Heredity & Evolution

Example One Discuss how new discoveries in genetics are contributing to our understanding of the HIV virus and how some folks exposed to HIV have been able to escape developing AIDS.

The HIV virus daily infects 14,000 people, however some individuals’ odds of contracting the virus are very low. Dr. Donald Mosier of the Script Institute was puzzled by this and launched a genetic study to determine why certain individuals are resistant to the HIV virus. What Dr. Mosier discovered was the resistant people inherited a deletion mutation that gave them protection. Within the deletion mutation, the receptor CCR5, is excluded. This deleted section of the CCR5 receptor functions as a lock, therefore people born with the mutation will not get the HIV virus. Those individuals that are homozygous – have two copies of the same deletion gene, are immune to the virus and are protected. Individuals that are heterozygous – have two different genes – have some protection from HIV because their body have half the “locks.” Dr. Mosier further studied populations and discovered the deleted mutation was higher in certain parts of the world and among Caucasians.

Explain the genetic connection between phenotype and genotype discovered by Mendel in the 19th century.

Genetics helps to understand human diversity, not only in today’s world but in the past as well. When studying genetics it is important to understand the relationship between phenotype and genotype. A phenotype is defined as an observable physical characteristic whereas a genotype is the set of specific genes an organism carries (Allen, Anton, Stanford 60). In the video lesson, Anne Stone commented the phenotype can be impacted by the environment. For example, if there is not sufficient food or there is disease, this can impact an individual’s height which is a phenotype. Anthropologist Geneticist Joanna Mountain explained a phenotype can be “measurements and anything we can describe about a person from appearance to metabolism.”

Utilizing the garden pea plant to conduct his experiment, Gregor Mendel was able to recognize traits were passed on from parents to offspring. He knew traits were inherited but did not know how this inheritance worked. Mendel’s Principles of Segregation which states in an organism, alleles occurs in pairs and when gametes sex cells get produced, alleles separate so each gamete contains one member of each pair. Further experiments by Mendel lead him to conclude in a unit of inheritance, meaning offspring received receive genes from each parent. Theses principles laid the foundation for future scientists to study inheritance.

Vocabulary

Phenotype – observable characteristics; expression of genetic instructions; something you can measure

Genotype – genetic make-up of an individual; every person has a unique genotype made of genes inherited from parents

Recessive – a masked trait or covered up

Dominant – mask recessive characteristics

Principles of Segregation – in an organism, alleles occurs in pairs; when gametes get produced alleles separate so each gamete contains one member of each pair

Homozygous – two copies of the dominant alleles are present

Heterozygous – two different alleles at the loci for a gene

Mendelian traits- effected at one gene locus; ex: clef chin

Locus – the location of a gene on a chromosome

Polygenic – a particular trait is influenced by multiple genes; ex: skin color, height …lots of gene contribute…”human variation is polygenic.”

Populations – communities of people; can be members of an ethnic group

Allele Frequency - the allele is the variant and may vary among populations

Micro evolution – small change in allele frequencies in a population over generations

Gene flow – the exchange of genes between populations

Gene drift – the genetic make-up of a population is altered by random factors because the population is small.

Example Two

a. Explain the genetic connection between phenotype & genotype discovered by Mendel in the 19th century.

c. Discuss how new discoveries in genetics are contributing to our understanding of the HIV virus & how some folks exposed to HIV have been able to escape developing AIDS.

The genetic connection between genotype and phenotype discovered by Mendel in the 19th century explains that Phenotype as explained by Joanna L. Mountain Phd. an Anthropologist Geneticist, “Anything that you can measure about a person or anyway that you can describe a person for example their appearance is described as the phenotype”. Genotype is the genetic makeup of an individual. Every individual has a unique genotype. The Genotype codes for the Phenotype. The power lesson explains that you can compare the genotype to a blue print or a plan versus the finished product or completed structure.

Donald Mosier Phd MD Immunologist is studying the types of genetic variation that makes people virtually immune to HIV as said in the DVD lesson. He explains how HIV resistant people

have a deletion mutation gene called CCR5 that deletes the section in DNA that contains receptors to enter the cell and become infected with HIV. The DVD lesson explains how some certain populations carry the mutation gene and how it is passed to on. According to the DVD lesson Microevolution is the change in allele frequencies that occur over time within a population. This change is due to 4 different processes, mutation or changes in DNA sequence of a cells genome, Selection or the process by which traits that make it more likely for an organism to survive and successfully reproduce become more common in a population, Genetic drift or the change is the frequency in a allele occurs in population due to random sampling, and gene flow or the exchange of genes between population.

Definitions:

Phenotype : the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Genotype: the genetic constitution of an individual organism

Recessive: pertaining to a gene whose phenotype is masked by a dominant gene.

Dominant: An allele or a gene that is expressed in an organism’s phenotype, masking the effect of the recessive allele or gene when present

Homozygous Dominant: two copies of dominant alleles are present.

Melanin: a dark brown to black pigment occurring in the hair, skin, and iris of the eye in people and animals.

Populations: all the inhabitants of a particular town, area, or country

Allele Frequency: Variant in frequency from one population to another.

Microevolution: is the change in allele frequencies that occur over time within a population

Gene flow: exchange of genes between population

Genetic Drift: the change is the frequency in a allele occurs in population due to random sampling