Genetic Variation Flashcards

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

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33 Terms

1
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What are the two main sections of Genetic Variation?

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

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Name the key concepts of Genetic Variation.

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

3
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What is a mutation?

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

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What are chromosomes?

Thread-like structures made of tightly coiled DNA.

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How many chromosomes do humans have?

46 chromosomes in total, 23 pairs of homologous chromosomes.

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What is a gene?

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

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What is an allele?

An alternative form of a gene.

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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.

9
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What are point/gene mutations?

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

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What are chromosome mutations?

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

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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.

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What is the ultimate impact of gametic mutations?

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

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What is Meiosis?

Cell division which produces gametes.

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What is Mitosis?

Cell division of all body cells (somatic cells).

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

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

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

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

17
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Define Haploid.

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

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Define Diploid.

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

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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.

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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.

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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.

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What are dominant alleles?

Alleles that will always be expressed when present.

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What are recessive alleles?

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

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Define Genotype.

The combination of alleles an individual possesses.

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Define Phenotype.

An individual's observable characteristics or traits.

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Define Homozygous.

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

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Define Heterozygous.

Holds two different alleles for a particular gene.

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What is complete dominance?

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

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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.

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What is codominance?

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

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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.

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What is a lethal allele?

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

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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.