10.2 Genotyping a known disease-causing mutation

Question 1

Determining genotype depends on isolating a gene and analyzing the _____

Answer 1

alleles

Question 2

What is Polymerase Chain Reaction (PCR)?

Answer 2

It is a method that was first developed in 1985 to make many copies of a target region on DNA.

Question 3

What are the advantages of using PCR?

Answer 3

1. Fast
2. Inexpensive
3. It is a flexible way to amplify specific fragments of DNA than molecular cloning
4. It is extremely efficient- it can amplify DNA from a single cell or from some archaeological samples

Question 4

What defines the target region of PCR?

Answer 4

Two oligonucleotide primers. One primer is complementary to one strand of DNA at one end of the target region. The other primer is complementary to the other strand of DNA at the other end of the target region.

Question 5

What are the three steps in each PCR amplification cycle?

Answer 5

1. Denature strands
2. Base pairing of primers
3. Polymerization from primers along templates

Question 6

Repeated amplification cycles of PCR amplify the ___________

Answer 6

target DNA

Question 7

Each amplification cycle aids how much DNA copies?

Answer 7

double of the previous cycle

Question 8

What causes sickle cell anemia?

Answer 8

It is caused by a SNP in the HbB gene

Question 9

Genotyping by sequencing PCR products can idenitfy ___________ and ____________ individuals

Answer 9

carriers; homozygous

Question 10

Determining genotype by PCR product size:

Answer 10

Target regions containing SSRs or DIPs can be amplified by PCR. The PCR products vary in size. Size variations can be detected by gel electrophoresis

Question 11

Analysis of the Huntington disease locus by PCR:

Answer 11

It is an autosomal dominant disorder. Normal allele has <34 CAG repeats but disease-causing alleles have 42=> CAG repeats. PCR is used to determine the number of triplet repeats at the HD gene.

Question 12

How does PCR genotype fetal and embryonic cells?

Answer 12

Prenatal genetic diagnosis:
- Genotyping fetal cells
- Cells are isolated by amniocentesis- fetal cells in the amniotic fluid are extracted using a needle
Preimplantation embryo diagnosis:
- Utilises in vitro fertilization and PCR
- Genotype embryos before placing in the womb

Question 13

What are the three steps of preimplantation embryo diagnosis

Answer 13

1. Ripe eggs are retrieved from the ovary with a syringe
2. Extracted eggs are fertilised with sperm
3. at the 6-10 cell stage, one cell is removed from each of six viable embryos