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Unit 1 principles of human biology > C1 - Genetic expression > Flashcards

C1 - Genetic expression Flashcards

1
Q

What do scientists use genetics for

A

Scientists use genetics to understand inheritance of characteristics, diseases, and genetic conditions.

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2
Q

What are nucleic acids?

A

Nucleic acids are large molecules found inside the nucleus of a cell, and they occur in all living organisms on Earth.

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3
Q

How many types of nucleic acid are there and what are they

A

The two types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

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4
Q

DNA and RNA are both polymers what are nucleotides

A

nucleotides are monomers of nucleic acids

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5
Q

What is the role of nucleic acids in genetic information?

A

Nucleic acids are responsible for storing genetic information and synthesizing proteins

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6
Q

What do nucleic acids contribute to in protein synthesis?

A

Nucleic acids are involved in protein synthesis by providing instructions for cells to build polypeptides.

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7
Q

What do polypeptides contribute to in the body

A

Polypeptides make up the structure and carry out most of the functions of the body.

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8
Q

What are the three components of a nucleotide?

A

The three components of a nucleotide are a pentose monosaccharide (5 carbon sugar), a phosphate group, and a nitrogenous base.

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9
Q

How are nucleotides formed?

A

Nucleotides are formed through condensation reactions between the sugar, phosphate, and nitrogenous base, resulting in the expulsion of water.

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10
Q

What are the five organic nitrogenous bases in nucleotides?

A

In DNA adenine (A), thymine (T), guanine (G), cytosine (C),

In RNA uracil (U) replaces thymine (T)

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11
Q

How are purines and pyrimidines classified?

A

Adenine and guanine are purines (double ring structure), while thymine, cytosine, and uracil are pyrimidines (simple ring structure).

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12
Q

How are polynucleotides formed?

A

Many nucleotides join together through phosphodiester bonds, where the phosphate group of one nucleotide bonds with the hydroxyl group of carbon 3 in the next nucleotide.

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13
Q

What forms the strong backbone of a polynucleotide?

A

The sugar-phosphate bonds in the polynucleotide structure form a strong sugar-phosphate backbone

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14
Q

What is the structure of DNA

A

DNA is a double-stranded polynucleotide arranged in a double helix.

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15
Q

What are the components of DNA nucleotides?

A

DNA nucleotides consist of deoxyribose sugar and the nitrogenous bases A, T, C, and G.

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16
Q

which bases go together

A

in DNA, A and T (apples in the tree)

C and G (car in the garage)

in RNA, A and U

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17
Q

Where is DNA organized in prokaryotic cells?

A

In prokaryotic cells (bacteria), DNA is found as one circular chromosome freely in the cytoplasm, along with smaller loops of DNA called plasmids.

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18
Q

how is DNA organized in eukaryotic cells?

A

In eukaryotic cells, DNA is mostly organized into chromosomes, which are associated with histone proteins.

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19
Q

How do the two polynucleotide chains in DNA interact?

A

The two polynucleotide chains run alongside each other in an antiparallel manner and are joined together by hydrogen bonds between complementary nitrogenous bases. A pairs with T (2 hydrogen bonds), and C pairs with G (3 hydrogen bonds).

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20
Q

What is the function of hydrogen bonds in DNA, and how does it contribute to stability?

A

The hydrogen bonds in DNA provide strength and stability to the molecule. They allow DNA to unzip for replication and transcription while maintaining its overall structure.

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21
Q

Where is genetic information stored in DNA?

A

Genetic information is stored within the double-stranded polynucleotide chain of DNA

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22
Q

How does DNA utilize its structure during cell division and protein synthesis?

A

DNA can unzip to copy itself before cell division and can also unzip a specific gene to serve as a template for messenger RNA synthesis before protein assembly.

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23
Q

How is the coded information in DNA protected?

A

protected within the sugar-phosphate backbones of DNA.

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24
Q

How is RNA structurally different from DNA?

A

RNA has a ribose sugar, while DNA has a deoxyribose sugar. RNA uses the nitrogenous bases A, U, C, and G (no thymine), and it is usually single-stranded.

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25
Q

Where do RNA and DNA occur in eukaryotic cells

A

RNA occurs in the nucleus (including the nucleolus) and cytoplasm, as well as in ribosomes. DNA occurs in the nucleus, chloroplasts, and mitochondria.

26
Q

What are the different types of RNA?

A

messenger RNA (mRNA) and transfer RNA (tRNA).

27
Q

What is the function of messenger RNA (mRNA)?

A

mRNA carries the genetic code of a gene from the nucleus to ribosomes, where it is used as instructions to assemble amino acids and synthesize proteins.

28
Q

What is the structure and function of transfer RNA (tRNA)?

A

tRNA is single-stranded and approximately 80 nucleotides long. It has two important regions called the anticodon and the amino acid attachment site. The anticodon allows tRNA to align the correct amino acid with mRNA during protein production. The sequence of three bases in the anticodon determines which amino acid joins the tRNA molecule

29
Q

When does DNA replication occur

A

DNA replication occurs during the S phase of interphase before cell division

30
Q

What happens to the DNA double helix during replication?

A

The DNA double helix unwinds, and hydrogen bonds between complementary base pairs break.

31
Q

How do free DNA nucleotides bind during replication?

A

Free DNA nucleotides bind to the exposed nucleotide bases through complementary base pairing, with A bonding with T and C bonding with G.

32
Q

What forms the new backbones during DNA replication?

A

Covalent bonds form between the sugar of one nucleotide and the phosphate group of the adjacent nucleotide, creating the new backbones

33
Q

Which enzymes catalyze the different steps of DNA replication?

A

Helicase catalyzes the unwinding of the DNA double helix, DNA polymerase catalyzes the binding of free nucleotides, and ligase catalyzes the formation of covalent bonds between nucleotides

34
Q

What is the outcome of DNA replication?

A

Two new molecules of DNA are produced, identical to each other and to the parent molecule.

35
Q

What type of replication is DNA

A

semi-conservative replication. Because Each new DNA molecule consists of one old strand and one newly synthesized strand,

36
Q

Where do genes exist and what is their function?

A

Genes exist on chromosomes and carry the code for making proteins needed in the body.

37
Q

How is protein structure determined?

A

The primary structure of a protein, which is the sequence of amino acids, determines its secondary structure and ultimately folds into its tertiary structure. The tertiary structure is crucial for the protein to carry out its function

38
Q

What is the relationship between the sequence of nucleotide bases and amino acids?

A

Each three-base section on the DNA strand, known as the triplet code, corresponds to a specific amino acid in the protein chain.

39
Q

Why is the genetic code considered degenerate?

A

The genetic code is degenerate because most amino acids have more than one base triplet code. This redundancy helps reduce the impact of point mutations as different triplets can code for the same amino acid.

40
Q

How is the genetic code read

A

The genetic code is read in groups of three bases (triplets) that occur one after another, without overlapping. If a base mutation occurs that adds or deletes a base, it causes a frame shift and alters the reading of every base triplet after the mutation.

41
Q

What are codons and where are they found?

A

Codons are base triplets found on messenger RNA (mRNA), which is produced during transcription and carries the genetic code from the nucleus to the ribosomes in the cytoplasm.

42
Q

What are anticodons and where are they found?

A

Anticodons are triplets of bases found on transfer RNA (tRNA) molecules. They are complementary to the codons on mRNA and help bring the specific amino acids to the ribosomes during protein synthesis

43
Q

What is a Point mutation

A

change in base sequence of DNA cause by a substitution of one base for an-
other, e.g., CGA becomes CCA

44
Q

What are the two main stages of protein synthesis

A

transcription and translation.

45
Q

What happens during transcription?

A

During transcription, the instructions on the coding strand of DNA are copied onto a messenger RNA (mRNA) molecule. This process occurs in the cell nucleus in eukaryotes

46
Q

What are the steps involved in transcription?

A
  1. The gene (DNA) unwinds and unzips as hydrogen bonds between the bases break.
  2. The bases of DNA nucleotides are exposed, creating a template strand.
  3. RNA nucleotides line up along the template strand and form temporary hydrogen bonds.
  4. Sugars and phosphate groups of adjacent RNA nucleotides bond together, forming a single polynucleotide chain of RNA.
  5. The resulting RNA molecule is complementary to the DNA template strand and serves as a copy of the coding strand.
  6. Each codon on the mRNA codes for a specific amino acid.
  7. The mRNA breaks away from the gene, and the DNA strands reassociate to form double-stranded DNA again.
47
Q

What is pre-mRNA?

A

The mRNA produced during transcription is referred to as pre-mRNA and requires further editing before it can function in the next stage of protein synthesis (translation)

48
Q

What are introns and exons?

A

Introns are non-coding regions of DNA within a gene, while exons are the coding or expressed regions of the gene

49
Q

What happens during transcription in relation to introns and exons?

A

During transcription, both introns and exons of a gene are transcribed, resulting in the formation of pre-mRNA

50
Q

What is splicing

A

Splicing is the process of editing the pre-mRNA. It involves the removal of introns and joining together of exons to form the final mRNA molecule.

51
Q

What is the role of endonuclease enzymes in editing and splicing?

A

Endonuclease enzymes may be involved in the processes of editing and splicing, aiding in the removal of introns and precise joining of exons.

52
Q

What can some introns become after splicing?

A

After splicing, some introns may become short non-coding lengths of RNA that are involved in gene regulation.

53
Q

How can genes encode more than one protein?

A

Genes can be spliced in different ways, allowing the same length of DNA with its introns and exons to produce multiple mRNA molecules and encode more than one protein.

54
Q

What is the role of ribosomes in translation?

A

Ribosomes catalyze the synthesis of proteins. They are composed of two subunits (a larger and a smaller) and facilitate the process of translation.

55
Q

What are the steps involved in translation at a ribosome?

A
  1. The mRNA molecule binds to a ribosome, with two of its codons attached to the small ribosomal subunit.
  2. The AUG codon, always the first exposed codon, is recognized by a tRNA molecule with the anticodon UAC, carrying the amino acid methionine. They form hydrogen bonds.
  3. A second tRNA molecule, complementary to the second codon, brings the next amino acid and binds to the codon.
  4. A peptide bond forms between the two adjacent amino acids.
  5. The ribosome moves along the mRNA, exposing new codons to the subunit.
  6. tRNA molecules continue to bind to the codons, bringing corresponding amino acids. The first tRNA molecule is released and can collect another amino acid of the same type.
  7. This process continues until a stop codon is reached, signaling the end of translation.
  8. The chain of amino acids leaves the ribosome and can undergo further modifications to form its functional structure.
56
Q

What are the three main classes of DNA mutations

A

The three main classes of DNA mutations are point mutations, insertion or deletion (indel) mutations, and expanding triple nucleotide repeats.

57
Q

What is a silent mutation?

A

A silent mutation is a point mutation where one base is substituted for another, but the base triplet still codes for the same amino acid. It does not alter the structure of the protein.

58
Q

What is a missense mutation?

A

A missense mutation is a point mutation that changes the base triplet, resulting in coding for a different amino acid

59
Q

What is a nonsense mutation?

A

A nonsense mutation is a point mutation that alters a base triplet, converting it into a stop codon. This causes premature termination of protein assembly, resulting in a truncated, non-functional protein.

60
Q

What is the effect of an indel mutation

A

Indel mutations, which involve the insertion or deletion of nucleotide pairs, cause a frameshift in the reading frame of the gene. This alters all subsequent base triplets, leading to the production of an abnormal and non-functional protein.

61
Q

What happens in expanding triple nucleotide repeats?

A

Some genes have repeating triplets, and in diseases like Huntington’s disease, the number of repeating triplets increases with DNA replication prior to meiosis. If the number of repeats exceeds a critical threshold, it leads to the development of symptoms associated with the disease.

Unit 1 principles of human biology (10 decks)

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