Genetics, populations, evolution and ecosystems

What are alleles?

Alternative forms of a particular gene with different base sequences.

What does co-dominant mean?

Alleles that both contribute to the phenotype in the heterozygous condition.

What is a dominant allele?

An allele that expresses itself in the phenotype in heterozygous organisms.

What is a gene?

A section of DNA on a chromosome that controls a feature by coding for specific polypeptides or functional RNA.

What is a genotype?

The combination of alleles present within the cells of an organism.

What does heterozygous mean?

An organism with paired alleles that are different.

What does homozygous mean?

An organism with paired alleles that are the same.

What are homologous chromosomes?

A pair of chromosomes, one from each parent, that have the same gene loci.

What is the locus?

The specific linear position of a gene on a chromosome.

What is monohybrid inheritance?

Inheritance of a single pair of alleles.

What is a phenotype?

The observable or biochemical characteristics of an organism resulting from its genotype and environmental effects.

What is a recessive allele?

An allele that does not express itself in the phenotype in heterozygous organisms.

What is the expected phenotypic ratio when two homozygous parents are crossed?

100% heterozygous offspring with the same phenotype.

What is the phenotypic ratio of offspring from two heterozygous parents (Gg)?

A 3:1 ratio of phenotypes, e.g., green:yellow pods.

What does co-dominance imply in genetics?

Both alleles are expressed in the phenotype as neither is recessive.

What factors can cause discrepancies between expected and actual offspring ratios?

Random fertilization, co-dominance, sex-linkage, and small population samples.

What causes genetic variation in gametes during meiosis?

Crossing over between chromatids and independent assortment of chromosomes.

Why are humans diploid organisms?

Because they have two copies of each chromosome (one from each parent) which means there are two alleles for each gene

What does F₁ mean

The first set of offspring of two parents