:1.

Law of Segregation

Alleles segregate independently during the formation of gametes.

Law of Independent Assortment

The inheritance of one trait does not affect the inheritance of another.

Principle of Dominance

Dominant alleles mask the presence of recessive alleles.

What does haploid mean?

Sex cells have 1 copy of each chromosome (1 allele per gene).

What is a homozygous genotype?

Alleles are the same.

What is a heterozygous genotype?

Alleles are different.

What is a hemizygous condition?

Only one allele is present, commonly seen in males for X chromosome genes.

Define genotype.

Allele combination for any given characteristic.

Define phenotype.

Physical expression of a given characteristic.

What is the purpose of a Punnett square?

To show the possible outcomes of a genetic cross and predict inheritance probabilities.

What did Mendel's first experiment primarily test?

The inheritance of one trait at a time.

What is the expected phenotypic ratio for a dihybrid cross?

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

What causes single gene disorders?

Mutations in the DNA sequence of a single gene.

What is an example of an autosomal recessive disorder?

Cystic Fibrosis.

What is the cause of Huntington's Disease?

A mutation in the HTT gene, with a repeating CAG sequence.

What is a chromosomal abnormality?

Structural changes to chromosomes, such as Down syndrome (trisomy 21).

What are mitochondria responsible for?

Mutations in mitochondrial DNA can lead to mitochondrial diseases.