Session 7 & 8 - Polygenic Inheritance in Humans and Brassica Rapa & PCR and Genetic Variation in Humans (P.1 of 2) Flashcards Preview

BIO2970 Lab > Session 7 & 8 - Polygenic Inheritance in Humans and Brassica Rapa & PCR and Genetic Variation in Humans (P.1 of 2) > Flashcards

Flashcards in Session 7 & 8 - Polygenic Inheritance in Humans and Brassica Rapa & PCR and Genetic Variation in Humans (P.1 of 2) Deck (25)
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1
Q

Polygenic traits

A
  • Exhibit a wide and continuous range of expression that is measurable – therefore, know as quantifiable traits
  • Many exhibit continuous variation – demonstrating a seemingly infinite number of variations over a wide range
  • referred to as multifactorial if the environment also impacts the expression of these traits
2
Q

Explain the relevance of the trichome number trait in Brassica Rapa

A

It is an inherited trait that is influenced by an unknown number of genes. The “hairiness” of a given population of plants does exhibit continuous variation, ranging from no trichomes to many on a given plant

3
Q

Fingerprint patterns of dermal ridges can be classified into these groups:

A

arches, loops and whorls

4
Q

Explain the characteristics of the arch pattern

A

It’s the simplest and least frequent pattern
Can be subclassified as plain if ridges rise slightly over the middle of the finger or tented when the ridges rise to a point

5
Q

What is a triradius?

A

A point at which 3 groups of ridges coming from 3 directions meet at angles of about 120 degrees

6
Q

What is a core?

A

Essentially a ridge that is surrounded by a field of ridges which turn back on themselves at 180 degrees

7
Q

What comprises the loop pattern?

A

A triradius and a core

8
Q

What are the subclasses of loops?

A

Either radial or ulnar;
A finger possesses a radial loop if its triradius is on the side of the little finger for the hand in question, and the loop opens toward the thumb.
A finger has an ulnar loop if its triradius is on the side of the thumb for that hand and the loop opens toward the little finger.

9
Q

What comprises the whorl pattern?

A

2 triradii, with the ridges forming various patterns inside. And a core.

10
Q

What is the frequency of the arch pattern in the general population?

A

5%

11
Q

What are the frequencies of the loop patterns in the general population?

A

radial loop: 5.4%

ulnar loop: 63.5%

12
Q

What is the frequency of the whorl pattern in the general population?

A

26.1%

13
Q

What is the ridge count for an arch?

A

0

14
Q

The ridge count on a finger with a loop is determined by

A

counting the # of ridges between the triradius and the center/core of the pattern.

15
Q

The ridge count on a finger with a whorl is made from

A

each triradius to the center of the fingerprint, but only the higher of the two possible counts is used.

16
Q

To obtain your total ridge count (TRC):

A

Add all 10 ridge counts together to obtain TRC

17
Q

How did we study genetic variation in humans?

A

Extracted DNA from cheek cells isolated from a sterile saline mouthwash; use PCR to amplify a region within the Tissue Plasminogen Activator (TPA) on Chromosome 8 to look for an insertion of a short DNA sequence called an ‘Alu’ element

18
Q

Describe Alu elements

A

a family of transposable elements of ~300 bp in length; derive their name from a single recognition site for the endonuclease Alu I located near the middle of the sequence. This family of short, interspersed, repeated DNA Alu elements are distributed throughout primate genomes and over 2000 different elements are thought to exist

~1 million copies of Alu elements in the human genome; comprising an estimated 10.7% of the genome. A few appeared relatively recently, and are not present in all individuals–such as TPA-25, which is found within an intron of the TPA gene.

19
Q

Regions of the human genome that exhibit a great deal of diversity are known as…?

How is this relevant to the TPA-25 Alu element?

A

variable sequences that are polymorphic;

The TPA-25 Alu element insertion is dimorphic, meaning that it is present in some individuals and not in others. PCR can be used to screen individuals for presence/absence.

20
Q

How will PCR be used in this experiment?

A

Oligonucleotide primers flanking the insertion site will be used to amplify a 100bp intronic region of the TPA gene. Thus, it’s expected if the TPA-25 Alu element insertion is present a 400bp PCR product will be produced; if absent, a 100bp fragment will be produced.

21
Q

How many alleles are in this analysis? What are the genotypes & phenotypes?

A

two allels, having the TPA-25 Alu element insertion or not, which gives us 3 possible genotypes:

  • homozygous TPA-25 (400bp only)
  • homozygous absent (100bp only)
  • heterozygous (400 and 100bp)
22
Q

What was added to the cheek cell pellet (or what was the cheek cell pellet added to)?

A

The cells were suspended in a solution containing ‘Chelex (beads)’, a resin that binds metal ions (which can inhibit a PCR reaction); this solution was then boiled to lyse the cells and centrifuged to remove debris

23
Q

What’s in the PCR mix (Alu AMP mix)?

A

oligonucleotide primers (2), dNTPs (the 4 deoxynucleotides), Taq DNA polymerase, buffers/magnesium chloride cofactor.

24
Q

What temperatures does the thermal cycler (PCR machine) cycle?

A
1st cycle: 94℃, 5 min
\+ 30 more cycles:
- 94℃ for 1 min
- 58℃ for 2 min
- 72℃ for 2 min
25
Q

Hardy-Weinberg Equilibrium Principle

A

States that both ALLELE and GENOTYPE FREQUENCIES in a POPULATION remain CONSTANT; i.e. they are in EQUILIBRIUM from generation to generation as long as these 3 criteria are satisfied:

1) Population size is “large” (INFINITE)
2) NO IMMIGRATION & NO EMIGRATION
3) RANDOM mating; NO SELECTION forces

⊨ p ≔ allele A frequency
∧ q ≔ allele B frequency
⇒ you can calculate/predict genotypes:
{ p² = AA ∧ 2pq = AB ∧ q² = BB : p² + 2pq + q² = 1 }