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BIOL 1005 Lecture Notes - Lecture 12: Allele Frequency, Population Genetics, Genetic Drift

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9 Mar 2016

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Document Summary

Population genetics: definitions (some old and new favorites) Population- a collection of interbreeding individuals, each of which is a collection of alleles. Genes- units of heredity with specific locations on chromosomes, for our purposes these genes control the heredity of a particular trait. Alleles- alternative forms of expression of a gene. Within an individual, there are two alleles for each trait. If they are the same the individual is homozygous, if they are different, heterozygous. Genotype - the genetic constitution of an individual, the collection of alleles in an individual. Phenotype- the external expression of the genotype, the physical characteristics. Gene pool- the sum total of all the alleles possessed by all of the individuals of the population. Microevolution-changes in the frequencies of alleles of specific genes within a population. Polygenic traits- phenotypes which are controlled by several different genes, e. g. height in humans.

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Related Questions

Jim is blood type A, his brother John is type O and his sister Jane is type AB. What are the genotypes of their parents?

Which of the following is true for alleles that show incomplete dominance?

Heterozygotes have a genotype like the dominant allele.

Homozygotes have a genotype like the recessive allele.

Heterozygotes have a phenotype intermediate between the dominant and recessive alleles.

Homozygotes have the same phenotype as the heterozygotes.

Which principle of inheritance concluded that when games are formed in meiosis, the two alleles of each gene separate from one another, and each gamete receives only one allele?

independent assortment

Which term best describes a condition in which alleles at one locus can alter the expression of alleles at another locus?

polygenic inheritance

multiple alleles

A single unit of genetic information located on a chromosome defines:

The physical expression (appearance or function) of an organism's genes defines:

a single characteristic

Palomino horses (golden color with a blond mane) are an incompletely dominant trait produced by the combination of the chestnut color allele and the cream color allele. If you wanted to produce as many palominos as possible, which mating strategy below would be the best choice?

Chestnut x Cream

Palomino x Cream

Palomino x Chestnut

Palomino x Palomino

Which term best describes the effect of a single gene on multiple aspects of the phenotype?

multiple alleles

polygenic inheritance

Which term best describes the separate expression of both alleles for a single trait in the same cell?

multiple alleles

polygenic inheritance

One form of a gene found on a single chromosome defines:

A chocolate lab (whose mother was a yellow lab) is mated with a black lab whose genotype is BbEe. What fraction of the offspring would be expected to be yellow labs?

What type of allele is always expressed regardless of whether the individual is homozygous or heterozygous for it?

Both the dominant and recessive alleles

Recessive allele

Allosteric allele

Dominant allele

Given the parents AABBGgHhrr Ã AabbGgHhRr, assume simple dominance and independent assortment. What proportion of the progeny will be expected to have the genotype AaBbggHHrr?

___________________ is defined as having two of the same type of allele for a particular trait.

Incomplete dominance

The physical position of an allele on a single chromosome defines:

Which term best describes two or more genes affecting the phenotype in an additive fashion?

polygenic inheritance

multiple alleles

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These all relate to exceptions to the inheritance patterns encountered by Mendel.â

Why do multiple and lethal alleles often result in modifications of the classic Mendelian monohybrid and dihybrid ratios?

Select the four correct statements.

-When an essential gene is mutated, it can result in a lethal phenotype. There are no classic Mendelian monohybrid and dihybrid ratios.

-In the case of codominance, heterozygotes produce gene products from both alleles of a gene. Classic Mendelian monohybrid and dihybrid ratios are modified by codominance.

-In the case of incomplete dominance, the phenotype of the heterozygote is distinct from and often intermediate to the phenotypes of homozygous individuals. Classic Mendelian monohybrid and dihybrid ratios are modified by incomplete dominance.

-Genes exist in a large number of allelic versions and a diploid organism has two homologous gene loci that may be occupied by different alleles of the same gene. This can result in many different phenotypes for traits, which may not follow typical Mendelian ratios.

-When an essential gene is mutated, it can result in a lethal phenotype. This results in a modification of classic Mendelian ratios.

-The phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. The joint expression of both alleles in a heterozygote is called codominance. There are no classic Mendelian monohybrid and dihybrid ratios.

-Genes exist in a large number of allelic versions, but in a diploid organism, only one allele of the gene can occupy one homologous gene loci. Classic Mendelian inheritance cannot explain this phenomenon.

-Each gene produces a unique gene product. The effect of one allele in a heterozygote completely masks the effect of the other. Classic Mendelian genetics cannot explain this phenomenon.

2 Genetics -Match the terms with the most suitable description.
(Points : 16)

Potential Matches:

: An allele that can be expressed byan individual that is heterozygous.

: The genetic make-up of anindividual.

: The control of more than onephenotypic character by a single gene.

: The visible physical expression ofan individual's genetic make-up.

: An allele that can only beexpressed when an individual is homozygous.

: A trait controlled by more thanjust a single pair of alleles.

: A trait controlled by a genelocated on either the X or Y chromosomes.

: An individual carrying only oneallele of a recessively inherited disorder.

3. Evolution- Match the terms with the most suitable description.
(Points : 16)

Potential Matches:

1 : hybrid sterility

2 : habitat isolation

3 : hybrid inviability

4 : geographic isolation

5 : mechanical isolation

6 : gamete mortality

7 : temporal isolation

8 : behavioral isolation

: Because of a single mutation in adevelopmental gene, two closely related species of wasps have aslightly different anatomy of their sex organs making interbreedingimpossible.

: Two species of snakes aremorphologically very similar but breed during differentseasons.

: Two similar species of treehopperslive and feed on two separate species of trees.

: Males of two species of birds usedifferent mating dances to attract their mates.

: Due to a geographic barrier, asmall portion of a population remains isolated and its gene pooldiverges from that of the original population.

: Sperm from a male of one speciesdies in the reproductive tract of the female of a different speciesbefore fertilization can occur

: Mules are a cross between a donkeyand a horse; they are viable, healthy animals, but they cannotreproduce.

: A cross between two species ofsalamanders yields offspring, but they do not survive long enoughto reproduce

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