Chapter 10.1: Variation Among Genomes

Question 1

What are the 3 reasons why most DNA polymorphisms do not influence phenotypes?

Answer 1

 Less than 2% of the human genome consists of codons within genes
 Even when they occur, mutations of codons are silent
 If a particular mutation is not silent and has deleterious effects, natural selection could often lead to its disappearance from the human population

Question 2

Define DNA marker

Answer 2

signpost in the genome

Question 3

Define single nucleotide polymorphisms (SNPs)

Answer 3

particular base positions in the genome where alternative letters of the DNA alphabet distinguish some people from others
 Most common type of genetic variant

Question 4

Define DNA polymorphisms

Answer 4

sequence differences

Question 5

What causes SNPs?

Answer 5

 Caused by rare mistakes in DNA replication, or exposure of the genome to mutagenic chemicals or radiation in the environment

Question 6

What causes SSRs?

Answer 6

 Arise from rare, random events that initially produce short repeated sequence with four to five repeat units

Question 7

What causes CNVs?

Answer 7

 Produced by unequal crossing-over

Question 8

What are anonymous DNA polymorphisms?

Answer 8

o The vast majority of sequence differences between genomes are anonymous DNA polymorphisms affecting neither the nature nor the amounts of any protein in the body

Question 9

Define simple sequence repeats (SSRs)

Answer 9

sequences of one to a few bases that are repeated in tandem less than 10 to more than 100 times

Question 10

Define deletion-insertion polymorphisms (DIPs)

Answer 10

short insertions or deletions of genetic material

Question 11

What causes DIPs?

Answer 11

 Caused by problems in DNA replication of recombination, and mistakes that occur when cells try to repair damage such as broken DNA strands

Question 12

Define copy number variants (CNVs)

Answer 12

genomes displaying DNA length polymorphisms involving more than just the few nucleotides characterizing SSRs and DIPs