Genetic Markers

Question 1

T or F: phenotypic variation based on alleles of a gene is the only type of variation between individuals

Answer 1

false! it’s just one type of variation

Question 2

T or F: much of the sequence variation in the human genome does not affect our phenotype

Answer 2

true

Question 3

What can be used as a marker to map the location of a gene?

Answer 3

sequence variation

Question 4

Describe genetic (molecular) markers

Answer 4

polymorphic DNA sequences used to map the location of a gene

Question 5

Where do genetic markers typically exist in the genome? Where else are they sometimes found?

Answer 5

typically in noncoding regions

sometimes within a gene

Question 6

What do genetic markers involve?

Answer 6

single nucleotide polymorphisms (SNPs)

restriction fragment length polymorphisms (RFLPs)

Question 7

Which type of genetic marker is more commonly used?

Answer 7

SNPs

Question 8

When do SNPs occur?

Answer 8

When one base pair is substituted by another base pair

ex.
A T C C G A C
T A G G C T G

A T C C G G C
T A G G C C G

Question 9

Approximately how many SNPs exist in the human genome?

Answer 9

~3.3 million

Question 10

Where are some SNPs located?

Answer 10

within a restriction enzyme recognition sequence

Question 11

What is a consequence of an SNP in a restriction enzyme recognition sequence?

Answer 11

a single nucleotide change within a restriction enzyme recognition sequence destroys the restriction site and causes a RFLP

Question 12

Describe RFLPs

Answer 12

Restriction Fragment Length Polymorphisms form when an SNP causes a single nucleotide change within a restriction enzyme recognition sequence and destroys the restriction site

ie., they are changes in DNA sequence

Question 13

How are RFLPs detected?

Answer 13

by DNA-cutting enzymes (restriction enzymes, specifically restriction endonucleases)

Question 14

What are the pieces of DNA that result from restriction enzymes cutting?

Answer 14

restriction fragments

Question 15

How do you know if there’s a restriction site present?

Answer 15

2 smaller fragments are created when the region is cut with a restriction enzyme

Question 16

How do you know if there’s no restriction site present?

Answer 16

one larger fragment is created when the region is cut with a restriction enzyme

Question 17

Why are DNA (restriction) fragments different lengths?

Answer 17

because of the single nucleotide difference in the DNA sequence (SNP)

Question 18

On an agarose gel, how would DNA (restriction) fragments differ?

Answer 18

they would have different band sizes

Question 19

What purpose do genetic markers serve?

Answer 19

they can be used to trace the inheritance of disease-causing alleles

Question 20

What can be determined by a genetic marker being within a gene?

Answer 20

the presence of the marker will indicate which allele a person has

Question 21

What is there risk of if a genetic marker is near a gene?

Answer 21

misdiagnosis due to crossovers

Question 22

How can the probability of misdiagnosis be determined?

Answer 22

knowing how far the genetic marker is from the gene

Question 23

What must first be determined before using a genetic marker to trace the inheritance of a disease-causing allele?

Answer 23

the arrangement of the genetic marker and disease-causing allele

ie., which version of the genetic marker is linked to the disease-causing allele

Question 24

What does it mean if an SNP disrupts a restriction enzyme site on the same chromosome as the recessive allele?

Answer 24

the presence of the restriction enzyme site can be used as a genetic marker for the presence of the dominant allele

Question 25

What can cause a misdiagnosis if the disease-causing gene and the genetic marker are on the same chromosome?

Answer 25

if crossover occurs during meiosis