Exam 3 Review

Question 1

What is the inducer molecule of the lactose operon:

Answer 1

allolactose

Question 2

Catabolite repression is utilized by E. coli to:

Answer 2

• ensure glucose is metabolized first
• increase metabolic efficiency
• increase rates of transcription

Question 3

An operon is controlled by an activator protein protein. When the activator binds to an allosteric effector, it binds to DNA near the operon. Control of this operon is:

Answer 3

positive inducible

Question 4

Which of the following statements is true about the tryptophan.
a. the trp operon is negative repressible operon
b. in the presence of tryptophan, the genes of the trp operon are not expressed
c. in the presence of tryptophan, the genes of the trp operon are expressed

Answer 4

a and b

Question 5

Mutations passed to the next generation only occur in ______ cells.

Answer 5

germline cells

Question 6

Fragile-X syndrome is an example of _____, which are caused by _____.

Answer 6

an expanding trinucleotide repeat mutation; polymerase slippage.

Question 7

Deletion of 2 base pairs will most likely lead to which kind of mutation.

Answer 7

frameshift mutation

Question 8

The nuclear membrane breaks down during:

Answer 8

prometaphase

Question 9

During prophase 1 of meiosis:

Answer 9

homologous chromosomes pair and crossover begins

Question 10

In a meiotic cell, ______ hold sister chromatids together through anaphase I due to the presence of ______/

Answer 10

cohesion, shigosin

Question 11

An elephant has a total of 56 chromosomes (2n=56). An egg of a female elephant will have ____ chromosomes.

Answer 11

28

Question 12

Meiosis increases genetic variation through __________ and _________.

Answer 12

crossing over: anaphase 1

Question 13

Spindle fibers attach to the __________ in order to separate sister chromatids during ________.

Answer 13

kinetochores; anaphase and anaphase II

Question 14

Homologous pair separate during _____.

Answer 14

anaphase 1

Question 15

Spermatogenesis produces ___ #sperm cells, while oogenesis produces ____ # egg cells.

Answer 15

4; 1

Question 16

One mechanism of epigenetics is histone acetylation, which _____ the rate of transcription.

Answer 16

increases

Question 17

Codon specifies new amino acid, but does not change protein function

Answer 17

neutral mutation

Question 18

Reversal of a phenotypic change by a second mutation in the same gene

Answer 18

intragenic suppressor

Question 19

reversal of a phenotype change by a mutation in a second gene

Answer 19

intergenic supressor

Question 20

causes premature death

Answer 20

lethal mutation

Question 21

amino acid sequence unchanged

Answer 21

silent mutation

Question 22

causes the appearance of a new trait

Answer 22

gain-of-function mutation

Question 23

codon becomes a stop codon

Answer 23

nonsense mutation

Question 24

list four ways meiosis is different than mitosis.

Answer 24

1. meiosis goes through two rounds of separation while mitosis goes through one.
2. meiosis produces haploid gametes and mitosis produces diploids
3. Mitosis produces daughter cells identical to the parent cell and meiosis produces cells that genetically vary from the parent cell and daughter cells.
4. mitosis produces two cells with the same number of chromosomes as the parent cell and meiosis produces 4 daughter cells with half the number or parent chromosomes.

Question 25

What is happening at G1?

Answer 25

cell growth and development is occurring

Question 26

What is happening at S?

Answer 26

DNA is synthesizing

Question 27

What is happening at G2?

Answer 27

Biochemical preparation for cell division is occurring

Question 28

Why is the G2/M checkpoint important?

Answer 28

The G2/M checkpoint is important because it is only passed if the DNA is fully replicated and undamaged. This is important so that damaged or not fully replicated DNA is not passed into more cells.

Question 29

Why do prokaryotic cells organize their genes into operons?

Answer 29

Prokaryotic cells organize their genes into operons for efficiency so that it takes less energy to get more proteins. This way they can get multiple proteins form one operon instead of doing transcription for 3 separate genes which would take more energy.

Question 30

Describe the cellular conditions required to transcribe the lac operon at a high rate. Describe how these conditions regulate transcription of the operon through the lac repressor and catabolite repression.

Answer 30

To transcribe the operon at a high rate there needs to be low levels of glucose, high levels of lactose, high levels of CAP, and high levels of cAMP. Glucose needs to be low because due to catabolite repression the cell would rather metabolize glucose the lactose . Lactose needs to be high to induce the operon by producing allolactose to inhibit the repressor protein. CAP needs to be high because it binds to the promoter sequence to initiate transcription and cAMP concentration inversely relates to the concentration of glucose and cAMP binds to the CAP. The CAP is also bound to the polymerase.

Question 31

I-

Answer 31

recessive mutation

Question 32

I^s

Answer 32

repressor no longer binds allolactose

Question 33

O^c

Answer 33

repressor no longer binds DNA

Question 34

I^-d

Answer 34

repressor no longer binds DNA

Question 35

explain O^c mutation

Answer 35

the sequence of the operator is changed which makes the repressor unable to bind to it. This results in transcription always being on in the presence and absence of lactose.

Question 36

explain I^s mutation

Answer 36

there is a mutation in the repressor protein and allolactose is unable to bind to the repressor. This makes transcription uninducible and transcription is always off in the presence and absence of lactose.

Question 37

a single bond is replaced with another base and the frameshift is not altered

Answer 37

base frameshift

Question 38

when there is an insertion or deletion of one or more bases causing a shift in the reading frame of a gene

Answer 38

frameshift mutation

Question 39

likely to cause a gain of function becasue changing the base could change the codon which could change on of the amino acids in a protein giving it a new function

Answer 39

base substitution

Question 40

List three causes of DNA damage.

Answer 40

1. UV light: UV light can cause thymine dimers and bend the DNA helix both of which block DNA polymerase 2. mutagens 3. Depurination; deprivation occurs when water removes a purine group form a nucleotide