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Human Biology > DNA > Flashcards

DNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is DNA?

A

DNA is a substance that encodes the genetic information of heredity in a chemical language.

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2
Q

Explain DNA structure.

A

DNA is a very long double-stranded molecule in the shape of a double helix. Each strand of DNA is made up from chemical units called nucleotides. A nucleotide is made up of three parts: a deoxyribose sugar, a phosphate and a base. The phosphate of one nucleotide is joined to the sugars carbon 5 (5’). This sequence of sugars and phosphates creates the sugar-phosphate backbone. There are 4 different types of bases: adenine, thymine, guanine and cytosine. The nucleotides of one strand are linked to the nucleotides on the second strand through their bases- the bases join the strands by complementary base pairing and held together by weak hydrogen bonds. Each strand has a sugar 3’ end and a phosphate 5’ end. The two strands run in opposite directions so are anti parallel.

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3
Q

What does the base sequence of DNA form?

A

The genetic code.

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4
Q

Why does DNA replication have to take place before a cell divides?

A

To ensure the daughter cells have the same DNA as the mother cells.

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5
Q

What 7 things are required for DNA replication?

A
  • the original strands to act as a temple strands
  • a supply of DNA nucleotides
  • primers
  • the enzyme helicase
  • the enzyme DNA polymerase
  • the enzyme ligase
  • ATP
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6
Q

Explain what happens in DNA replication.

A

The enzyme helicase unwinds the double helix and breaks the weak hydrogen bonds between the bases. A primer, which is a short complementary strand of nucleotides, binds to the 3’ end of the template strand allowing the DNA polymerase to add DNA nucleotides. DNA polymerase then adds complementary DNA nucleotides to the open strand. As the strands are anti parallel and also as the enzyme DNA polymerase can only add nucleotides in the 3’ to 5’ direction, one strand will be leading and one will be lagging. The leading strand runs 3’ to 5’ so can be copied continuously in one long piece whereas the lagging strand runs 5’ to 3’ and so is replicated in fragments. These fragments are then joined together by the enzyme ligase.

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7
Q

What is PCR?

A

The polymerase chain reaction (PCR) is a laboratory technique for the amplification of DNA.

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8
Q

What are primers in PCR?

A

In PCR, primers are short strands of nucleotides which are complementary to specific target sequences at the two 3’ ends of the region of DNA being amplified.

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9
Q

After one cycle of PCR how many more copies of the region of DNA are there?

A

One cycle doubles the number.

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10
Q

Explain the process of PCR.

A

DNA is firstly heated to between 92°c and 98°c to separate the strands (denaturation). It is then cooled to between 50°c and 65°c to allow the primers to bind to the target sequence (annealing of primers). It is then heated to between 70°c and 80°c for a heat- tolerant DNA polymerase to replicate the region of DNA.

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11
Q

What are the practical applications of PCR?

A

PCR can amplify DNA to help solve crimes, solve paternity disputes and diagnose genetic disorders.

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12
Q

What is gene expression?

A

Gene expression is the process by which specific genes are activated to produce a required protein.

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13
Q

Explain the 4 differences between DNA and RNA.

A
  • DNA is made of two strands in a double helix whereas RNA has one single strand
  • DNA has the bases adenine, thymine, guanine and cytosine whereas RNA doesn’t have thymine instead has uracil.
  • DNA is found in the nucleus whereas RNA can be found in nucleus, cytoplasm and at ribosomes.
  • DNA has a deoxyribose sugar whereas RNA has a ribose sugar.
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14
Q

What are the three types of RNA.

A
  • messenger (mRNA)
  • transfer (tRNA)
  • ribosomal (rRNA)
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15
Q

Where do translation and transcription each take place?

A

Translation- nucleus

Translation- ribosomes

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16
Q

Exalting the process of transcription.

A

The enzyme RNA polymerase unwinds and unzips the double helix of the gene to be expressed, breaking the hydrogen bonds. RNA polymerase then synthesises a primary transcript of mRNA using complementary base pairing. mRNA then carries a copy of the DNA code from the nucleus to the ribosome. Once the mRNA molecule is produced it is spliced to produce the mature transcript (containing only exons, the introns have been removed).

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17
Q

What is a codon?

A

Each triplet of bases on the mRNA molecule is called a codon and codes for one specific amino acid.

18
Q

What is a tRNA molecule?

A

A tRNA molecule has an anticodon (an exposed triplet of bases) at one end and an attachment site for a specific amino acid at the other end. Each tRNA molecule carries its specific amino acid to the ribosome.

19
Q

Explain the process of translation.

A

The mRNA molecule travels through the cytoplasm and attaches to the ribosome. tRNA molecules transport specific amino acids to the ribosome. Each mRNA codon codes for a specific amino acid. The first codon of an mRNA molecule is a start codon. This signals the start of translation. The anti codons and codons match up to form completely base pairs. Peptide bonds form between the adjacent amino acids to form the polypeptide (protein). The last codon of an mRNA molecule is a stop codon which signals the end of translation.

20
Q

What happens to used tRNA molecules?

A

They exit the ribosome and collect another specific amino acid.

21
Q

How can divider to proteins be expressed from one gene?

A

Because of alternative RNA splicing differ mature mRNA transcripts are produced from the same primary transcript depending on which axons are retained.

22
Q

What do the polypeptide chains fold together to form?

A

The three-dimensional shape of a protein, held together by hydrogen bonds and other molecular interactions between individual amino acids.

23
Q

What part of a protein determines their function?

A

Their shape.

24
Q

What two tings affect the phenotype of an individual organism?

A

Gene expression and environmental factors.

25
Q

What are mutations?

A

Mutations are changes in DNA (genome) that can result in the absence of a protein of the production of an altered protein.

26
Q

Are mutations planned?

A

No they are spontaneous and random. In absence of external factors they are rare.

27
Q

What is a genome?

A

A genome is the entire set of genetic information for an organism.

28
Q

What is single gene mutation?

A

A mutation in the order (sequence) of DNA nucleotides.

29
Q

Name the there types of single gene mutation.

A
  • substitution
  • insertion
  • deletion
30
Q

What is a missense mutation?

A

It is a types of substitution mutation. It results in one amino acid being changed for another. This can give a non-functional protein or have little effect on the protein.

31
Q

What is a nonsense mutation?

A

It is a type of substitution mutation. It results in a premature stop codon being produced, which gives a shorter protein.

32
Q

What is splice- site mutation?

A

It is another type of substitution mutation. It can result in some introns being retained and/or some Exxon’s not being included in the mature transcript.

33
Q

What two single gene mutations cause frame shift?

A

Insertion and deletion.

34
Q

What is a frame shift mutation?

A

Frame shift mutations cause all of the amino acids after the mutation to be changed. This causes a major effect on the structure of protein produced.

35
Q

What is chromosome structure mutations?

A

Chromosome structure mutations involve alterations to the structure of a chromosome. They include duplication, deletion, inversion and translocation.

36
Q

What is duplication in a chromosome structure mutation?

A

Duplication happens when a section of a chromosome is repeated.

37
Q

What is deletion in chromosome structure mutations?

A

In deletion a section of a chromosome is removed.

38
Q

What is an inversion mutation?

A

A type of chromosome structure mutation. It is when a section of chromosome is reversed.

39
Q

What is translocation mutation?

A

Translocation happens when a section of a chromosome is added to another chromosome that is not its homologous partner.

40
Q

What is bioinformatics?

A

When computers are used to compare sequence data and predict the likelihood of developing of developing certain diseases.

41
Q

What is pharmacognetics?

A

The use of genome information in the choice of drugs.

42
Q

What oils personalised medicine based on?

A

An individuals genome.

Human Biology (6 decks)

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