Sarah Craig

Numerade Educator
Researcher

Biography

I think biology is fascinating.

Education

Sarah has not yet added their education credentials.

Educator Statistics

Numerade tutor for 4 years
61 Students Helped

Topics Covered

Mendelian Genetics: Understanding Inheritance Patterns
The Central Dogma: Understanding Gene Expression

Sarah's Textbook Answer Videos

1

Sarah's Quick Ask Videos

00:40
Biology

In DNA replication,
a. two copies are made of each chromosome, and each copy
contains one of the DNA strands from the original chromosome.
b. the chromosome is copied to RNA, which is then copied to DNA
for a new chromosome.
c. two new copies are made of each chromosome, and the original
chromosome is destroyed.
d. one new copy is made of each chromosome, and the original
chromosome remains intact.
e. 23 copies are made of each chromosome.

Sarah Craig
04:26
Biology

Recall that the trp repressor binds to a site in the operator
region of tryptophan-producing genes when tryptophan is abundant,
thereby preventing transcription. What would happen to the
expression of the tryptophan biosynthetic enzyme genes in the
following scenarios? Fill in the blanks with one of the following
phrases:
never be expressed/always (constitutively) be expressed
The cell produces a mutant trp repressor that cannot bind to the
operator. The enzyme genes will _____.
The cell produces a mutant trp repressor that binds to its
operator site even if no tryptophan is present. The enzyme genes
will ________.
The cell produces a mutant sigma factor that cannot bind the
promoter region. The enzyme genes will ______.
Elongation of the leader sequence is always stalled after
transcription of region 1. The enzyme genes will ____________.

Sarah Craig
06:05
Biology

The original DNA sequencing procedure invented by Fred Sanger used a DNA template (the molecule whose sequence you wish to determine), a radioactively labeled oligonucleotide primer, DNA polymerase, deoxyribonucleotide triphosphates (dATP, dCTP, dGTP, and dTTP), and dideoxyribonucleotide triphosphates (ddATP, ddCTP, ddGTP, ddTTP).

a) Explain why ddATP, ddCTP, ddGTP, and ddTTP were included in the sequencing procedure.

b) What will happen if the researcher mistakenly adds ten times less dideoxyribonucleotide triphosphates to the Sanger sequencing reaction?

Sarah Craig
01:41
Biology

Deamination of cytosine converts cytosine to uracil. Deamination
of methylated cytosine converts methylated cytosine to thymine.
Which of these covalent modification poses a greater challenge for
DNA repair enzymes? Why? How does this impact the mutation
frequency of CpG islands?

Sarah Craig
02:34
Biology

A mutant E. coli cell has a
mutated lac repressor that is unable to bind
allolactose, but can still bind to
the lac operator. What would be the activity of
the lac operon:
In the presence of high glucose and low lactose?
In the presence of high glucose and high lactose?
In the presence of low glucose and high lactose?
Explain your answers using your knowledge of
the lac operon and the elements that control its
expression.

Sarah Craig
02:46
Biology

What is the Philadelphia chromosome? How is this chromosome related to cancer? Identify how this chromosome appears physically different on a karyotype than it appears on a karyotype of normal chromosomes.

Sarah Craig
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