Bio112 Exam 2

Meiosis 1

The first round of cell division; results in non-identical chromosomes.

Prophase 1

Crossing over occurs at the chiasmata; bivalents (homologous pairs with sister chromatids) are present.

Metaphase 1

Random assortment occurs as homologous Paris line up in the center of the cell.

Anaphase 1

Homologous pairs separate, but sister chromatids do not.

Meiosis vs. Mitosis

Meiosis is sexual (4 unique daughter cells, 2 rounds of devision) while mitosis is asexual (2 identical daughter cells, 1 round of division).

Nondisjunction

Results in missing or extra chromosomes; occurs in Anaphase.

Nondisjunction (First Divison)

Homologous pairs fail to separate, resulting in a missing chromosome.

Nondisjunction (second Division)

Sister chromatids fail to separate, resulting in extra chromosomes and a missing chromosome.

Down syndrome

Trisomy 21

Patau syndrome

Trisomy 13

Edward Syndrome

Trisomy 18

Klinefelter Syndrome

47, XXY (extra y)

Turner Syndrome

45, X (missing X).

Law of Dominance

The principle involving AA, Aa, and aa genotypes.

Law of segregation

Half the gametes receive one allele of a gene, and half receive the other allele. (Relates to the 3:1 ratio).

Law of Independent Assortment

Two contrasting characteristics behave independently of each other. (Relates to the 9:3:3:1 ratio).

True Breed

Physical appearance is identical in each successive generation.

Population Genetics

The study of genetic variation in a natural population (same species, same area).

Hardy-Weinberg principle

Allele and genotypes frequencies do not change over time, assuming no evolutionary forces.

Hardy-Weinberg assumptions

No mutation, no selection, no migration, large population, random mating.

Hardy-Weinberg equation

P²+2PQ+Q²=1 and P+Q=1

P²(in H-W)

Frequency of Homozygous Dominate geneotype

2PQ(in H-W)

Frequency of heterozygous genotype.

Q²(in H-W)

Frequency of homozygous Recessive genotype.

Evolution

Change of frequency of alleles or genotypes in a population over time.

Natural selection

Increases the frequency of advantageous traits and decreases the frequency of harmful traits from generation to generation

Stabilizing selection

Intermediate phenotypes are more fit/ favored over the extremes. Graph is narrow with the middle as the highest point (mountain peak)

Directional selection

One extreme phenotype is more fit or favored. Graph is wider is wider and shifts toward the favored extreme.

Disruptive selection

Two extreme phenotypes are more fit or favored over the intermediate. Graph is M-shaped with two peaks and the middle as the Lowest point.

Genetic Drift

Allele frequency changes due to chance, not selection.

Founder Effect

A small group leaves the main group and starts a new population

Bottleneck Effect

A large population is reduced to a disaster.

Heterozygote Advantage

Heterozygotes are more fit than homozygotes, resulting in the balance of natural selection.

Fixation

The process by which one allele replaces all other alleles in a population

Non-Random Mating

Results in an increase homozygous and a decrease in heterozygous individuals, but does not change alleles frequencies.

Speciation

The process that produces new species; a byproduct of Genetic Divergence of separated populations.

Biological Species Concept (BSC)

Species are actually or potentially interbreeding populations that are isolated from each other. A group of species that can share genetic material through interbreeding to create viable life. (Does not include asexual or extinct species).

Ecological Species Concept

A one-to-one correspondence between a species and its niche (includes asexual and extinct species).

Cryptic species

Two species believed to be one single species due to phenotype, but found to be distinct through DNA sequencing.

Allopatric Speciation

Species are separated geographically (dispersal or vicariance).

Sympatric specitation

Species are in the same geographic location.

Adaptive radiation

Natural selection speeds up, causing changes in species to happen rapidly.

Which of the following is the correct order of cellular division in Meiosis I & II?

Prophase- Metaphase - Anaphase -Telophase

True or False: 1st division nondisjunction is where sister chromatids fail to separate.

False(2nd Division Nondisjunction)

Prezygotic Factors

Prevent the fertilization of the egg.

Examples: Geographic, Ecological, Temporal, Behavioral, Gametic, Mechanical isolation.

Postzygotic Factors

The failure of a fertilized egg to develop into a fertile individual.

Examples: Hybrid invisibility (embryo fails to develop) or Hybrid sterility (offspring is sterile)

Which of these is not a rule used to combine probabilities?

Tripling

Which Term matches this definition: The proportion of the total variation of a trait in a population due to genetic differences among individuals.

Heritability

T/F: complex traits are those influenced both by the actions of many genes and by environmental factors

True

Describe the two types of twins and how they differ from each other.

Monozygotic (MZ/ identical) twins result from the fertilization of a single egg and are genetically identical.

Dizygotic (DZ/ fraternal) twins result from the fertilization of two eggs and are genetically related to each other in the same way that other siblings are related to each other.

There are three types of speciation: which of the following includes all three types?

Stabilizing, Disruptive, Directional

True or false: Genetic drift occurs due to natural selection.

False

Founder Effect.

The founder effect is when a subset, or group, of a singular species becomes separated from the main population in some way typically by geographical

location.

Species that were traditionally thought of to be a part of a single species because they look the same, but are two different species due to differences in DNA are called...

Cryptic Species

Asexual organisms fall under the BSC (Biological Species Concept)?

False. Organisms need to be able to reproduce to fall under the BSC.

Which of the following is an example of a postzygotic isolating factor?

Hybrid Sterility

T/F: Meiosis 1 Begins with a diploid cell

True

Nondisjunction results in __ chromosome

Extra, and/or Missing

How many cells are made in male and female meiosis?

Males make four sperm cells; females make one egg and three polar bodies.

T/F: Complex traits are influenced by both the actions of many genes and environmental factors.

True

Heritability refers to the proportion of the total variation in a trait that can be attributed due to ____ differences among individuals.

Genetic

_zygotic (DZ, or fraternal, twins result fro the fertilization of two eggs and are genetically related to each other in the same way that other siblings are related to each-other

Do

In a population of rabbits, the allele for black fur (B) is dominate over the allele for white fur (b). If 36%of the rabbits are white, what are the allele frequencies of B and b in population, assuming Hardy-Weinberg equilibrium?

p=0.6, q=0.4

Why do two isolated groups become different over time?

Because they get different mutations

In a population of birds, individuals with very small beaks struggle to crack seeds, and those with very large beaks have difficulty handling small seeds. Birds with medium sized beaks survive best and reproduce more successfully. Which type of natural selection is this an example of?

Stabilizing selection

T/F: Genetic divergence can prevent interbreeding if given enough time.

True

Speciation is defined as…

Speciation is the process that produces new species.

Which one species splits into two, this is called__.

Mutation

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