7B Flashcards

1
Q
  1. What are the components of DNA and its three-dimensional structure?
    C-3
    S-6
A

Components: PO4, deoxyribose, nitrogenous base. Structure: double stranded, double helix, antiparallel, twisted ladder, side of sugar and PO4 (backbone), rungs H bonds between nucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q
  1. State the Chargaff’s rul
A
  1. The amounts of thymine and adenine in DNA are the same and the amounts of cytosine and guanin are the same (A=T, G=C). 2. The proportion of adenine and gunaine differs among species.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q
  1. What evidence enabled Watson and Crick to decipher the structure of DNA?
A

Rosalind Franklin’s research in x-ray crystallography revealed the shape of DNA molecule: alpha helix. (final piece of evidence.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q
  1. Explain how hydrogen bonds contribute to the structure of DNA.
A

Connect complementary bases forming the “rungs” of the DNA twisted ladder structure. Strengthen DNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q
  1. Explain the roles of DNA, RNA, and protein in the central dogma.
A

Gene expression: A multistep process including transcription and translation, by which genetic information encoded by a gene is converted into a structural or functional part of a cell or body. DNA—>transcribed into mRNA—> translated into Protein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q
  1. Describe the structural differences between RNA and DNA.
    4
A

Single vs. double strand, Uracil instead of Thymine, Ribose vs. Deoxyribose, RNA smaller than DNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q
  1. Describe the functional differences between RNA and DNA.
A

DNA: stores RNA/protein encoding information, transfers information to next generation of cells. RNA: carries protein-encoding information, helps to make proteins, catalyzes some reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does mRNA contribute to protein synthesis?

A

Carries the information that specifies a protein. Has the information in the form of codons (genetic code word that corresponds to one amino acid.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does rRNA contribute to protein synthesis?

3

A

Main component of ribosomes where polypeptide chains are built. Correctly aligns ribosome and mRNA, catalyzes the formation of peptide bonds between amino acids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does tRNA contribute to protein synthesis?

A

A “connector”, binds an mRNA codon at one end and a specific amino acid at the other. Delivers the amino acid to the ribosome at the correct spot along the mRNA molecule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q
  1. Where in the cell does transcription occur?
A

Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the role of RNA polymerase in transcription?

A

Def: Enzyme that uses a DNA template to produce a molecule of RNA. (builds the RNA chain) A catalyst!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the stages of transcription?

A

Initiation, elongation, termination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens during the Initiation stage of transcription?

A

In the Initiation phase, enzymes unzip the DNA double helix exposing the template strand. RNA polymerase then attaches to a promoter (a DNA sequence that signals the gene’s start.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens during the Elongaton stage of transcription?

A

In elongation, RNA polymerase moves over the gene in a 3’ to 5’ direction, unwinds the DNA helix, reads the base sequence, and joins free RNA nucleotides into a complemetary strand of mRNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens during the Termination stage of transcription?

A

In termination, a terminator sequence signals the end of the gene, and the RNA, DNA and RNA polymerase separate. DNA becomes a double helix again. A RNA copy of a gene has been produced.

17
Q
  1. What are the roles of the promoter sequences in transcription?
A

The promoter is a DNA sequence that signals the gene’s start. It attracts RNA polymerase and transcription factors so transcription can start.

18
Q
  1. What are the roles of the terminator sequences in transcription?
A

The terminator is a DNA sequence that signals where the gene’s coding region ends. Upon reaching the terminator sequence, the RNA polymerase separates from the DNA template and releases the newly sythesized RNA.

19
Q
  1. Explain how mRNA is processed after transcription in eukaryotic cells.
A

Post transcription modification is a process in which eukaryotic cells tailor their RNA before it leaves the nucleus (pre-mRNA to mature mRNA.) After transcription, a sequence of modified nucleotides called a cap is added to the 5’ end of the mRNA. This cap helps mRNA bind to ribosomes. On the 3’ end, adenines are added forming a poly A tail. This tail determines the longevity of the mRNA. In addition, catalytic RNAs and proteins remove the introns from the mRNA. The remaining exons, which will eventaully be expressed, are spliced together. The mature mRNA leaves the nucleus ready to be translated.

20
Q
  1. Define Genetic code.
A

The correspondence between specific nucleotide sequences and amino acids.

21
Q
  1. Where in the cell does translation occur?
A

Cytoplasm

22
Q

What are the sequences of translation?

A

Initiation, elongation, termination

23
Q

What happens in the Initiation sequence of translation?

A

An initiation complex is formed. The leader sequence at the 5’ end of the mRNA molecule binds with a small ribosomal subunit. The start codon of the mRNA (AUG) pairs with the anticodon (UAC) of tRNA, which carries the amino acid Methionine. A large ribosomal subunit attaches to the small subunit to complete initiation.

24
Q

What happens in the Elongation sequence of translation?

A

Carrying a second amino acid, another tRNA molecule’s anticodon binds to the 2nd codon. The first and second amino acids form a covalent (peptide) bond. With the bond in place, the ribosome releases the first tRNA, which can be reused. The ribosome moves down the mRNA by one codon and a 3rd tRNA enters carrying an amino acid. The amino acid bonds to the 2nd amino acid and the polypeptide chain grows. tRNA brings successive amino acids until the ribosome…

25
Q

What happens in the Termination sequence of translation?

A

The ribosome encounters a stop codon (UGA, UAG, UAA) and polypeptide synthesis ends. tRNA does not bind to the stop codon. Instead, release factors bind to it and the participants of protein synthesis separate. The ribosome releases the last tRNA, the ribosomal subunits separate and are recycled and the new polypeptide is released into the cytoplasm or rough ER.

26
Q
  1. Explain how bacterial cells use operons to regulate gene expression.
A

An operon is a group of genes plus a promoter and an operator. Lac operon encodes for lactose degrading proteins which allow the bacteria to utilize lactose. If glucose is present or lactose is absent the bacteria does not use lactose and producing the lactose degrading protein would waste energy. So, a repressor protein binds to the operator preventing RNA polymerase from transcribing the genes for the lactose degrading proteins. If the bacteria needs to use lactose, the lactose will bind to the repressor which changes its shape and the repressor detaches from the DNA. RNA polymerase can now transcibe the genes for the lactose degrading protein and the lactose can be utilized.

27
Q
  1. Describe the points at which eukaryotic cells can regulate gene expression in the nucleus.
A

In the nucleus, gene expression can be regulated in the DNA or mRNA. Transcription factors, activators or repressors, either initiate or inhibit transcription of the DNA. Gene expression can also be regulated the chemical modification of DNA. DNA methylation compresses chromosomes preventing transcription while histone acetylation unravels the chromosome which promotes transcription. In mRNA, alternative splicing mixes up the gene increasing the variety of proteins. mRNA transport inhibits gene expression - if a mRNA got messed up during processing, then it will not be able to leave the nucleus inhibiting expression.

28
Q
  1. Describe the points at which eukaryotic cells can regulate gene expression in the cytoplasm.
A

In the cytoplasm, the number of poly a tails on mRNA can inhibit protein production. Micro RNA can also be an inhibitor. If too much mRNA is present then micro RNA will chop it up. Protein processing also regulates expression. A protein must fold correctly to be viable, it must get transported to its destination (Golgi, cell membrane). Processed??

29
Q
  1. How can substitution mutations can alter a protein.
A

Substitution changes the base triplet. In a silent mutation, the substitution encodes for the same protein as the original version (i.e. CCC and CCU both proline.) In a missense mutation, the substituted amino acid may drastically change the shape of the protein which changes the function also (i.e. sickle cell). In a nonsense mutation, a base triplet specifying a protein is changed into one that specifies a stop codon.

30
Q
  1. How can insertion and deletion mutations can alter a protein.
A

The addition or deletion of one or more nucleotides to a gene. These cause frameshift mutation which disrupt the codon reading frame. A missense mutation alters the amino acid sequence (the cat ate the rate example). A nonsense mution causes stop codons to be either inserted or deleted.