Historical Context

Question 1

What are the requirements for natural selection to occur?

Answer 1

1. Variation between individuals in a population
2. Fitness differences based on traits
3. Inheritance of traits

Question 2

What are the Pre-Mendelian understandings of genetics?

Answer 2

1. Preformationism
2. Acquired characteristics
3. Blending inheritance

Question 3

Describe pre-formationism. How does it differ from Mendelian understandings of genetics?

Answer 3

Preformationism claims that only men pass along their genetics. A version of the baby is present in the sperm, already premade in the gamete. In contrast, we know men and women pass along their genetics. Only genetic information is present in the gametes, no full baby is present.

Question 4

Describe acquired characteristics. How does it differ from Mendelian understandings of genetics?

Answer 4

Acquired characteristics become more notable the more they are used. Eventually the traits are able to be passed on to offspring.
Nothing acquired during life can be passed down to children.

Question 5

Describe blending inheritance. How does it differ from Mendelian understandings of genetics?

Answer 5

Blending inheritance claims both parents pass on a bit of their genetic material. Eventually, all offspring will have a homogenized phenotype.
In contrast, variation always exists among offspring. This system does not account for where that variation arises from.

Question 6

What is a gene?

Answer 6

a unit of inheritance, 2 copies present in each parent

Question 7

What is an allele?

Answer 7

an option of expression a gene can take

Question 8

What is Mendel’s Law of Segregation?

Answer 8

2 alleles per parent separate during gamete formation and 1 from each parent reunites in random combinations during fertilization

Question 9

What evidence is the basis for Mendel’s Law of Segregation?

Answer 9

Parents of different colors reproduce an F1 generation of all the same color. That generation produces an F2 generation of multiple colors, revealing that the information to make another color was always present in the F1 generation, regardless of its expression.

Question 10

What is Mendel’s Law of Independent Assortment?

Answer 10

Different pairs of alleles from different genes separate independently from one another during gamete formation

Question 11

What evidence is the basis for Mendel’s Law of Independent Assortment?

Answer 11

Assessing pea plants with 2 different traits, coming up with a 9:3:3:1 ratio for the F2 generation even though the F1 generation were heterozygotes for both traits

Question 12

Name 4 “complications” that can cause phenotype numbers and proportions to differ from those expected by the Laws of Segregation and Independent Assortment.

Answer 12

1. Many genes are continuous, not discrete.
2. Alleles are not always transmitted at expected rates (could have lack of success mating or survivorship could be influenced)
3. Many alleles are additive, not dominant or recessive.
4. Independent assortment does not always occur. Genes can be physically linked by proximity on the chromosome.

Question 13

List some major technological advances that have facilitated genetic and genomic analyses since 1970.

Answer 13

1. DNA sequencing in 1977
2. PCR Invention in 1983
3. Human Genome Sequencing Project in 1986-2000
4. Targeted genome editing in 2010

Question 14

How does PCR work?

Answer 14

Step 1 - Denaturation
The solution contained in the tube is heated to at least 94°C using a thermal cycler. The heat breaks the hydrogen bonds of the original DNA sample and separates the DNA into single strands.

Step 2 - Annealing
The sample mixture is then cooled to between 50 to 60°C, allowing the DNA primers and the DNA polymerase enzyme to bind to the individual DNA strands that were denatured and separated. At this point, the nucleotides from the added mixture solution will pair with the individual separated strands of DNA that resulted from the heating process.

Step 3 - Extension
Once joined together, they form a new complementary strand of DNA. Thus, a new duplicate double-stranded DNA molecule has been formed from each of the single strands of the original sample molecule.

The temperature cycles from 95°C to 50 to 60°C. The cycle is then repeated about 35 to 40 times using the thermal cycler which automatically repeats the heating and cooling cycles of the process. Resulting DNA sequence is doubled each time the heating/cooling cycle is conducted by the cycler. Thus, what started out as a single short segment of DNA from one sample can be amplified to form millions of copies after 35 doubling cycles.

Question 15

What is denaturation?

Answer 15

when heat (94 degrees C) is applied during PCR to a double helix of a primer, causing the strands to separate into single strands; step 1 of PCR

Question 16

What is annealing?

Answer 16

when primers and DNA polymerase attaches to denatured strands of DNA between 50 and 60 degrees C; nucleotides from added mixture solution pair with individual separated strands of DNA; step 2 of PCR

Question 17

What is extension?

Answer 17

when primers, single nucleotides, and DNA polymerase work together to form a complementary strand of DNA; step 3 of PCR

Question 18

What is segregation?

Answer 18

when two alleles separate during gamete formation

Question 19

How does PCR result in an exponential amplification in DNA?

Answer 19

The DNA sequence is doubled each time the heating/cooling cycle is conducted. Thus, what started out as a single short segment of DNA from one sample can be amplified to form millions of copies after 35 doubling cycles.

Question 20

What temperatures does PCR demand? Why?

Answer 20

Step 1 - 94 degrees Celsius to denature the DNA strands, which are held together by strong hydrogen bonds
Step 2 - 50-60 degrees Celsius to allow primers and DNA polymerase to attach to formerly denatured strands

Question 21

What are the 2 effects of using PCR?

Answer 21

Can make massive amounts of DNA, which can then be sequenced
Easy to manipulate DNA via cloning (synthetic and transgenes)

Question 22

What does a thermal cycler do during PCR?

Answer 22

Carries out temperature cycles, from 94 to between 50 and 60 degrees Celsius.

Question 23

What is independent assortment?

Answer 23

when different pairs of alleles from different genes separate independently from one another during gamete formation; the random orientation of homologous chromosome pairs during metaphase I allow for the production of gametes with many different assortments of homologous chromosomes

Question 24

What is selection?

Answer 24

when some traits allow organisms to survive in a specific environment better than others, increasing the chances of being passed on to the next generation

Question 25

What is a genetic model organism?

Answer 25

An organism suitable for studying a specific trait, disease, or phenomenon, due to its short generation time, characterized genome, or similarity to humans; examples are a fly, fish, rodent or pig, whose biology is well known and accessible for laboratory studies. Mendel used pea plants as his model organism.

Question 26

What is dominance?

Answer 26

when a gene only requires one allele to show up phenotypically

Question 27

What is recessivity?

Answer 27

when a gene must have two of the same alleles to show up phenotypically

Question 28

What is additivity?

Answer 28

when two separate genes have an equal contribution to the phenotype as though they were contributing alone

Question 29

What is a continuous trait?

Answer 29

traits with many intermediate forms, wide range of variety (ex. height, skin color)

Question 30

What is a discrete trait?

Answer 30

traits with two forms only, no intermediates (“either-or” traits)