bio s2

What is meiosis?

The process by which gametes are formed.

What are the gametes in humans?

Sperm in males and egg in females.

What is the purpose of crossing over in meiosis?

To make genetic variation.

How many rounds of cell division occur in meiosis?

2 rounds.

What is the probability that biological parents create another offspring genetically identical to you?

1 in 70 trillion.

What is the function of mitosis?

To make exact copies of cells.

What major event occurs in Prophase I of meiosis that does not occur in mitosis?

Homologous chromosomes twist tightly and undergo crossing over.

What happens in Anaphase I of meiosis that doesn't happen in mitosis?

Pulls 2 DNA strands instead of 1.

How many Americans are affected by cancer each year?

1.7 million.

How many Americans die from cancer each year?

600,000.

What percentage of cancer cases have no known cause?

40%.

What are known preventable causes of cancer?

Smoking, unhealthy diet, sunlight radiation, asbestos, and viruses.

Why is cancer called 'The Emperor of All Maladies'?

Because it is a timeless disease that can strike any part of the body.

Why is it important to treat cancer with multiple drugs?

Cancer can easily become resistant to one drug.

How many genes are thought to be important in causing cancer?

About 200 genes.

Why is gene mapping important in developing cancer treatments?

It helps target specific pathways that cancers use.

What is the relationship between UV radiation and skin color?

Skin color variation is influenced by UV radiation levels.

What is the latitude of the equator?

0 degrees.

What is the general relationship between the UV index and latitude?

UV rays are most concentrated at the equator and latitudes closest to it.

What was the UV index of my location?

8.

What is one factor other than latitude that contributes to UV intensity?

Altitude; for example, UV radiation is higher on mountains like the Colorado Mountains.

What is the pigment molecule in human skin that helps absorb UV radiation?

Melanin.

How does human skin pigmentation correlate with location on Earth?

Human skin pigmentation is an evolutionary adaptation to UV radiation, with people near the equator generally having darker skin.

What are the two main variants of skin pigment molecules in humans?

Pheomelanin and eumelanin.

How do pheomelanin and eumelanin differ?

Pheomelanin gives a lighter color, while eumelanin gives a darker color.

Why is skin reflectance measured on a subject's inner arm?

It has less exposure to the Sun, allowing for a more accurate measurement.

What is the relationship between skin reflectance and latitude?

Skin reflectance increases as latitude increases, due to less UV radiation exposure.

What does it mean for a trait to be under negative selection?

It means the trait is disadvantageous.

How diverse is the MC1R allele among African populations?

It isn't very diverse due to high levels of UV radiation eliminating mutations for lighter skin.

Why does Dr. Jablonski dismiss the hypothesis that protection from skin cancer provided selection for darker skin?

Because skin cancer usually develops after a human's peak reproduction stage.

What are two possible negative consequences of low folate levels in humans?

Birth defects in offspring and unhealthy development of sperm in males.

Describe the relationship between folate levels and UV exposure.

The more UV radiation people are exposed to, the lower the amounts of folate they have.

What is the revised hypothesis explaining the selective pressure on the evolution of human skin color?

Human skin color evolved as a balance between UV protection and protein synthesis.

Can the effects of UV exposure on folate levels explain the full variation of skin color that exists in human populations today?

No, there are other factors that contribute to diverse skin color.

What nutrient does our skin manufacture when exposed to UVB light?

Vitamin D.

Why do we need vitamin D?

It helps absorb calcium for strong bones and supports a healthy immune system.

How do the data support the hypothesis that the evolution of lighter skin was driven by selection for vitamin D production?

Darker skinned individuals cannot produce enough vitamin D, while lighter skinned individuals can.

Which human populations are least likely to synthesize sufficient amounts of vitamin D?

Human populations with dark skin color in all shaded regions on the map.

Does the risk of vitamin D deficiency vary throughout the year for someone living far from the equator?

Yes, it varies due to different amounts of sunlight and intensity throughout the year.

What are the predicted effects of using a tanning booth on vitamin D and folate levels?

It will increase vitamin D levels but decrease folate levels.

How have different shades of human skin evolved over the course of human history?

To adapt for protection against UV radiation and to produce enough vitamin D.

Which subpopulation is at greatest risk for vitamin D deficiency?

The non-Hispanic black ethnic population.

Which subpopulation is at least risk for vitamin D deficiency?

The non-Hispanic white ethnic population.

What should someone do if they are at high risk for vitamin D deficiency?

Take supplements and increase sun exposure safely.

Will the average skin reflectance of Northern Australians change in the next few hundred years due to selective pressure?

No, because natural selection would only shift skin reflectance if there were consistent survival advantages tied to skin color.

What was the most interesting finding about the evolution of skin color?

It balances the needs for sufficient vitamin D and the reduction of damage to folate.

What is polygenic inheritance?

Two or more genes contribute to one phenotype.

How many major genes influence skin color?

At least seven major genes.

What does independent assortment refer to?

Unlinked genes segregate independently during meiosis.

What is the result of independent segregation of unlinked genes?

Greater number of potential gamete combinations and variety of phenotypes.

What is the genotypic ratio of offspring from a cross of RrYy and RRyy?

4 RRYy: 4 RRyy: 4 RrYy: 4 Rryy.

What is the phenotypic ratio of offspring from a cross of RrYy and RRyy?

8 round & yellow: 8 round & green.

What is the probability that a heterozygous round and heterozygous yellow pea plant crossed with a homozygous dominant round and green pea plant produces an offspring that is round and green?

50%.

What is the genotype of a woman who is a carrier for ALD?

X^AX^a.

What is the genotype of her husband who does not have ALD?

X^AY.

What is the genotype for red hair caused by the MC1R gene?

Recessive allele (aa).

What are the genotypes for the woman and her husband for hair color if she has red hair and he is heterozygous for brown hair?

Woman: aa, Husband: Aa.

What is the dominant allele for black wool in sheep?

B.

What is the dominant allele for horns in sheep?

H.

What happens to chromosomes during prophase?

Genetic material condenses and spindle fibers form.

What occurs during metaphase?

Centromeres of duplicated chromosomes line up in the center of the cell.

What happens during anaphase?

Chromosomes split and move to opposite sides of the cell.

What is the final stage of mitosis called?

Telophase/Cytokinesis.

What happens to the cytoskeleton during mitosis?

It reshapes into spindle fibers to pull chromosomes apart.

What are the dark lines in the center of each cell during mitosis?

Chromosomes.

What is the function of spindle fibers?

To pull chromosomes apart during cell division.

What is the purpose of the cell cycle?

To understand how and why cells divide.

What is the first phase of the cell cycle?

G1 Phase.

What occurs during the S Phase of the cell cycle?

Chromosomes are replicated.

What is the role of the cytoskeleton in cell division?

It forms spindle fibers and helps in pinching the cell.

What type of inheritance pattern results from two unlinked genes?

Complex inheritance patterns.

What is a Punnett Square used for?

To predict genotypic and phenotypic outcomes.

What is the significance of homologous pairs during metaphase I of meiosis?

They orient randomly, leading to independent assortment.

What is the expected phenotype ratio in the F2 generation from a two-factor cross?

Depends on the specific genotypes used.

What is the phenotype of AA or Aa mice?

Agouti.

What is the phenotype of aa mice?

Albino.

What is the purpose of the microscope investigation in the cell cycle?

To observe cells in various stages of division.

What happens to chromosomes from prophase to telophase?

They condense, align, and then separate.

What is the role of spindle fibers during cell division?

To connect centromeres to spindles and pull chromosomes apart.

What happens to the cell at the 1:00 minute mark in the video?

The cell is shaking and twitching; chromosomes come from different areas of the cell and go to the middle.

What is the role of DNA Helicase?

DNA Helicase 'unzips' DNA by breaking bonds between the two template strands.

What does DNA Polymerase do?

DNA Polymerase attaches to each exposed template strand and joins complementary nucleotides to the template strands.

What is the outcome of DNA replication?

Two new copies of DNA are created, each containing one strand from the original DNA molecule.

What is a gene?

A gene is a segment of DNA that contains the instructions for building a protein.

What is a genome?

A genome is the complete set of genes or genetic material present in a cell or organism.

How are human genomes similar to each other?

Human genomes are similar because they share a high percentage of identical DNA sequences.

How are human genomes different?

Human genomes differ due to variations in alleles and genetic mutations.

What is the principle of dominance?

The principle of dominance states that some alleles are dominant over others and will be expressed in the phenotype.

What is the function of a Punnett Square?

A Punnett Square is a tool used to predict possible allele combinations for a trait.

What is segregation of alleles?

Segregation of alleles occurs during gamete production (meiosis), where the two alleles for each gene separate into different gametes.

What are X-linked traits?

X-linked traits are controlled by genes located on the X chromosome.

What is the inheritance pattern of color blindness?

Color blindness is a recessively inherited trait located on the X chromosome.

What is hemophilia?

Hemophilia is a recessively inherited condition characterized by the inability to clot blood after injury.

What is adrenoleukodystrophy (ALD)?

ALD is an X-linked recessive genetic disease that affects the nervous system.

How can gene therapy be used in treatment?

Gene therapy involves altering genes to treat or prevent diseases, including genetic disorders like ALD.

What is the role of stem cells in treatment?

Stem cells can be used to regenerate damaged tissues and may be involved in therapies for genetic diseases.

What is the significance of the 1950 discovery regarding DNA?

It was found that the relative amounts of adenine + thymine and guanine + cytosine in all organisms were equal.

What did the 1952 x-ray study of DNA reveal?

The x-ray study showed that DNA structure was repeated and had a helical shape.

What is the bond pattern between adenine and thymine?

There are 2 hydrogen bonds between adenine and thymine.

What is the bond pattern between cytosine and guanine?

There are 3 hydrogen bonds between cytosine and guanine.