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Bio 111 > Final Exam > Flashcards

Final Exam Flashcards

1
Q

What direction does DNA replication occur in

A

5’ to 3’ direction only

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2
Q

What does primase do during replication?

A

Adds RNA primers to start DNA synthesis.

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2
Q

What is proofreading in DNA replication?

A

DNA polymerase removes mismatched bases as it adds new ones.

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2
Q

What enzyme relieves supercoiling ahead of the fork?

A

Topoisomerase.

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3
Q

Which enzyme unzips the DNA double helix?

A

Helicase

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3
Q

What are Okazaki fragments?

A

Short DNA fragments on the lagging strand

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4
Q

What enzyme connects Okazaki fragments

A

DNA ligase

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5
Q

What is nucleotide excision repair

A

Removes bulky DNA lesions like UV-induced dimers.

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6
Q

What repairs mismatches after replication?

A

Mismatch repair enzymes

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7
Q

What are telomeres

A

Repetitive DNA caps at chromosome ends to protect from degradation

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8
Q

What does telomerase do?

A

Extends telomeres in germ and stem cells.

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9
Q

Why do cells regulate gene expression?

A

To save energy and respond to environment or development.

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10
Q

What is transcriptional control?

A

Regulation of mRNA production from DNA

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10
Q

What is translational control?

A

Regulation of whether mRNA is translated into protein

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10
Q

What is post-translational control?

A

Modifying proteins after translation (fastest but energy-costly).

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10
Q

What happens when lactose is present in the lac operon system?

A

It binds to the repressor and allows transcription.

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10
Q

What gene codes for the lac operon repressor?

A

lacI.

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10
Q

What is the lac operon?

A

A group of genes in bacteria regulated to metabolize lactose.

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10
Q

What is positive control of gene expression?

A

Activators increase gene expression.

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10
Q

What is negative control of gene expression?

A

Repressors inhibit gene expression.

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10
Q

What is methylation?

A

Addition of a methyl group to cytosine (CpG) to repress gene expression.

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10
Q

What is phenotypic plasticity?

A

One genotype produces different phenotypes in different environments.

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10
Q

Why is methylation essential for life?

A

It regulates genes; loss of DNMT3 is lethal in embryos.

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10
Q

What enzymes perform methylation?

A

DNMTs (DNA methyltransferases).

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10
What is incomplete dominance?
Blending of traits (e.g., red + white = pink).
10
How is methylation linked to cancer?
Abnormal methylation patterns can silence tumor suppressor genes.
11
What is a Barr body?
Inactivated X chromosome in females formed via methylation.
11
Is all methylation plasticity?
No—some is stable, like Barr body formation.
11
What is the purpose of mitosis?
Growth, repair, and asexual reproduction (produces identical cells).
11
What is the purpose of meiosis?
Create gametes for sexual reproduction (produces unique haploid cells).
11
What is a test cross?
Crossing with a homozygous recessive to determine unknown genotype.
11
What happens in Prophase I of meiosis?
Homologs pair up and crossing over occurs.
11
What separates in Meiosis I?
Homologous chromosomes.
11
What is the Law of Segregation?
Alleles separate during gamete formation.
11
What separates in Meiosis II?
Sister chromatids.
11
How does meiosis increase genetic variation?
Crossing over and independent assortment.
11
How many daughter cells does mitosis make?
2 diploid identical cells.
11
How many daughter cells does meiosis make?
4 haploid unique cells.
11
What is the expected phenotype ratio for a dihybrid cross (AaBb x AaBb)?
9:3:3:1.
11
What is the Law of Independent Assortment?
Genes for different traits sort independently.
11
What is epistasis?
One gene affects the expression of another.
11
What is codominance?
Both alleles are expressed equally (e.g., AB blood type).
12
What is transcription?
The process of making RNA from a DNA template.
13
Where does transcription occur in eukaryotes?
In the nucleus.
13
What enzyme carries out transcription?
RNA polymerase.
13
What are the three stages of transcription?
Initiation, elongation, and termination.
14
What is a promoter?
A DNA sequence where RNA polymerase binds to start transcription.
14
What happens during initiation of transcription?
RNA polymerase binds to the promoter region of DNA.
14
What is the TATA box?
A common promoter sequence in eukaryotes.
14
What is translation?
The process of making a protein from an mRNA strand.
14
What happens during elongation? | Transcription
RNA polymerase adds RNA nucleotides complementary to the DNA template.
14
What type of RNA is made during transcription?
mRNA (messenger RNA).
15
What happens during termination? | Transcription
RNA polymerase reaches a termination signal and releases the RNA strand.
15
What is RNA processing in eukaryotes?
Capping, adding a poly-A tail, and splicing out introns.
15
What are introns and exons?
Introns are non-coding sequences removed; exons are coding sequences kept.
16
Where does translation occur?
In the cytoplasm at a ribosome.
16
What molecule carries amino acids to the ribosome?
tRNA (transfer RNA).
16
What are the three stages of translation?
Initiation, elongation, and termination.
16
What is an anticodon?
A three-base sequence on tRNA that pairs with a codon on mRNA.
16
What is a codon?
A three-base sequence on mRNA that codes for one amino acid.
17
What happens during initiation of translation?
Ribosome binds to mRNA and finds the start codon.
17
What is the start codon?
AUG, which codes for methionine.
18
What happens during elongation of translation?
tRNAs bring amino acids and ribosome forms peptide bonds.
19
What happens during termination of translation?
Ribosome reaches a stop codon and the polypeptide is released.
20
What are the stop codons?
UAA, UAG, UGA.
21
What is the role of the ribosome?
It facilitates the matching of tRNA anticodons to mRNA codons and builds the polypeptide chain.
22
What determines the sequence of amino acids in a protein?
The sequence of codons in mRNA, which comes from DNA.
23
What does DNA ligase do during replication?
Joins Okazaki fragments on the lagging strand by forming phosphodiester bonds.
24
What is the role of the CAP-cAMP complex in the lac operon?
It enhances transcription by helping RNA polymerase bind when glucose is low.
25
What happens in the lac operon when lactose is present and glucose is high?
The repressor is removed, but cAMP levels are low → CAP doesn’t bind → transcription is low.
26
Which site on the ribosome holds the tRNA carrying the growing peptide chain?
The P site.
27
Where are codons and anticodons found?
Codons = mRNA; Anticodons = tRNA (they match up during translation).
28
What’s the difference between proto-oncogenes and tumor suppressor genes?
Proto-oncogenes promote cell division; when mutated → become oncogenes. Tumor suppressors stop division or trigger apoptosis; when mutated → cell grows uncontrollably.
29
What does the M checkpoint in the cell cycle ensure?
That all chromosomes are attached to spindle fibers before division continues.
30
Is p53 a proto-oncogene or a tumor suppressor?
Tumor suppressor. It halts the cell cycle or triggers apoptosis when DNA is damaged.
31
What is epigenetics?
Study of gene expression changes that occur without altering the DNA sequence (e.g., methylation).
32
What does methylation do to gene expression?
Represses it—makes DNA less accessible to RNA polymerase.
33
What’s the key difference between mitosis and meiosis I?
Mitosis separates sister chromatids; Meiosis I separates homologous chromosomes.

Bio 111 (8 decks)

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