Chapter 16: How Genes Work

Question 1

Genetic code is ____ but not ___

Answer 1

Redundant (multiple codons code for same amino acid)

Ambiguous (no codon codes for more than 1 amino acid)

Question 2

How can 4 bases code for 20 amino acids?

Answer 2

Codons

Question 3

A duplication repeats a chromosomal segment

Answer 3

Duplication chromosomal mutation

Question 4

A chromosomal segment from one chromosome is moved to a non homologous chromosome

Answer 4

Translocation chromosomal mutation

Question 5

What types of mutations are most severe and why?

Answer 5

Frameshift mutations more severe than point mutations bc it almost always produces a nonfunctional protein

Question 6

How can a missense mutation have a large effect?

Answer 6

Small non polar to large charged amino acid or changing the shape of the active site

Question 7

What do chromosome mutations cause?

Answer 7

Changes in chromosome number (polyploidy (extra) and aneuploidy (missing)) and changes in structure

Question 8

3 properties of codons

Answer 8

Nonoverlapping - each codon is read separately
Nearly universal - All codons code for same aa in all organisms with some exceptions
Conservative - when there are multiple codons for an aa, the first 2 bases are usually the same

Question 9

Substitution that codes for the same amino acid

Answer 9

Silent mutation

Question 10

Mutation possibly due to the redundancy of the genetic code

Answer 10

Silet mutation

Question 11

What did Beadle, Tatum, Srb, and Horowitz discover in the 1940s?

Answer 11

They created mutants by bombarding neurospora with X-rays. They found different mutants with different defective enzymes needed different supplements to grow.
A ———-> B ———-> C
enzyme A enzyme B

Question 12

Synthesis of RNA using the information in the DNA

Answer 12

Transcription

Question 13

Changes in a single or small number of base pairs

Answer 13

Point mutations

Question 14

Replacement of one base pair with another

Answer 14

Substitutions. Point mutations

Question 15

What is the current definition of a gene?

Answer 15

A region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule

Question 16

What are two exceptions to the Central Dogma?

Answer 16

1. Some genes code for RNAs that are never translated (tRNA and rRNA)
2. Sometimes RNA—>DNA (retroviruses like HIV)

Question 17

What did Archibald Garrod suggest in 1902?

Answer 17

Genes determine phenotype. He found enzymes catalyze specific rxns so inherited diseases are due to faulty enzymes

Question 18

Mutation that can range from little to no effect to completely destroying the proteins function

Answer 18

Missense mutation

Question 19

How do mutations happen?

Answer 19

Errors in replication = spontaneous mutations

Exposure to certain physical or chemical agents = mutagens

Question 20

3 types of substitutions

Answer 20

Silent mutation, missense mutation, nonsense mutation

Question 21

What does DNA sequence determine? What can a single base change cause as a result?

Answer 21

DNA sequence determines amino acid sequence which determine 3D protein structure. A single base change can change the final protein

Question 22

Can be caused by either insertions or deletions of a base. Change the groupings of 3 (codons)

Answer 22

Frameshift mutations

Question 23

Mutation that causes translation to stop early and usually creates a nonfunctional protein

Answer 23

Nonsense mutation

Question 24

Substitution that codes for a stop codon

Answer 24

Nonsense mutation

Question 25

What are most mutagens?

Answer 25

Carcinogens. They also cause cancer

Question 26

How many codons are there?

Answer 26

64 codons that code for the 20 amino acids

Question 27

What is the range of how large mutations can be?

Answer 27

Large scale (chromosomal rearrangements) or small scale (changes in a few nucleotides)

Question 28

What are the parts of the Central Dogma?

Answer 28

Transcription and translation

Question 29

Substitution that codes for a different amino acid

Answer 29

Missense mutation

Question 30

Characterized by severe mental impairment, behavioral problems, feeding problems, poor growth, and characteristic cry

Answer 30

Cri du chat

Question 31

Instructions for building a polypeptide written as non overlapping triplets

Answer 31

Codons

Question 32

What is sickle cell anemia the result of?

Answer 32

Missense mutation. T is changed to A

Question 33

A segment of chromosome is reversed within a chromosome

Answer 33

Inversion chromosomal mutation

Question 34

How do frameshift mutations occur?

Answer 34

If the number of base pairs inserted or deleted is not a multiple of 3, the reading frame is shifted

Question 35

When are frameshift mutations most severe and why?

Answer 35

The earlier on the mutation occurs bc every codon from that point on will be changed and usually will end in a premature stop codon

Question 36

A deletion of a chromosomal segment

Answer 36

Deletion chromosomal mutation

Question 37

Synthesis of a polypeptide using the information in the RNA message (one language to another; nucleic acid to amino acid)

Answer 37

Translation

Question 38

What is progeria the result of?

Answer 38

Silent mutation

Question 39

What are the 4 types of chromosome mutations?

Answer 39

Deletion, duplication, inversion, and translocation

Question 40

How is progeria caused by a silent mutation?

Answer 40

Creates a cryptic splice site that leads to incorrect splicing that creates a shortened protein that is unable to correctly be modified. 50 amino acids get cut out due to the cryptic splice site

Question 41

Caused by a partial deletion of chromosome 5

Answer 41

Cri du chat

Question 42

What are all substitutions?

Answer 42

Point mutations

Question 43

Permanent change in an organisms DNA that creates new alleles

Answer 43

Mutation