Lecture 17 - Genetic Variation & Disease #1

Question 1

What is an allele?

Answer 1

An allele is an alternative form of genetic variant located at the same position on a gene

Question 2

How many copies of each gene does a diploid organism have?

Answer 2

Two copies, one from each parent, called the homologous paid

Question 3

What is a phenotype

Answer 3

The observable characteristics or traits in an individual, determined by their genotype i.e. physical appearance

Question 4

What is a genotype?

Answer 4

The combination of alleles a person has for a particular genetic variant

Question 5

What is the inheritance pattern of dominant alleles?

Answer 5

Only one dominant allele is needed for the trait to be expresses, either in homozygotes dominant (RR) or heterozygote (Rr)

Question 6

What is the inheritance pattern of recessive alleles?

Answer 6

Two copies of the recessive allele (rr) are required for the trait to be expressed

Question 7

What is a gain-of-function allele?

Answer 7

An allele that causes protein to work too well or to perform a new function, often showing dominant inheritance

Question 8

What is a loss-of-function allele?

Answer 8

An allele that results in a non-functional protein, often showing recessive inheritance because the other allele can compensate for the loss

Question 9

What are monogenic traits?

Answer 9

Traits controlled by a single gene, often following simple dominant/recessive inheritance patterns

Question 10

What are polygenic traits?

Answer 10

Traits controlled by multiple genes, typically showing complex inheritance patterns influenced by both genetics and environment

Question 11

Two monogenic diseases

Answer 11

1. Retinitis Pigmentosa
2. Phenlyketonuria (PKU)

Question 12

What is the role of Rhodopsin receptor in retinitis pigmentosa?

Answer 12

Genetic variants disrupts its ionic lock, causing the receptor to remain constantly active, leading to retinal degeneration and blindness overtime

Question 13

What causes PKU?

Answer 13

A recessive genetic condition where non-functional phenylalanine hydroxylase leads to the build up of phenyalanine, causing brain damage if untreated.

Question 14

How can PKU be managed?

Answer 14

Through a low phenylalanine diet to prevent the harmful accumulation of phenylalanine in the body

Question 15

What is genotyping?

Answer 15

The process of determining the specific alleles present in an organism’s DNA

Question 16

What are some methods used for genotyping organisms?

Answer 16

1. PCR-RFLP
2. Fluorescence-based methods
3. Sequencing

Question 17

What is genetic testing used for?

Answer 17

To identify specific alleles in an individual’s DNA, which can predict the risk of diseases or confirm a diagnosis

Question 18

What are the steps in the Polymerase Chain reaction (PCR) process?

Answer 18

1. Denaturation - separating DNA by heating to very high temperature
2. Annealing - Cooled, so DNA primers can attach to target sequence.
3. Elongation - heat increased slightly so heat-tolerant DNA polymerase can bind primer and replicate DNA.

Question 19

What does genotyping usually rely on?

Answer 19

PCR - Polymerase chain reaction

Question 20

What are reaction components for PCR?

Answer 20

1. DNA sample - extracted
2. Primers - Small segment of DNA, complementary to DNA of interest
3. Polymerase - Heat tolerant DNA enzyme
4. Nucleotides (dNTPs) - DNA nucleotides to build new DNA strand

Question 21

What is PCR-RFLP used for?

Answer 21

It’s a genotyping technique that uses PCR, restriction enzymes, and gel electrophoresis to identify genetic variants by cutting DNA at specific sites.

Question 22

What is the role of restriction enzyme in PCR-RFLP?

Answer 22

They cut DNA at specific sequences, allowing researcher to distinguish between different alleles based on fragments size after gel electrophoresis

Question 23

What is a fluorescence - based genotyping method?

Answer 23

A technique that uses fluorescent probes specific to genetic variants, detected during PCR to determine the presence of certain alleles

Question 24

What is whole - genome sequencing used for in genotyping?

Answer 24

To determine the complete DNA sequence of an organism, allowing identification of genetic variants across the entire genome