Chapter 8

Question 1

Science of genetics depends on…

Answer 1

mutations because we can track genes only through the phenotypic effects of their mutant variants.

Question 2

Complementation testing reveals …

Answer 2

whether two mutations are in a single or in different genes

Question 3

Gene:

Answer 3

a function unit directing the appearance of a molecular product contributing to a particular phenotype

Question 4

almost all [] mutations disrupt a [] genes function

Answer 4

recessive; genes function

Question 5

Complementation:

Answer 5

the process in which heterozygosity for loss-of-function mutant recessive alleles for two different genes produces a normal phenotype.

Question 6

If the recessive mutations on the two homologous chromosomes are in the same gene …

Answer 6

no wild type of the allele gene exists in the individual and neither mutated copy of the gene will be able to perform the normal function.

Question 7

complementation group:

Answer 7

a collection of mutations that do not complement each other. Often used synonymously with gene.

Question 8

complementation test:

Answer 8

method of discovering whether two mutations are in the same or separate genes. Two mutant strains with the same (or similar) mutant phenotype are crossed. If the progeny are all wild type (complementation occurred), the strains had mutations in different genes; if the progeny are all mutant (no complementation occurred), the strains had mutations in the same gene.

Question 9

complementation table:

Answer 9

a method of collating data that helps visualize the relationships (which pairs of mutants complement) among a large group of mutants.

Question 10

A gene is a set of nucleotide pairs able to…

Answer 10

mutate independently and recombine with each other

Question 11

Mutations affecting a single gene are..

Answer 11

likely to be close together.

Question 12

fine structure mapping:

Answer 12

recombination mapping of mutations in the same gene.

Question 13

trans configuration:

Answer 13

on different DNA molecules.

Question 14

cis configuration:

Answer 14

on the same DNA molecule.

Question 15

Benzers 3 Conclusion of gene structure and function:

Answer 15

A gene consists of different parts, each able to mutate
Recombination can occur between different mutable sites in the same gene
Mutation of only part of a gene from functioning normally.

Question 16

A gene is a…

Answer 16

discrete linear set of nucleotide pairs

Question 17

Can use deletions…

Answer 17

to map mutations approximately

Question 18

Large deletions are …

Answer 18

mutations removing many contiguous nucleotide pairs along a DNA molecule.
No recombinant progeny can arise when there are large deletions because neither chromosome carries the proper information and the location of the mutation.
Can appear if the mutation lies outside the region deleted from the homologous chromosome.

Question 19

Crosses between any [] and a [] will immediately reveal whether the mutation resides in the region deleted from the other page chromosome, providing a rapid way to find the general location of a mutation.

Answer 19

uncharacterized mutation; known deletion

Question 20

Can use [] to determine the relationship between deletions.

Answer 20

recombination

Question 21

Can find the individual points of mutations …

Answer 21

by observing the deletions able to recombine with each point mutant to yield wild-type progeny.

Question 22

A mutation can arise …

Answer 22

from the change of a single nucleotide pair and recombination can occur between adjacent nucleotide pairs.

Question 23

A gene is composed of …

Answer 23

a continuous linear sequence of nucleotide pairs within the DNA.

Question 24

Some sites within a gene mutate []

Answer 24

spontaneously

Question 25

Mutation hotspots:

Answer 25

sites within a gene that mutate more frequently than others, either spontaneously or after treatment with a particular mutagen.

Question 26

Treatment with [] turns up hotspots but because

Answer 26

mutagens; mutagens have specificity for particular nucleotides, the highly mutable sites turning up with various mutagens are often at different positions in a gene than the hotspots resulting from spontaneous mutations.

Question 27

intragenic:

Answer 27

within the same gene.

Question 28

intergenic:

Answer 28

between different genes.

Question 29

A complementation test ...

Answer 29

determines whether two different recessive mutations occur in the same gene or in different genes.

Question 30

At the DNA level, a gene []

Answer 30

is a linear sequence of nucleotide pairs in a discrete region of a chromosome conferring a specific unit of function.

Question 31

Recombination can occur...

Answer 31

between any two nucleotide pairs, whether they are within the same gene or not.

Question 32

Mendel’s experiments established []

Answer 32

an individual gene can control a visible characteristic but his laws do not explain how genes govern the appearance of traits.

Question 33

Investigators studies the biochemical changes caused by mutations...

Answer 33

in an effort to understand genotype-phenotype connections.

Question 34

Garrod suggested

Answer 34

many inborn errors of metabolism occurred from mutations preventing a particular gene from producing an enzyme required for a specific biochemical reaction. A wild/ normal type of a gene would allow for the production of an enzyme while a mutant would not

Question 35

One gene, one enzyme hypothesis:

Answer 35

A gene contains the information for producing a specific enzyme.

Question 36

George Beadle Edward Tatum Experiment

Answer 36

Experimented on Neurospora Crassa (Bread mold) Demonstrated a direct relationship between genes and enzymes catalyze specific biochemical reactions Isolated number of mutations disrupting the synthesis of arginine, needed for Neurospora growth. Hypothesized different mutations blocked different steps in the biochemical pathway. Cell with any of the mutations were unable to make arginine and could grow in a minimal medium containing salt and sugar only if it was supplemented with arginine. Recombination analyses located the mutated genes in four distinct regions of the denome, and complementation tests showed each of the four regions correlated with a different complementation group. Names the specific genes ARG-E, F, G, and H

Question 37

biochemical pathway:

Answer 37

an orderly series of chemical reactions within a cell in which molecules are converted stepwise into a final product.

Question 38

auxotroph:

Answer 38

a mutant microorganism that can grow on minimal medium only if it has been supplemented with one or more nutrients not required by wild-type strains. needing the supplementation indicates a mutation

Question 39

prototroph:

Answer 39

``` a microorganism (usually wild type) that can grow on minimal medium. Not mutated ```

Question 40

Genes encode []

Answer 40

enzymes

Question 41

A [] in a gene clocks a biochemical pathway, because...

Answer 41

mutation; the cell lacks the corresponding enzyme breaking down a protein.

Question 42

Not all biochemical pathways are ...

Answer 42

linear and easily interpretable.

Question 43

Genes specify...

Answer 43

the identity and order of amino acids in polypeptide chains.

Question 44

proteins:

Answer 44

arge polymers composed of hundreds to thousands of amino acids strung together in a specific linear order. Proteins are required for the structure, function, and regulation of the body’s cells, tissues, and organs.

Question 45

amino acids:

Answer 45

the building blocks of proteins. 20 amino acids All amino acids have the same structure: NH2 - CHR - COOH COOH: Carboxylic acid NH2: Amino group R: Side chain distinguishing every amino acid

Question 46

peptide bond:

Answer 46

a covalent bond that joins amino acids during protein synthesis.

Question 47

Polypeptide:

Answer 47

amino acid chain making up proteins containing hundreds to thousand of amino acids joined by peptide bonds.

Question 48

N terminus:

Answer 48

the end of a polypeptide chain that contains a free amino group that is not connected to any other amino acid.

Question 49

C terminus:

Answer 49

the end of the polypeptide chain that contains a free carboxylic acid group.

Question 50

Mutations can...

Answer 50

alter amino acid sequences

Question 51

Mutations [] one amino acid for another can have the power to change the structure and function of a protein.

Answer 51

substituting

Question 52

missense mutation:

Answer 52

a mutation in a gene that changes a codon for one amino acid to a codon that specifies a different amino acid.

Question 53

A proteins amino acid sequence dictates...

Answer 53

its three dimensional structure

Question 54

denaturation (denature, denatured):

Answer 54

the disruption of hydrogen bonds within a macromolecule that normally uses hydrogen bonds to maintain its structure and function. Hydrogen bonds can be disrupted by heat, extreme conditions of pH, or exposure to chemicals such as urea. When normally soluble proteins are denatured, they unfold and expose their nonpolar amino acids, which can cause them to become insoluble. When DNA is denatured, double-stranded molecules break apart into two separate strands.

Question 55

Polypeptides are stabilized by:

Answer 55

hydrogen bonds, electrostatic bonds, hydrophobic interactions, and disulfide bridges.

Question 56

One gene, one polypeptide:

Answer 56

Each gene governs the construction of a particular polypeptide.

Question 57

Many genes also specify...

Answer 57

RNAs not translated into polypeptides.

Question 58

Most genes specify the [] in a polypeptide. This sequence determined the [].

Answer 58

specify the linear sequence of amino acids in a polypeptide; polypeptides' three dimensional structure and thus its function.

Question 59

A missense mutation changes []

Answer 59

the identity of a single amino acid in a polypeptide.

Question 60

Multimeric proteins:

Answer 60

include two or more polypeptides (subunits). If these subunits are different, they must be encoded by different genes.

Question 61

unequal crossing-over:

Answer 61

rroneous recombination following misalignment of homologs where one homologous chromosome ends up with a duplication, and the other homolog sustains a deletion.

Question 62

[] levels of protein structure

Answer 62

four

Question 63

[] and [] group form the two ends of a chain of amino acids

Answer 63

amino; carboxyl