Genetics and Natural Selection Review

These flashcards cover key genetic concepts, definitions of terms, and principles of natural selection to help students prepare for their exam.

What is a gene and how does it work?

A gene is the basic unit of heredity, a segment of DNA on a chromosome that carries information for protein or RNA synthesis. It works by directing protein production through transcription and translation.

Define homologous chromosomes.

Homologous chromosomes are a pair of chromosomes, one from each parent, that are similar in shape, size, and gene arrangement, carrying the same genes at corresponding loci.

What is a dominant allele?

A dominant allele is one that expresses itself in both homozygous and heterozygous conditions, masking the expression of the recessive allele.

What are alleles?

Alleles are alternative forms of the same gene that occupy the same position on homologous chromosomes.

What is a recessive allele?

A recessive allele expresses itself only in the homozygous condition and remains unexpressed in the presence of a dominant allele.

Differentiate between homozygous and heterozygous genotypes.

Homozygous means having identical alleles for a trait, while heterozygous means having two different alleles for a trait.

What is codominance?

Codominance is a phenomenon where both alleles express themselves equally in a heterozygous condition without blending, such as in human blood group AB.

List the main factors in the theory of natural selection.

1. Overproduction of offspring 2. Struggle for existence 3. Variations among individuals 4. Survival of the fittest 5. Natural selection 6. Inheritance of favorable variations 7. Formation of new species.

How does artificial selection differ from natural selection?

Artificial selection is human-controlled selection for desirable traits, while natural selection is the environment selecting organisms best adapted for survival.

Describe the Watson and Crick model of DNA.

The Watson and Crick model describes DNA as a double helix made of two polynucleotide strands, explains base pairing, and outlines how DNA can replicate accurately.

What is the process of gene expression?

Gene expression is the process of using information in a gene to produce a functional product like protein, involving transcription, RNA processing, translation, and protein folding.

State Mendel’s Law of Segregation.

During gamete formation, the two alleles of a gene separate so that each gamete receives only one allele.

Explain the F₂ generation ratio in a dihybrid cross.

In a dihybrid cross, the F₂ generation ratio is typically 9:3:3:1, representing the phenotypic ratios of two contrasting traits.

What are the main points of Darwin's theory of natural selection?

1. Overproduction of offspring 2. Struggle for existence 3. Variation among individuals 4. Survival of the fittest 5. Inheritance of useful variations 6. Speciation.