Chapter 2: Population Genetics

Question 1

Who was Jean-Baptiste Lamarck (1774-1829)?

Answer 1

They were a person that believed that psychological events, such as use or disuse, determined whether traits were passed on to offspring. Also stated that living things have a “drive for complexity” and that humans were the perfection. (obviously it’s wrong, humans are vulnerable)

Ex: Giraffes, in their continual struggle to reach the highest foliage stretched their necks by a few millimeters in the course of their lifetime. This increase in neck length was passed on to their offsprings, which continued the process until the necks of giraffes reached their current proportions. This was proven wrong.

Question 2

Charles Darwin?

Answer 2

He proposed the theory of evolution by natural selection and is considered the founder of modern evolutionary theory. Went on a voyage “the beagle” to the Galapagos Islands and had intensive research/data.

–> found out that animals - such as the Geochelone elphantopus- exhibited different growth from on different islands.

Question 3

Malthusian theory of population? and what does this mean in terms of natural selection and survival of the fittest?

Answer 3

An idea/theory by Thomas Malthus –> “because Earth was not overrun by humans, food shortage, disease, war, or conscious control must limit population growth.
–> Darwin applied this theory to plant and animal populations. It was how he realized that only the best would survive and reproduce. (aka natural selection; better-adapted organisms would acquire more resources and leave more offspring ) In other words, nature “selects individuals with traits that allow them to flourish and reproduce (aka survival of the fittest).

Question 4

Adaptation?

Answer 4

given an evolutionary time span, a population’s characteristics change to make its member better suited to their environment
example: giraffes born with longer necks would feed better since they could reach more vegetation, thus they are more successful in reproducing than short-necked giraffes. Then the dominant trait would be long-necked giraffes and passed on to their offspring, and over time, then boom long neck population dominant.

Question 5

Alfred Russel Wallace?

Answer 5

He was a co-discover of the chief mechanisms of evolution. He worked with Darwin

Question 6

Example of Natural Selection?

Answer 6

Example: Peppered moth. industrialized areas, lichens are killed off, tree bark becomes soot covered and darker, and the dark moths are more cryptic- Kettlewell demonstrated that birds were the selective force by releasing hundreds of pale forms and dark from of moths marked with a small spot of paint into urban and industrialized areas, during the industrialized dark moth were prominent, while in time of no industrialization, white moth made a comeback

Question 7

Gregor Mendel? Self-fertilization? (flashcard 1)

Answer 7

Gregor Mendel performed classic experiments on the inheritance of traits. Worked with garden pea due to their characteristics (character traits) and because they are normally self-fertilizing (meaning a female gamete is fertilized by a male gamete from the same plant) making it easy to produce plants that breed true to a given trait, meaning that the trait does not vary from generation to generation (in other words, a purple pea plan will also produce purple pea plants when bred)

Self-fertilization: They have both eggs and sperms in their body and at fertilization, one sperm cell fuses with oocyte to form an embryo.

Question 8

Gregor Mendel? True breeding line (flashcard 1)

Answer 8

True breeding line: a variety that continues to exhibit the same trait after several generations of self-fertilization is called a true-breeding line (it was established by Mendel that pea plants have true breeding lines)

Question 9

cross-fertilization? Hybridization? // Example?

Answer 9

Cross-fertilization is also known as hybridization: when two individuals with different characteristics are mated or crossed to each other

Example: crossing a purple-flowered pea plant with white-flowered pea plant

Question 10

P-generation (p-cross), F1 generation, monohybrids, F2 generation, Mendel finding?

Answer 10

P-generation: the true parents (the og parents), and a cross of that is called the P-cross

F1 generation: after the p-cross, this is the result, the first generation of the og parents

monohybrids: when the true-breeding parents differ in a single- trait, the F1 offsprings are called single-trait hybrids or monohybrids

F2 generation: self-fertilized and 3/4 of the pants were purple and one was white, this how he figured out dominant and recessive genes

Question 11

Laws of segregation? (Mendel)

Answer 11

Law of segregation: the idea that two copies of a gene segregate from each other during transmission from parent to offspring is known today as Mendel’s law of segregation

Question 12

genotype? homozygous? heterozygous? phenotype?

Answer 12

Genotype: genetic composition of an individual.

Homozygous: an individual with two identical copies of a gene is said to be homozygous (RR and rr)

Heterozygous: individual carries two different alleles of the same gene (aka Rr)

Phenotype: refers to the physical characteristics of an organism, which are the result of the expression of its gene

Question 13

Gene mutation?

Answer 13

gene mutation involves changes in the four nucleotide bases that make up the double-stranded DNA base pairs (adenine, thymine, guanine, and cytosine)

Question 14

What two types of changes in genes can a mutation cause? Point mutation (example)?

Answer 14

Mutations can cause two types of changes to genes. First, the base sequence can be changed, second, nucleotides can be added or deleted.

Point mutations: exchange a single nucleotide for another
–> ex: the human disease known as sickle-cell disease involves a point mutation in the B-glob gene, which encodes for hemoglobin, the oxygen-carrying protein in the red blood cells. A point mutation alters the nucleotide sequence so that the sixth amino acid is changed from glutamic acid to valine. This change is enough to cause mutant hemoglobin subunit(s) to stick to one another when the oxygen concentration is low. The aggregated proteins form fiber-like structures within red blood cells, which causes the cells to lose their normal morphology and become sickle-shaped. This simple amino acid substitution has a profound effect on the structure of cells.

Question 15

Frameshift mutation? flavobacterium?

Answer 15

2nd type of mutation–> involves the addition or deletion of nucleotides, this shifts the “reading frame” with which the genetic code is deciphered, so that a completely different amino acid sequence occurs downstream from the mutation
–> change is large enough to disrupt protein function (some unique genes may have evolved due to this mutation)

Question 16

Chromosomes? the 4 types of changes amongst chromosomes and where do they occur?

Answer 16

Chromosomes mutations alter the order of genes (they do not subtract or add from the variability of the gene pool; they merely rearrange it, creating certain gene combinations)

Deletion: Duplication: Inversions: translocation:

Occur^? All through meiosis when chromosomes are being duplicated

Question 17

4 type of chromosome changes

Answer 17

Deletion: simple loss of part of a chromosome and is the most common source of a new mutation (lethal unless higher organisms have many genes to have duplicated)

Duplication: occurs when two chromosomes are not perfectly aligned during crossing over; the result is one chromosome with a deficiency of genes, and one with a duplication of genes. (duplication may be advantageous, especially in yeast- an increase of enzyme acid monophosphatase enables cells to a more efficiently exploit low concentrations of phosphate in the medium in which the cells are growing)

Inversion: occurs when a chromosome break in two places and the middle segment then turns around and re-fuses with the same pieces.

Translocation: two nonhomologous chromosomes break simultaneously and exchange segments

Question 18

Small populations? Negative or positive? Inbreeding?

Answer 18

Negative. Population sizes become too small, individuals accumulate deleterious (harmful) mutations, and the survival of offspring is threatened.

Inbreeding: mating between closely related relatives, increases the chances of both parents carrying the same harmful alleles and thus of the production of the homozygous offspring that exhibits the effects

Question 19

Heterozygous populations?

Answer 19

In most populations, the size is so great that when heterozygotes carry a rare, recessive allele mate, their partner likely will not carry the same allele. So, when they do reproduce half the offspring would be heterozygous, and half would be homozygous for the common form of the allele. None of the offspring would be homozygous for the deleterious allele. Thus, a win for the population. (that’s why breeding bad bc if they do breed then that means there is 1/4 of the offspring carrying the deleterious allele and basically you already sit your kid up for failure)

Question 20

Genetic drift? Example? Math?

Answer 20

Genetic drift refers to random changes in allele frequencies over time.

Example: Basically a male fails to mate, and if he had a rare gene, and because he failed to mate, the gene is lost, resulting in a loss of genetic diversity in the population.

1/(2N) - N=Population size
if N=50, then 1/((2)(50)) = 1/100 = 0.01 or 1%, so this means that a population of 50 will lose 1% of genetic diversity after ten generations

Question 21

artificial selection?

Answer 21

Darwin recognized that breeders of domestic animals and plants could influence their traits
- used artificial selection based on phenotypic traits
- tried to accumulate changes in strains to produce beneficial new straing os animals and plants

Question 22

convergent evolution?

Answer 22

the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities
- this has led to the emergence of similar looking floras and faunas in different realm where environmental conditions are similar; they could have different ancestors, but the common environment and food source promote the evolution of similar morphologies in different species

Question 23

biogeographic realms?

Answer 23

this is the timeline of life. How we went from nothing to having oxygen and now our world has biodiversity

bacteria and archea were on earth 4-3 billion years ago and algae came to be 2-1 billion years ago because of changes in atmosphere (we began to have oxygen and less than a billion years ago we began to have plants, animals, fungi)

Question 24

micro vs macro evolution?

Answer 24

microevolution: the short-term adaptations that result from changes in the environment (i.e changes in allele frequency ) ex: effects of industrial revolution on moth population
macroevolution: the process of the development of new species from a common ancestry (that that functions above the species level) –> aka the evolution of fingers on humans, lizard, cat, whale, bat etc., they all got fingers but evolved differently)

Question 25

Law of independent assortment?

Answer 25

The law of independent assortment states that genes located on different pairs of homologous chromosomes sort independently during meiosis.
Mendel’s law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene

Question 26

monohybrid cross?

Answer 26

e hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait.”

Question 27

dihybrid cross?

Answer 27

a mating experiment between two organisms that are identically hybrid for two traits.

Question 28

intermediate traits

Answer 28

a measurable trait in which there is some evidence of the operation of a simple major cause, but in which the variation within the putative categories is such as to cause overlap and hence ambiguity in the classification of any particular reading.
example: The trait from dad mixes with the trait from mom and the child gets an intermediate appearance. This type of inheritance, or passing down of traits from parent to offspring, is called intermediate inheritance, also known as incomplete dominance.

Question 29

somatic cell vs gametic cells

Answer 29

Somatic cells and gametes are two types of cells which are involved in asexual and sexual reproduction of organisms, respectively. Somatic cells can be found everywhere in the body whereas gametes are restricted to reproductive organs

Question 30

diploid/ haploid cells?

Answer 30

The most obvious difference between Haploid and Diploid is the number of chromosome sets that are found in the nucleus. Haploid cells are those that have only a single set of chromosomes while diploid cells have two sets of chromosomes.

Question 31

modern synthesis?

Answer 31

darwin was like “idk why organisms change inherently”., so in the 1930s and 40s scientist were like “yo we can understand behavior through a molecular basis also known as “modern synthesis”

Question 32

inbreeding? extinction vortex? effective population size?

Answer 32

inbreeding- bad, reduces the genetic pool/ variability
extinction vortex- this is what happens when like the number of males decreases, so inbreeding increases, resulting in a decrease in fertility so the whole thing spirals toward extinction - can’t produce children bc of inbreeding, f*cking their population size and just dying