Genetic Variation Flashcards

Flashcards covering key concepts from lecture notes on genetic variation, including mutations, meiosis, patterns of inheritance, and dihybrid crosses.

What are the two main sections of Genetic Variation?

Sources of variation at the population level and sources of variation at the individual level.

Name the key concepts of Genetic Variation.

Mutations, Meiosis, Patterns of inheritance, Dihybrid crosses vs monohybrid, Genetic drift + migration, Natural selection.

What is a mutation?

A permanent, random change to the base sequence of DNA caused by exposure to mutagens that creates new alleles.

What are chromosomes?

Thread-like structures made of tightly coiled DNA.

How many chromosomes do humans have?

46 chromosomes in total, 23 pairs of homologous chromosomes.

What is a gene?

A segment of DNA which sits in a particular place on a chromosome and determines a particular characteristic.

What is an allele?

An alternative form of a gene.

What is a mutagen?

A physical or chemical agent that changes the DNA of an organism and thus increases the frequency of mutations above the natural background level.

What are point/gene mutations?

Changes in a single base pair by insertion, deletion, or substitution.

What are chromosome mutations?

Changes to the chromosome through deletion, inversion, translocation, and duplication.

What is the difference between somatic and gametic mutations?

Somatic mutations only impact the organism in a specific area during its lifetime, while gametic mutations are passed down to future generations.

What is the ultimate impact of gametic mutations?

Change the allele frequency of populations and the species long term.

What is Meiosis?

Cell division which produces gametes.

What is Mitosis?

Cell division of all body cells (somatic cells).

How many daughter cells are produced in meiosis and are they identical?

Meiosis produces 4 daughter cells, and the daughter cells are genetically unique.

How many daughter cells are produced in mitosis and are they identical?

Mitosis produces two daughter cells. Daughter cells are genetically identical.

Define Haploid.

One copy of each chromosome, designated as 'n' (gametes).

Define Diploid.

Two copies of each chromosome, designated as '2n' (somatic cells).

What is Independent Assortment?

The random arrangement of homologous chromosomes along the cell equator during meiosis, resulting in unique combinations of chromosomes and alleles in gametes.

What is Crossing Over?

The exchange of sections of chromosomes (alleles) between neighboring homologous chromosomes during meiosis I (prophase 1) in a process called recombination.

What is Segregation?

During meiosis, pairs of alleles are segregated when homologous chromosomes split so that each gamete receives only one allele for each pair.

What are dominant alleles?

Alleles that will always be expressed when present.

What are recessive alleles?

Alleles that are only expressed if there are only recessive alleles.

Define Genotype.

The combination of alleles an individual possesses.

Define Phenotype.

An individual's observable characteristics or traits.

Define Homozygous.

Holds two copies of the same allele for a particular gene.

Define Heterozygous.

Holds two different alleles for a particular gene.

What is complete dominance?

When the dominant allele completely masks the physical expression of the recessive allele when both alleles are present.

What is incomplete dominance?

The action of one allele does not completely mask the action of the other. Neither is dominant, and an intermediate phenotype is expressed.

What is codominance?

Both alleles in a heterozygote contribute to the phenotype. Both alleles are independently and equally expressed.

What are multiple alleles?

Where there are more than 2 alleles for 1 gene. An allele may be dominant to another allele but then recessive to a different one. It results in more than 2 different phenotypes.

What is a lethal allele?

An allele that produces a phenotypic effect that causes the death of the organism (at any stage of life).

What occurs during Dihybrid Crosses?

When we look at 2 pairs of alleles i.e. 2 traits and the probability of two genes being inherited.